RISK FACTORS FOR BECOMING A PERSISTENT CARRIER OF SALMONELLA DUBLIN IN INFECTED DAIRY HERDS

摘要

Salmonella enterica subsp. enterica serovar Dublin (Salmonella Dublin) is of concern in the cattle industry due to welfare problems and economic losses in infected herds and due to a serious zoonotic hazard to humans. Approximately 25% of Danish dairyherds are expected to be infected with the bacteria. Therefore, control of the infection is highly desired. Salmonella Dublin has a tendency to produce asymptomatic, persistent carriers in cattle, and these carriers are important for the spread of infection. Therefore, an important part of control strategies involve test-and-cull procedures of carriers, and there is a need for new knowledge regarding prevention of production of new carriers in infected herds. Results of the present study suggest that cattle that become infected with Salmonella Dublin as heifers (above 1 year old to 70 days before first calving) and cattle that become infected close to first calving or during first parity have the highest risk of becoming persistent carriers upon infection. Also, low herd prevalence of Salmonella Dublin leads to higher risk of becoming persistent carriers upon infection than high herd prevalence. Finally, significant variation was found between herds.