NO DETECTABLE PRECOLOSTRAL ANTIBODY RESPONSE IN CALVES BORN FROM COWS WITH COTYLEDONS POSITIVE FOR COXIELLA BURNETII BY QUANTITATIVE PCR

摘要

Samples from 45 dams (milk/colostrum, faeces, vaginal fluid and blood on days 171-177 of gestation and at parturition, and cotyledons at parturition) and their calves (blood collected before colostrum intake and weekly until days 29-35) were analysed to examine the vertical transmission of Coxiella burnetii and links between shedding and seropositivity. All calves were born C. burnetii seronegative. Only those born to seropositive dams seroconverted following colostrum intake. Logistic regression analyses indicated that the likelihood of dam seropositivity was 21 and 4.85 times higher for multiparous than for primiparous (65.6% vs. 8.3%, P = 0.006) and for prepartum shedding cows (75% vs. 38.2%, P = 0.03) compared to the remaining animals, respectively. In conclusion, the results of this study indicate no detectable precolostral antibody response in calves born from dams with cotyledons positive for C. burnetii by qPCR. In order to analyse the possibility of persistent infection due to immunotolerance to an early in utero infection, further studies will need to test for C. burnetii DNA. In addition, in the present study multiparous cows showed a significantly higher seroprevalence than primiparous cows and heifers, colostral antibodies were efficiently transferred to newborn calves, and there was a link between bacterial shedding on days 171-177 of gestation and Coxiella seropositivity of the dam.