Investigation of small ruminant brucellosis among smallholder farms: The missing link in control programmes of endemic areas.

Brucellosis is a neglected zoonotic infection with a worldwide distribution and high levels of endemism in some regions, including the Middle East. In Iran, sheep and goats constitute a major part of the livestock population, often kept by small-scale farmers for their own consumption and economic purposes. This investigation aimed at characterizing the Brucella spp. and biovars circulating in sheep and goats under smallholder farming and their potential spillover across farms. For this purpose, from two randomly selected pastoral districts of Alborz and Fars provinces in Iran, a total of 54 aborted foetuses (38 from sheep and 16 from goats) and 528 blood samples were collected from sheep (n = 435), goats (n = 77), farmers (n = 11) and dogs (n = 5). Then, serological, bacteriological and molecular characterization of Brucella isolates was performed using standard methods. Our results showed the high seroprevalence of brucellosis in pastoral districts of Fars and Alborz provinces reaching 16.3%, 11.7% and 12.7% by using the Rose Bengal plate test (RBPT), serum agglutination test (SAT) and indirect enzyme-linked immunosorbent assay (iELISA) test, respectively. Furthermore, the results of bacterial culture, conventional biotyping and PCR analyses showed the presence of Brucella melitensis biovar 1 and 2 infections among goat, farmers and dog of the Alborz farms and B. melitensis biovars 1, 2 and 3 among sheep of the Fars farms. Among nine seropositive farmer and dog blood samples (four farmers and five dogs), only three (two farmers and one dog) were positive in both culture and PCR tests. These results stress the need to strengthen screening and control measures in small flocks of small ruminants in Iran that could be the starting point of new outbreaks at the livestock/human interface. The present study also suggests that infected dogs may further maintain the risk of exposure to Brucella pathogens in small farms and beyond.