Seroprevalence of Brucella suis in eastern Latvian wild boars (Sus scrofa)

Brucellosis due to Brucella suis biovar 2 is one of the most important endemic diseases in wild boar (Sus scrofa) populations in Europe. The aim of the present study was to determine the seroprevalence of brucellosis in wild boars in the eastern part of Latvia. Wild boars killed by hunters in the period from January to April 2015 (n = 877) and from March to April in 2016 (n = 167) were examined for antibodies against B. suis by the Rose Bengal test (RBT), a complement fixation test (CFT), and by enzyme-linked immunosorbent assays. In 2015, 199 samples (22.7%) were positive by RBT and/or CFT while 36 samples (21.6%) were seropositive in 2016. Of the Brucella seropositive samples from 2015 and 2016 (n = 235), 162 (68.9%) were also seropositive to Yersinia enterocolitica. Considering cross-reactivity of serological tests, the seroprevalence of B. suis biovar 2 exposure in wild boars in the eastern part of Latvia was calculated to 14.0% in 2015 and 9.6% in 2016. From selected seropositive samples (42 in 2015 and 36 in 2016) total DNA was extracted and analyzed with an IS711-based nested polymerase chain reaction (PCR) assay. Species and biovar identification was conducted for bacteria isolated in monoculture from PCR positive samples by species specific primers and Bruce-ladder multiplex PCR. Brucella suis biovar 2 was isolated from 12/20 samples in 2015 and 9/9 samples in 2016. The average seroprevalence was relatively low compared to that found in certain other European countries. Males and females had an equal level of seropositivity, but a positive age-trend was observed for both males and females.