Epidemiological and molecular characterization of Brucella species in cattle

Abstract

Background: Bovine brucellosis is a severe threat to livestock and mankind as it is a food-borne and occupational zoonosis. Rapid transmission, high morbidity and mortality are the main features of zoonotic diseases, leading to great personal and economic losses within a short period of time. Therefore, this study aimed for prompt identification and characterization of Brucella species in livestock to control the spread of infection and epidemiological data for the planning of disease control strategies is required. Methodology: Five hundred milk and blood samples were collected from cattle from different regions of Karnataka. All milk and blood samples were examined by Milk Ring Test (MRT) and Rose Bengal Test (RBT) to detect Brucella antibodies, polymerase chain reaction to detect Brucella specific DNA. Low-stringency Single Specific Primer Polymerase Chain Reaction (LSSP-PCR) gene signatures and Single-Strand Chain Polymorphism Polymerase Chain Reaction (SSCP-PCR) were used to study polymorphic variations of Brucella species. Results: Amongst a total of 500 blood and 500 milk samples, 4.6% prevalence of brucellosis was found in Karnataka. The PCR assay was affirmative with the Rose Bengal Test (RBT) (4.6%) and Milk Ring Test (MRT) which yielded (3.4%) lower prevalence. The positive samples were confirmed as Brucella abortus by Bruce-ladder multiplex PCR. The LSSP-PCR, SSCP-PCR gene signatures showed high genetic similarity and intraspecific similarity which are reproducible. Conclusion: Symptoms of brucellosis are not pathognomonic, diagnosis rely mostly on the laboratory tests. Hence, the SSCP-PCR, LSSP-PCR gene signatures can be used as an alternative for detection of brucellosis, screening a large number of clinical samples and identify epidemiological diversity. It also minimizes the drawback of cross-reactivity and only suspected mutants can be sequenced.