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Serological and Bacteriological Survey of Brucellosis in Wild Boar in Belgium

25 July 2012, at 12:00am

More than half of the wild boar tested in Belgium were positive for brucellosis and seroprevalences appear to be increasing, which represents a growing risk to outdoor pig farms, according to new research from Liège.

Brucellosis is frequently reported among wild boar populations in Europe, according to a paper published recently in BMC Veterinary Research. Fabien Grégoire of the University of Liège and co-authors there and at the Veterinary and Agrochemical Research Centre (VAR-CODA-CERVA) in Brussels explain that the aim of their study was to assess the epidemiological situation in Belgium, regarding the steady increase of wild boar populations over the last decades.

Several serological tests were used and compared with culture and IS711 polymerase chain reaction (PCR) to determine the most suitable combination of diagnostic tools for conducting a successful prevalence study in wildlife.

An indirect enzyme-linked immunosorbent assay (iELISA) was used on 1,168 sera from hunter-killed wild boar sampled between 2003 and 2007 in four natural regions of southern Belgium.

Results gave an apparent prevalence of 54.88 per cent (95 per cent CI: 52.03-57.73).

Prevalence was significantly affected by age and by the year of study but not by sex nor by the region of sampling.

The relative sensitivities of the complement fixation test (CFT), the Rose Bengal test (RBT), and the slow agglutination test (SAT) versus the iELISA differed widely between tests, reaching 62.67 per cent, 46.68 per cent and 34.77 per cent, respectively. The relative specificities of the CFT, RBT and SAT versus the iELISA were respectively 99.01 per cent, 92.49 per cent and 99.1 per cent. From seropositive animals (iELISA), nine per cent were positive by culture and 24 per cent by PCR when testing spleen and/or tonsils. Sensitivity of the PCR was higher on tonsils than on spleen. All bacterial isolates were identified as Brucella suis biovar 2.

Grégoire and co-authors concluded that their results confirm brucellosis to be widespread among wild boar in southern Belgium, with seroprevalence having increased over 10 years, and constitutes a growing risk of spill-back to outdoor-farmed pig herds. The iELISA showed a better sensitivity than the CFT, RBT and SAT. Serological tests must be associated with direct diagnosis and PCR proved more sensitive than culture under wildlife sampling conditions.

The Belgian group added that spleen and tonsils are lymphoid tissues usually sampled in multi-disease monitoring programmes. They remain top-grade organs for direct diagnosis of brucellosis, with a preference for tonsils.

Reference

Grégoire F., B. Mousset, D. Hanrez, C. Michaux, K. Walravens and A. Linden. 2012. A serological and bacteriological survey of brucellosis in wild boar (Sus scrofa) in Belgium. BMC Veterinary Research, 8:80. doi:10.1186/1746-6148-8-80



Further Reading

You can view the full report (as a provisional PDF) by clicking here. You can find out more about brucellosis by clicking here.


July 2012