Récurrence de mammite clinique chez la vache laitière : incidence, facteurs de risque et impacts
Clinical mastitis (CM) is one of the most common and most costly diseases of dairy cows in dairy herds. A frustrating aspect of CM is its recurrent nature. Currently, no study has reported in an exhaustive and comprehensive manner information about risk of recurrent CM, risk factors for CM recurrence and its impacts. However, the information about CM recurrence in dairy cows were investigated in many, but disconnected studies. Therefore, a scoping review was conducted to synthesize knowledge on risk of recurrent CM, its risk factors, and negative impacts. Two databases (PubMed and CAB Abstracts), and one search platform (Web of Science) were searched to identify relevant English or French scientific literature published after 1989. Fifty-seven articles were selected for qualitative synthesis. Description of recurrent CM, its negative impacts, and risk factors were reported in 33, 19, and 37 selected studies, respectively. Then, meta-analysis and meta-regression analysis were applied to compute risk ratio (RR) comparing risk of CM in cows that experienced one CM case in the current lactation to risk of CM of healthy cows. The total number of lactations followed and the number of lactations with ≤ 1 and ≤ 2 CM cases were reported in nine studies and the information was used in meta-analysis. These nine studies were then separated into two groups based on recurrent CM definition; those requiring only 24 h and those requiring ≥ 5 d between two CM cases to consider a CM case as a new CM event. For studies requiring only 24 h, cows that already had one CM case in the current lactation had a 1.5 times higher RR for recurrent CM than healthy cows. However, for studies using ≥ 5 d between two CM cases, risk of repeated cases of CM was not different in cows that suffered one CM case in a given lactation as compared with healthy cows (RR: 0.99; 95% CI: 0.86, 1.1). In this study, milk yield reduction and increased risk of mortality and culling were identified as important negative impacts of recurrent CM. Moreover, the most important CM recurrence risk factors were older dairy cow, high-producing dairy cow, and not having cure of treatment following initial CM case. A better understanding of the cow’s, pathogens’ and herd’s characteristics associated with recurrent CM events may possibly help controlling these recurrent events, decrease the associated costs as well as reduce amounts of antibiotics used on dairy farms. Moreover, these knowledges may be also useful in predicting the probability of a repeated CM event and could, therefore, be used to develop tools to inform dairy producer’s CM-related management decisions.
Dairy cow Clinical mastitis Recurrence Systematic review Meta-analysis