Risk of exposure to Coxiella burnetii from ruminant livestock exhibited at Iowa agricultural fairs.

Abstract

Coxiella burnetii is a zoonotic pathogen typically associated with clinical and asymptomatic infection in ruminant livestock. A re-emerging pathogen of significant public health importance, C.burnetii has caused recent epidemics in the United States and Europe, and public livestock exhibitions are increasingly scrutinized as a potential source of C.burnetii exposure. Although C.burnetii prevalence data among North American domestic ruminants are extremely limited, contemporary studies suggest that this pathogen is both geographically widespread and highly prevalent on a herd basis, especially in dairy cattle and goat populations. We utilized a real-time PCR assay to detect C.burnetii faecal shedding by clinically normal, non-periparturient beef cattle, meat goats and sheep exhibited at Iowa agricultural fairs. Individual faecal samples were collected from beef cattle, meat goats and sheep exhibited at twelve Iowa county fairs during the summer of 2009. The sample pool was blocked by species and fair, and ten samples from each block were randomly selected for the diagnostic assay; this test pool is considered sufficient to identify with 95% confidence a shedding animal in a population prevalence of 2.85% (cattle and sheep) and 6.25% (goats). Detection of C.burnetii DNA was determined through use of a real-time PCR assay validated for use in bovine, ovine and caprine faeces; threshold of detection is one DNA copy per PCR (sensitivity 95.8%, specificity 100%). All tested samples were negative for C.burnetii DNA. We conclude that non-dairy, non-periparturient ruminants exhibited at Iowa fairs are unlikely to shed C.burnetii in their faeces and that this population should not be considered to be a significant exposure risk to other livestock or fair attendees.