Shedding routes ofCoxiella burnetiiin dairy cows: implications for detection and control

Abstract

-Reliable detection of Coxiella burnetii shedders is a critical point for the control of the spread of this bacterium among animals and from animals to humans. Coxiella burnetii is shed by ruminants mainly by birth products (placenta, birth fluids), but may also be shed by vaginal mucus, milk, and faeces, urine and semen. However, the informative value of these types of samples to identify shedders under field conditions is unknown. Our aim was then to describe the responses obtained using a real-time PCR technique applied to milk, vaginal mucus and faeces samples taken from 242 dairy cows in commercial dairy herds known to be naturally infected with Coxiella burnetii, and to assess their putative associations. Positive results were found in all types of tested samples even in faeces. No predominant shedding route was identified. Among the shedder cows, 65.4% were detected as shedders by only one route. By contrast, cows with positive results for all three samples were scarce (less than 7%). Testing a cow based on only one type of biological sample may lead to misclassify it with regards to its shedding of Coxiella burnetii and thereby underestimate the risk of bacterial spread within a herd. dairy cows / Coxiella burnetii / shedding routes / real-time PCR / Q fever

Association betweenCoxiella burnetii shedding in milkand subclinical mastitis in dairy cattle

“…shell vial culture) or live animal inoculation, immunohistochemical and PCRbased detection [1,8,17,18]. Previous reports have demonstrated that viable organisms may be variably shed in the milk of dairy cattle for extended periods of greater than one year and across multiple lactations [1,7,17], and that within a herd the proportion of cows shedding in milk may range from 15 to 62% [7,9]. Our finding that 45% of cows in this commercial herd were CbPCR positive in milk samples is consistent with these previous reports.…”

“…In the United States there are currently no approved C. burnetii are inconsistent [8,15,24]. In past studies, a major limitation may have been the reliance on serology to define C. burnetii infection status, as serology is poor indicator of active C. burnetii shedding in individual animals [1,5,6,9,18]. Classically, confirmation of active infection in cattle required isolation of the organism either by laboratory animal or cell culture inoculation [1,4,7,13,16], and currently few laboratories carry out isolation due to legal limitations, risk of human exposure, and lack of sensitivity of the technique [1,9,18].…”

“…Classically, confirmation of active infection in cattle required isolation of the organism either by laboratory animal or cell culture inoculation [1,4,7,13,16], and currently few laboratories carry out isolation due to legal limitations, risk of human exposure, and lack of sensitivity of the technique [1,9,18]. A small number of recent studies have described PCR-based DNA detection to identify shedding of C. burnetii in ruminants, including dairy cattle with reproductive disorders [5,6,9,24].…”

“…PCR has been used to identify shedding patterns of C. burnetii DNA in ruminant milk [1,2,6,9], although it is currently unclear whether shedding in milk is related to mammary specific manifestations of infection.…”

Coxiella burnetiishedding by dairy cows

“…This quantitative approach allows one to scale different bacterium sources, with regards to the risk of Coxiella burnetii transmission among animals and from animals to humans. Coxiella burnetii is shed mainly by birth products (birth fluids, placenta), but may also be shed by cattle via vaginal mucus [7,11], milk [1,30,35], faeces [13], urine [15] and semen [19]. However, while shedding routes of Coxiella burnetii have been identified, the characteristics of Coxiella shedding in terms of kinetic and bacterial burden are still unknown.…”