Brucella suis in feral pigs in Australia: what is the risk?

Abstract

In Australia, feral pigs (Sus scrofa) are the primary host for Brucella suis. The incidence of B. suis brucellosis in dogs in Queensland (QLD) and New South Wales (NSW) has increased, likely due to hunting and consumption of feral pig meat. This study aimed to update estimates of B. suis seroprevalence and spatial distribution in feral pigs and assess the risk of transmission to dogs. Serology results from 686 feral pigs in QLD and NSW were analysed, with seroprevalence correlated to pig population density. Serology results from 3074 dogs in QLD and NSW were mapped to local government areas (LGAs) and compared with pig density. Raw feral pig meat sold for pet consumption was tested for B. suis. Thirty-seven feral pigs were seropositive, with a survey adjusted true seroprevalence of 17% (95% confidence interval [CI] 12% to 22%) in QLD and 11% (95% CI 8% to 14%) in NSW. No positive spatial autocorrelation between positive and negative pigs was identified. Six hundred dogs from 26 QLD LGAs and 37 NSW LGAs were seropositive, showing a positive association with pig density. Brucella suis DNA was detected in commercially sold feral pig meat. This study found an increased prevalence and geographical expansion of infected pig populations potentially increasing the risk for B. suis transmission. The wide distribution and high level of detection in at-risk dogs highlight the links to pig hunting. Investigating human and dog cases could help identify infected pig populations, enabling hunters to reduce contact with infected pigs in those areas.