Evaluation of some risks factors in bovine salmonellosis.

Previous work has given evidence of the frequency of Salmonella carriage by healthy dairy cows, the increased excretion of Salmonella by talent carriers at the calving time, and the frequency of clinical salmonellosis during that period. From this the authors evaluated the relevance of 3 risks factors supposed to play a role in the triggering clinical salmonellosis, namely: metabolic and hepatic parameters; Fasciola hepatica infestation; and bovine virus diarrhoea (BVD) infection. The prevalence of F hepatica and BVD, identical in infected and control herds, suggested that flukes and BVD did not play a significant role in the development of salmonellosis in the conditions of the present work. Although the mean values of metabolic and hepatic parameters were not different between healthy animals within infected herds and controls, the sequential monitoring performed in 2 reference herds gave evidence of important modifications at the calving time and during the early stages of milk production. If not formally demonstrated in this study, it is suggested that metabolic and hepatic changes observed during the peripartum, could result in a disruption of the intestinal ecosystem (pH, volatile fatty acids, NH3, peristalsis) and in the emergence of a Salmonella population. The excretion of considerable amounts of Salmonella by the first sick animals allows it to spread to the others, especially those with impaired hepatic functions.