Analisi dei parametri riproduttivi e valutazione dei fattori di rischio per la febbre Q in aziende di bovine da latte=Analysis of reproductive parameters and evaluation of risk factors for Q fever in dairy herds

Introduction - Q fever is a zoonosis caused by an obligate intracellular Gram-negative bacterium, Coxiella burnetii, and it is diffused throughout the world. The microorganism is able to survive in the environment despite temperature changes and desiccation, and to elude the host immune response. Q fever is typically transmitted by inhalation of contaminated aerosols, and the shedding of the bacterium with milk and feaces can last up to 13 months after parturition or abortion. Aim - The present study investigates the correlation i) among the main risk factors for the disease and the diffusion of the infection in dairy cows in two Lombardy provinces; ii) between presence/absence of Q fever and reproductive disorders. Materials and methods - Bulk tank milk from 83 dairy herds was screened for C. burnetii using PCR, following the protocol previously described8. Thereafter, 28 herds were enrolled in a case-control study. Inclusion criteria were the presence (case) or the absence (control) of the infection, herd size and location (case and control were <12 Km apart). A questionnaire was developed and used to collect the data regarding the risk factors for the disease, the presence of neosporosis, the direct purchase of raw milk, the occurrence of abortion and other reproductive disorders. Heat detection rate, conception rate and available heats (calculated on lactating cows, starting from 50 days after parturition) were also recorded. For the statistical analysis, a binary logistic regression was used, with the presence/absence of C. burnetii as the dependent variable. The results were considered as significant at P values <0.05. Results and discussion - Overall 16 herds out of 83 tested (19.3%) were infected by C. burnetii. Among the risk factors considered, only the presence of flocks grazing on the meadows of the herd was significantly correlated with Q fever. Such result is likely related to the poor hygienic practices used during parturition in all the herds considered but two. The number of available heats and that of days-open were significantly higher in the cases than in the controls. The data regarding the abortion rate were biased by the presence of neosporosis and the occurrence of abortions caused by the parasite in the control group. It should be highlighted that raw milk was purchased in almost half of the herds in the case group: if the ingestion as a route of infection is still debated, the regular consumption of infected raw milk has been documented as an important risk factor for human Q fever. Conclusions - Veterinarian and farmer awareness of Q fever should be improved for different reasons: economic ones and reasons related to the public health. On the one side, the presence of Q fever in the dairy cow was significantly associated with an economic loss for the farmer, due to the increased days-open. On the other side, the correlation of flocks grazing on herd meadows with the infection in the dairy cow raises the risk of human infection by aerosol. Finally, a possible risk for the regular consumer of raw milk cannot be ruled out.

La febbre Q è una patologia zoonosica diffusa in tutto il mondo, sostenuta da Coxiella burnetii. Le vie di trasmissione sono diverse, quella inalatoria è la più frequente negli animali e nell’uomo. L’obiettivo dello studio è valutare la presenza e gestione dei fattori di rischio associati all’infezione, in aziende di bovine da latte nelle province di Como e Lecco (Lombardia) e correlare la presenza/assenza del patogeno con l’andamento dei parametri riproduttivi. I campioni di latte di 83 aziende sono stati esaminati mediante PCR: 28 di queste sono state quindi incluse in uno studio caso-controllo (positive vs. negative). Su un totale di 83 aziende, 16 (19,3%) sono risultate positive a C. burnetii. Fra i fattori di rischio, solo il passaggio di greggi sui terreni agricoli delle aziende si è dimostrato significativamente correlato con la positività alla malattia. Sia la frequenza di calori disponibili, sia il periodo parto-concepimento sono risultati statisticamente più elevati nelle aziende positive, rispetto ai controlli. La mancata differenza significativa del numero di aborti nei casi e nei controlli può essere legata alla maggior diffusione di Neospora caninum nelle aziende controllo. La fotografia delle aziende infette da C. burnetii mostra come le bovine tardino ad essere fecondate, con la conseguenza diretta di una perdita economica notevole. Inoltre sono presenti molti fattori di rischio per l’infezione degli animali e dell’uomo. Da segnalare come quasi la metà delle aziende positive pratica la vendita diretta al consumatore: l’infezione per via digerente è tuttora discussa, però è stato descritto un focolaio di febbre Q in un piccolo gruppo di consumatori abituali di latte crudo. Si postula perciò lo sviluppo di sistemi di controllo efficaci incentrati sulla figura del veterinario aziendale.