To determine the most prevalent biovar responsible for brucellosis in sheep and goat populations of Iran, a cross-sectional study was carried out over 2 years in six provinces selected based on geography and disease prevalence. Specimens obtained from referred aborted sheep and goat fetuses were cultured on Brucella selective media for microbiological isolation. Brucellae were isolated from 265 fetuses and examined for biovar identification using standard microbiological methods. Results showed that 246 isolates (92.8%) were B. melitensis biovar 1, 18 isolates (6.8%) were B. melitensis biovar 2, and, interestingly, one isolate (0.4%) obtained from Mazandaran province was B. abortus biovar 3. In this study, B. melitensis biovar 3 was isolated in none of the selected provinces, and all isolates from 3 provinces (i.e., Chehar-mahal Bakhtiari, Markazi, and Ilam) were identified only as B. melitensis biovar 1. In conclusion, we found that B. melitensis biovar 1 remains the most prevalent cause of small ruminant brucellosis in various provinces of Iran. 1. Introduction Brucellosis is a worldwide bacterial zoonosis posing hazards to the public health and causing economic losses for livestock production industry [1–3]. Animal brucellosis is mainly characterized by reproductive involvement resulting in abortion and infertility [2], whereas human brucellosis is a febrile illness known as undulant fever which can lead to chronic debilitating complications [3, 4]. The disease results from facultative intracellular bacteria belonging to the genus Brucella which are Gram-negative, nonspore-forming and noncapsulated coccobacilli [3, 5, 6]. Currently, the genus consists of 10 species classified based on their host preferences and phenotypic differences [2, 7]. Three species are also divided into biovars which are B. abortus, B. melitensis, and B. suis with 7, 3, and 5 biovars, respectively [3]. In sheep and goats, brucellosis is primarily due to B. melitensis which is the most pathogenic species for human beings, responsible for the main proportion of human cases in endemic regions including Mediterranean and Middle East countries [1, 3, 8–10]. Humans catch the disease via direct contact with infected animals, their vaginal discharges, and aborted fetuses; dealing with pure cultures; and consumption of unpasteurized contaminated milk and milk products [3, 6, 11]. The latter is the major way through which B. melitensis is transmitted to people in endemic areas [1, 5]. Identification of B. melitensis biovars involved in small ruminant brucellosis is a critical component
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