Epidemiological studies on camel diseases in the eastern Sudan

H. Agab and B. Abbas

At the time of writing, the authors were with the Camel Research Project, PO Box 475, Gedaref, Sudan, and the Faculty of Veterinary Science, University of Khartoum, PO Box 32, Khartoum North, Sudan, respectively.

Their current addresses are: PO Box 2373, Al Qaseem, and Buraida, Saudi Arabia, and King Saud University, College of Agriculture and Veterinary Medicine, PO Box 1482, Buraida, Saudi Arabia.

Acknowledgements. The assistance received from the Institut d'Elevage et de Médecine Vétérinaire des Pays Tropicaux (France) and from the Sudan Commissioner for Refugees, Showak Office, in the establishment of the Camel Research Station is highly appreciated.

ÉTUDES ÉPIDÉMIOLOGIQUES SUR LES MALADIES DES CAMÉLIDÉS DANS L'EST DU SOUDAN

La population de dromadaires (Camelus dromedarius) du Soudan s'élève, d'après les estimations, à 2,8 millions de têtes et elle est concentrée dans deux principales régions, à savoir l'Etat de l'Est, où les dromadaires sont présents dans les plaines de Butana et dans les collines de la mer Rouge, et la région de l'ouest (Etats du Darfour et du Kordofan), où des dromadaires sont présents dans le nord. Les présentes études ont été menées dans l'est du Soudan dans le cadre d'un projet de recherche sur: la croissance individuelle et des troupeaux de dromadaires dans les conditions naturelles; les obstacles à la production de dromadaires; l'épidémiologie des principales maladies du dromadaire; les connaissances locales concernant les maladies du dromadaire et la médecine traditionnelle. On souhaite présenter ici des informations préliminaires sur les principales maladies et les problèmes sanitaires touchant les dromadaires pendant les différentes saisons. La prévalence de certaines maladies des dromadaires a été étudiée pendant un an et l'incidence et les causes de mortalité observées dans 15 troupeaux ont été consignées pendant la même période.

ESTUDIOS EPIDEMIOLÓGICOS DE LAS ENFERMEDADES DEL DROMEDARIO EN SUDÁN ORIENTAL

La población de dromedarios (Camelus dromedarius) en el Sudán se estima en 2,8 millones de cabezas y está concentrada en dos regiones principales, el estado Oriental, donde los dromedarios están en las llanuras de Butana y las colinas del mar Rojo, y en segundo lugar en la región occidental (estados de Darfur y Kordofan), en su parte septentrional. La presente investigación se llevó a cabo en el Sudán oriental como parte de un proyecto que tenía por objeto estudiar el crecimiento de dromedarios aislados y de hatos de dromedarios en condiciones naturales; los obstáculos para la producción de estos animales; la epidemiología y los conocimientos locales acerca de las principales enfermedades que los afectan y la medicina tradicional. Se presenta información preliminar sobre las enfermedades y los problemas de salud más importantes que afectan a los dromedarios en las distintas estaciones. Se estudiaron los niveles de prevalencia de determinadas enfermedades durante un año y se registraron en el mismo período la incidencia y las causas de la mortalidad en 15 hatos de camellos.

The camel (Camelus dromedarius) population in the Sudan is estimated to be 2.8 million (Saint-Martin et al., 1992) and is concentrated in two main regions: the Eastern State where camels are found in the Butana plains and the Red Sea hills; and the Western Region (Darfur and Kordofan States) in which camels are found in the northern parts.

The Butana plains, where this study was conducted, occupy the area lying between the River Nile in the West and the Atbara River in the east (Map 1). The total area is about 120 000 km² with a camel population of 750 000 (Musa et al.,1989). The Butana is inhabited by different camel-owning tribes such as the Shukriya, Lahawiyin, Kawahla and Rashaida, all ancient camel breeders who have maintained a pastoralist life for centuries. Owing to fluctuations in rainfall and a security of pasture, especially in the rather long dry season (November-July), these tribes practise a transhumant mode of range utilization (Abbas et al., 1992b). They move from one area to another following certain migratory routes. The Rashaida, for example, spend the rainy season (July-October) around Kassala and move for about 400 km to spend the dry season (March-June) at the southern fringes of the traditional camel range in the Doka area (Map 2). Some of the Rashaida, however, spend most of the dry season on the Red Sea coast around the Sawakin and Tokar areas. These groups arrange their migration to coincide with the availability of good-quality range, which develops as a result of the Red Sea coastal winter rains. Members of the Shukriya, Lahawiyin and Kawahla stay in the Butana plains for the rainy season and move out during the dry season, either to the south (Gedaref), or to the southeast following the Atbara River course (Map 2). A significant proportion of these tribes also graze animals for brief periods before taking them for long marches, sustaining the animals on crop residues from the surrounding rainfed sorghum and sesame fields (under mechanized production) in the Gedaref, Showak and Kassala agricultural areas.

The present surveys were conducted in the eastern Sudan as part of a research project covering:

· the growth of individual camels and of camel herds under natural conditions;
· constraints to camel production;
· the epidemiology of the major diseases affecting camels;
· local knowledge about camel diseases and traditional medicine.

This article presents preliminary information on the most important diseases and health problems affecting camels in the different seasons. The prevalence levels of certain diseases of camels were studied for one year, during which time the incidence and causes of mortalities occurring in 15 camel herds were recorded.

1
The main study area in Butana, the eastern Sudan
Zone de Butana, dans l'est du Soudan (sur laquelle porte l'étude) Zona del estudio principal en Butana, Sudán oriental

2
The migrations of camel herds throughout the study period (March 1991-February 1992)
Les migrations de troupeaux de dromadaires pendant la période étudiée (mars 1991 - février 1992)
Migraciones de los hatos de dromedarios durante el período del estudio (marzo de 1991-febrero de 1992)

Note: The numbers beside the arrows (1-15) indicate the herd number.

METHODS OF STUDY

Fifteen camel herds whose owners were willing to cooperate in the study were selected. Their total population was 3 731 camels at the beginning of the study. About 20 to 30 camels of both sexes and different ages from each herd were identified with plastic ear tags for follow-up. The herds were visited monthly for one year (March 1991-February 1992). During visits all sick camels in each herd were individually inspected and the herder's account of disease history and symptoms was obtained. Clinical examination and diagnosis were made on each sick animal and samples were collected for further investigation and confirmation of the tentative clinical diagnosis wherever possible.

Routine diagnostic procedures (e.g. haemogram, faecal examination, skin scraping, agglutination test) were carried out in the field station at Showak while other diagnostic methods of more technical requirements (e.g. chemical analysis, electron microscopy) were carried out at the Faculty of Veterinary Science, University of Khartoum or at the Central Veterinary Research Laboratory (CARL), Khartoum.

Mortality occurring in each herd was recorded together with the herder's description of the circumstances or signs leading to these deaths. The tagged camels were also used for estimation of body growth and fecundity of females under pastoral conditions. This is part of an ongoing project on camel productivity, but in the present study these animals were very valuable as sentinels, since they were measured and inspected regularly. Data on this cohort of animals will be handled separately. The owner/herder received the required treatment of sick animals at cost price, except in the case of tagged animals, where treatments were given free in compensation for the herder's assistance.

A young camel calf severely affected by mange. Note the loss of hair and wrinkling of the skin
Jeune dromadaire gravement touché par la gale. A noter la perte de poils et le plissement de la peau
Dromedario joven gravemente afectado por la sarna. Obsérvese la pérdida de pelo y el agrietamiento de la piel
Photo/foto: H. agab

DATA ANALYSIS

Data on diseases encountered in the 15 herds were pooled and individual camels were handled statistically as if belonging to one herd. Rates of disease prevalence, morbidity and mortality were calculated by conventional procedures (Schwabe, Riemann and Franti, 1976). Seasonal distribution of the encountered diseases as well as parasitic load (faecal egg counts) in a sample of camels were analysed for differences by the X2 test.

RESULTS

On average, the research team was able to make one complete herd visit per day for the greater part of the study. Sometimes it was possible to visit two herds in one day, but rarely three. Herds were scattered extensively, especially during the rainy season (Map 2). The best arrangement was to make the visit coincide with watering days in the summer and on the range in both autumn and winter.

A total of 3 934 clinical complaints were addressed, which gave a general morbidity rate of 112 percent for the entire period of study. Cases recorded during autumn (July-October) amounted to 1 793 out of 3 681 examined animals, giving a higher morbidity rate than the rate recorded during both summer (March-June, 40 percent) and winter (November-February, 20.1 percent) (Table 1).

1
Seasonal distribution of diseases encountered in 15 herds of camels in the eastern Sudan
Répartition saisonnière des maladies observées dans 15 troupeaux de dromadaires dans l'est du Soudan
Distribución estacional de las enfermedades encontradas en 15 hatos de dromedarios en el Sudán oriental

¹ As a percentage of the total number of diseased cases throughout one year.

The numbers and percentages of camels affected by different disease conditions are shown in Table 2. Mange (Sarcoptes scabie) was the most prevalent disease problem in the study area (31.6 percent).

2
Prevalence rates of clinical diseases in 15 herds of camels in the eastern Sudan (1991-1992)
Prévalence des cas cliniques dans 15 troupeaux de dromadaires dans l'est du Soudan (1991-1992)
Tasas de prevalencia de enfermedades clínicas en 15 hatos de dromedarios en el Sudán oriental

The faecal egg count of nematodes in a sample of camels in the study area is shown in Table 3. Egg counts of up to 600 per gram of faeces (e.p.g) were considered to be light, whereas counts above 600 e.p.g were considered as heavy infestation (Blaizot, 1976). It is noticeable that the proportion of camels with positive faecal samples was almost constant during the three seasons, whereas the degree of infection was different. Most of the camels found positive during the summer (63.2 percent) and winter (58.2 percent) were lightly parasitized, whereas most of those found to be infected during autumn (58.6 percent) were heavily parasitized. Vitamin A deficiency was manifested by night blindness as a pathognomonic sign. Affected individuals were usually noticed during the routine gathering and checking of the herd after sunset. Such animals appeared lost and often had difficulty in recognizing objects or animals. This deficiency was often associated with other health problems such as diarrhoea, rough coat, mange or ringworm.

3
Faecal egg count of nematodes in a sample of clinically affected¹ camels in the Butana area, the eastern Sudan (1991-1992)
Comptage des œufs de nématodes dans les excréments d'un échantillon de dromadaires présentant des signes cliniques dans la zone de Butana, à l'est du Soudan (1991-1992)
Recuento de huevos fecales de nematodos en una muestra de los dromedarios afectados clínicamente en la zona de Butana, Sudán oriental (1991-1992)

Season	No. examined	+ve samples		Light infection		Heavy infection
		No.	%	No.	%	No.	%
Summer	58	38	65.5 a,b,c2	24	63.2 a,b	14	63.8 a,c
Autumn	106	70	66.0 b,a,c	29	41.4	41	58.6 b,c
Winter	168	110	65.5 c,b,a	64	58.8 c,b,a	46	41.8 c,a

¹ Camels with faecal egg counts exceeding 600 e.p.g and manifesting at least one sign of helminthiasis (e.g. loss of weight, rough coat, weakness, diarrhoea).
² Rates with similar letters are not significantly different (p = 0.001).

The number of dead camel calves (less than one year old) and the causes of their death during the three seasons are shown in Table 4. Out of 415 calves born during the study period, 199 died, giving a crude mortality rate of 48 percent.

4
Rates and causes of mortality among camel calves in 15 herds in the Butana area, the eastern Sudan (March 1991-February 1992)
Taux et causes de mortalité chez les jeunes dromadaires dans 15 troupeaux de la zone de Butana, à l'est du Soudan (mars 1991-février 1992)
Tasas y causas de mortalidad en los dromedarios jóvenes de 15 hatos de la zona de Butana, Sudán oriental (marzo de 1999-febrero de 1992)

It was reported that during the study period 222 adult camels died out of a total of 1 516, giving a crude mortality rate of 14.6 percent. During the summer, 35.9 percent of the deaths were caused by helminth infections, while tick paralysis and bent-neck syndrome accounted for 23.1 percent of the deaths. Helminth infections were also the main killing disease during autumn (57.9 percent), followed by tick paralysis (23.6 percent) and pneumonia (7.9 percent). Out of the five adult camels that died during the winter, four died of helminth infections, while the fifth suffered from a severe septicaemic metritis arising as a complication of placental retention (Table 5).

5
Rates and causes of mortality among adult camels in 15 herds in the Butana area, the eastern Sudan (March 1991- February 1992).
Taux et causes de mortalité chez les dromadaires adultes dans 15 troupeaux de la zone de Butana, à l'est du Soudan (mars 1991-février 1992)
Tasas y causas de mortalidad en los dromedarios adultos de 15 hatos de la zona de Butana, Sudán oriental (marzo de 1991-febrero de 1992)

The overall crude mortality rate was 21.8 percent in the pooled data. Helminth infections were the major cause of death (45.6 percent), followed by tick paralysis (21.6 percent), calf diarrhoea (14.3 percent), contagious ecthyma (5 percent) and pneumonia (3.3 percent).

A young camel calf affected by dermatophytosis (ringworm)
Jeune dromadaire souffrant de dermotophytose (teigne)
Dromedario joven afectado por la dermatofitosis (tiña)
Photo/foto: H. agab

DISCUSSION

Mange, the most prevalent clinical condition encountered in camels in eastern Sudan, was confirmed by the successful demonstration of the causative mite (Sarcoptes scabie) in skin scrapings taken from affected animals. Other workers (Higgins, 1984; Kumar, Raisinghani and Manohar, 1992) had also observed the seasonal pattern of camel mange recorded in this study. Close contact and gathering of camels late in the summer, particularly at watering points, could be responsible for increased exposure during late summer and the early weeks of the rainy season. The lower prevalence of mange during the summer could be owing to the high ambient temperature possibly leading to reduction in the activity of mite (Rathore, 1971).

An anti-suckling device (Surar) used by camel pastoralists in the eastern Sudan to secure milk for themselves - this is a major predisposing factor to camel mastitis
Dispositif anti-têtée (Surar) utilisé par les éleveurs dans l'est du Soudan pour disposer de lait. Un important facteur prédisposant à la mammite
Dispositivo para impedir mamar (surar) utilizado por los pastores de dromedarios en el Sudán oriental a fin de asegurarse la leche para sí mismos. Este es un factor importante que predispone a la mastitis de las dromedarias
Photo/foto: H. agab

Helminthiasis is a well-recognized problem in free-ranging camels. Previous studies have shown that 70 to 80 percent of pastoralist camels, sheep and cattle in the Sudan were infected by one or more helminth parasites. Mixed infections with Haemonchus sp., Trichuris sp., Cooperia sp. and Trichostrongylus sp., to name a few, are the most common (Steward, 1950; Malek, 1959; Fadl, Magzoub and Burger, 1989). In the present study, while the infection rate was almost constant throughout the year (65 percent), camels infected during autumn sustained a heavier parasite load (Table 3). Autumn is apparently the only season during which the developmental stages of nematodes can resume activity in the Sudan. Furthermore, the early weeks of autumn are a time of stress for camels as pastures are still sparse, and the animals are not yet in their prime body condition.

A three-year-old camel calf with a swollen head as a result of contagious ecthyma
Jeune dromadaire de trois ans ayant la tête gonflée à cause de l'ecthyma contagieux
Dromedario de tres años con la cabeza hinchada debido al ectima contagioso de los camellos
Photo/foto: H. agab

In an effort to reduce the health risk of helminthiasis, a control programme has been set up in which camels are given therapeutic doses of a broad-spectrum anthelmintic twice a year (May-June and October-November). So far the response has been very good, with a significantly reduced occurrence of clinical signs in treated camels (data not shown). This exercise has also revealed that pastoralists are willing to cooperate in the control of animal diseases and that they are willing to pay and participate positively in the required handling of diseased animals.

Anthelmintics and acaricides were the two items in greatest demand by the pastoralists. An efficient method for delivery of the much needed veterinary service to a widely scattered, continuously moving population of animal keepers has still to be established.

Mastitis in camels has been reported worldwide and is usually caused by a mixture of organisms, notably Staphylococcus sp., Streptococcus sp., Corynebacterium sp., Salmonella sp., E. coli, Klebsiella sp. and several other organisms (Higgins, 1986). In the present study, teat lesions caused by tick infestation and crude as well as traumatic anti-suckling devices were noticed in the majority of affected udders (Obeid, 1983). Most cases of mastitis were well advanced by the time of examination, but improvement was remarkable following intramammary and systemic antibiotic therapy in conjunction with udder disinfection and the external application of an acaricide gel.

Wounds and abscesses were the third most common disease problem (8.4 percent) affecting the surveyed camels, with peak incidence during the rainy season. Heavy tick infestation during the summer, especially in the southern parts of the camel range, as well as complete reliance on thorny bushes for browsing throughout most of the dry season, could be partially responsible for this seasonality. Abscesses of the inferior cervical lymph nodes and traumatic injuries of the footpad were commonly encountered during this study.

Night blindness (nyctalopia) resulting from vitamin A deficiency (Agab et al., 1993) was the fifth clinical disease condition (7.5 percent). Almost all of the cases (98.2 percent) were encountered during the summer and only 1.8 percent during the winter. This condition disappeared completely during autumn, owing to the availability of green fodder as a source of B-carotene, the precursor of vitamin A. The disease affected all age groups, but was more frequent in younger camels. In one herd, the condition assumed outbreak proportions in camel calves born during the second annual peak of calvings (December-March).

Younger camels of up to three years of age were those affected most by ringworm (dermatophytosis), while older camels were rarely affected. The incidence of ringworm was highest during the summer and lowest during winter, an observation similar to that made by Khamiev (1982), who also reported summer outbreaks of ringworm in camels in Kazahkastan. In the present study, Trichophyton verrucosum was isolated as the sole aetiologic agent.

"Haboub" syndrome is a condition of unknown aetiology, manifested initially by musculoskeletal stiffness and pain, particularly in the head and neck region. Later on during the course of the disease, affected animals suffer from abdominal pain and develop abscesses in the flank, chest and limbs. Since most of the camel herds followed in this study spent the summer period, the season of high incidence, in the southern part of Butana and around the Gedaref area, the ecological conditions prevailing there, such as high temperature, heavy tick infestation and poor pastures, might have predisposed or precipitated this syndrome. No direct relationship could be established between this syndrome and certain prevailing diseases such as trypanosomiasis, brucellosis and helminth infections according to laboratory investigations conducted on samples from affected animals. Attempts to treat the condition using different chemotherapeutic agents met with inconclusive results, although there was improvement following anti-inflammatory therapy. Further studies are needed to determine the aetiology of this disease, particularly the role of vitamin or mineral deficiency, plant poisoning or chronic bacterial infection.

Pneumonia associated with chronic cough was the ninth most common disease problem (4.4 percent) with peak incidence during autumn. This is associated with sudden climatic changes as well as the stress of migration from the south to the north during early rainfall. The beginning of autumn, locally referred to as Rushash (light showers), is also characterized by poor body condition as range is usually just beginning to improve. A penicillin-streptomycin combination was superior to oxytetracycline in the control of an outbreak, which involved five of the study herds (data not shown).

Contagious skin necrosis was found to affect mostly young animals, while adults seemed to be relatively resistant, owing perhaps to previous exposure. In some herds, this disease took the form of an outbreak, while in all other herds it was sporadic. Edelsten and Pegram (1974), however, reported a sporadic and milder form of the disease in Somalia, which affected mainly adult camels. In our studies, the lesions were mostly located on the neck, shoulders or legs, but other sites such as the flank region or ventral abdomen were also affected.

Lameness or locomotory disturbances were recorded as a less common clinical problem and were mainly due to joint and muscle lesions. The long distance that camels had to cross in search of pasture during the summer and on the way back from the south in the early rainy season (Map 2) could predispose camels to these disease problems.

Calf diarrhoea was reported in 91 out of 415 one-year-old calves studied (21.9 percent), with the peak of occurrences during early summer coinciding with the peak of the calving period for camels in the Sudan (Saint-Martin et al., 1990). The cause of camel calf diarrhoea is not sufficiently known, but salmonella infections (Abbas et al., 1992a) and bad management practices such as withdrawal of colostrum (Khanna, Tandon and Sahani, 1992) have been incriminated. This disease is a significant cause of mortality and poor weight gain and thus contributes to slow herd growth.

Camel contagious ecthyma was encountered only during the rainy season and affected 1.7 percent of the animals examined. It occurred mainly among young calves less than one year old, while older animals rarely get the disease. Browsing on thorny trees during the early rainy season could be an important predisposing factor as the traumatic injuries inflicted while browsing could facilitate the entry of the causative agent, parapox virus, into the body (Munz, 1992; Khalafalla, Agab and Abbas, 1994).

Trypanosomiasis was reported in 1.44 percent of the animals, with the lowest prevalence during the dry season (7.4 percent) and the highest during the rainy season (76 percent). This seasonal pattern of camel trypanosomiasis was also reported by Yagi and Razig (1972) in the Sudan and Gruvel and Balis (1965) in Chad. This was attributed to the seasonal abundance of Tabanidae, the insects most capable of mechanical transmission of T. evansi (Mahmoud and Gray, 1980).

Abortions amounted to 3.9 percent of the adult females (age > 4 years; n = 1 305) in this study. However, this figure is obviously an underestimate and does not give a true appreciation of the significance of abortion in camels. This is because the reference group (females above four years of age) usually included a high proportion of non-breeding females throughout the year. In one comprehensive study of camel herd productivity in eastern Sudan, only 33 percent of the adult females (> 4 years) were breeding during one year (Abbas, Saint-Martin and Planchenault, 1993). In the present study, two herds had abortion rates as high as 25 percent and 40 percent of the pregnant animals, occurring over a period of four to six weeks during the early part of autumn. Data on this outbreak were presented as part of a study of the relative risk of brucellosis in camels (Agab, 1993). In Kenya, abortion rates of up to 15 percent were reported in camels. Trypanosomiasis, chronic helminthiasis and nutritional stress were variably responsible (Schwartz, 1992).

A healing lesion of contagious skin necrosis on the ventral abdomen. Note the signs of firing around the lesion
Lésion cicatricielle provoquée par la nécrose cutanée contagieuse sur la partie ventrale de l'abdomen. Remarquer la cautérisation autour de la lésion
Lesión de necrosis cutánea contagiosa en la parte ventral en fase de cicatrización. Obsérvese la cauterización alrededor de la lesión
Photo/foto: H. agab

Lesions of the eye, namely keratitis, conjunctivitis and wounds, peaked during autumn. Some of these conditions have resulted from traumatic injuries by thorny trees or from ticks attached to the eyelids.

The bent-neck syndrome (or wry neck) is a condition of unknown aetiology. It is a slowly developing disease which usually terminates either fatally, owing to the inability of the affected animal to extend its neck to graze, or the animal recovers, but with an irreversible bending of the neck. Several parameters were investigated in affected animals including aspartate aminotransferase (ASAT), sorbitol dehydrogenase (SDH) and total proteins, but no abnormalities were detected. Poisoning by the shrub Capparis tomentosa was incriminated as the primary cause of this condition by Idris et al. (1979) who produced a similar condition by experimentally dosing camels with the leaves of this plant.

Snake bites were more common during the summer than in autumn and winter. Most bites occurred during the night hours when the camels had to graze to maximize food intake during the critical dry season.

The few diagnosed incidences of poisoning were caused by plants or accidental exposure to pesticides. The effect of poisonous plants was noticeable in the early rainy season as a result of the new growth to which camels may not have been accustomed (Fowler, 1992). Agrochemical or pesticide poisoning resulted, following their application by camel herders for the treatment of mange and helminthiasis. This is a reflection of the poor supply of recognized effective products.

A chronic case of bent-neck syndrome . Note the signs of the traditional firing therapy on the left side of the neck
Cas chronique de syndrome de torsion du cou. Remarquer les cautérisations sur le côté gauche du cou (thérapie traditionnelle)
Caso crónico de síndrome de cuello inclinado. Obsérvese la zona cauterizada en el lado izquierdo del cuello como sistema terapéutico tradicional
Photo/foto: H. agab

Since only three cases of pox were reported in this study, this well-known and feared camel disease (Munz, 1992) was considered to be of minor importance. However, outbreaks of pox could occur rather erratically and vaccination has been recommended (Munz, 1992; Higgins et al., 1992).

Diseases of the digestive system were incriminated as the main cause of death among young camels in India, partly owing to traditional practices followed by some camel- keeping tribes such as overfeeding or underfeeding with colostrum (Khanna, Tandon and Sahani, 1992).

Several researchers (Osman, 1976; Schwartz and Dioli, 1992; Khanna, Tandon and Sahani, 1992) reported the role of tick infestation and tick paralysis as causes of mortality. Musa and Osman (1990) described an outbreak of tick paralysis in camels in Darfur State (western Sudan) in which a mortality rate as high as 34.3 percent was recorded.

Death from camel contagious ecthyma could be caused by starvation resulting from inability of the affected calves to graze or by secondary bacterial infections (Munz et al., 1986). This disease, however, was encountered in Somalia as a transient infection without mortality (Abdurahman and Bornstein, 1991). This might reflect the existence of more than one ecthyma virus as in the case with camel pox (Munz, 1992).

Most of the deaths were caused by helminth infections, which could be considered the leading cause of camel mortality in eastern Sudan. The severest forms of clinical camel helminthiasis were encountered during the late summer and the early weeks of autumn. They are in fact precipitated by the severe stress brought on by the long migratory trip the camels are subjected to in the early rainy season. During this time, camels are also weak and have poor nutritional status since this period (mid-May to mid-July) marks the end of the very long dry season. The role of helminth infections as a cause of mortality in camels is well documented (Steward, 1950; Malek, 1959; El Amin, Tageldin and Yagoub, 1984).

Further studies are needed to elucidate the aetiology and epidemiology of many diseases in pastoralists' camels. Specific diseases such as contagious skin necrosis, brucellosis and calf diarrhoea need special emphasis. The two newly recorded conditions, namely the bent-neck syndrome (wry neck) and the "Haboub" syndrome, need to be studied more closely to determine their aetiological and predisposing factors. Efforts should also be directed towards the significant causes of mortality, particularly among camel calves. 

Bibliography

Abbas, B., Mohamed, G. E., Agab, H., Yagoub, S.O. & Mustafa, K. 1992a. Clinical observations on field cases of some clinical diseases with emphasis on diarrhoea in camel calves. In Proc. 5th Conf. General Federation of Arab Veterinarians, January 1992, Khartoum, Sudan Veterinary Association.
Abbas, B., Chabeuf, N., Saint-Martin, G., Bonnet, P., Millaird, A., Bashir, H. & Musa, B.E. 1992b. Camel pastoralism in the Butana and northeastern Sudan. Nomadic Peoples, 31: 64-84.
Abbas, B., Saint-Martin, G. & Planchenault, P. 1993. Constraints to camel production in eastern Sudan: a survey of pastoralists' conceptions. Sudan J. Vet. Sci. Anim. Husb., 32: 33-39.
Abdurahman, O.A. Sh. & Bornstein, S. 1991. Diseases of camels (Camelus dromedarius) in Somalia and prospects for better health. Nomadic Peoples, 29: 104-112.
Agab, H. 1993. Epidemiology of camel diseases in eastern Sudan with emphasis on brucellosis, p. 184. University of Khartoum. (M.V.Sc. thesis)
Agab, H., Abbas, B., Le Horgne, J.M. & Saint-Martin, G. 1993. A note on vitamin A deficiency in camels in Sudan. Sudan J. Vet. Sci. Anim. Husb., 32(1): 9-14.
Blaizot, C. 1976. Doctorate Thesis, Vet. Alfort, No. 9. Cited by Dakkak, A. & Ouhelli, H. (1987). In Rev. Sci. Tech. Off. Int. Epiz., 6(1): 477-641.
Edelsten, R.M. & Pegram, R.G. 1974. Contagious skin necrosis of Somali camels associated with Streptococcus agalactiae. Trop. Anim. Hlth Prod., 6: 255-256.
El Amin, M.A.G., Tageldin, M.H. & Yagoub, I.A. 1984. Investigation on camel haemonchosis in the eastern regions of Sudan. Bull. Anim. Hlth Prod. Afr., 32(4): 412-414.
Fadl, M., Magzoub, M. & Burger, H.J. 1989. Prevalence of gastrointestinal nematodes of camels in the Butana grazing area. In Proc. Int. Symp. Development of Animal Resources in the Sudan, January 1989, Faculty of Veterinary Science, University of Khartoum.
Fowler, M.E. 1992. Plant poisoning in camels. In Proc. First Int. Camel Conf., Dubai, p. 403. UK, R&W Publications (New market).
Gruvel, J. & Balis, J. 1965. Trypanosoma evansi infection of camels in the Chad Republic, principal vectors. Rev. Elev. Med. Vet. Pays Trop., 18: 435-439.
Higgins, A.J. 1984. Sarcoptic mange in the Arabian camel, diagnosis and treatment. World Anim. Rev., 49: 2-5.
Higgins, A.J. 1986. The camel in health and disease, p.168. London, Bailliere Tindall.
Higgins, A.J., Silvey, R.E., Abdelghafir, A.E. & Kitching, R.P. 1992. The epidemiology and control of an outbreak of camel pox in Bahrain. In Proc. First Int. Camel Conf., Dubai, p. 101-104. UK, R&W Publications (New market).
Idris, O.F., Salih, Y.M., Wahbi, A.A. & Abdelgadir, E. 1979. Toxicity of Capparis tomentosa administered to camels. Workshop on Camels, Khartoum, IFS Provisional Report No. 6, p. 373-386.
Khalafalla, A.I., Agab, H. & Abbas, B. 1994. An outbreak of contagious ecthyma in camels (Camelus dromedarius) in eastern Sudan. Trop. Anim. Hlth Prod., 26: 253-54.
Khamiev, S.Kh. 1982. Epidemiology of ringworm (Trichphyton infection) among camels in Kazakhstan. Veterinariya (Moscow), 9: 42.
Khanna, N.D., Tandon, S.N. & Sahani, M.S. 1992. Calf mortality in Indian camels. In Proc. First Int. Camel Conf., Dubai, p. 89-93. UK, R&W Publications (New market).
Kumar, D.S., Raisinghani, P.M. & Manohar, G.S. 1992. Sarcoptic mange in camels: A review. In Proc. First Int. Camel Conf., Dubai, p. 79-82. UK, R&W Publications (New market).
Mahmoud, M.M. & Gray, A.R. 1980. Trypanosomiasis due to Trypanosoma evansi. A review of recent research. Trop. Anim. Hlth Prod., 12: 35-47.
Malek, E.A. 1959. Helminth parasites of the camel in the Sudan. J. Parasitol., 45(2): 36-39.
Munz, E. 1992. Pox and pox-like diseases in camels. In Proc. First Int. Camel Conf., Dubai, p. 43-46. UK, R&W Publications (New market).
Munz, E., Schillinger, D., Reimann, M. & Mahnel, H. 1986. Electronmicroscopical diagnosis of Ecthyma contagiosum in camels (Camelus dromedarius). First report of the disease in Kenya. Zentfl. Vet. Med., 33(1): 73-77.
Musa, M.T. & Osman, O.M. 1990. An outbreak of suspected tick paralysis in one-humped camels (Camelus dromedarius) in the Sudan. Rev. Elev. Med. Vet. Pays Trop., 43(4): 405-410.
Musa, B.E., Chabeuf, N., Abbas, B., Bonnet, P. & Planchenault, D. 1989. Survey of camel raising in the Butana region of the Sudan. In Proc. Int. Symp. Development of Animal Resources in the Sudan, p. 13-27. Khartoum.
Obeid, A.I. 1983. Field investigation, clinical and laboratory findings on camel mastitis. University of Khartoum. (M.V.Sc. thesis)
Osman, A.M. 1976. A review on tick-borne diseases in Sudan and their control. Bull. Off. Int. Epiz.
Rathore, M.S. 1971. Studies on sarcoptic mange in the camel (Camelus dromedarius). University of Udaipur, India. (M.V.Sc. thesis)
Saint-Martin, G., Maillard, A., Roy, F. & Musa, B.E. 1990. Performance de reproduction de camelines en milieu naturel: exemple d'une enquête dans le Butana au Soudan. In Proc. Workshop Improvement of Reproductive Performance of the Camels, Paris, 10-12 September 1990.
Saint-Martin, G., Delmet, C., El Zubeir, A.R.Y., Peyre de Fabriques, B., Harbi, M.S.M.A. & Bagadi, H.O. 1992. Camel Project of Butana: Feasibility study for an extension of the on-going project. Final Report. Khartoum, Maison Alforts.
Schwabe, C., Reimann, H.P. & Franti, C. 1976. Epidemiolo y in veterinary practice. New York, Academic Press.
Schwartz, H.J. 1992. Productive performance and productivity of dromedaries (Camelus dromedarius). Anim. Res. Dev., 35: 86-98.
Schwartz, H.J. & Dioli, M., eds. 1992. The one-humped camel in eastern Africa. A pictorial guide to diseases, health care and management, p. 282. Germany, Josef Margraf.
Steward, J.S. 1950. Notes on some parasites of camels in the Sudan. Vet. Rec., 62: 835-837.
Yagi, A.I. & Razig, M.T. 1972. Seasonal abundance of Tabanidae in southern Darfur District, Sudan. Rev. de Zoologie et de Botaniques Africaines (Bruxelles), 86: 293-301.