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Breed, Environment and Diseases. (Cont.)

The Socio-economic Environment of Newcastle Disease Control Strategies for Backyard Poultry Systems1,2

Roger Oakeley

Veterinary Epidemiology and Economics Research Unit
Department of Agriculture, The University of Reading
Earley Gate, P.O. Box 236, Reading RG6 6AT
E-mail: [email protected]


Backyard poultry are an important source of income for many rural households in Africa, but is constrained by the presence of Newcastle disease. With limited resources available to control the disease, heat-stable Newcastle disease vaccines have been championed as a means of generating community participation in control strategies. Trials in Zimbabwe have examined both the technical effectiveness of heat-stable vaccines in controlling Newcastle disease, and their suitability for involving the rural community in vaccination activities. Reliability of the vaccines using alternative delivery methods and the capacity of rural communities to apply those methods are questioned. Sustainable Newcastle disease control strategies for extensive poultry systems cannot ignore the wider production and health concerns of extensive producers.

Key words: Backyard poultry, Newcastle Disease, Vaccine Approaches, disease control

1. This paper is based on project TCP/ZIM/8821(A) ‘Emergency Assistance for the Control of Newcastle Disease’ funded by the FAO. The views expressed are not necessarily those of FAO.
2. The author would like to acknowledge the contributions of Dr Vilmos Palya, staff of the Department of Veterinary Services in Zimbabwe and backyard poultry producers throughout Zimbabwe in generating the information upon which this paper is based.


Zimbabwe is subject to sporadic outbreaks of Newcastle disease particularly in extensively raised poultry. In 1996, the ‘Emergency Assistance for the Control of Newcastle Disease’ project was initiated to develop a sustainable, community-based strategy for the control and prevention of Newcastle disease in backyard flocks. The project focused on the identification of an effective technical package, and the appropriateness of that package in the production and socio-economic context of the backyard system. This paper reviews the results of technical vaccine trials, but focuses on the production and socio-economic context within which those trials were conducted.

Conventional methods for controlling Newcastle disease are based on live vaccine delivered by the intra-nasal, intra-ocular or intra-muscular routes. Live vaccines have traditionally been heat-sensitive and require storage at or below 4°C. Consequently, there has been need for an effective cold chain in which to store vaccine until the point of vaccination. Complete and effective cold chains are expensive and difficult to maintain and this has limited Newcastle disease control in small and dispersed backyard flocks in tropical climates.

Additional constraints cited for conventional vaccines include the suggestion that extensively raised birds are difficult to catch, and that vaccination is laborious and labour intensive (Spradbrow, 1994). Vaccination campaigns have remained the responsibility of veterinary professionals and technicians, with the inevitable high level of associated labour costs. A combination of cold chain, labour requirements and the search for a suitable vaccine has continued to hamper development of sustainable Newcastle disease control strategies for backyard poultry in tropical regions.

More recently, two heat resistant vaccine strains have been developed, known as V4 and I2, and two potential advantages have been put forward for backyard producers. In theory, they remove the need for a complete cold chain and are potentially cheaper to deliver. Also, the heat-stable properties favour alternative delivery methods such as via coating on bird feed, or in water. Heat-stable vaccines may, therefore, offer the potential for a more cost-effective, community-based method of controlling Newcastle disease in backyard poultry.

The search for a community-based control strategy

A comprehensive survey of the backyard poultry production system and its socio-economic context was undertaken across 5 Provinces of Zimbabwe (Madzima et al, 1998a). The survey included a longitudinal production study, a seasonal study and informal interviews with women producers. The following discussion summarises key factors drawn from this survey relevant to the development of a communitybased Newcastle disease control strategy.

Use of feed grains as vaccine carriers

From trials into potential feed carriers for V4 and I2, only rapoko3 was found to be suitable, but not maize, rice, millet or sorghum. This indicates that the V4 and I2 vaccines are highly sensitive to the grain they are delivered on, and that no single grain type can be identified as suitable. This is confirmed by similar findings in both Africa and Asia. (Rushton, 1995; Spradbrow, 1994). To develop a feed-borne vaccine strategy, therefore, requires examination of all potential grains in any country, and possible separate trials in different areas of the country, since grain characteristics may vary from region to region. There is also limited understanding of the impact on the vaccine of grain variety, quality and condition, chemical additives present, and also the surfaces grains are fed on.

3. A small brown grain used for food and brewing.

Significantly, in Zimbabwe only 15 % of producers provide supplementary feed for their birds, and feeding regimes vary significantly. If feed grains are not a traditional input for many backyard producers, basing a vaccine strategy on their use represents a significant constraint. As an example, rapoko is not grown in all areas of the country, nor is it widely available at all times of the year (Mavhenyengwa, pers. comm.4).

Although called ‘heat-stable’, no quantified definition has been applied to this term, and it is unclear how many hours and at what temperatures the vaccine can be kept before its potency deteriorates (Palya, 1998; Jackson, 1992). Vaccine performance is also affected by excessive vibration and extended exposure to direct sunlight (Madzima et al, 1998b). Feed-based vaccination, however, inevitably requires vibration during mixing and exposure to sunlight during application. Finally, the feeding rates of individual birds are difficult to monitor and control. To achieve protection, individual birds must consume a given quantity of grain and vaccine, but feeding rates and pecking order in flocks can disadvantage younger and weaker birds (Spradbrow, 1994; Jackson, 1992).

4. Dr M. Mavhenyengwa, Project Co-ordinator, project TCP/ZIM/8821 (A) Emergency Assistance for the Control of Newcastle Disease.

Backyard flock dynamics

The epidemiology of Newcastle disease under backyard systems remains unclear (Awan et al, 1994), but it is estimated that within a population, the disease can be considered under control if less than 30% of birds are infected (Palya, pers. comm.). The average backyard flock in Zimbabwe numbers 20 birds, and is composed of 8 chicks, 6–7 growers, 4–5 hens and 1 cock (Oakeley, 1998a). Based on rates of egg incubation and loss, and mortality in chicks and growers, flock turnover rate due to the introduction of ‘new’ birds, means that from a point in time, the average flock may comprise of 30% unprotected birds within 4 months. This indicates the need for vaccination between 2 and 3 times a year if effective cover is to be maintained in these flocks (Oakeley, 1998b).

These statistics must be viewed in the light of vaccine trial results. Field trials focused on the use of rapoko as a carrier for both V4 and I2, but also examined water-based application of V4, and eye-drop delivery of I2 and the conventional vaccine La Sota. Birds in the various trial groups were vaccinated every month, for up to 6 months, and tested for antibody levels using the haemagglutination-inhibition test. (Madzima et al, 1998a). Both I2 and La Sota delivered by the intra-ocular route afforded adequate protection rates after a single application. Water-borne V4 achieved less than 40% protection of flocks after three vaccinations, and feed-borne I2 and V4 less than 30% and zero protection, respectively, after six applications (Palya, 1998).

These test results confirm findings from trials elsewhere in Africa and Asia (Palya, 1998; Aini et al, 1990; Fontanilla et al, 1994; Tantaswasdi et al, 1992; Bell et al, 1995; Spradbrow, 1994). The findings suggest the need for further development and improvement of heat-stable vaccines before feed - or water-based delivery strategies can offer an effective technical solution to Newcastle disease control (Bell et al, 1995; Oakeley, 1998b). However, there remains the question of how any control strategy can incorporate community participation, and thereby offer a more sustainable approach to Newcastle disease control in backyard poultry systems.

The prioritisation of Newcastle disease control

Ultimately, maintaining control of Newcastle disease in backyard flocks will depend on the involvement of the farming community, and farmer enthusiasm reflects the level of priority they give the disease. A complex array of production and health constraints is associated with varying levels of technical, management and husbandry input in Zimbabwe. The survey identified massive variation between flocks in the levels of egg and bird off-take at every stage of the production cycle. While impossible to attribute to any single factor, this variation results from differential levels of egg and bird management, feeding, health care, chick rearing and other husbandry activities.

Despite the evident variation in backyard flock productivity, 78% of extensive producers surveyed claimed to have no support or contact with the formal veterinary and extension services. There is evidence that the research and extension system does not cater adequately, either for women producers, who are the primary stakeholders in extensive poultry, or for the system of extensive poultry production as a whole. Poultry production must be seen as only one of many household and farm activities, and is rarely the priority concern, even of women who tend to value it more highly than men. Other responsibilities such as household duties, other livestock or seasonal crop-related work can take precedence over poultry activities. It is, therefore, not clear how much additional time some households are prepared to commit to activities like poultry disease control.

Customary practices can also complicate vaccination campaigns. The transfer and movement of chickens between villages and regions is a fundamental part of the extensive system, enabling owners to use birds for celebrations, gifts and as ready sources of cash. These movements influence the epidemiology of the disease, and complicate the monitoring and control of vaccination cover. Mass vaccination campaigns have also been hampered by absence of producers at key times, and reports of outbreaks following previous campaigns (Mavhenyengwa, pers. comm.).

Most producers appear well informed about Newcastle disease and its impact, but it is only one of numerous health constraints threatening backyard flocks. There is widespread incidence of fowl pox, infectious bursal disease, losses to predators, and internal and external parasites, as well as considerable management and husbandry constraints (Oakeley, 1998b). No information is available on what proportions of losses are a result of different diseases or problems, and no quantitative data are available on the specific losses attributable to Newcastle disease.

The absence of a complete production and health extension package specifically aimed at extensive poultry producers was highlighted by the study. Since a sustained control strategy depends upon producer commitment, the benefits of that commitment must be clear and acceptable to the farming community. While there remain gaps in the services offered to backyard producers, limited commitment toward isolated health campaigns such as Newcastle disease vaccination can only be expected. This may be one reason why extensive poultry producers have limited interest in New castle disease control.

In addition, it is not clear how great a threat backyard producers perceive Newcastle disease to be. In commercial systems, the threat is significant when large numbers of birds, in confined areas, can die within short time periods as a result of an outbreak. In extensive flocks, however, some birds can be salvaged in the face of an outbreak, through consumption, sale or gift (Spradbrow, 1994). Such strategies will greatly effect the true economic loss associated with an outbreak, but may not be reflected in the statistics of birds that die or are slaughtered in response to an outbreak.

Concluding discussion

A question remains over the readiness of backyard producers to adopt any strategy based on the use of supplementary feeds that do not currently feature in many backyard production systems. Not only does the purchase of feed grain represent a constraint to some producers, delivery procedures are also open to misapplication and problems of monitoring. Involving producers in feed-based vaccine delivery may, in practice, prove no less problematic than facilitating their participation in more conventional techniques. Zimbabwe now uses V4 delivered by intra-ocular route (Oakeley, 1998b), and is training individual producers how to handle and apply the vaccine in this way. It appears that the skills are being readily transferred to producers that catching birds is not a problem, and that subsequent vaccinations will be handled by producers themselves, with only limited input from veterinary staff.

It is clear that the potential risk of Newcastle disease to the poultry industry in Zimbabwe will ensure the issue remains a high priority. Equally clear is the need to sustain producer commitment and co-operation if the disease is to be controlled in the extensive poultry flock. New castle disease represents only one of many constraints to the backyard sector in Zimbabwe. Other health, management and husbandry limitations have been largely ignored by the service sector, and community support for Newcastle disease control will depend on the commitment of the service sector to meet this much broader range of needs.


Aini, I., Ibrahim, A.L. and Spradbrow, P.B. (1990). “Vaccination of chickens against Newcastle disease with a food pellet vaccine”, Avian Pathology,19, 371–384.

Awan, M.A., Otte, M.J. and James, A.D. (1994). “The epidemiology of Newcastle disease in rural poultry: A review”, Avian Pathology, 23, 405–423.

Bell, J.G., Fotzo, T.M., Amara, A. and Agbede, G. (1995). “A field trial of the heat resistant V4 vaccine against Newcastle disease by eye-drop inoculation in village poultry in Cameroon”, Preventative Veterinary Medicin,e 25, 19–2.5

Fontanilla, B.C., Silvano, F. and Cumming, R. (1994). “Oral vaccination against Newcastle disease of village chickens in the Philippines”, Preventative Veterinary Medicine, 19, 39–44.

Jackson, A.R.B. (1992). “Observations on Some Difficulties Encountered in Trials with Oral Newcastle Disease Vaccination”, in Spradbrow, P.B. (ed), Proceedings: Newcastle Disease in Village Chickens. Control with Thermostable Oral Vaccines, No. 39, Canberra: ACIAR.

Madzima, W.N., Gwaze, G., Mavhenyengwa, M., Chitate, F., Guta, M., Madekurozwa, R.,

Munyombwe, T., Nquindi, J. and Ncube, C. (1998a). Progress Report 3: Emergency Assistance for the Control of Newcastle Disease in Zimbabwe, Project TCP/ZIM/8821 (A), Rome: FAO.

Madzima, W.N., Gwaze, G., Mavhenyengwa, M., Chitate, F., Guta, M., Madekurozwa, R.,

Munyombwe, T., Nquindi, J. and Ncube, C. (1998b). Progress Report 4: Emergency Assistance for the Control of Newcastle Disease in Zimbabwe, Project TCP/ZIM/8821 (A), Rome: FAO.

Oakeley, R.D. (1998a). Emergency Assistance For The Control Of Newcastle Disease, Consultancy, Report on Rural Poultry Production-Socio-Economy, May 25th - June 9th 1998, Project TCP/ZIM/8821 (A), Rome: FAO.

Oakeley, R.D. (1998b). Emergency Assistance For The Control Of Newcastle Disease, Consultancy, Report on Rural Poultry Production-Socio-Economy, December 12th - 22nd 1998, Project TCP/ZIM/8821 (A), Rome: FAO.

Palya, V.J. (1998). Assistance For The Control of Newcastle Disease Phase II Of TCP/ZIM/4553 (E), Consultancy Report on Feed-Based Newcastle Disease Vaccine, December 12th-22nd 1998, Project TCP/ZIM/8821 (A), Rome: FAO.

Rushton, J. (1995). Assistance to Rural Women in Protecting their Chicken Flocks Against Newcastle Disease, Consultancy Report on Rural Poultry Production-Socio-Economy, December 1995, Project TCP/RAF/2376, Rome: FAO.

Spradbrow, P. (1994). “Newcastle Disease in Village Chickens”, Poultry Science Review 5, 57–96.

Tantaswasdi, U., Danvivatanaporn, J., Siriwan, P., Chaisingh, A. and Spradbrow, P. B. (1992). “Evaluation of an oral Newcastle disease vaccine in Thailand”, Preventative Veterinary Medicine,12, 87–94.

A general Review on Some Important Diseases in Free Range Chickens

Anders Permin & Magne Bisgaard

Department of Veterinary Microbiology
The Royal Veterinary and Agricultural University
Bülowsvej 13, 1870 Frederiksberg C, Denmark
E-mail: [email protected] and [email protected]


Scavenging poultry is the most widely owned animal and the poultry suffer from a number of diseases as presented in this paper. However, long-term cohort studies, examining the causes of death, have to date not been carried out in the free range production systems. As knowledge on the proportion of the individual disease of the overall mortality is not available, it is postulated that other diseases than Newcastle Disease are present in free range poultry production systems and that a successful development of the system will be possible only when the exact causes of mortality are known. Post mortem examinations are not expected to be accepted by existing international peer-reviewed journals and it is proposed an international journal dealing with problems relating to scavenging and family poultry should be established as it would ensure rapid implementation of research results obtained.

Key words: Scavenging, poultry, diseases, causes, importance, developing countries.


Poultry production has undergone rapid changes during the past decades due to the introduction of modern intensive production methods, new breeds and improved biosecurity and preventive health measures. Moreover, the management methods place high demands on proper health, hygiene and require only a small, but very skilled labour force.

In developing countries, however, adoption of this type of production has been limited due to the high inputs as listed above. The progress in industrial poultry production methods has thus had little effect on subsistence poultry production in the rural and peri-urban areas in developing countries. In these countries access to poultry meat and eggs depends on village-level poultry production. Although poultry production is considered as secondary to other agricultural production systems it has an important role in supplying villagers with additional income and high quality protein. This system provides valuable protein through a low input system, now representing 30% or more of the protein consumed (FAO, 1998).

Almost all families in developing countries keep a chicken flock with an average size of about 10 adult chickens, varying from 5 to 50 animals. The majority of these animals are kept in free-range scavenging systems, where the birds scavenge around the house during daytime. Primitive housing of the birds during the night, however, is often seen. Supplementary feed consists mainly of household wastes, insects, larvae and seeds (Minga et al. 1989; Kabatange et al. 1990; Aini, 1990; Pandey, 1992).

Mortalities observed are in the range of 80 – 90% within the first year after hatching (Matthewman, 1977; Wilson et al. 1987). For the same reasons the owners never include chicks when they refer to the flock size. The mortality is believed to be caused by mismanagement, lack of supplementary feeding, predators and diseases (Aini, 1990; Pandey, 1992). Little research has been published on rural poultry health, despite the fact that up to 80% of the poultry population in Africa and Asia is kept by the households as free range chickens (Minga et al. 1989; Aini, 1990). Although solid data have not been published, Newcastle Disease (ND) is regarded as the principle factor limiting rural poultry production in all African and Asian countries. ND may kill up to 80% of household poultry in Africa (Minga et al. 1989; Aini, 1990; Bell, 1992), but is not expected to account for the high early mortality rate according to the authors. In addition, detailed epidemiology of the disease in the village situation is largely unknown (Yongolo, 1997). Furthermore, recent studies have shown that other diseases are present in scavenging poultry communities (Bell et al. 1990; Cumming, 1991; Bell, 1992; Chrysostome et al., 1995; Permin et al. 1999). Since most of our knowledge relies on seroprevalence studies, solid longitudinal studies on causes of mortality are strongly needed to improve our knowledge of the prevalence and significance of the individual diseases under village conditions. The following data therefore mainly reflect experience obtained under backyard conditions in developed countries.


According to Jordan et al. (1996) and Calnek et al. (1997) poultry diseases can be divided into five groups, namely bacterial (table 1), viral (table 2), fungal (table 3), parasitic (table 4) and nutritional (table 5) diseases. Only the diseases of expected importance under village conditions, e.g. those causing high mortality rates in chickens are mentioned in these tables.

As seen a wide variety of diseases are expected to occur under village conditions. Some of these diseases are age specific, whereas others are encountered in all age groups.

A General Review on Some Important Diseases in Free Range Chickens

Table 1. Important bacterial diseases in free range poultry and the age group where the disease is most often observed

DiseaseAge group
Escherichia coliAll ages, but mainly chicks
Salmonella spp.All ages, but mainly chicks
Salmonella pullorumChicks < 3 weeks
Salmonella gallinarumGrowers, adults
Pasteurella multocidaGrowers, adults
Haemophilus paragallinarum (Coryza)Growers, adults
Clostridium perfringensAll ages, but mainly growers
Mycobacterium aviumAdults
Mycoplasma gallisepticumAll ages
Mycoplasma synoviaeAll ages

Table 2. Important virus diseases in free range poultry and the age group where the disease is most often observed

DiseaseAge group
*Marek's disease> 6 weeks
Newcastle diseaseMainly growers and adults
Fowl PoxAll ages
Infectious LaryngotracheitisGrowers, adults
*Infectious Bursal Disease "Gumboro> 8 weeks

* immunosuppressive disease

Table 3. Important fungal diseases in free range poultry and the age group where the disease is most often observed

DiseaseAge group
MycotoxicosesAll ages

Table 4. Important parasitic diseases in Free range poultry and the age group where the disease is most often observed

DiseaseAge group
CoccidiosisChicks, growers, (adults)
Histomoniasis1–3 months
NematodesAll ages
HaemoparasitesChicks, growers
EctoparasitesChicks, growers

Table 5. Important nutritional diseases in free range poultry and the age group where the disease is most often observed

DiseaseAge group
Vitamin A, D & EChicks, growers
Other vitamins, minerals and amino acidsChicks, growers


Approximately 80% of the world poultry population is kept as free range poultry (Minga, 1989; FAO, 1998). The free range poultry production system has also been designated as the “low input - low output” system (Pandey, 1992). Mortality in this system is in the range of 80 – 90% within the first year after hatching (Matthewman, 1977; Wilson, 1987) and is belived to be caused by mismanagement, lack of fresh water and supplementary feed, predators and diseases (Aini, 1990; Pandey, 1992). Of these, diseases are believed to be the main limiting factor to the production of indigenous chickens (Aini, 1990). Among causes of early mortality nutritional diseases might be expected to dominate due to shortage of supplementary feed before and after hatch. In addition, the quality of hatching eggs might be questioned under the climatic conditions present in these countries. Lack of vitamins and protein weaken the chicks and make them vulnerable to other diseases and predators. Diseases are also easily contracted under free range conditions due to scavenging habits (Soulsby, 1982; Pandey, 1992). With an unconfined type of management, disease control is very difficult to carry out and is therefore rarely practised by the owners.

As mentioned earlier, Newcastle Disease is believed to be the most important disease in free range systems (Minga, 1989; Aini, 1990; Bell, 1992). During out-breaks of the disease up to 80% of the population may die. This, however, is dependant on different factors including the virulence of the strain causing the out-break (Alexander, 1997). A recent study in Nicaragua (Kyvsgaard, 1999; personal communication) has, however, shown that in ND-immunised birds mortality is still high. The majority of the mortality is found in chicks up to 3–4 months of age. In this group up to 52.5% of the animals died due to other causes than ND. Similar Studies in Mali by Wilson et al. (1987) have shown that chick mortality is in the range of 60% within the first 3 months after hatching.

A study in Morocco (Bouzoubaa et al., 1992) has revealed that up to 58% of the village chickens had antibodies against Salmonella gallinarum and S. pullorum. Similar findings were reported by (Adesiyun et al. 1984) from Nigeria. Chryosostome and his co-workers (1995) reported that 10% of the village chickens had antibodies against S. pullorum and that 62% had antibodies against Mycoplasma gallisepticum. Furthermore, 65% of the animals had antibodies against ND. In Mauritania, Bell et al. (1990) found that 17.5% of the birds had antibodies against S. pullorum and that up to 46.2% of the birds had antibodies against Gumboro disease. In the same animals 7.5% had antibodies against ND. In the Tanzania, Permin et al. (1999) examined 600 live chickens and found the presence of a range of diseases. All animals were parasitised with one or more (up to 14 species) species of endoparasites. In total 29 different species were detected in the study. Furthermore, 65.7% of the animals were parasitised with Cnemidocopt-es mutans, Dermanyss-us gallinae and/or Echidnopha-ga gallinacea. The animals were also infected with a range of haemoparasites, the most common being Plasmodium juxtanucleare and Aegyptinella spp. Antibodies against Newcastle disease was seen in 7.3%, against Salmonella enteriditis in 2.0%, against Salmonella gallinarum/pull-orum in 52.7%, against Infectious Laryngotracheitis in 58.3% and against Gumboro disease in 42.3%. Similar studies have to the knowledge of the authors not been carried out in Asian countries. The significance of all these disease, however, remains to be investigated. In addition, it should be noted here that a general trend for these studies is that they have only looked for antibodies against selected diseases.


Long-term cohort studies, examining the causes of death, have to date not been carried out in the free range production systems. Important knowledge on the proportion of the individual disease of the overall mortality is thus not known. It is consequently postulated that other diseases than ND are present in free range poultry production systems and that a successful development of this production system is only achieved when the exact causes of death is known. Since publications on disease prevalence based upon post mortem examinations are not expected to be accepted by existing international peer-reviewed journals the W.P.S.A. should be addressed to establish and international journal dealing specifically with problems relating to scavenging and family poultry. Establishing such a journal would ensure a rapid implementation of research results obtained.


Adesiyun, A.A., Bishu, G., Adegboye, D.S. and Abdu, P.A. (1984). “Serological survey of Salmonella pullorum antibody in chickens around Zaria, Nigeria”, Bulletin of Animal Health and Production in Africa, 32, 81–85.

Aini, I. (1990). “Indigenous chicken production in South-east Asia”, World's Poultry Science Journal, 46, 51–57.

Alexander, D.J. (1997). “New castle Disease and Other Avian Paramyxoviridae Infections”, in B.W. Calnek, H.J. Barnes, C.W. Beard, L.R. McDougald, and Y.M. Saif (1997), Diseases of Poultry, Ames, Iowa: Iowa State University Press, 541–569.

Bell, J.G. (1992). “The village chicken and disease control”, Tanzanian Veterinary Journal, 12, 44–47.

Bell, J.G., Kane, M.and Le Jan, C. (1990). “An Investigation of the Disease Status of Village Poultry in Mauritania”, Preventive Veterinary Medicine, 8, 291–294.

Bouzoubaa, K., Lemainguer, K. and Bell, J.G. (1992). “Village chickens as a reservoir of Salmonella pullorum and Salmonella gallinarum in Morocco”, Preventive Veterinary Medicine, 12, 95–100.

Calnek, B.W., Barnes, H.J., Beard, C.W., McDougald, L.R. and Saif, Y.M. (1997). Diseases of Poultry, Ames, Iowa: Iowa State University Press, 1–1080.

Chrysostome, C.A.A.M., Bell, J.G., Demey, F. and Verhulst, A. (1995). “Seroprevalences to three diseases in village chickens in Benin”, Preventive Veterinary Medicine, 22, 257–261.

Cumming, R.B. (1991). Village Chicken Production: Problems and Potential in Newcastle Disease in Village Chickens. ACIAR Proceedings.

FAO (1998). FAOstat. Statistical database of Food and Agriculture Organization of the United Nations, Rome, Italy.

Jordan, F.T.W. and Pattison, M. (1996). Poultry Diseases, London: W.B. Saunders Company Ltd.

Kabatange, M.A. and Katule, A.M. (1999). “Rural poultry production systems in Tanzania”, in E.B. Sonaiya (ed)., Rural poultry in Africa. Conference Proceedings, Ile-lfe, Nigeria, 171–176.

Kyvsgaard, N. (1999). Personal communication.

Minga, U.M., Katule, A.M., Maeda, T., and Musasa, J. (1989). Potential and Problems of the traditional chicken industry in Tanazania. Proceedinga of the 7th Tanzania veterinary scientific conference. Arusha, 207–215.

Matthewman, R.W. (1977). A Survey of Small Livestock Production at the Village level in the Derived Savanna and Lowland forest Zones of South West Nigeria, University of Reading, Department of Agriculture and Horticulture, Study No. 24, ISBN No. 0-70490242-7. pp 40–41.

Pandey, V.S. (1992). “Epidemiology and economics of village poultry production in Africa: Overview”, in V.S. Pandey and F. Demey (eds.), Village poultry production in Africa, 1992. Conference Proceedings. Rabat, Morocco, 124–128.

Permin, A. Magwisha,. H., Kassuku, A.A., Minga, U.M., Yongolo, H.M., Jørgensen, P., Nansen, P., Bisgaard, M., Frandsen, F. (1999). Diseases in rural scavenging poultry in the Morogoro Region, Tanzania. In prep.

Soulsby, E.J.L. (1982). Helminths, Arthropods and Protozoa of Domesticated Animals, East Sussex: Bailliére Tindall.

Wilson, R.T., Traore, A., Kuit, H.G. and Slingerland, M. (1987). “Livestock production in central Mali: Reproduction, growth and mortality of domestic fowl under traditional management”, Tropical Animal Health and Production, 19, 229–236.

Yongolo, H.M (1997). Epidemiology of Newcastle Disease in Village Chickens in Tanzania, M.Sc. Thesis, Morogoro, Tanzania: Sokoine University of Agriculture.

Diseases as a Risk Factor in Relation to the Rural Poultry Model in Bangladesh

Jens P. Christensen

Department of Veterinary Microbiology
The Royal Veterinary and Agricultural University
13 Bülowsvej, DK-1870 Frederiksberg C, Denmark
E-mail: [email protected]


Only minor improvement of the health status of chickens at most levels of the production pyramid of the poultry model has been obtained during the most recent years. Chicken Rearers have reported mortalities as high as 36 % within an 8-week rearing period. Due to insufficient record and reporting systems no specific mortality rates from the DLS hatchery farms have been obtained, but it is considered to be very high. In the private commercial sector where biosecurity has reached a higher level than at the government farms 15% mortality during rearing of the parent flocks is considered good. Also the NGOs express their concern about the disease situation and experience disease problems to an unknown extent. Presently, the buildings and infrastructure at the DLS farms are not suitable for breeding and support of breeding stock. The personnel at the farms are not well aware of “risky procedures” and good management practices just as no consistent vaccination policy has been made. No serological or bacterial routine monitoring of the flocks are performed before the start of laying or during the laying period. The NGOs are in a phase where they construct new production facilities according to the highest biosecurity standards, but they lack human expertise to run the sites. As with the Government farms, the NGOs require a sound disease monitoring and control system. The technical knowledge and procedures required to perform a simple but still beneficial disease monitoring and control programme for the breeding flocks appear to be present at CDIL (mainly monitoring the salmonella-, mycoplasma-, Newcastle disease virus status of the breeding flocks). However, it is impossible for the present number of scientific staff at CDIL to run the number of tests required in a monitoring and control programme in parallel with their diagnostic duties. In general, there is a significant lack of chemicals, reagents, media etc. at these laboratories just to be able to solve the present diagnostic tasks.

Key words: Poultry, disease, Bangladesh model, risk factor.

Introduction: Disease situation

In addition to the question of breed quality of the chickens used in the SLDP, it has been underlined several times during evaluations of projects that the poor health status of the day-old chickens provided by the poultry model represents a major problem.

A number of people (avian pathologists associated the Department of Livestock Services' (DLS) poultry farms, directors of DLS farms, staff at Central Disease Investigation Laboratory (CDIL), Bangladesh Livestock Research Institute (BLRI), Bangladesh Agricultural University (BAU), the NGOs BRAC and PROSIKA, consultants to the private poultry sector, chicken- and key rearers at village level) have all expressed that little improvement of the health status of chickens at most levels of the production pyramid of the poultry model has been obtained during the most recent years.

Important poultry diseases for any production system such as Newcastle disease, fowl typhoid, pullorum disease, fowl cholera, Gumboro, Marek's disease and fowl pox have all been diagnosed in Bangladesh and are suspected to be responsible for a high percentage of the significant mortality reported. Other infections, which are known to influence production results negatively such as mycoplasma infections, infectious bronchitis, coryza and parasites, are probably common. A chicken rearer recently reported that the highest total mortality she had experienced in one of her batches of chickens (420) over a two-year period was approximately 36% within the 8-week rearing period. Due to insufficient record and reporting systems no specific mortality rates from the goverment hatchery farms have been obtained but it is considered to be very high. From time to time, the NGOs also experience high mortalities and disease outbreaks. In the private commercial sector where biosecurity has reached a higher level than at the government farms 15% mortality during rearing of the parent flocks is considered good. It is estimated that the mortality at most of the government hatchery farms at times can be significantly higher. Not all mortality is due to disease but such mortality rates clearly indicate that the disease situation represents a major problem in the breeding and multiplication system and therefore also to the rural poultry model. In this respect it can be mentioned that the diagnosis made often are based on a few uncertain criteria even at official laboratories. Newcastle disease, for instance, is often diagnosed only on the basis of bleedings of the alimentery tract. As a result of this other significant forms of Newcastle may be overlooked. Consequently, no information about the real situation of Newcastle in Bangladesh is available.

Biosecurity and management aspects

DLS farms

Presently, the buildings and infrastructure at the government farms are not found suitable for breeding and support of breeding stock and the personnel at the farms are not well aware of “risky procedures” and good management practices.

“Open” or “semi-closed” poultry houses used for different purposes such as laying, rearing and brooding are often located within a very small radius on the farms resulting in a high risk for transmission of diseases between houses. The same houses are constructed with openings in the walls covered with wire, which are almost impossible to clean and disinfect. The open houses are also very vulnerable to diseases, which are known to have a reservoir in the wild life. These include influenza, Newcastle disease, salmonella infections and fowl cholera. None of the houses have shower-in facilities for the personnel.

Eggs and chickens of various ages are exchanged quite intensively between the different DLS farms and represent a serious risk of spreading of diseases. The reason for this exchange is the lack of an overall production and multiplication plan.

The staff at the farm goes in and out of the different houses without any precautions and no fixed procedures have been implemented. Simple precautions such as the use of foot-dips or change of clothes etc. at the entrance to all houses are not taken.

Vaccines (primarily Gumboro) are still not always available. When the farms run out of vaccine stock the application procedure for supply of new batches of vaccines may take a long time with a resulting temporary lack of vaccine. Another problem is that efficacy testing has not been carried out on vaccines produced by DLS and no consistent vaccination policy has been made. Vaccination against Marek's disease is only performed in case of acute problems. But the diagnosis of Marek is based on insufficient pathological criteria, which may result in wrong conclusions. Storage and use of vaccines are not performed strictly according to the manufactures' recommendations.

No serological or bacterial routine monitoring of the flocks are performed before the start of laying or during the laying period. Routine post mortems of dead birds are not performed.

In addition, the layout of the hatcheries does not always comply to sound biosecurity standards, and the staff at the hatcheries are not aware of common hygienic precautions needed to be taken when handling hatching eggs, including proper disinfection and storage. The lack of disinfection of hatching eggs under the conditions existing in Bangladesh should be regarded as unacceptable.

NGO poultry farms


The most recent farms build by BRAC are modern parent-stock farms constructed according to high biosecurity standards. That is, closed, fully ventilated houses where the rearing unit is located at a reasonable distance from the production houses. Shower-in facilities are used. The associated hatcheries are also distant from the poultry units and have their own entrance shower-in facilities etc. The layout of the hatcheries is according to highest standards and planning has been done in collaboration with the manufacturer of the hatchers.

However, also semi closed production systems with a resulting minor level of biosecurity exist within the production system of BRAC (two farms).

Farm management has a high priority according to BRAC and internal courses are frequent. The farm managers meet at one of the BRAC centers once a month to coordinate working routines and standards. Staff is sent to the manufacturer of the setters and hatchers for training in hatchery management. Due to the lack of qualified local veterinarians within poultry production, BRAC has employed a veterinarian from abroad. He is visiting the farms, doing post mortems and trains the staff etc.

BRAC is interested in setting up a monitoring and control system, but does not have the possibility with the existing laboratory facilities. According to BRAC there is an urgent need for diagnostic laboratory capacity in Bangladesh and they are constructing their own laboratory, which is expected to be operational late summer 1999. In the meantime serology (mainly ELISA) is performed at a laboratory run by a private poultry company.


Currently PROSIKA has two parent-stock farms in operation. One modern closed housing farm and another semi-closed farm. Both farms contain a mixed population of commercial hybrid parent-stock for broiler- and layer production.

In 1999 two more closed housing system farms are expected to be fully operational. Both these new farms will be parent-stock farms with a mixed population of commercial hybrid parent-stock for broiler-and layer production.

Training of farm managers is performed abroad by the breeding company supplying the parent-stock. Hatchery management training has to some extend been done in India. The overall impression of farm management/level of biosecurity etc. is that PROSIKA do take precaution but they to could improve on these issues.

This organization has also expressed the need for extended diagnostic services.

Laboratory back-up facilities

The nucleus of “Veterinary Investigation Service in Bangladesh” is CDIL located in Dhaka, but also eight “Field Disease Investigation Laboratories” (FDIL's) located at Mymensingh, Manikganj, Joypurhat, Barisal, Gaibanhda, Serajgonj, Sylhet and Feni are part of the system.

The main tasks of the CDIL are to examine specimens received from the field veterinarians, farmers, government and private livestock and poultry farms or any other source and to render diagnosis along with appropriate line of treatment and suitable control measures. The CDIL receives specimens mostly from rural and urban areas in and around Dhaka. It also receives specimens from the EDIL's.

The technical knowledge and procedures required to perform a simple but still beneficial disease monitoring and control programme for the breeding flocks appear to be present at CDIL (mainly monitoring the salmonella-, mycoplasma-, Newcastle disease virus status of the breeding flocks). However, it is impossible for the present number of scientific staff at CDIL to run the number of test required in a monitoring and control programme in parallel with their diagnostic duties. The other laboratories will have major problems in implementing the procedures needed. In general, there is a significant lack of chemicals, reagents, media etc. at these laboratories just to be able to solve the present diagnostic tasks.

The support, which would be needed from these laboratories in case of the introduction of a monitoring and control system of the breeding flocks, would further increase the demand for media and chemicals.

More detailed diagnosis and subsequent control measures cannot be obtained from any of these laboratories at present. Newer diagnostic tools such as commercial available ELISA tests are not available. As a consequence of this, one private poultry breeding company has started a serological laboratory where several ELISA tests are performed. BRAC is using this laboratory from time to time.

Future actions recommended to be taken

Within the DLS production system, a new production set-up is needed in order to be able to control the production as well as the disease situation. It is recommended that the DLS farm located at Savar operates as a central grandparent farm and the other DLS hatchery farms as parent-stock units (see SLDP II feasibility study, 1999). Attention should be given to the fact that housing of birds of different ages on the same site increase the risk of persistence and cross-infection and reduces or prevents the opportunity of achieving a total depopulation and proper cleaning of the site. On a multi-age farm it is also more difficult to maintain effective live vaccination programmes.

It is recognized that the DLS hatchery farms probably cannot be run as all-in, all-out sites, but due to the high disease pressure which is suspected at these government farms it is strongly recommended that the sites as a minimum are depopulated and cleaned and disinfected prior to the arrival of stock within a new production structure. This could be done for one farm at a time. As soon as possible after a house has been depopulated, dry cleaning followed by wet cleaning and disinfection, and sanitization of the drinking- and feeding systems according to a written protocol should be performed.

Traffic to and on farm and general hygiene, handling of equipment, rodent and pest control, hatchery management and hygiene, feed storage and vaccination are all important aspects, which need to be addressed by DLS, in particular (see below).

The NGOs and DLS should work together in setting up health monitoring and disease control programmes of breeding flocks which initially should seek to eradicate pullorum disease, fowl typhoid, mycoplasma infections, Newcastle disease, Gumboro and leucosis from the top of the production pyramid.

Training of personnel at all levels of the production (including hatchery operation) is necessary to be able to achieve significant improvements.

Upgrading of laboratory back-up facilities must have a high priority with special emphasis on increasing the number of scientific staff.

Proper use of vaccines and consequent use of vaccination programmes is likewise needed and require the availability of the relevant and efficient vaccines.

Research in the significance, prevalence, epidemiology etc. of diseases should be initiated as recommended in the “Applied research and study component - poultry development” (Darudec, 1998).

In the following, a more detailed outline of important aspects to be addressed will be given.

Traffic and hygiene

Traffic onto the farm is a major source of disease introduction, and humans are the single most important factor in the form of e.g. truck drivers, sales people and service crew who routinely go from farm to farm and flock to flock in a short period of time. The following can control human traffic at relevant farms:

In addition, it is strongly recommended that descriptions of the following routine operations at the farms are available for the staff and that they are understood:


Equipment used in handling, managing and moving birds, feed, eggs or manure is capable of mechanically transmitting diseases from one location to another. Movement of equipment from one farm to another should consequently be avoided. Trucks, particularly load-out trucks and associated equipment, can be heavily contaminated and should if possible be avoided on the farm. If they have to enter they should be carefully washed and disinfected before entering the farm.

Rodents and other pests

Wild birds and other animals are significant sources of poultry diseases such as avian influenza, Newcastle disease and fowl cholera. Rodents and different beetles may be important sources of salmonella, E. coli,, infectious bursal disease (Gumboro) and fowl cholera. Files can transmit Marek's disease and intestinal worms. The following measures should be used to reduce these pests on the farm.

Hatchery management considerations to be made

Location. Should be located at a distance from the poultry farm. (This is not always the case at the DLS hatchery farms).

Layout. Careful planning of the working areas of the hatchery can greatly assist in allowing hygienic work practices by separating “clean” and “dirty” areas.

Ventilation. Should be operated to support separation of clean and dirty areas.

Waste disposal. Proper arrangements for the disposal of hatchery waste will reduce the risk of contaminating nearby poultry units.

Site security. As with farms, proper security and control of visitors is essential cleaning and disinfection procedures of site as well as equipment.

Hand hygiene of staff is important throughout the various stages of handling hatching eggs

Written procedures for most working routines including collection of eggs at the farms.

Hatching & hatchery hygiene

The egg laid, is vulnerable to damage and bacteria and should be collected quickly. In that respect the number of floor eggs should be reduced by proper actions such as to ensure a sufficient number of nests placed optimally in the houses. It has been observed that this could be improved at the government hatchery farms. Production planning is important to be able to produce DOC in right numbers at the right time. Better timing and planning could be obtained in Bangladesh if better analysis and arrangements were made in collaboration between the NGO's and the government farms. God hatching eggs must:


Besides quality control of feedstuff, measures should be taken to prevent contamination of feed with pathogens. Food stores should be bird and rodent proofed to prevent contamination with e.g. Newcastle disease virus from wild birds and salmonella. Stores should be cleaned between flocks.

Monitoring of the flock's health status

The following should be evaluated and recorded daily:

Considering the poultry health situation in Bangladesh it is strongly recommended that a disease control programme be implemented in a new production system. It should include the following aspects but must not be taken as a complete programme. The setting up of such a programme would require further analysis

Pullorum disease and fowl typhoid

As these diseases are transmitted vertically to the progency, it must be sought to eliminate these infections in top of the production pyramid. Consequently, repeatedly blood testing of breeding flocks and culling of reactors must be performed. All birds at the breeding farms should be tested twice between 16 weeks and point of lay and subjected to consecutive clear tests 1 month apart. An annual clear test of 60 birds/flocks should be initiated. Screening should also be performed at the hatchery farms. The need requires further analysis. The test used can be the rapid plate agglutination (RPA) test already used by CDIL.


The microorganisms are also transmitted through the egg and elimination is the goal. Before the GP and P flocks come into lay in should be tested by rapid serum agglutination test (RSA) for Mycoplasma gallisepticum and synoviae infection. This test is already used by CDIL.

A programme of eradication should be established and leucosis could be included.

Newcastle disease

Proper vaccination programmes should be established based upon local experiences. Further analysis of the situation is required before final recommendations can be made. Such analysis may actually save vaccine. Today, some of the farms vaccinate once a month. This could be avoided by clarification of the problems.

Gumboro disease

It would be most helpful in the understanding of the Gumboro problem to use the ELISA test in the breeding flocks to obtain information on the size of the problem. A proper vaccination programme should be implemented based upon management used and virulence of strains prevalent.


It should be kept in mind that the first step in a good vaccination programme is proper management including biosecurity. It further depends on:

A vaccination programme for the breeders should initially include

How to start this effectively and the extent of it depends upon:

It is recognized that this cannot be implemented all at once, but it should be aimed for in the future just as the use of other vaccines. In addition to the periodical lack of vaccine supply there does not seem to be efficacy control with vaccines produced by DLS including Newcastle vaccine. It is strongly recommended to set up a control scheme for these self-produced vaccines.

Another aspect to realize is that, under field conditions vaccinations alone is insufficient to bring about effective control of Newcastle disease and other diseases and must therefore be accompanied by good hygiene. In poorly managed, over-crowded, badly ventilated conditions with inevitable underlying bacterial infections even the mildest vaccine strains may produce severe disease.


Danida (1998). Formulation of Applied Research and Study component. Poultry development Bangladesh, Draft report, DARUDEC, August 1998.

Danida (1999). Report on Feasibility Studies of Poultry Breeding Farm and Regional Training Center for Rural Poultry Development, Draft report, Rambøll, March, 1999.

Investigations on Disease Status of Scavenging Poultry in Morogoro, Tanzania and the Significance of Detailed Characterization of Pathogens Obtained

A.P. Muhairwa,a, b M.M.A. Mtambo, a J.P. Christensen b and M. Bisgaard b

aDepartment of Veterinary Medicine and Public Health
Sokoine University of Agriculture
P.O. Box 3021 Morogoro, Tanzania

bDepartment of Veterinary Microbiology
The Royal Veterinary and Agricultural University
Stigbøjlen 4, DK-1870 Frederiksberg C, Copenhagen, Denmark

E-mail: [email protected], [email protected], [email protected] and [email protected]


Causes of mortality were investigated in 30 dead village chickens parallel to survey and characterization of Pasteurella multocida isolates from village poultry and animals kept in contact with poultry. Post-mortem examinations, bacteriological culture and parasitological examinations were used to confirm causes of death where appropriate. Newcastle disease, nephropathia and skin granuloma were shown in chickens ranging from 2 to 6 months old, whereas colisepticemia and fleas caused deaths in chickens of less than six weeks of age. Deaths caused by physical injuries were shown in chickens of various ages. The results of this preliminary study suggest that mortality in village chickens is caused by a number of different factors. Use of postmortem in studying causes of mortality is suggested to address source of mortality in different age groups in village chickens. The survey of P. multocida showed that 0.7% chickens, 7% ducks, 3% of dogs and 68% of cats were carriers of P. multocida. Other species of Pasteurella were shown in dogs and cats. Comparative investigations using 14 and 79 tests for phenotyping of Pasteurellaceae, indicated that extended characterization was superior to 14 tests in separating the species. Delayed reactions and insufficient number of tests were shown to be the main reasons for differences in the results. It is recommended that extended phenotypic characterization should be used in confirming the isolates of Pasteurella against the use of limited number of tests. While there are indications of fowl cholera in chickens and ducks, dogs and cats can possibly become transient carriers of P. multocida from poultry under village conditions. Genetic characterization of isolates obtained remains to be performed to investigate the significance of animals in contact in the persistence and transmission of P. multocida in village poultry.

Key words: Poultry Diseases, Newcastle disease, nephropathia, skin granuloma, P. multocida.


Village scavenging poultry is the dominant form of poultry keeping in Tanzania and other developing countries. According to National Census of Agriculture (MOA, 1995) out of 27 million poultry in Tanzania, 93% are indigenous chickens. Evidently most poultry products consumed in the country are from an indigenous source, and poultry keeping represent an important source of income to women in villages (Aboul-Ella, 1992). However, despite the economical, social, and other benefits, village poultry has only been accorded limited importance in both disease control and husbandry.

Diseases and poor management are the major constraints to the health and productivity of village poultry (Minga and Nkini, 1986; Bell et al., 1990). Newcastle disease has been described as a leading killer of village chickens in Tanzania (Yongolo, 1996). A review of village poultry diseases by Gueye (1998) showed that periodic outbreaks of Newcastle disease devastate scavenging chicken populations wherever they are found in the world. A high mortality rate caused by Newcastle disease is thought to take away the focus from other diseases, and thus mask other diseases in village chickens (Bell, 1992). Reduction of mortalities due to Newcastle disease has been reported in vaccinated chickens (Bell, 1992), however; only limited efforts have been done to control this disease in Tanzania.

Other conditions that affect village poultry include Gumboro disease, fowl typhoid, colibacillosis, and infectious coryza (Thitisak et al., 1989; Kelly et al., 1994). However, the reports show that these conditions are occasional causes of mortality, while some of the diseases such as fowl typhoid and mycoplasmosis (Minga et al., 1987; Chrystostome et al., 1995) have been detected by serological methods only. To add information on clinical and pathological importance of different diseases, we designed our study to include post-mortems of dead poultry and bacteriological culture.

Traditional management has been found to encourage parasite infestations in village poultry (Sæidu et al., 1994; Permin et al., 1997). A study by Msanga and Tungaraza (1985) showed a high incidence of both internal and external parasites in indigenous poultry in Tanzania. Although parasites are rarely the sole cause of mortality, they have been found responsible for weight loss and poor nutritional status of village chickens (Sæidu et al., 1994; Permin et al., 1997). High mortalities that might be expected associated with coccidiosis under scavenging conditions have for unknown reasons not yet been reported to the knowledge of the authors.

In the scavenging poultry system, shelter is provided during the nights only, while during the day the flock is let out to search for feed. This leaves unlimited contact between neighbor flocks, also with other animals such as dogs, cats, and pigs kept around. Consequently, transmission of diseases between flocks, attacks and predation of poultry by cats, dogs, and hawks are common (Mwalusanya, 1998). Indications exist that the cats, being natural carriers of P. multocida, can be transient carriers of pathogenic strains of Pasteurella multocida to poultry (Van Sambeek et al., 1995). Under village conditions it seems possible for cats, dogs or pigs to transmit P. multocida kept in the same environment. Information about exchange of P. multocida clones between different domestic animals is rather limited. Therefore, the current study was designed to isolate and compare strains of P. multocida from chickens, ducks, dogs and cats. To investigate the effect of environment on the presence of P. multocida (Simmensen et al, 1980) the study was done in three climatic zones (hot, warm and cool).

The objectives of this project were to study the causes of mortality in village poultry by post-mortem and to investigate the significance of animals kept in contact in the transmission of P. multocida to poultry. Since the last part of these investigations will be published elsewhere (Muhairwa et al., submitted for publication) the present publication will focus on post mortem findings and on the significance of detailed characterization of pathogens obtained. The total findings are expected to add to baseline data on disease of local chickens. These will help formulating control measures for improving the health and productivity of village scavenging chickens with the ultimate aim of poverty alleviation in the rural population.

Materials and methods

Study area

The study was conducted in Morogoro Region, Tanzania. A study of causes of mortality in chickens was conducted on one village. The sampling of carriers of P. multocida was divided into hot, warm and cool zones. In each zone two villages were selected as follows; Kipera and Kongavikenge from hot area (Mlali), Kiroka and Mkuyuni from warm zone (Mkuyuni) and Langali and Nyandira from cool highland area (Mgeta). Differences in the temperatures, altitude and animal population in the three zones are shown in Table 1.

Table 1. Differences in temperatures, altitude and animal population in three zones


Post-mortem examinations

Dead chickens were obtained from one village (Kongavikenge) through visits and assistance of local veterinary extension officer. Post-mortem examinations were conducted as described by Fowler (1996) and appropriate samples taken for micro-biological and parasitological evaluation. The data on age of chickens, mortality rate, and size of flock were recorded.

Characterization of pathogens and verification of diagnosis

Preliminary identification of pure culture isolated from dead chickens was characterized according to methods described by Barrow and Feltham (1993). Subsequent characterization of isolates suspected to be E. coli, were confirmed by reactions of lactose, indole test, Simon citrate, and growth at 44°C in Mackonkey lactose bile broth (Wray and Woodward, 1994). Identification of parasites was done by methods described by Soulsby (1982).

Investigation of carriers of P. multocida

Sample size, collection of samples, bacterial culture and mouse inoculation were carried out as described by Muhairwa et al. (1999 submitted for publication).

Identification of Pasteurella species

Routine identification of Pasteurella species included Gram staining, motility test, glucose fermentation test, oxidase and catalase reactions. The strains obtained were typed by using the following reactions; ornithine decarboxylation, urease production, indole formation and production of acid from sucrose, maltose, mannitol, dulcitol, and sorbitol. Identified species were subsequently brought to Denmark for verification and extended phenotypic characterization according to Bisgaard et al. (1991)

Statistical analysis

Statistical analysis of data to determine significance of results was performed using the chi square test.


Post-mortem findings and diagnosis

The results of thirty dead chickens submitted for post-mortem investigations are summarized in Table 2.

Table 2. Results of thirty dead chickens submitted for post-mortem investigations

 Post-mortem findings/Clinical observationsDiagnosisAge of birdsCases
1Hemorrhages on the proventriculus mucosa, enteritis. Increased mortality and nervous symptoms in the flock. A. galli was found in 4 chickensNewcastle disease2-4 months7
2Fibrinous airsacculitis fibrinous perihepatitis, hepato-splenomegalyColisepticaemia5-6 weeks31
3Peritonitis, inspissated yolk in the abdomen.Egg peritonitis18 months1
4E. gallinacea. Pale mucous membranes and carcasses.Ectoparasites2-4 weeks52
5Superficial wounds, fractured bones, ruptured livers, blood in the peritoneum. A. galli and T. americana in 3 chicks.Fracture of wings, metatarsals and internal injuries4 weeks-10 months5
6Renomegaly, nephropathiaNephropathia2-6 months4
7Panophthalmitis, rhinitis and conjunctivitisInfectious coryza?4 months2
8Loss of feathers, skin granuloma. A. galli found in 1 chicken. Both A. galli and T. americana in 2 chickensSkin granuloma3-4 months3

1. All chicks came from the same clutch.
2. All chicks from the same flock.

Age of the chickens ranged from one week to approximately 18 months old, adult chickens. Post-mortem signs consistent with Newcastle disease were seen in seven birds, which were obtained from different flocks. All chickens had hemorrhages in proventriculus just as four chickens had a concurrent Ascaridia galli infestation. Increase in the mortality in the flocks of origin of affected chickens was reported. Polyserositis was diagnosed in three chicks from one clutch. All three carcasses had perihepatitis and air sacculitis. Pure culture of Escherichia coli was isolated from livers of these chicks. One case of egg peritonitis was diagnosed in a hen.

Mortalities attributable to sticktight fleas (Echidnophaga gallinacea) were recorded in five chicks. These chicks had massive flea infestation on the head, especially around the eye, and pale mucous membranes suggestive of anaemia. Five dead chickens had external and internal injuries including bruises, cuts, liver rupture and fractures. Three of these chickens were also infested with A. galli and Tetrameres americana.

Nine cases were not definitely diagnosed. Of these, four chickens had pale kidneys characterized by distinct lobulations (nephropathia). Three chickens had upper respiratory tract infection, with yellowish white flakes in the eyelids. Bacteriologi-cal investigations showed a mixed flora, and further characterization could not be performed. The three remaining chicks had granulomatous skin lesions, accompanied by loss of feathers and thickening of the skin, which extended from the head down to the neck. Two chickens with skin disease were also mixed infested with A. galli and T. americana, whereas one was infested with A. galli only.

Prevalence of P. multocida in chickens ducks dogs, cats and pigs

P. multocida was confirmed in 0.7% of chickens, 7% of ducks 68% of cats and, dogs in all three zones investigated (Muhairwa et al., 1999 submitted for publication). Prevalence in chickens was significantly lower (P<0.05) than all other hosts, whereas prevalence in cats was significantly higher than (P<0.001) other animals investigated. None of the pigs were found carrying P. multocida. Other species demonstrated in dogs and cats only included P. canis, P. stomatis, P. dagmatis, and an organism of uncertain affiliation tentatively named Pasturella taxon 16 (Bisgaard and Mutters 1986).

Occurrence of P. multocida spp. multocida in the three zones

The prevalence of P. multocida spp. multocida in chickens of the warm zone was not statistically different (P>0.05) from other zones. The prevalence of P. multocida spp. multocida in ducks of the warm zone was significantly higher (P<0.001) than that of ducks in the cool and warm zones. P. multocida ssp. multocida was shown in a single dog each in the hot zone and warm zone, which did not differ significantly (P>0.05) from the cool zone. A carrier rate of P. multocida ssp. multocida in cool zone cats was significantly higher compared with that of warm and hot zones (Muhairwa et al., 1999, submitted for publication).

Comparative investigations using 14 and 79 tests for characterization and identification of 100 Pasteurellaceae isolates appear from Table 3. Twenty-five isolates identified by 14 tests appeared different on extended characterization. Delayed reactions and interpretation of weak positive and negative reactions were the major differences in the classification of P. multocida into species septica and multocida. Number of tests used (14 tests) could not adequately separate all species of P. stomatis, P. canis, P. dagmatis, and Pasteurella taxon 16.

Table 3. Comparative investigations of 25 misclassified strains of Pasteurella. Correct classification, misclassification and major differences observed.

Extended phenotyping-79 testsLimited phenotyping-14 testsMajor differences
IdentificationNo.Misclassified identification (n) 
P.multocida.ssp.multocida3P. multocida ssp. septica (1)
unclassified Pasteurella (2)
Delayed fermentation of sorbitol. Weak fermentation reactions.
P.multocida. ssp. septica7P. m. multocida (5), unclassified Pasteurella (2)Weak and late sorbitol reaction species
P. stomatis2P.canis (1)P. dagmatis (1)14 tests insufficient to separate the species
P.dagmatis2P.canis14 tests insufficient to separate the species
Pasteurella Taxon 168P.multocida ssp multocida (3),
Unclassified Pasteurella (5). P. dagmatis. (1)
Delayed reactions. 14 tests insufficient to separate the species
Unclassified Pasteurella3Pasteurella Taxon 16Weak reactions in many sugars.

Twenty-five isolates identified by 14 tests appeared different on extended characterization. Delayed reactions and interpretation of weak positive and negative reactions were the major differences in the classification of P. multocida into species septica and multocida. Number of tests used (14 tests) could not adequately separate all species of P. stomatis, P. canis, P. dagmatis, and Pasteurella taxon 16.

Further characterization of strains of P. multocida showed two different phenotypic clones in chickens and one clone in ducks. One isolate from chickens was similar to duck isolates in all features. The clones from chickens and ducks differed from dog and cat strains in one or more of the following reactions: glycerol, L (+) arabinose, xylose and trehalose. Ducks and chickens carrying the same clone of P. multocida ssp. multocida were in the same vicinity, though they were kept in different households.

Investigations on Disease Status of Scavenging Poultry in Morogoro, Tanzania…


In the present study infectious and non-infectious conditions were shown to cause mortality in the village chickens. Mortalities caused by E. coli and fleas were demonstrated in addition to Newcastle disease and injuries. Miscellaneous undiagnosed conditions were also seen. Availability of dead carcasses was limited by lack of reliable transport, and cool storage facilities in the villages, which resulted in decomposition of carcasses. Also number of carcasses obtained per day could not always justify the local contact personnel to bring the carcasses to the University. On the other hand many villagers are normally throwing away dead chicks, whereas moribund adult chickens can be slaughtered for family or animal consumption.

Post-mortem examination results showed that mortalities in seven out of 30 chickens submitted for examination were caused by Newcastle disease. The results support the previous observations that Newcastle disease is prevalent in rural scavenging chickens in Morogoro (Minga et al., 1989; Yongolo, 1996). Age of birds with Newcastle disease ranged from 2 to 4 months. This is within the same age group Thitisak et al. (1988) found in village chickens in Thailand.

E. coli infections, which are so far scantily documented in scavenging village chickens, appeared in four chickens. In the present study three chickens (30%) with colisepticemia were diagnosed from a single clutch with 10 chicks. Unhygienic conditions and poor ventilation in chicken shelters (Mwalusanya, 1998) might favor contamination of eggs or early infection of chicks with the bacterium. Similar management in all families might suggest that E. coli is prevalent in many flocks of village chickens. However, because population at risk is mainly chickens less than four weeks, the impact of E. coli infections is low if compared with diseases like Newcastle disease. However, their significance in immunosuppressed animals should not be underestimated. Shortage of reports of E. coli infections in village chickens might also be due to lack of routine post-mortem examination in village chickens in Tanzania (Msanga and Tungaraza, 1985).

Fleas (E. gallinacea) have been reported to cause debilitation in indigenous chickens (Cooper, 1967; Msanga and Tungaraza, 1985) and mortality in chicks (Sæidu et al., 1994). In the current investigation mortalities in five chicks from one flock was caused by fleas. None of the mortalities was, however, caused by endoparasites, which were found in 9/30 of the carcasses investigated. However, poor nutritional condition of worm-infested birds might have contributed to susceptibility to other diseases.

Injuries through management problems appear to cause a significant proportion of mortalities in village chickens. All chickens that died because of injuries were suspected to have been beaten by neighbors. The present findings support the findings of Mwalusanya et al., (1998) that accidents and injuries cause 10% losses in the flocks per annum. This is common during the sowing season if chickens are found in the farms. Seasonal fencing of the birds can significantly reduce mortality caused by management problems (Sonaiya, 1990).

Nine out of 30 cases were not definitely diagnosed; four chickens with renal lesions and three chicks with skin lesions, and two chickens with upper respiratory tract changes. Sæidu et al. (1994) reported the existence of skin tumors in village chickens. However, details of the lesions were not available. The nature of the skin lesions in the current study remains to be investigated by histopathological techniques. The mortality in these chicks was probably caused by starvation caused by shutting of eyelids caused by thickening skin. Assistants in the villages acknowledged that this skin disease is one of the common diseases that affect chicks in their villages.

The diverse structure of flocks in the village chickens is probably the reason for a biased attention to epidemics that usually affect birds of all age's groups. In village management a flock of chickens is made up of birds of different age groups, including chicks (below 8 weeks), growers (2–6 months), and adults (after 6 months) in widely different proportions. Consequently, the population at risk to age predisposed diseases is variable and investigation of mortality should address age specific causes. In the present investigation colisepticemia and fleas caused mortality in young chicks, while Newcastle disease affected growers of 2 to 4 months. The present results are comparable to those of Thitisak et al. (1988), who found that infectious coryza and avian pasteurellosis were equally important to Newcastle disease in village chickens. In that study causes of mortality in different age groups were compared. Most farmers visited during this study understand that Newcastle disease is the leading killer of their flocks, but they also know that survival of chicks below eight weeks of age is very low. The wide variety of conditions obtained in the present study implies that application of post-mortem is vital for investigation of causes of mortality in village chickens.

P. multocida has been reported from a wide range of animal hosts (Mutters et al., 1989). Snipes et al. (1988) showed that strains of P. multocida from wild animals could cause infection in turkeys. Subsequent investigation by Korbel et al. (1992) demonstrated P. multocida infection in dead feral birds injured by cats. In the present study P. multocida has been obtained from dogs and cats kept in contact with domestic poultry. Cat bites are more likely than dog bites to transmit P. multocida, when considering the high prevalence shown in cats. Studies of animal bite woulds in human beings have shown that cat wounds are more likely to cause P. multocida infection than dog bites (Zbinden et al., 1988). On the other hand village dogs and cats may be transient carriers of P. multocida strains from poultry through consumption of dead carcasses. However, determination of persistence of clones of poultry origin in cats and dogs, and consequences of exchange of clones on the pathogenecity remains to be addressed.

The application of 14 tests for identification and typing of P. multocida from different animals could not separate isolates from different animals. In addition, using only a limited number of tests for identification resulted in misclassification of species (Table 3). However, the P. multocida strains were separated by extended phenotypical typing (Muhairwa et al., 1999 submitted for publication). The strains of P. multocida from different species could be distinguished despite being similar by using only a few characters. Two phenotypical clones were obtained from chickens, while only one clone was obtained from ducks. One isolate from chickens was shown to be similar in all 79 features to isolates from ducks, which were clonal too. This suggests that clones of P. multocida can be exchanged between chickens and ducks kept in the same environment. Further characterization by molecular techniques to confirm the observations is in progress.


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