The epidemiology of Coxiella burnetii in goats in Indiana
Coxiella burnetii is an obligate, intracellular bacterium and the etiologic agent of the zoonotic disease Q fever. Through the presence of an environmentally resilient small cell variant, C. burnetii can persist outside of a host in the face of extremes in temperature, humidity, and pressure. C. burnetii is considered to be ubiquitous in the environment and endemic in cattle, sheep and goat populations. These same species are the main reservoirs for human infection with C. burnetii . The overall goal of this project was to develop a baseline understanding of the epidemiology of C. burnetii in goats in Indiana. Specific areas addressed were: Individual and herd level prevalence of infection with C. burnetii as evaluated by serologic and molecular methods, geographic distribution of individuals and herds positive for infection with C. burnetii, and evaluation of potential risk factors for infection with C. burnetii among individual goats and herds. Six-hundred-fifty-four does representing 95 herds were included in the study sample as a whole. Six-hundred-forty-nine of the does from 94 farms were from Indiana. Based on the use of a commercial enzyme-linked immunosorbent assay (ELISA), there was a 3.8% estimated individual level and 11.2% estimated herd level seroprevalence for C. burnetii in Indiana. Through use of a real-time polymerase chain reaction (PCR) assay targeting the IS1111 transposon of C. burnetii in DNA samples from either milk, vaginal mucus samples or feces, there was a 7.5% estimated prevalence of shedding C. burnetii at the individual level and a 20.2% estimated prevalence of shedding C. burnetii DNA at the herd level. There was no statistically significant difference detected between regions of Indiana in regards to does testing positive for C. burnetii. However, a statistically significant association was detected between does testing positive for C. burnetii and the Public Health Preparedness District (PHPD) of Indiana in which the farm was located. Finally, 3 potential risk factors of interest: The presence of cattle, sheep or camelids on the farm; history of abortion, stillbirth or weak offspring within the herd; and whether or not the goats were housed primarily indoors were evaluated for associations with seropositivity for or shedding of C. burnetii. Of these 3 factors, only the presence of cattle, sheep or camelids on the farm demonstrated a statistically significant association with the likelihood of detecting either anti-C. burnetii antibodies or shedding of C. burnetii DNA. Rather than increasing the likelihood of detecting C. burnetii, the presence of these other species on the farm appears to have a protective effect.
Moore, Purdue University.
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