TCP/ZIM/8821 (A) TECHNICAL COOPERATION PROGRAMME ASSISTANCE FOR THE CONTROL OF NEWCASTLE DISEASE PHASE II OF TCP/ZIM/4553 (E)   Consultant's report (12 - 22 December 1998) By Dr. Vilmos J. Palya International Consultant, Feed-Based Newcastle Disease Vaccine Specialist December 1998

Table of Contents

I. SUMMARY OF RECOMMENDATIONS

II. INTRODUCTION

TERMS OF REFERENCE

ACKNOWLEDGEMENTS

III. FINDINGS

1. Confined Laboratory Vaccination Trials

2. Field Trials with V4, I2 and LaSota strain-based vaccines

3. Mass Vaccination Campaign Targeting Rural Poultry Populations

IV. CONCLUSION

Table 1: Field Trial Sites and Sample Sizes for the Different Vaccines and Vaccine Delivery Methods*

Table 2: Seroconversion and Challenge Results after Different Methods of Newcastle Disease Vaccine Application

Appendix 1.:PEOPLE MET AND HAVE DISCUSSION

I. SUMMARY OF RECOMMENDATIONS

1. In light of the findings generated under the two phases of the project, the use of feed as a vaccine delivery method cannot be considered as an effective nor sustainable means of community-based Newcastle disease control.. The results obtained in Zimbabwe with ND-HR V4 and I2 vaccines delivered on feed confirmed the findings of similar studies elsewhere in Africa. In the face of these findings, the control of Newcastle disease in rural backyard poultry flocks should not be based on feed-based vaccination method.

2. Since the natural turnover in village flocks is short, generally 30 to 40 % of the birds are replaced by new ones in 4 months time, it seems that only those ND vaccines and vaccination methods can be effective in controlling ND in village chicken populations which give adequate level of protection even after one application. Evidence from trials conducted in Zimbabwe and other African countries shows that vaccines delivered by eye drop offers the best and most reliable protection at population level, at the lowest level of resource use. Therefore, eye drop application of vaccine should be considered as one of the most appropriate method on which a mass vaccination campaign to control Newcastle disease in rural chicken flocks can be based.

3. An effective programme to control Newcastle disease in backyard poultry flocks of rural areas in Zimbabwe and most probably in other African countries should repeat vaccination at least every 4 to 6 months.

4. Continuation and speeding up of the mass vaccination of communal poultry flocks is considered to be definitely necessary to reduce the incidences of Newcastle disease outbreaks in Zimbabwe.

5. The serological results obtained on the post-vaccination samples are discouraging if they are considered as the indicators of the effectiveness of the vaccination campaign. Therefore, the post-vaccination sero-monitoring shoud be broadened and speeded up to get more analysable results. At the same time the method of storage, preparation and application of vaccine should closely be reviewed in the field.

6. Continuation of the monitoring and evaluation of the current mass vaccination programme in Zimbabwe is of primary importance . It will help to identify a transferable and sustainable model for community-based Newcastle disease control. The experiences gained during this programme should be taken into account by other countries in Africa as well when a vaccination campaign for the control of Newcastle disease is going to be instituted.

7. The results and the experieces generated under this project should be complied by the National Project Team in such form which can be published and disseminated to African countries.

II. INTRODUCTION

Project TCP/ZIM/4453 `Emergency Assistance for the Control of Newcastle Disease' started in early 1996 and was closed at the end of December 1997. Phase I of the Project had the objective of testing and developing a community-based program of vaccinating chickens in the backyard poultry systems of Zimbabwe against Newcastle disease. Between 1996 and the end of 1997, a series of tests were conducted on the heat-resistant ND-HR V4 vaccine and various application methods including feed-based delivery. Due to problems of vaccine supply and quality, several field activities of the project linked to the use of this vaccine could not be accomplished by the end of Phase I. Therefore, the Project was extended until the end of 1998 under Phase II (TCP/ZIM/8821-A) to carry out the remaining activities which include:

� replacement of the 15 million doses of inferior quality of ND-HR/V4 vaccine stock by a new consignment of quality certified vaccine stock,

� continuation of production and field testing of the I2 strain-based vaccine,

� testing of the best feed as vaccine carrier for orally administered ND-HR/V4 & I2 vaccines,

� using the above vaccines with already selected feed for field trials in designated villages for backyard poultry in order to obtain concluding and comparable results to those carried out in other parts of Africa,

� competition of socio-economic studies.

Phase II of the Project aimed to define a suitable model of community-based prevention of epidemics of Newcastle disease in rural poultry population, through an appropriate vaccination programme. In the light of results from Phase I, field trials were designed and carried out with feed-based, eye drop and drinking water delivered vaccines, to compare the appropriateness of delivery methods and efficacy of the V4, I2 and LaSota strain based vaccines.

The consultant's mission and the following report aim to evaluate and analyze the results generated under Phase I (TCP/ZIM/4453) and Phase II (TCP/ZIM/8821-A) of the Project with reference to the feasibility of using the ND V-4 or I-2 vaccines for vaccination schemes and the applicability of feed-based vaccination versus other routes of vaccine administration with special focus on protecting the smallholders and back-yard poultry flocks.

TERMS OF REFERENCE

Feed-Based Newcastle Disease Vaccine Specialist

Duties:

Under the supervision of AGAH, RAFR, and SAFR and in close co-operation with the National Project Co-ordinator and Counterparts the incumbent will:

� Evaluate the results of confined and field vaccination trials with NDV-4 and I-2 vaccines.

� Analyse the results in a context of those from previously conducted experiments in Zambia, Ethiopia and The Gambia.

� Advise on a feasibility of using the NDV-4 and I-2 vaccines for vaccination schemes with special focus on protecting the smallholders and back-yard poultry flocks.

� Advise on applicability of feed-based vaccination versus its intra-ocular administration.

� Advise on the appropriate and practical ways of the above mentioned vaccines QC and in case of I-2 vaccine production by the National Laboratory.

� Evaluate the results of the vaccination campaign in Zimbabwe under the phase I and II of the project.

� Participate in organisation and implementation of the National Workshop on the Subject to be conducted in Harare on 18 December 1998.

� Prepare and submit in electronic form a consultancy report according to applied FAO standards and prepare elements for the draft Terminal Statement.

� Perform any other related duties as required.

Itinerary:

12 December 1998 Budapest - London BA869

12 - 13 December 1998 London - Harare BA2053

20 - 21 December 1998 Harare - London BA2052

21 December 1998 London - Rome BA 554

22 December 1998 Rome - Budapest MA 403

ACKNOWLEDGEMENTS

I would like to thank all the project team members for their help and support during my mission, and in particular Dr. Mavhenyengwa, National Project Co-ordinator and Mr. James, Chief lab. technician for their readiness and co-operation in providing all required information and for their assistance in evaluating the collected results. I am also grateful for the input and assistance from my fellow consultant Mr. Roger Oakeley.

I greatly appreciate the co-operation of the staff at the FAO Representation in Harare who assisted with my mission in Zimbabwe.

III. FINDINGS

1. Confined Laboratory Vaccination Trials

1.1 Vaccination by Conventional Method Using V4 and I2 Strain-based Vaccines

Two vaccination trials by eye-drop administration of the vaccine were carried out to determine the potency of the Webster's ND-HR V4 vaccine. It was demonstrated that by applying the vaccine through eye-drop route at the recommended dose 100 % protection could be achieved even after one vaccination.

The locally produced ND I2 strain-based vaccine, in comparison with the Webster's ND-HR V4 vaccine, was also tested for potency in laboratory trial by administering the vaccine through eye-drop route at different dose rate. The results obtained indicated that the ND I2 strain-based vaccine produced locally gave full protection after one vaccination even at a dose rate that was 100 times less than the generally recommended dose. The protection offered by I2 vaccine through eye-drop application was comparable to those results obtained after the similar application of the ND-HR V4 vaccine.

1.2 Feed-based Vaccination Trials with V4 and I2 Strain-based Vaccines

To select the best vaccine carrier for field trials sorghum, millet, rapoko, crushed maize and rice were tested as vaccine carriers under laboratory condition. The birds in each trial group were vaccinated five to six times at monthly intervals via the feed, and by eye-drop in the groups serving as positive controls. During these laboratory trials it was demonstrated that even in well-controlled laboratory conditions the best performing feed-based vaccine gave only about 30 to 40 % protection after two vaccinations, and even after six vaccinations the highest protection rate achieved was about 80 %. On the other hand in several trials the eye-drop vaccination resulted in 100 % protection after one application of the vaccine. In these trials RAPOKO performed best as vaccine carrier.

The basic concern arisen from these trials is the length of time which was required to reach an acceptable level of protection. Taking into account the natural turnover within a village chicken flock and the short generation time in rural poultry populations it can be predicted that when applying this vaccination method a significant proportion of birds in the vaccinated populations is susceptible to Newcastle disease at any given time.

2. Field Trials with V4, I2 and LaSota strain-based vaccines

The primary objective of this phase of the project has been to determine under field condition whether the feed delivered V4 or I2 vaccines would protect village chicken against ND as effectively as the vaccines applied by conventional vaccination method. To achieve this objective field trials in different Provinces and villages have been set up to compare the efficacy of the different vaccine and vaccine delivery methods. The criteria for the selection of the trial sites was the absence of ND outbreaks and vaccination in recent years. It was found that the majority of the blood samples taken before the trials commenced at each of the trial site were free from antibodies to ND and therefore the chicken population selected were susceptible to ND and found to be appropriate for the trials. The location, sample sizes and the baseline serological results of the different trial groups are given in Table 1.

2.1 Feed-based vaccination with V4 and I2 vaccines

On the basis of previous laboratory tests - virus recovery experiments and laboratory feed-based vaccination trials - RAPOKO was chosen as the most suitable vaccine carrier for the field trials. The vaccine coated grain was given to birds in shed soon after mixing thoroughly. In the majority of cases the birds finished the feed in less than 20 minutes.

Vaccinations were done six times at monthly intervals and the chicken population in each trial group were sampled for serology and buy-back challenge tests 20 to 30 days after the third and the last vaccination. The results obtained in these trials are presented in Table 2.

It seems that under field condition the performance of feed-based vaccines was very poor, significantly poorer than the also poor performance realized in the laboratory feed-based vaccination trials. The best protection rate achieved was 27 % after six vaccination with I2 vaccine. Most of the case the levels of protection recorded at different stages of the vaccination programme were zero or very law.

Using the rate of seroconversion and the rate of survival after challenge as an indication of the levels of protection to ND it can be concluded that oral application of either V4 or I2 strain-based ND vaccines delivered on locally available grain has not resulted under field condition in a level of protection which could be considered as adequate to control Newcastle disease. The practicality of this vaccination method/regime may also be questioned simply due to the length of time and the numbers of vaccinations required before any level of protection can be expected.

2.2 Vaccination through Drinking Water with V4

At each household immediately before use, the required number of vaccine doses was mixed with available clean deep well water and put in the shed at the favourite resting places for the chickens. On the whole it was difficult to observe the time taken to finish up the treated water.

From the data presented in Table 2 it can be seen that V4 vaccine delivered through drinking water gave significantly better result than the V4 or I2 vaccines delivered on feed (p< 0.001 and p< 0.01 respectively). The rate of seroconversion, however, was between 30 and 38 % after two and three vaccination which can not be weighed as adequate to control Newcastle disease outbreaks.

2.3 Eye-drop Vaccination with I2 and LaSota Vaccines

Vaccines was reconstituted in sterile water and delivered by droppers through the intra-ocular route so as each drop contained one dose of the vaccine. Birds were vaccinated three times during the trial, on day 0, day 30 and day 90. Seroconversion and challenge results are given in Table 2.

High prevalence of antibodies to ND were recorded in birds vaccinated either by LaSota or I2 vaccine. The rate of seroconversion after two and three vaccinations was above 75 % in both trial groups. Statistical analysis of seroconversion results showed however that the proportion of birds that seroconverted in the LaSota trial group (93-95 %) was significantly higher than that of birds in the I2 vaccine trial group (76-80 %) (p< 0.01). Both vaccines gave also very high protection rate against challenge, however the results of challenge tests should be taken cautiously since the numbers of birds challenged were few and represented only limited number of households from the trial sites.

3. Mass Vaccination Campaign Targeting Rural Poultry Populations

The main objective of Project TCP/ZIM/4453 was to establish a community based programme for the control and prevention of Newcastle disease epidemics in the rural poultry population by the use of the reportedly heat-resistant ND V4 vaccine which was supposed to be administered by oral route using local grains as vaccine carriers. Unfortunately the 15 million doses of ND-HR/V4 vaccine purchased in March 1996 that were intended to be used in that vaccination programme were found to be of poor quality and were rejected of using it.

In the meantime due to the serious disease situation in the rural poultry population an emergency mass vaccination campaign of communal poultry flocks using commercially available vaccine (LaSota) administered by the conventional eye-drop method had been instituted in 1996 - 1997. This vaccination campaign resulted in a reduction of the disease spread, however the disease has continued to be present throughout the country causing sporadic outbreaks. All of the recent outbreaks have been confined to rural back-yard chickens and no commercial flocks have been affected.

Since the average life-span of rural poultry birds has been estimated at six to twelve months, the birds vaccinated during the 1996/97 vaccination campaign had been replaced by new birds which had never received vaccination. Therefore, a new vaccination campaign, on a community-based approach targeting the rural poultry population using the ND-HR/V4 vaccine stock received as the replacement for the inferior quality consignment, was launched in May 1998. Before the nation-wide vaccination campaign started a smaller scale vaccination had been carried out in a Pilot Province (Mashonaland Central) to identify any problems which could occur along with the community based approach programme.

Because of the controversial results obtained in the laboratory trials with feed-based vaccine delivery method the conventional eye-drop vaccination method was chosen for the mass vaccination campaign. In selecting the method the need to have a delivery system of vaccine which can be carried out by the farmers was also taken into consideration. To monitor the efficiency of the campaign and the potency of the vaccine it was proposed that chicken would be blood sampled from a random selection of households before and after vaccination.

It was anticipated that the first vaccination would be completed in all of the eight provinces by the end of July, 1998. However, the nation-wide vaccination campaign commenced only in mid July 1998 after the problems highlighted by the pilot mass vaccination were addressed by the National Project Co-ordination. Different approaches depending on the given circumstances have been in practice which include:

� The local VEA trains a group of people from his community who will collect the vaccine from a central place and carry out the vaccination according to an agreed schedule. The VEA will continue to provide a supervisory role.

� For places far away from the Animal Health Centre, the VEA approaches the local leadership and request them to select young people to be trained in handling and application of the vaccine. These trained persons come and collect the vaccine from the VEA at a central point and carry out the vaccination according to an agreed schedule.

� In some areas the settlement pattern does not allow community involvement. In these places each household receives enough vaccine to cover its birds. Vaccine droppers are collected later.

In Table 3 below the figures given represents the first vaccinations done up to mid November 1998 per Province.

Table 3: National Vaccination Campaign - Number of Birds Vaccinated per Province up to Mid November 1998

According to the data generated under this project it is estimated that the total rural poultry population is not more than 10 millions, but most probably between 6 and 8 millions. From these figures it can be reckoned that since the beginning of the mass vaccination campaign, during a six months period, only about 40 % of the rural poultry population has been covered by vaccination. This low vaccination coverage can be one of the reasons why the numbers of Newcastle disease outbreaks have not decreased during this period compared to the same period of last year. In 1977 a total of 45 outbreaks were reported, while since the beginning of this year up to end of November 80 outbreaks have been reported.

However, if we look at the incidence of ND outbreaks, as it shown in Table 4 below, recorded in 1998 before and after the vaccination commenced a pattern of decline in the incidence of outbreaks can be observed as the vaccination progressed.

Table 4: National Vaccination Campaign - Incidence of Newcastle Disease Outbreaks Before (Pre-vaccination) and After (Post-vaccination) July 1998

To monitor the efficiency and the effectiveness of the campaign pre- and post-vaccination bleeding for serological test have been done from randomly selected villages and households. The very limited results available at this stage of the vaccination campaign are given in Table 5 below.

Table 5: National Vaccination Campaign - Pre- and Post-Vaccination Prevalence of Antibodies to Newcastle Disease

a) = numbers of villages sampled/numbers of villages with chicken populations which have antibodies to ND at least in a certain portion of the tested households.

ND = not done

The serological results obtained on these post-vaccination samples are very discouraging if we consider them as the real indicators of the effectiveness of the vaccination. Therefore, the post-vaccination sero-surveillance should be broadened and speeded up to obtain more statistically analysable results, At the same time the method of vaccine storage, transport, preparation and application should be reviewed in the field.,

3.1 Constraints encountered

Transport has been the major problem which has limited the progress in all the Provinces.

Another restraining factor has been the shortage of vaccine droppers. The door to door concept of vaccine dropper movement by the households might not be possible as within the community there are some element of mistrust between families. Therefore, the identification of neutral persons by the local leadership seems to be more ideal and operable.

While there is enthusiasm in some sectors of the communities, the community priorities might be different at a given time and therefore they are not co-operative all the time. It should be noted that community based vaccination against ND as a new concept can take more years before people accept and appreciate it. Therefore, the introduction of this concept for national vaccination campaign with a short deadline for a nation-wide coverage might not be feasible.

IV. CONCLUSION

Laboratory experiments carried out in a number countries in Africa with ND-HR V4 or I2 vaccine, using various feed grains as vaccine carriers have failed to confirm reported success of similar trials carried out in South East Asia.

In controlled laboratory vaccination trials, feed delivered ND-HR V4 or I2 vaccines necessitated four to six applications before adequate immunity levels could be achieved, while in several trials birds vaccinated by eye drop had achieved 100 % protection after only one application of the same vaccines. As it was assumed field conditions, due to the time lapse between preparation of the vaccine and application, and less controlled vaccination process, further aggravated this problem.

It can be concluded that oral application of either V4 or I2 strain-based ND vaccines delivered on locally available grain has not resulted under field condition in a level of protection which could be considered as adequate to control Newcastle disease. The practicality of this vaccination method/regime may also be questioned simply due to the length of time and the numbers of vaccination required before any level of protection can be expected.

One of the basic concern arisen from trials with feed delivered vaccines is the length of time which was required to reach an acceptable level of protection. Taking into account the natural turnover within a village chicken flock and the short generation time in rural poultry populations it can be predicted that when applying this vaccination method a significant proportion of birds in the vaccinated populations is susceptible to Newcastle disease at any given time.

Evidences gathered from laboratory and field trials conducted in a number of countries in Africa have shown that feed-based delivery of ND-HR V4 or I2 vaccines cannot be relied upon to control the disease in the rural backyard poultry flocks.

Since the natural turnover in village flocks is short, generally 30 to 40 % of the birds are replaced by new ones in 4 months time, it seems that only those ND vaccines and vaccination methods can be effective in controlling ND in village chicken populations which give adequate level of protection even after one application. Evidence from trials conducted in Zimbabwe and other countries in Africa shows that vaccines delivered by eye drop offers the best and most reliable protection at population level, at the lowest level of resource use. It has been proved by several trials carried out in different countries of Africa that LaSota, Hitchner B1, V4 or I2 vaccines perform almost equally good when administered by the intra-ocular route.

The continuing outbreaks of Newcastle disease in Zimbabwe underline the need for both an effective and a sustainable disease control program based on vaccination of rural poultry population. Based on the results and experiences gained from the laboratory trials, the Department of Veterinary Services decided to experiment with intra-ocular vaccine application for its mass vaccination campaign.

The use of eye droppers seems to represent a sustainable means of community participation. It should be noted, however, that community based vaccination against ND as a new concept can take more years before people accept and appreciate it. Therefore, the introduction of this concept for national vaccination campaign with a short deadline for a nation-wide coverage might not be feasible.

It has been realised through the analysis of socio-economical data generated in this project that on average after every four months 30 to 40 % of the chickens in rural poultry populations have been replaced by new ones which are susceptible to ND. With such a population dynamic it seems to be justified and adequate to advise that re-vaccination of rural poultry flocks should take place on a regular basis at 4 to 6 months intervals so as to curb ND outbreaks. For the time being this requirement, however, seems to be impossible to be met by the Department of Veterinary Services from an operational resource point of view. On the other hand for very evident reasons, the community based concept of mass national vaccination has not yet reached the stage of progress when it can be fully relied on in such a vaccination campaign.

The succes or failure of this program and its farmer training activities may offer valuable knowledge in the development of a transferable model for the control of Newcastle disease in Africa.

TABLE 1: FIELD TRIAL SITES AND SAMPLE SIZES FOR THE DIFFERENT VACCINES AND VACCINE DELIVERY METHODS*

* See map of trial sites location in appendix.

TABLE 2: SEROCONVERSION AND CHALLENGE RESULTS AFTER DIFFERENT METHODS OF NEWCASTLE DISEASE VACCINE APPLICATION

NB.: Birds receiving vaccine by eye-drop or in drinking water were sampled for serology and challenge after 30 days of the second vaccination in Test 1 and after 60 days of the third vaccination in Test 2. Birds receiving vaccine on feed were sampled after 30 days of the third vaccination in Test 1 and 20 days after the sixth vaccination in Test 2.

* Representing only one household from the trial site

** 80 % of the birds which succumbed of ND were from one household

APPENDIX 1.:PEOPLE MET AND HAVE DISCUSSION

FAO Sub-regional Office, Harare

Dr. Julio J. De Castro, Animal Production and Health Officer

Mr. Oakeley, R., Consultant - Rural Poultry Production Socio-economist

Department of Veterinary Services, Harare

Dr. Hargreaves, Director of Vet. Services

Dr. Ushewokunze-Obatolu, Deputy Director of Vet. Services, R & D

Dr. Mavenyengwa, National Project Co-ordinator

Dr. Chitate, Epidemiologist

Dr. Madekurozwa, Virologist

Dr. Guta, Poultry Pathologist

Mr. Christopher M. Ncube, Research Technician

Ms. Munyombwe, Statistician

Mr. James, Chief Lab. Technician