1. Mass Vaccination Campaign Targeting Rural Poultry Population
1. That mass vaccination of communal poultry flocks on regular bases according to an established schedule under a national vaccination campaign should be brought into existence to reduce the incidences of Newcastle disease outbreaks and to develop disease-free regions/areas in the country.
2. That to monitor the efficiency of the current vaccination campaign and the potency of the vaccine used it is proposed that chicken should be blood sampled from a random selection of households before the first vaccination and one month after the second vaccination.
3. That after the competition of the mass vaccination campaign using V4 vaccine by the eye-drop route, sero-survey of vaccinated birds in selected villages/households over an extended period of time according to the formula recommended by Mr. Rushton in his consultancy's report in 1996 should be carried out in order to determine the recommended time period between vaccination of the communal poultry populations.
4. That the data collected on the age structure of flocks and average life spans of back-yard chickens in the communal area should be analysed and the results made available as soon as possible to allow the establishment of the most appropriate vaccination regime/programme to control Newcastle disease in the rural poultry population.
5. That to meet the principle objective of the present phase of the project, that is to determine whether the feed delivered V4 or I2 vaccine would protect village poultry against Newcastle disease as effectively as the conventional vaccination methods and programme, field trials should be conducted according to the protocol and work-plan detailed in Appendix 2 of this report.
6. That the Field Trials set up during this consultancy mission with the V4 and I2 strain-based vaccines delivered both on feed and by the conventional vaccination methods should continue for at least 5 to 6 months to generate sufficient number of data on which basis the efficacy of the feed-based vaccine delivery methods and its workability under rural village conditions for controlling Newcastle disease can be assessed.
7. That the efficacy of the different vaccines and vaccine delivery methods should be monitored both by serology and buy-back challenge.
8. That a separate field trial with either the locally produced I2 or the Webster's ND-HR V4 vaccine delivered in drinking water should be set up according to the Protocol given in Appendix 2. The most appropriate location for conducting this trial shall be in the proximity of the village participating in the V4 feed-based vaccination trial.
9. That the second mission of consultant to make the final evaluation of the field vaccination trials should commence in the second half of November 1998.
In recent years Newcastle disease has been identified as one of the major constraints to rural poultry production in Zimbabwe. Chicken can be protected from Newcastle disease by vaccination, but most of the vaccine delivery methods require handling of the birds. In many rural poultry systems handling chicken is very difficult or not possible to achieve. The potential of food-based vaccination, using V4 or I2 heat-resistant strain-based vaccine, and its reported success in Asia has led to an interest in the use of this technology and vaccination policy in several countries of Africa. If the high mortality in flocks due to Newcastle disease is reduced by introducing a convenient vaccination method using a relatively heat resistance vaccine which does not need cold-chain during transport and application, and the vaccination can be carried out by the farmers, they will be encouraged to consider poultry keeping as a less risky activity, which in turn could lead to improved production levels. However, this will not occur rapidly, and it will require a lot of extension work, training and a long-term vaccination programme to ensure that the poultry flocks maintain high levels of immunity to Newcastle disease at any given time.
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. Its objectives were to build a community-based programme for the control and prevention of Newcastle disease in rural chicken population, and to establish the most appropriate method for a sustainable vaccination programme. However, during the implementation of the project unanticipated problem has been faced with regard to the potency and the heat stability of the vaccine received from Websters-Cynamid, Sydney, Australia. As a consequence, several field activities of the project linked to the use of this vaccine could not be accomplished before the closure of the project. Therefore, the Director-General of FAO has exceptionally approved a Phase II project under symbol TCP/ZIM/8821 (A) to carry out the remaining activities which include:
i. replacement of the 15 million doses of inferior quality of ND-HR/V4 vaccine stock by a new consignment of quality certified vaccine stock,
ii. continuation of production and field testing of the I2 strain-based vaccine,
iii. testing of the best feed as vaccine carrier for orally administered ND-HR/V4 & I2 vaccines,
iv. 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,
v. competition of socio-economic studies.
The objectives of Consultant's mission were to advise on and assist the Project management in setting up concluding field trials with feed-based vaccines in parallel with other conventional routes of vaccine application with both the ND-V4 and I2 vaccines to determine whether the feed-delivered vaccines protect village poultry against ND as effectively as the conventional vaccination methods/programmes used in the country.
Feed-Based Newcastle Disease Vaccine Specialist
Project: TCP/ZIM/8821(A): "Assistance for the control of Newcastle Disease (Phase II)"
Duration: 1.5 months in two missions of 3 weeks each
Duty Station: Harare, Zimbabwe
Qualifications:
The candidate should be a veterinary graduate with a post-graduate qualification in Virology/Immunology. He/She should have established experience in the diagnosis and control of poultry diseases, particularly Newcastle disease, and in the preparation and application of feed-based Newcastle disease vaccine as well as designing and supervising Newcastle disease vaccination programmes for village poultry units in developing countries.
Duties:
Under the supervision of AGAH, RAFR, and Sub-regional FAO office in Harare, the incumbent will be the lead consultant for the project. He/She will guide the National Project Co-ordinator and other project staff to ensure a balanced programme of work that is likely to yield scientifically valid and analysable results. In particular he/she will:
First mission:
1. Advise the Government on the use of the ND V4 and I2 thermo-stable vaccine by the routes that are conventionally used for Newcastle disease vaccination.
2. Advise on setting up the concluding feed-based vaccination trials with both vaccines in rural poultry population.
3. Advise on the selection of local grains, vaccine delivery methods and monitoring vaccine efficacy.
4. Train those veterinary extension staff that will be involved in the community-based trials in techniques for handling and application of the feed-based vaccine.
5. Perform any other duties as required.
6. Submit a consultancy report at the end of the first mission.
Second mission:
1. Evaluate the results of the vaccination campaign.
2. Prepare a consultancy report and elements for the draft Terminal Statements.
Itinerary:
14 May 1998 Budapest - Rome AZ 527
16 May 1998 Rome - Addis Ababa ET 763
16 May 1998 Addis Ababa - Harare ET 863
03 June 1998 Harare - Addis Ababa ET 832
04 June 1998 Addis Ababa - Rome ET 543
05 June 1998 Rome - Budapest AZ 524
I would like to thank to my counterparts, especially Dr. Mavenyengwa, National Project Co-ordinator, Dr. Chitate, Epidemiologist and Mr. James, Asst. Chief Vet. Lab. Technologist who were extremely helpful and invaluable guides in the field and in providing all required background information. My two fellow consultants on the mission, Dr. Aichi Kitalyi and Mr. Roger Oakeley, were always helpful and knowledgeable.
I greatly appreciate the co-operation of the staff at the FAO Representation in Harare who assisted with my mission in Zimbabwe.
During the recent epidemic (1994 - 96) Zimbabwe experienced the worst outbreaks of Newcastle disease since 1986 which killed about six million birds in the communal areas. The project TCP/ZIM/4453 came as an emergency assistance of FAO whose main objective 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 developed by Australian scientists.
Primarily ND-HR/V4 vaccine was supposed to be administered by oral route using local grains as vaccine carriers, however due to the grave disease situation an emergency mass vaccination campaign of communal poultry flocks using V4 vaccine by eye drop was considered necessary to reduce the incidence of Newcastle disease in Zimbabwe. Unfortunately the 15 million doses of ND-HR/V4 vaccine purchased from Webster's Cyanamid, Sydney, Australia in March 1996 that were intended to be used in that vaccination campaign were found to be of poor quality and were rejected of using it for any field vaccination.
In the meantime the Newcastle disease emergency was addressed with commercially available vaccine (LaSota) administered by the conventional eye-drop method. This vaccination campaign and other measures/epidemiological factors resulted in a significant reduction of the disease spread, however the disease has continued to be present throughout the country causing sporadic outbreaks. In 1997 a total of 45 outbreaks were reported, most of the incidents occurred in the second half of the year. Since the beginning of this year there has been 30 reported outbreaks. All of the outbreaks which occurred during the recent years have been confined to rural back-yard chickens and no commercial flocks were affected. It seems that the disease has been restricted to the following provinces: Manicaland, Mashonaland Central, Matebeland North, Matebeland South, Midlands and Masvingo provinces. (See attached map on ND incidences)
Live Newcastle disease vaccines give short lived immunity to the disease, certainly much shorter than the time passed since the competition of the last nation-wide ND vaccination programme. Poultry flocks are not static, the average life-span of rural poultry birds has been estimated at six to twelve months; this means that most of the birds vaccinated during the last vaccination campaign have already been replaced by new birds which have never received vaccine. Taking these facts and the recent epidemiological situation into consideration, mass vaccination of communal poultry flocks under a national vaccination campaign is considered to be definitely necessary to reduce the incidences of Newcastle disease outbreaks and to develop at least some disease-free regions/areas in the country. Therefore, the Department of Veterinary Services decided that a vaccination campaign on a community-based approach targeting the rural poultry population and covering all provinces will be instituted.
The 15 million doses of ND-HR/V4 vaccine stock received recently from Websters, as the replacement for the inferior quality consignment of 1996, and some 9 million doses of I2 strain-based vaccine produced locally are going to be utilised in this campaign.
The urgency of protecting communal poultry flocks from Newcastle disease and the controversial results obtained in the laboratory trials on alternative vaccine delivery methods suggested that the conventional eye-drop vaccination method be used in the mass vaccination campaign. In selecting the method to be used in the mass vaccination campaign, the need to have a delivery system of vaccine which can be carried out by the farmers was also taken into consideration. Vaccination will be repeated once at three to four weeks after the fist vaccination.
To monitor the efficiency of the campaign and the potency of the vaccine it is proposed that chicken will be blood sampled from a random selection of households before the first vaccination and one month after the second vaccination. Seven villages will be randomly selected in each of the eight provinces and two randomly selected households per village. The total number of households selected will be 112. In each selected household all birds will be sampled if the flock size is less than 10 and 10 birds if the flock size is equal or greater than 10. The potential number of samples per test would be 1120.
In some of the provinces the vaccination has already been commenced during consultant's mission and it is anticipated that the first vaccination will be completed in all of the eight provinces by the end of July, 1998.
It has been decided by the Department of Veterinary Services that in each of the eight provinces of Zimbabwe the following staff should be trained in techniques for handling and application of V4 vaccine by eye-drop for the planned nation-wide vaccination programme:
- All Provincial Veterinary Officers to supervise further
training
- All Provincial Co-ordinators
- All Animal Health Inspectors in the province
- All Veterinary Extension Assistants (VEA) in the province
The training started on 8 of May 1998 and is supposed to be completed during the first week of June, 1998. During consultant's mission the following places and provinces have been visited:
Rusape, Manicaland
Mutare, Manicaland
Masvingo, Masvingo
Neshuro Mwenezi, Masvingo
Marimo, Goromonzi district, Mashonaland East
During the training the following subject matters have been covered: (i) reconstitution of the freeze-dried V4 vaccine, (ii) storage of the reconstituted vaccine during transport from provincial/district office to the communal farmer, (iii) method of vaccine delivery to the birds, and (iv) recording of vaccinated birds, villages etc. A written protocol of the procedure had been prepared by the project co-ordination which was distributed among the participants of the training.
It is planned that during the fist vaccination the Veterinary Extension Assistants (VEA) will train the farmers and village people, especially the women, how to apply the vaccine to their own chickens and during the second vaccination the VEAs will only distribute the vaccine to the villages and supervise its application by the farmers.
To determine a suitable carrier for the delivery of vaccine to village chickens the following grains have been tested in laboratory virus recovery experiments: millet, sunflower, crushed maize, rapoko, barley and sorghum. Good virus recovery was noted on millet, sunflower, rapoko and sorghum.
It should be noted however, that all virus recovery experiments were performed right after the coating process had been completed without leaving some period between the time of coating and the time of virus recovery. Therefore, these findings give limited indications on what will be the results under field conditions where the time-lapse between the preparation of the vaccine and its consumption, i.e., when it is actually taken by the birds, will most probably be much longer (at least a few hours).
The water tested included borehole, well and rain water. It appeared that bore-hole and rain water from almost all provinces were found suitable, while well water from all provinces were found unsuitable.
On the bases of these results it has been decided by the national project co-ordination that drinking water method for the application of the vaccine will not be tested in field trials. In spite of the results obtained in these laboratory tests, consultant strongly suggested that either with the locally produced I2 or the Webster's V4 vaccine a field trial should be conducted to get some results on this vaccine delivery method compared to those obtained in the other trials. During the field visits, the observations taken by consultant further supported the need to test this vaccine delivery method under field conditions because it seemed to be more manageable and controllable than the feed delivery method.
Droppers from four different suppliers were tested for virucidal effect by measuring the rate of viral inactivation in the reconstituted vaccine at room temperature at different time points after being placed in the droppers under investigation.
Based on the results obtained dropper B, which is a brown colour glass dropper, was selected for use in the vaccination campaign. This dropper delivers 150 droplets per 10 ml (the capacity of the dropper), giving a droplet size of 66 ul.
The results of the thermo-stability test carried out by PANVAC, Ethiopia on the freeze-dried vaccine indicated that after exposing the vaccine to temperature of 37 0C and 45 0C for 2 weeks significant drops in titres were observed at both temperatures. Therefore, it was advised that the vaccine be kept at + 4 0C during storage and cold-chain be maintained during the transport and distribution of the vaccine.
The stability of the reconstituted vaccine at different temperatures (+ 4 0C, room temperature and + 40 0C) using different diluents have been investigated in repeated tests in order to adapt the likely situations that may be found in the field.
In summarising the results obtained in several tests there has been a strong indication that the reconstituted vaccine prepared in different diluents (1 % gelatine, commercial diluent or sterile water) can be stored at + 4 0C for up to a week with no significant drop in titre. However, at ambient temperature between + 30 0C to + 40 0C, it is strongly recommended to use the reconstituted vaccine within a couple of hours, but all the time protect it from direct sunshine.
From the results of several laboratory tests performed on both the freeze-dried and the reconstituted V4 vaccine it can be concluded that the thermo-stability of this vaccine in both the freeze-dried and the liquid state is relative and does not allow the full negligation of the maintenance of the cold-chain during transport and distribution.
2.5.1 V4 vaccination trial by conventional method
Two vaccination trials by eye-drop administration of the vaccine using a total of 53 indigenous chickens (34 birds in the first experiment and 19 birds in the second one) were carried out to determine the potency of the Webster's ND-HR V4 vaccine. In these trials birds were vaccinated twice three to four weeks apart. The efficacy of the vaccine was measured by serological test and also by challenge test in the second trial.
It was established that by applying the vaccine through eye-drop route at the recommended dose (106 EID50/bird) 100 % protection could be achieved even after one vaccination as measured by serological or by challenge three to four weeks after vaccination.
2.5.2 I2 strain vaccination trial by conventional method
To test the potency of the locally produced I2 strain-based vaccine a laboratory vaccination trial involving 106 indigenous chickens were carried out applying the vaccine twice 3 weeks apart by eye-drop route at different dose rates (ranging from 104 to 107 EID50/bird). For comparison the Webster's ND-HR V4 vaccine at a dose rate of 106.3 EID50/bird was also included in the trial. The levels of protection were measured by monitoring the antibody responses and the survival rate after challenge.
The results obtained indicated that the I2 strain-based vaccine produced locally gave full protection against virulent ND virus challenge after one vaccination even at a dose rate of 104 EID50/bird and that this protection was comparable to those obtained after the similar application of the V4 strain-based vaccine.
In the course of these laboratory trials it has been clearly established and proven that either of the two vaccines (V4 strain or I2 strain) can provide high level of protection after one or two vaccination against the disease when administered through the conventional eye-drop route.
During an eight month period sorghum, millet, rapoko, crushed maize and rice were tested as vaccine carriers in chickens under laboratory conditions. A total of 154 indigenous chicken, divided into eight groups including one group for eye drop vaccination as the positive control and one unvaccinated group, were used in these feed trials. The birds in each group were vaccinated six times at monthly intervals via the feed, and by eye drop in the positive control group. The levels of protection were monitored by measuring antibody response and the rate of survival after challenge. Challenge tests were carried out two times during the experiment; first after 3 weeks of the second vaccination and the second time 3 weeks after the last vaccination.
The results obtained indicated that even under laboratory conditions the best feed-based vaccine gave only about 30 to 40 % protection after two vaccinations, and the protection rate achieved about 80 % only after six vaccination while in several trials the eye-drop vaccination resulted in 100 % protection after applying the vaccine one occasion. It seemed that similarly to the virus recovery tests in these trials also rapoko performed best as vaccine carrier.
The size of the treatment groups in these trials allowed the determination of statistically significant differences only when the difference in the efficacy of two treatment groups was very large, therefore these laboratory trials were not particularly helpful in determining the best vaccine carrier for the field trials with feed-based vaccines.
Although the vaccine delivered on rapoko gave reasonable level of protection against Newcastle disease in birds vaccinated six times it should be noted that due to the small numbers of birds in the trial groups the 95 % confidence intervals were very large, therefore it is impossible to predict what will be the level of protection that can be achieved in large population of birds in the field using the same vaccine delivery method. Another concern is the length of time required to reach the required level of protection. The natural turnover within the flocks and the short generation time in rural poultry population would result that at any given time a significant proportion of birds in a flock would be susceptible to Newcastle disease.
Limited field trials with V4 and I2 vaccines , administered by eye-drop, were initiated at the end of March 1998. In the trial with V4, involving only six households in Chiweshe, Central Mashonaland, 44 birds were vaccinated and 42 birds were left as contact control. While in the trial with I2 vaccine involving five households in Mutare, Manicaland 32 birds were vaccinated and 32 ones left unvaccinated as contact control. At both places at the commencement of the trials some birds were found to have antibodies to NDV indicating that these birds had been exposed to field challenge or were vaccinated previously. The prevalence of sero-positive birds in one household that gave more than half of the trial group reached almost 50 %.
Regarding the small size of the trial groups and the prevalence of antibodies to NDV at the start of the trials it is very unlikely that these trials with eye-drop vaccination will provide conclusive results or any further beneficial data on the efficacy of either of the two vaccines or on the effectiveness of this kind of vaccine delivery methods.
In a separate trial with V4 feed-based (rapoko) vaccine started on 12 May 1998 in Marimo, Goromonzi district, Mashonaland East, involving six households, 78 birds were vaccinated and 28 birds left as controls. At the commencement of the trial this group of birds was found by serological and challenge test to be fully susceptible to Newcastle disease. It is suggested that this trial shall continue according to the original work-plan for 6 months.
In order to meet the principle objective of the present phase of the project, that is to determine whether the feed delivered V4 or I2 vaccine would protect village poultry against Newcastle disease as effectively as the conventional vaccination methods and programme, the following field trials have been designed to compare the efficacy of the different vaccine delivery methods:
Trial group 1 (V4 strain-based vaccine)
Subgroup 1/1: vaccination by oral route with feed-based vaccine
Subgroup 1/2: unvaccinated control
Trial group 2 (I2 strain-based vaccine)
Subgroup 2/1: vaccination by eyedrop route
Subgroup 2/2: vaccination by oral route with feed-based vaccine
Subgroup 2/3: unvaccinated control
Trial group 3 (LaSota strain-based vaccine)
Subgroup 3/1: vaccination by eyedrop route
Subgroup 3/2: unvaccinated control
Trial group 4 (V4 or I2 strain-based vaccine)
Subgroup 4/1: vaccination by drinking water route
Subgroup 4/2: non-vaccinated control (NB.: 1/2 subgroup can serve as subgroup 4/2 if the trial site is in the proximity of trial group 1)
The criteria for the selection of the locations of the trial sites was that the trials should be done in areas which had not experienced Newcastle disease and had not been vaccinated against ND in recent years.
During Consultant's mission, blood samples were collected and tested for antibodies to Newcastle disease at each of the trial sites from each of the household selected, except trial subgroup 1/2 and trial group 4, to obtain a sort of baseline information on the susceptibility of the flocks. It was found that the majority of blood samples did not contain antibodies to Newcastle disease, therefore the poultry population of these households are susceptible to Newcastle disease, consequently they are appropriate for the vaccine trials.
Taking into consideration that both in the virus recovery test and the laboratory feed-based vaccination trials RAPOKO performed best it has been decided that in the field trials only this grain will be tested as vaccine carrier.
To improve the accuracy of the determination of statistical differences of the efficacy levels between the different treatments, the necessary flock numbers required in each subgroup for the duration of the trials (6 months) have been agreed to be not less than 30 flocks (households). Villages and households suitable to participate in these pilot trials had been identified, sampled for serological studies and the first vaccinations were carried out on the following dates:
Trial group 1 (V4 strain-based vaccine): 30 May 1998
Trial group 2 (I2 strain-based vaccine): 26 May 1998
Trial group 3 (LaSota strain-based vaccine): 27 May 1998
Trial group 4 (V4 or I2 strain-based vaccine in drinking water):should start not later then during the first week of June 1998.
The following measures will be the bases for comparing the performance of the feed-based vaccines with the other treatment subgroups:
- Protection-in-face-of-field challenge. Households participating in any of the trials should be monitored by the current disease surveillance methods.
- Individual bird haemagglutination inhibition test. This is the principle means to assess whether the vaccine is getting into the birds successfully and to detect field challenge by ND.
-Buy-back challenge trials. When comparing challenged feed-based vaccinated birds with challenged conventionally vaccinated controls, there should be no significant difference between the two trial subgroups.
The Work-plan for vaccination, sero-monitoring and buy-back challenge tests are given in Appendix 2.
PEOPLE MET AND HAVE DISCUSSION
FAO Sub-regional Office, Harare
Mrs. V. Sekitoleko, FAO Representative
Dr. Julio J. De Castro, Animal Production and Health Officer
Dr. Mrs. Kitalyi, A., Consultant - Back-Yard Poultry Production
Mr. Oakeley, R., Consultant - Rural Poultry Production Socio-economist
Department of Veterinary Services, Harare
Dr. Hargreaves, Director of Vet. Services
Dr. Madzima, Deputy Director of Vet. Services
Dr. Ushewokunze-Obatolu, Deputy Director of Vet. Services, R & D
Dr. Mavenyengwa, National Project Co-ordinator
Dr. Chitate, Principal Vet. Officer (Epidemiologist)
Dr. Madekurozwa, Principal Vet. Research Officer (Virologist)
Dr. Guta, Vet. Research Officer (Poultry Pathologist)
Mr. Christopher M. Ncube, Research Technician
Ms. Munyombwe, Senior Research Officer (Statistician)
Mr. James, Asst. Chief Veterinary Lab. Technologist
Dr. Mpofu, District Vet. Officer, Mutare, Manicaland
Mr. Nkomo, Veterinary Extension Assistance, Mutare, Manicaland
Dr. Mafara, District Vet. Officer, Rusape, Manicaland
Dr. Muusha, Provincial Vet. Officer, Mutare, Manicaland
Dr. Dzimwasha, Provincial Vet. Officer, Masvingo
Dr. Makwangudze, District Vet. Officer, Gutu, Masvingo
WORK-PLAN FOR THE FIELD TRIALS WITH ND-V4, I2 AND LA-SOTA STRAIN-BASED VACCINES
The following field trials have been designed to compare the efficacy of the different vaccines and vaccine delivery methods:
Trial group 1 (V4 strain-based vaccine)
Subgroup 1/1: vaccination by oral route with feed-based vaccine
Subgroup 1/2: unvaccinated control
Trial group 2 (I2 strain-based vaccine)
Subgroup 2/1: vaccination by eyedrop route
Subgroup 2/2: vaccination by oral route with feed-based vaccine
Subgroup 2/3: unvaccinated control
Trial group 3 (LaSota strain-based vaccine)
Subgroup 3/1: vaccination by eyedrop route
Subgroup 3/2: unvaccinated control
Trial group 4 (V4 or I2 strain-based vaccine)
Subgroup 4/1: vaccination by drinking water route
Subgroup 4/2: non-vaccinated control (NB.: 1/2 subgroup can serve as subgroup 4/2 if the trial site is in the proximity of trial group 1)
Trial sites
The selected households at the vaccination trial sites should be clustered into subgroups for the different vaccine delivery methods and for serving as non-vaccinated controls.
Trial group 1 (V4 strain-based vaccine): Marimo village, Goromonzi district, Mashonaland East Province
- feed-based vaccination: 38 households with a chicken population of 691, 109 birds sampled for serology
- non-vaccinated: to be selected and blood sampled during the fist week of June, 1998
Trial group 2 (I2 strain-based vaccine): Magaha, Nyariya and Haparari villages, Mutasa district, Manicaland province.
- feed-based vaccination: 24 households with 475 chicken population, 66 birds sampled for serology
- eye-drop vaccination: 18 households with 229 chicken population, 57 birds sampled for serology
- non-vaccinated: 22 households with 302 chicken population, 43 birds sampled for serology
Trial group 3 (LaSota strain-based vaccine): Chimombe village in Gutu district, Masvingo province.
- eye-drop vaccination: 30 households with 557 chicken population,109 birds sampled for serology
- non-vaccinated: 22 households with a population of 582 chickens,114 birds sampled for serology
Trial group 4 (V4 or I2 strain-based vaccine): trial site and number of participating households to be determined. Suggest to commence not later than 10 June 1998.
- drinking water vaccination: should be not less than 30 households
- non-vaccinated:
Vaccination Schedule
NB.: In order to complete the suggested field trials and obtain analysable data and results by the NTE of the Project, all trials should commence not later than the beginning of June 1998.
Subgroups receiving vaccine by eye-drop route
Vaccinate all available chicken by eye-drop route with the relevant vaccine on:
Day 0 (1st vaccination). Also bleed for sero-monitoring.
Day 30 (2nd vaccination).
Day 60 Bleed for sero-monitoring and purchase chicken for carrying out the buy-back challenge tests (including non-vaccinated subgroup). 20 birds should be challenged from each subgroup, 5 households/subgroup, 4 birds/household.
Day 90 (3rd vaccination)
Day 150 Bleed for sero-monitoring and purchase chicken for carrying out the buy back challenge tests (including non-vaccinated subgroup). 20 birds should be challenged from each subgroup, 5 households/subgroup, 4 birds/household.
Subgroups receiving vaccine on feed
Vaccinate all available chicken with feed-based vaccine administering the relevant vaccine on:
Day 0 (1st vaccination). Also bleed for sero-monitoring.
Day 30 (2nd vaccination).
Day 60 (3rd vaccination)
Day 90 (4th vaccination) Also bleed for sero-monitoring and purchase chicken for carrying out the buy-back challenge tests (including non-vaccinated subgroup). 20 birds should be challenged from each subgroup, 5 households/subgroup, 4 birds/household.
Day 120 (5th vaccination)
Day 150 (6th vaccination)
Day 170 Bleed for sero-monitoring and purchase chicken for carrying out the buy-back challenge tests (including non-vaccinated subgroups). 20 birds should be challenged from each subgroup, 5 households/subgroup, 4 birds/household.
Grain should be taken to the villages in separate containers of 1 kg (100 doses). Immediately before use, mix each 1 kg grain thoroughly with 100 ml vaccine containing not less than 106 EID50/ml. Ensure a nominal dose per chicken of >106 EID50. Therefore, a chicken dose of grain vaccine should be delivered as 10 g grain + 1.0 ml vaccine containing not less than 106 EID50 vaccine virus.
Subgroup receiving vaccine through drinking water
Vaccinate all available chicken by administering the relevant vaccine in the drinking water on:
Day 0 (1st vaccination). Also bleed for sero-monitoring.
Day 30 (2nd vaccination).
Day 60 Bleed for sero-monitoring and purchase chicken for carrying out the buy-back challenge tests (including non-vaccinated subgroup). 20 birds should be challenged from each subgroup, 5 households/subgroup, 4 birds/household.
Day 90 (3rd vaccination)
Day 150 Bleed for sero-monitoring and purchase chicken for carrying out the buy-back challenge tests (including non-vaccinated subgroups). 20 birds should be challenged from each subgroup, 5 households/subgroup, 4 birds/household.
Reconstitute the vaccine with sterile distilled water so as each ml of the vaccine shall contain not less than 106 EID50/ml. At each household, immediately before use, mix the required number of vaccine doses (1 ml of reconstituted vaccine = 1 dose) with the available clean drinking water and offer it to the chicken in a clean container which has been rinsed with clean water to ensure it does not contain detergent or any disinfecting agents. A chicken dose of drinking water vaccine should be delivered as 10 to 20 ml of drinking water mixed with 1.0 ml of vaccine containing not less than 106 EID50 vaccine virus.
NB.: Blood samples should be collected as indicated in the vaccine schedule from each household in each trial subgroup including the non-vaccinated subgroups at each time point of testing. 4 or 6 birds from different age groups should be sampled from each household. Two or three birds from the adult population and two or three birds from the young grower population.
