Yersinia is the cause of sporadic cases of enteritis in cattle, usually affecting a single animal. In the last year however, we have seen several quite large outbreaks. This bacteria, Yersinia pseudotuberculosis, is normally present in the gut of healthy cattle, and causes disease more commonly in New Zealand than in other countries.
Yersinia is the main cause of diarrhoea in farmed deer and is present in the intestines of all domestic animals, wild mammals and birds. Where sheep, deer and cattle are farmed together, the sheep and deer act as the source of infection for cattle. Disease mainly involves young animals after weaning, and for the bacteria to cause disease, some stress factor must be involved, notably bad weather. We frequently see cases after transportation, when there are feed shortages or concurrent infection with worms or Coccidia. Occasionally, Yersinia is seen in well fed animals, and there is evidence that BVD infection may allow Yersinia to take hold. Animals with diarrhoea cause heavy pasture contamination resulting in rapid exposure of other animals to infection.
The infection causes inflammation and ulceration of the gut lining and abcessation of the gut wall. These changes can result in long term damage to the gut, resulting in poor absorption of nutrients and poor growth. Generally, it affects animals 6-12 months old, and they present with diarrhoea which might contain mucus or blood. Animals are commonly dehydrated and depressed and they can sometimes present with poor growth, stunting or wasting without diarrhoea. Diagnosis is by finding the bacteria in a fecal sample.
Treatment is with antibiotics and Yersinia usually responds well to long acting Tetracyclines (Bivatop). Treatment is successful if instigated early before excess gut damage has occurred. Cases that appear not to respond are probably due to this gut damage rather than antibiotic failure. Control of the disease is achieved by minimising stress factors along with good feed and drench management.