Infectious bronchitis virus and infectious bursal disease virus : a study performed at Universidad Nacional of Costa Rica

Abstract: Infectious Bronchitis and Infectious Bursal Disease, also called Gumboro Disease, are two important poultry diseases, causing serious illness in chickens and major production losses. In Costa Rica, as in many other developing countries, poultry production is an important industry and their products are important parts of every day food supply. During ten weeks the author was working at the laboratory of virology at Universidad Nacional in Costa Rica. Three viral isolates of Infectious Bronchitis Virus, IBV, were characterized by Restriction Fragment Length Polymorphism (RFLP), one isolate was found to be a Massachusetts strain and the two others a new Costa Rican variant the IBV-CR-53 strain. Sera from 182 wild birds, sampled between 2000 and 2002, were investigated for presence of antibodies to IBV using a blocking ELISA. Two pigeons of the species Zenaida asiatica were positive and two pigeons of the species Columba fasciata were suspected positive. Two commercial ELISA kits were compared and the results were similar. Seven samples from macerated bursas and cell cultures from suspected cases of Infectious Bursal Disease, IBD, were characterized using a antigen-capture ELISA and were shown to be classical strains of IBD virus. In virus neutralization test using chicken sera sampled at three, ten and 18 days of age it was shown that the neutralizing antibody titers were significantly lower against a wild type strain than against a vaccine strain and that the half-life of antibodies was 2.5 days rendering the chickens with little protection at 18 days of age. A Costa Rican chicken production plant was visited in order to view typical premises. The pens had open net walls and thus some problems with biosecurity. Blood samples sent to the laboratory for routine antibody control showed that in spite of vaccine strategies, protection against IBV was low at 44 days of age.