Molecular studies of brucellosis in selected wild animal species in Serengeti ecosystem, northern Tanzania

Masters Thesis

Brucellosis is a contagious bacterial zoonotic disease worldwide of public health and economic importance. The disease affects all species of livestock, wild animals and humans leading to severe economic losses in animals and permanent injury, disabling sequel and financial loss in humans. A cross-sectional study was carried out in Serengeti ecosystem between November 2017 and June 2018 to explore occurrence and magnitude of Brucella infection and circulating Brucella strains in wild animal species in Serengeti ecosystem, Northern Tanzania, using molecular techniques. The study also compared the effectiveness of different molecular techniques in detecting the Brucella strains in wild animals. The study used 189 whole blood, serum and amniotic fluid samples collected from seven different wild animal species. Wild animal species used were 46 buffaloes, 80 wildebeest, 25 zebra, 19 lions, 5 baboons, 10 impala and 4 hyenas. Most of the animals used in this study were female (96.3%), adults (99.5%) and those sampled from the Serengeti part of the ecosystem were 115 (60.3%). The tests used in the analysis were Multiplex polymerase chain reaction (AMOS PCR), Quantitative Real-Time PCR (RT-qPCR) and real-time speciation (RT-speciation) assay. The results indicated that out of 189 samples screened, DNA extracts from 12 (6.4%) and 24 (12.7%) were Brucella positive by AMOS PCR and RT-qPCR, respectively. The most affected wild animal species were lions (52.6%) and buffaloes (19.6%). A total of 16 (66.7%) out of 24 samples were confirmed as B. abortus. The other Brucella species identified were: B. suis (n=2; 8.3%), B. melitensis (n=2; 8.3%) and B. ovis (n=2; 8.3%). Two samples; one from buffalo and one from impala had three Brucella species each namely B. melitensis, B. suis and B. ovis. Overall comparison of the molecular tests showed better agreement and diagnostic performance with the real-time PCR techniques compared to the conventional AMOS PCR. The sensitivity of the AMOS PCR and RT-qPCR as compared to the real-time speciation assay was 16.7% and 72.7% respectively, while the specificity was found to be 92% and 100% respectively. The detection of different strains of B. abortus, B. suis, B. melitensis and B. ovis in wild animals of Serengeti ecosystem implies that domestic animals and humans in the interface areas are at risk of acquiring the infection. The RT-qPCR is more superior in screening of Brucella than AMOS PCR. One health approach collaboration is important to establish the methods of brucellosis management in wild animals.

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