Epidemiology of bovine tuberculosis and brucellosis on the periphery of Abeche, Chad

Abstract

This study was carried out to specify the epidemiology of bovine tuberculosis and brucellosis in the dairy basin of Abeche (district of Ouaddai, Eastern Chad). The populations studied for tuberculosis and brucellosis comprised over oneyear- old animals and over one-year-old females only, respectively. The sample was selected with a two-degree survey (village then breeder). The diagnosis of tuberculosis was established by the single intradermal tuberculin test (SIT), followed by the intradermal comparative tuberculin test (ICTT), and that of brucellosis by a serological analysis [the rose bengal test (RBT), followed by the complement fixation test (CFT)]. A questionnaire was systematically filled out to characterize the type of husbandry, and the case history of selected animals was recorded. These factors were included in a multivariate analysis. A total of 848 animals located in 58 herds were tested by SIT, then 151 of them by ICTT. In the studied populations real prevalences of Mycobacterium bovis and M. avium infections were estimated at 0.8 ± 0.6% and 2.0 ± 0.9% (α = 5%), respectively. Herd prevalences of M. bovis and M. avium infections were estimated at 12.4 ± 8.5% and 17.8 ± 9.8%, respectively. With regard to brucellosis, 634 animals located in 56 herds were tested by RBT, and 35 samples from 21 herds by CFT. Brucellosis real prevalence was estimated at 2.6 ± 1.2% (α = 5%) and herd prevalence at 20.0 ± 10.5%. The main risk factors identified for bovine tuberculosis were an older age, the origin of the animal (birth outside of the herd) and the presence of animals from other breeders left in the care of the herd-person. The main risk factors identified for avian tuberculosis were the number of birds and the attendant type (breeder’s children). The main risk factors identified for brucellosis were the ethnic group (Arab) and the attendant type (breeder’s children). Bovine tuberculosis and brucellosis seem to develop slowly within many herds, but the conditions of extensive husbandry limit their spread to the boundaries of the contaminated herd. Given this epidemiologic profile, these diseases might be eradicated on condition that animals undergo a control before being introduced into a disease-free herd. Should dairy production develop in Abeche suburbs, this approach could be adopted.