The prevalence of Coxiella burnetii shedding in dairy goats at the time of parturition in an endemically infected enterprise and associated milk yield losses

Abstract

BackgroundThis was a panel study of the prevalence of C. burnetii infection in does in an endemic dairy goat enterprise in Victoria, Australia. Our first objective was to determine the prevalence of does shedding C. burnetii at the time of parturition and to quantify the concentration of genome equivalents (GE) present in each C. burnetii positive sample. Our second objective was to determine the proportion of positive does that were persistent shedders. Our final objective was to quantify the association between C. burnetii qPCR status at the time of kidding and daily milk volumes produced during the subsequent lactation.ResultsVaginal swabs (n= 490) were collected from does at the time of kidding and analysed using a quantitative polymerase chain reaction (qPCR) assay. Shedding of C. burnetii was detected in 15% (95% CI: 12% to 18%) of the sampled does. Does were classified as qPCR-negative, qPCR-positive low and qPCR-positive high based on the estimated concentration of GE from the qPCR. Persistent shedding at relatively low concentrations was detected in 20% (95% CI: 10% to35%) of shedding does sampled again at their subsequent parturition. After controlling for possible confounders and adjusting for variation in daily milk yields at the individual doe level, daily milk yields for qPCR-positive high does were reduced by 17% (95% CI: 3% to 32%) compared to qPCR-negative does (p= 0.02).ConclusionsShedding concentrations of C. burnetii were highly skewed, with a relatively small group of does shedding relatively high quantities of C. burnetii. Further, high shedding does had reduced milk yields compared to qPCR-negative does. Early detection and culling of high shedding does would result in increased farm profitability and reduce the risk of Q fever transmission.

Surveillance of Coxiella burnetii Shedding in Three Naturally Infected Dairy Goat Herds after Vaccination, Focusing on Bulk Tank Milk and Dust Swabs

“…During the kidding season in 2019 and 2020, the farmers were instructed to carefully collect vaginal swabs from goats within 48 h after parturition. Due to the risk of single ‘super-shedders’ [ 3 , 27 ], as many vaginal swabs as possible were analyzed to describe the C. burnetii excretion to the greatest possible extent. Unfortunately, it was not possible to always sample the same goats during the study period because of difficulties in herd management on the farms.…”

“…Without control measures, C. burnetii may circulate in goat herds for several years [ 24 , 26 , 27 ]. To prevent Q fever outbreaks in livestock, an inactivated C. burnetii phase I vaccine has been licensed for cattle and goats in several European countries [ 28 ].…”

A cross-sectional study of Q fever in Camels: risk factors for infection, the role of small ruminants and public health implications for desert-dwelling pastoral communities

“…In ruminants, Q fever is an important production disease causing reproductive losses through abortions, stillbirths and infertility, alongside milk drop and chronic mastitis (8). Bacteria are shed in high numbers through infected birth products, as well as in milk, faeces and urine (9).…”

Coxiella burnetii in the environment: A systematic review and critical appraisal of sampling methods

“…These organisms can become airborne and spread up to 10 km (Clark & Magalhaes, 2018). Economic losses may be experienced by infected farms through increased abortion rates and loss of milk production (Canevari et al., 2018).…”