| Livestock Research for Rural Development 18 (5) 2006 | Guidelines to authors | LRRD News | Citation of this paper |
Village chickens in Kaduna State, Nigeria were vaccinated once with a Malaysian heat-resistant Newcastle disease vaccine (NDV4HR) given in feed. In all, 1605 chicken in 223 households covering 33 villages and 13 Local Government Areas were tagged and bled before vaccination and two weeks after vaccination. Antibodies to Newcastle disease virus were titrated by haemagglutination inhibition test and titres > 3 (log2) were assumed to be protective. Presumed protective titres were recorded in 143 (8.91%) of chickens before vaccination and in 957 (65.5%) after vaccination.
Recommendation is made for the widespread adoption of this technology.
Keywords: Antibody response, Newcastle disease vaccine, thermostability, vaccination, village chicken.
Newcastle disease (ND) is reported as the most important viral disease of poultry in the world including developing countries (Nawathe et al 1975; Adu et al 1986; Adene 1990; Spradbrow 1997). It has a devastating effect on commercial as well as village poultry industries (Philips 1973; Nawathe et al 1975; Nawathe 1988; Okeke and Lamorde 1988; Shamaki et al 1989; Adene 1997). The resource derivable from the chickens cannot be fully utilized unless the disease is controlled particularly in the village poultry flocks that are believed to keep the virus in circulation and act as reservoirs and carriers to themselves and the more susceptible exotic breeds in commercial farms (Nawathe et al 1975; Ezeokoil et al 1984; Gomwalk et al 1985; Adu et al 1986; Nwosu and Okeke 1989; Olabode et al 1992).
Vaccination has been reported as the only safeguard against endemic ND (Orajaka et al 1999; Usman 2002). The village chickens, in multi - age flocks scattered in small numbersover villages, are difficult to catch for formal vaccination as adopted in commercial chicken enterprises (Aini et al 1990; Orajaka et al 1999; Usman 2002). It therefore takes great effort and time trying to vaccinate them. More importantly, these conventional vaccines are not heat-stable and therefore require complex cold-chains to link the vaccine producers and users (Aini et al 1990; Usman 2002).
Preliminary work conducted elsewhere indicates that heat-stable avirulent V4 or 12 strains selected for heat resistance and applied through eye drop, drinking water or food and feed particles has been found to be a suitable oral vaccine for village chickens (Saglid and Spalatin 1982; Spradbrow 1988; Spradbrow 1992; Bell et al 1995; Tu et al 1998). This V4 or 12 vaccine has been successfully used in many African countries such as The Gambia (Jarra et al 1991), Cameroon (Bell et al 1995). Ghana (Amakye-Anim et al 1998) and many countries of South -East Asia (Copland 1987). Maize byproducts after processing have been found to be good carriers for V4 in the vaccination of birds against ND in Nigeria (Olabode 1996).
In Malaysia, a 60% protected rate was recorded on challenge of village chickens with the virulent NDV strain and farmers in Malaysia have benefited from the oral food vaccination of their flocks with NDV4HR (Aini et al 1990). It therefore became necessary to assess the immunological status of Nigerian village chickens and to conduct field trails with this newly developed vaccine for the purpose of determining its suitability as a rural poultry vaccine in Kaduna State, Nigeria. In view of the economic importance of ND in Nigerian village chickens, indications are that local poultry farmers would welcome ND vaccinations capable of protecting their flocks. The objective of this study was to investigate the sero-prevalence antibody status of ND in Nigerian local chickens and to conduct field vaccination trails with NDV4HR in village chicken flocks in Kaduna State, Nigeria. The outcome of the results obtained would form the basis for recommendations on whether the new vaccination technology will be adopted in Kaduna State, Nigeria.
The study covered thirteen (13) Local Government Areas of Kaduna State located within the semi-arid and sub-humid zones of North Central Zone of Nigeria. Kaduna State is situated between 80 45' and 11030' N and 60 10' and 90E. The mean annual temperature is about 340C with the hottest months being from March -April (400C) and the coldest period (13.20C) is between December and January during the severe harmattan (cold). Rainfall varies between 1,000mm and 1,500mm and the rainy season lasts for 150-200 days (Mid April-end of October). The dry season occurs from late October to early April (RIM 1993).
The analysis was carried out based on survey data from 33 villages in 13 of the 23 Local Government Areas of Kaduna State. Chickens were listed for sampling based on the areas with high concentration of village chickens and presence of the United Nations Development Programme (UNDP) activities on agriculture.
The selection of the households within the study area was done using stratified and systematic random sampling techniques. The survey covered a total of 223 households and 1605 village chickens. Village poultry households were listed for selection in this study using the method described below. In each village, a meeting was held with the village head, one representative of farmer association, one representative of women group and a community animal health worker/extension officer to list the households in each village to be considered for selection and sampling. In each household all the village chickens were vaccinated with the thermostable (V4) Newcastle disease vaccine mixed in feed. At least half of the population of the village chickens per household were bled pre and post vaccination.
Structured questionnaires for household interview were used to collect information from the household members. The interviews were conducted in the local languages (Hausa and Fulfude) at household premises. The household -members were meant to understand the purpose of the study in order to provide reliable information to the interviewers. In many cases, both husband and wife were at the interviews, so that they could complement each other to give detailed information in respect of the history of Newcastle disease outbreak and vaccination records in their village chicken flocks. Also information on the number of village chickens per household sampled was generated. The questionnaire was able to assess the basic information supplied at the household level in line with the objectives of the study.
In order to assist in data collection, four assistants were selected locally and trained in each area for the purpose of data collection, vaccination of chicken and blood sampling.
These assistants were selected locally because they understand the culture and languages of the villagers and could also in some cases collect the data during the day or in the evening depending on when farmers are available. Households were given feeds and poultry vitamin drugs as incentives. The authors, livestock/poultry extension officers of the State and local governments and the trained assistants from the local areas of the study carried out the actual surveys.
The NDV4HR used for the field trials is a freeze-dried live thermostable strain vaccine imported from Malaysian Vaccine and Pharmaceutical SND, BHD. Each vial of the vaccine contains 100 bird doses. It is a lentogenic live virus selected for its heat resistance. The vaccine dose per bird was 106.0 EID EID50 (50% embryo infective doses).
Vials of the NDV4HR were reconstituted in the feed as recommended by the manufacturer and administered to the birds. The chick mash used was obtained from Sanders Feeds (SEEPC Nigeria Limited), Kaduna Depot, Nigeria. The chick mash contained 5.00% crude fibre and 2700 kilocalorie per kg metabolisable energy. The required dose per flock in each household was calculated based on the recommendation of 10g of the feed per bird (Aini et al 1990). In the calculated amount of feed was added an equivalent amount of diluent (well water), 10ml of well water containing 106.0 EID50 of vaccine per 10g of feed. The moist mixture was then put in a clean feeding trough under a shade for the birds to consume. All the chickens in the flock selected were vaccinated. About 50% or more of the chickens in each vaccinated flock were caught and wing -tagged. A total of 1,605 wing -tagged village chickens were bled before and after vaccination. Both pre and post vaccination sera were tested for NDV heamagglutination inhibition (HI) antibodies.
The antigen was prepared from NDV-LaSota vaccine obtained from the National Veterinary Research Institute, Kaduna Field Station. The 200 dose vial of the NDV-LaSota vaccine was reconstituted in 8ml of distilled water. The haemagglutination (HA) titre was determined as described by Beard (1980) and diluted to contain 4HA units for use in the HI test as described by Allan and Gough (1974).
Numbers of birds with detectable NDV antibody titres were calculated. Sera with HI titres > 3 (log2) were considered positive or protective based on the reports of Allan and Gough (1974) and Aini et al (1990). Chi-square was used to determine the relationship between the number of village chickens that had antibody titre > 3 (log2) pre and post vaccination periods.
Out of a total of 1,605 village chickens screened for NDV antibody, 143 (8.91%) had antibody titre > 3 (log2) pre vaccination, only 135 (8.41%) had protective titre > 3 (log2) post vaccination. Very few proportion (5.59%) of the birds that tested positive before vaccination tested negative after vaccination.
About 65.5% (95%CI = 63.02% <P<67.88%) of the birds that had antibody titre < 3 (log2) before vaccination were converted to higher HI titre > 3 (log2) post vaccination as indicated in the table. Presumed protective titre were recorded in 1092 (68.0%) of birds post vaccination as in table 1. There was a statistically significant difference in the frequency of protective titre pre vaccination and post vaccination (X2 = 48.9, 1df, P< 0.001).
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Table 1. Number of birds with protective antibody titres to ND pre and post vaccination |
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|
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Post vaccination |
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Prevaccination |
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Titre > 23 |
Titre < 23 |
Total |
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Titre > 23 |
135 (94.4%) |
8 (5.59%) |
143 (100%) |
|
|
Titre < 23 |
957 (65.5%) |
505 (34.5%) |
1462 (100%) |
|
|
Total |
1092 (68.0%) |
513 (32.0%) |
1605 (100%) |
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HI Titre > 23 were considered protective |
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In this study, the HI titre >3 (log2) were considered positive (protective) based on the findings of Allan and Gough (1974) and Bell et al (1991a) who reported that birds with HI titres >3 (log2) were protective against challenge with a virulent strain of ND virus. The protective antibody titres >3 (log2) recorded in 143 (8.91%) out of 1605 village chickens screened for HI antibody before vaccination suggested previous exposure of the birds to field strains of ND virus (velogenic). This is in agreement with the report of Alexander (1998) who showed that in all paramyxoviruses, birds that have not been immunized or infected usually have HI titres >3 (log2) and that non-specific titres above this levels are rare in avian species. Also farmers and veterinary staff interviewed reported that no ND vaccination had been conducted in these villages and their respective neighbourhoods during the past 12 months prior to the study. Reports of ND outbreaks in the monthly returns from the Local Government Veterinary Officers, Ezeokoli et al (1984) and personal communications with the farmers confirmed ND as a widespread problem in the study area. It was also observed that a small proportion (5.59%) of the birds that were protected pre vaccination, tested negative post vaccination. This observation contrasts with the previous findings of Bell et al (1991b) who found that positive breeders (naturally exposed) responded serologically and that the number of birds with titres >3 (log2) increased significantly following vaccination. In addition, about 65.5% of the birds that had antibody titre <3 (l og2) before vaccination were converted to protective level >3 (log2) post vaccination. The statistically significant difference in the frequency of protective titre pre vaccination and post vaccination signifies that the vaccine, NDV4HR, is immunogenic and capable of provoking antibody response (Aini et al 1990).
Recommending the use of NDV4HR vaccine to Nigerian rural farmers requires that the local conditions, protective ability of the vaccine and ease of administration are taken into consideration. In Kaduna State of Nigeria, where rural poultry farming is predominant, many farmers are yet to be convinced of the benefits of ND vaccination. Achieving good level of protection with the use of NDV4HR in vaccination of chicken will stimulate the interest of rural farmers in adopting the new vaccine technology.
The use of NDV4HR in a single oral vaccination of village chickens in this study, has achieved a 65.5% protection. Therefore, subsequent application of more doses of the vaccine at intervals to be determined by further research may result in the development of a higher protection in a greater proportion of chickens and subsequent reduction in the outbreaks of ND.
Controlling ND in the endemic rural areas of Nigeria through the use of NDV4HR will subsequently control the spread of the ND virus in the neighouring countries such as Cameroun, Tchad, Niger and Benin Republic.
We are grateful to Prof (Dr) Aini Ideris of the Faculty of Veterinary and Animal Science, Univerisiti Pertanian, Malaysia, Prof (Dr.) Abd Latif Ibrahim of the National Biotechnology Directorate, Ministry of Science, Technology and Environment, Malaysia, Dr Roshidah Ismail and Dr Mazian Mohammad of Malaysian Vaccines and pharmaceuticals SDN, BHD, Malaysia for their efforts in making the vaccine, NDV4HR available to us at no cost. We also acknowledge the cooperation of Mrs J.C. Atawodi, laboratory technologist, Department of Veterinary Public Health and Preventive Medicine, Ahmadu Bello University, Zaria, Nigeria.
Other people worthy of note for their contributions include Dr Y. B. Audi, Director of Veterinary Services, Kaduna State, Nigeria and Mr J.A. Alabi of the Federal Department of Livestock and Pest Control Services, Kaduna, Nigeria.
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Received 7 November 2005; Accepted 9 January 2006; Published 11 May 2006