SOME EPIDEMIOLOGICAL ASPECTS AND ECONOMIC IMPACT OF MAREK’S DISEASE IN SOME PARTS OF NIGERIA
SOME EPIDEMIOLOGICAL ASPECTS AND ECONOMIC IMPACT OF MAREK’S DISEASE IN SOME PARTS OF NIGERIA
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Date
2014-02
Authors
WANDER, LUKA DABA
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Abstract
ABSTRACT
There has recently been an increase in reports of Marek’s disease (MD) in commercial chickens in Nigeria. A retrospective study carried out gave 60.6% overall prevalence for MD (p< 0.05) from 2000-2009 out of viral cases in selected towns in Nigeria. Chickens older than 17 weeks had the highest prevalence of 85.5% (p <0.0001). MD prevalence in wet and dry seasons were 63.6% and 55.4%, respectively (OR 1.4 p < 0.0003). Questionnaire on MD was carried out at Awka involving 360 veterinary surgeons with retrieval rate of 45.28 % (163/360) to test their knowledge on MD. Seventy five per cent veterinarians put frequency of MD occurrence compared to other diseases between 5-10% and 25% put it at 20-30%. Mortality due to MD was 10-50%; drop in egg production between 10-40%. Paralysis (64%) ranked the highest sign followed by emaciation (47%) as the most common signs of MD. Liver (71%) and spleen (47%) were the most affected organs. Nodular lymphomas (60%) and diffused enlargement (39%) were the common lesions seen. Herpes turkey virus (HVT) vaccine (39%) was regularly administered. 68% of veterinarians diagnosed MD based on signs and gross lesions, while 12% on signs, gross and microscopic lesions. A questionnaire on MD was administered to 200 poultry famers across Nigeria to test their knowledge. Seventy nine per cent of the poultry farmers were aware of MD and 87.9% vaccinated against it. Intensively managed flocks experienced MD most (OR 29.6, p < 0.0001). Eighty five per cent of the farmers reported MD outbreak from chicks obtained from the same source. Farms rearing chicks of different ages with adults suffered MD more (OR 8.2, p< 0.0009). For a five year seroprevalence for MD in poultry in northern part of Nigeria was conducted
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from 2005-2009. A total of 2,452 sera were evaluated using agar gel precipitation test and MD prevalence was 65.95% (p < 0.0001). Prevalence by bird type was 88.4% for layers, 65.8% pullets, and 29.8% cockerels. The overall MD antibody prevalence in 151 avian species using indirect enzyme linked immunosorbent assay was 62.91% with 68.52% in vaccinated commercial chickens, 76.47% in indigenous unvaccinated chickens, 41.67% in turkeys, 25% in quails while ducks tested negative. Marek’s disease virus (MDV) antigens were detected in different organs (lungs, liver, kidneys, spleen and skin) of avian species using polymerase chain reaction. Prospective study was carried out to compare gross and microscopic lesions of MDV in experimentally challenged chickens with field outbreaks. Neoplastic lymphomas in most organs were either nodular, diffused or a mixture. The most affected organs were the liver and spleen. Histopathological findings of the field and MDV experimentally challenged chickens were comparable. Financial analysis of 31 farms with MD outbreak showed an average loss per bird to be N9, 120.61 ± 268.64, egg production loss per farm was N15, 114,465.63 and total loss of 31 farms was N95, 811,486:00 ($766,491:89USD). The cost benefit analysis showed that, for every N1 invested, a farmer was losing 27 kobo due to MD, while for the farms not experiencing MD, for every N1 invested, a farmer made a return of N5.00. Marek’s disease was high and more prevalent in both immature and mature chickens (71.4-85.5%). Turkey herpes virus was the most common vaccine used. Occurrence of MD compared to other poultry diseases was 20%. Estimated reduction in eggs production due to MD was up to 40%. Marek’s disease occurred more frequently in intensively managed farms and birds of different ages. Neoplastic lymphoprolipheration was observed in both organs of naturally
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affected or experimentally infected chickens with MD. Marek’s disease viral antigen was detected in organs of birds that suffered from the disease. Marek’s disease was found to cause significant financial losses to the poultry industry in Nigeria. The financial implication for farmers whose flocks suffered MD outbreaks showed that they were running at a loss. Farmers should routinely vaccinate chicks with highly potent MD vaccines. Veterinarians need more knowledge on MD. Farmers should minimize the number of flocks with different ages in the same farm. Commercial poultry should not to be raised with indigenous chickens and be prevented from contact with quails and cattle egrets. All stakeholders should cooperate in the control of MD in Nigeria.
Description
A DISSERTATION SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD OF THE DEGREE OF DOCTOR OF PHILOSOPHY IN VETERINARY MEDICINE
DEPARTMENT OF VETERINARY MEDICINE, FACULTY OF VETERINARY MEDICINE, AHMADU BELLO UNIVERSITY ZARIA, NIGERIA
FEBRUARY 2014
Keywords
EPIDEMIOLOGICAL,, ECONOMIC IMPAC,T, ECONOMIC IMPACT,, NIGERIA.