VETERINARY MEDICINE

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Browsing VETERINARY MEDICINE by Author "ABDU, PAUL AYUBA"

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    STUDIES ON THE PROFILE AND RELATIONSHIP OF MATERNAL AND VACCINAL ANTIBODIES IN THE PREVENTION OF INFECTIOUS BURSAL DISEASE IN CHICKENS
    (1985-11) ABDU, PAUL AYUBA
    The presence of infectious bursal disease virus maternal antibody in broiler chicks was checked every other day from day-old for 29 days and its decay pattern determined. Maternal antibody was found in the chicks sampled and its decay pattern linear. It was present in all the chicks sampled at day-old but absent in all the chicks sampled at 19 days old. These findings suggest that vaccinating these chicks against infectious bursal disease at day-old would be ineffective since maternal antibody has been shown to interfere with vaccination and that if these chicks were exposed to infectious bursal disease virus at day-old they would be protected. On the other hand, all the chicks would be expected to be susceptible at 19 days old. Different sets of chicks similar to those used above were each vaccinated with infectious bursal disease vaccine at weekly intervals from day-old for 29 days. The presence of active infectious bursal disease virus antibody was determined at three, seven, 14 and 35 days post-vaccination. It was detected at 35 days post-vaccination in chicks vaccinated at one, eight or 15 days old and at 14 and seven days post-vaccination in chicks vaccinated at 22 or 29 days old respectively. The prompt immune antibody response observed in chicks vaccinated at 22 or 29 days old than in. chicks vaccinated at one, eight or 15 days old was possibly due to the absence of maternal antibody in the chicks vaccinated at 22 or 29 days old since maternal antibody level decreases with age and is usually absent by the time a chick is three or four weeks old. Chicks similar to those used in the vaccination trials above were challenged with a virulent field infectious bursal disease virus at weekly intervals from day-old for 29 days. Chicks challenged at eight, 15, 22 or 29 days old were susceptible based on bursal atrophy, bursal lesions and presence of infectious bursal disease virus precipitin antigen in the bursa of Fabricius. However, only 40 and 90% of the chicks challenged, at eight or 15 days old respectively were susceptible while all the chicks challenged at 22 or 29 days old were susceptible. Only the chicks challenged at 29 days old showed clinical signs. The results suggest that the initial level of maternal antibody at day-old in the chicks challenged at 22 or 29 days old was not high enough to have lasted 22 or 29 days and that chicks as young as eight days old could be infected with infectious bursal disea virus without showing clinical signs. In the field this is possible because infectious bursal disease is enzootic in Nigeria. Chicks exposed this early may be permanently immune-suppressed. In conclusion, it is recommended that maternallyimmune chicks be vaccinated against infectious bursal disease at seven and 21 days of age and the chances of exposure to field infectious bursal disease virus be minimized by good management and hygienic practices.