Prevalence of Coxiella burnetii in bulk milk in herds of dairy cows and possible correlation with Italian reproductive problems

Introduction - Q fever is a zoonosis caused by an obligate intracellular bacterium, Coxiella burnetii, and is endemic throughout the world. Abortion, stillbirth and non-viable neonates are the main clinical signs in sheep and goats, while placenta retention, metritis, infertility and, rarely, late abortion, are the main signs in cattle. Many epidemiological data are available in Europe. In Italy, recently a wide study about the occurrence of C. burnetii in bulk tank milk was published, but few data are available about the possible correlation between the infection and the incidence of metritis and abortion. Aim - To assess the prevalence of C. burnetii infection in Italian dairy herds by identification of segment of 687 bp genomic segment of the transposon-like region, in samples of bulk tank milk and the possible correlation of positivity with an incidence of abortion greater than 5% and of metritis/clinical endometritis greater than 15-17%. Materials and methods - In the first part of the study, bulk tank milk samples from 344 Italian dairy herds between October 2011 and July 2013 were collected. In the second part of the study, from 246 of the 344 farms, data about the incidence of metritis/clinical endometritis and of abortion were recorded. Results - 138 of 344 farms (40.1%) were positive. Out of the 246 farms included in the second part of the study, for which anamnestic information are available concerning the presence of a significant incidence of abortion and metritis / clinical endometritis, 106 farms (43.1%) were positive. The difference between positive and negative herds for C. burnetii using PCR on bulk tank milk, was not statistically significant (p: 0.6601 - Odds ratio: 0.89) for as regards the incidence of abortions. The difference between positive and negative herds, was statistically significant (p: 0.0005 - Odds ratio: 2.49) for as regards the incidence of metritis / clinical endometritis, with a probability of about 2.5 times greater for positive herds to show a high incidence of the investigated clinical signs. Discussion and conclusions - The data collected during the study confirm the wide spread of C. burnetii infection into the Italian dairy herds and indicate the positivity in bulk tank milk, detected by PCR, as a potential risk factor for a higher incidence of metritis and / or clinical endometritis.