Abstract
BackgroundBrucellosis is a disease of worldwide public health and economic importance. Successful control is based on knowledge of epidemiology and strains present in an area. In developing countries, most investigations are based on serological assays. This study aimed at investigating a dairy herd experiencing abortions in order to establish within-herd seroprevalence to Brucella spp., identify, characterize Brucella strains by Multiple Loci Variable Number of Tandem Repeats Analysis (MLVA-VNTR) and investigate possible spillover to other species.ResultsThe within-herd seroprevalence in cattle (n = 200) was 48 % (95 % CI 41–55), using an indirect ELISA, while the Rose Bengal Test (RBT) yielded lower prevalence (21.5 %; 95 % CI 16–27). Two sheep (n = 35) and one goat (n = 50) were seropositive using ELISA while none of the dogs (n = 6) was positive with the RBT. Three Brucella were isolated from an aborted fetus and associated membranes. Real time PCR (IS711), Bruce-ladder and classical biotyping classified the isolates as B. abortus biovar 3. MLVA-VNTR revealed two different but closely related genotypes. The isolates showed unique profiles, providing the first genotypic data from Tanzania. These genotypes were not related to B. abortus biovar 3 reference strain Tulya originally isolated from a human patient in Uganda in 1958, unlike the genotypes isolated and characterized recently in Kenya. High within-herd prevalence, isolation of the pathogen and abortion confirm that B. abortus is circulating in this herd with cattle as reservoir hosts. A low seroprevalence in sheep and goats suggests a spillover of B. abortus from cattle to small ruminants in the herd.ConclusionsThis is the first isolation and characterization of B. abortus biovar 3 from a dairy cow with abortion in Tanzania. The origin of the Tanzanian genotypes remain elusive, although they seem to be related to genotypes found in Europe, Turkey and China but not related to B. abortus biovar 3 reference strain or genotypes from Kenya. Importantly, replacement heifers are commonly sourced from large farms like this to smallholder farmers, which poses risk of spread of bacteria to other herds. B. abortus is a significant zoonotic risk and animal health problem in this production system, therefore further studies on humans is recommended.
Highlights
Brucellosis is a disease of worldwide public health and economic importance
Serological findings Ninety six out of 200 serum samples from cattle were positive in ELISA giving a within-herd prevalence of 48 %, while 43 of the 200 serum samples were positive with Rose Bengal Test (RBT) resulting into within-herd prevalence of 21.5 %
All sheep goat and dog sera were negative in RBT
Summary
Brucellosis is a disease of worldwide public health and economic importance. Successful control is based on knowledge of epidemiology and strains present in an area. Brucellosis is a zoonotic disease of high economic and public health importance worldwide [1,2,3] It is caused by Brucella spp. and manifests itself as abortion and infertility in domestic and wild animal species and reduced milk production in cattle. Brucellosis in humans is almost always associated with infected domestic and wild animals or their products and poses more risk to farmers, animal handlers, abattoir workers and veterinarians [9]. It causes a debilitating disease with unspecific symptoms comparable to other febrile conditions such as malaria, which may be chronically disabling.
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