Yersinia in Calves

In December we start to see outbreaks of Yersinia in weaned calves, typically from post-weaning through to about May. Yersinia bacteria are found in the intestines of most calves – 85% of herds (calves) have Yersinia as a normal gut resident. Stress/immunosuppression associated with parasites, nutrition, trace element deficiencies and BVD may result in an overgrowth of this bug in the intestines. Overgrowth results in a severe scour. Because of a constantly irritated bowel, faeces are often seen dribbling down on to the back legs.

As infection spreads, so does infection pressure and faecal-oral transmission then occurs. Large percentages of a mob are often affected severely checking growth rates. Mortality rates of 5-10% are not uncommon. Faecal culture confirms the diagnosis; however, a presumptive diagnosis can often be made on history and clinical signs. Isolation of affected animals to reduce the spread and treatment with oxytetracycline antibiotic for 3-5 days is an effective treatment/control.