| seroprevalence of infectious bursal disease in non-vaccinated indigenous and exotic chickens on selected farms around gaborone, botswana. | sera from nine out of 30 (30.0%) apparently healthy unvaccinated indigenous (tswana) chickens had precipitating antibodies to infectious bursal disease (ibd) virus using the agar gel precipitation test. similarly, sera from 11 out of 49 (22.4%) chickens of exotic breeds with no history of vaccination against ibd were positive for antibodies against the virus. | 1999 | 10486831 |