Yersiniosis in deer

Yersiniosis is a bacterial infection that can affect all mammals and birds, but is especially problematic in young farmed deer. It is one of the most serious and common diseases of farmed deer in New Zealand (NZ).


The bacteria, Yersinia pseudotuberculosis, is widespread in the environment and carried by birds, rodents, rabbits, hares, sheep, cattle and pigs so exposure is inevitable but it is concurrent stress to the animals that can show up as clinical disease. Stresses can include transport, bad weather, poor nutrition, trace mineral deficiency and/or parasites. 


The signs of clinical disease in young deer are foul-smelling, watery diarrhoea that progresses to bloody diarrhoea and death. Deer may also appear to go off their food, stand alone and become dehydrated and weak. Typically it will be seen in four to eight month old fawns in their first autumn/winter. An outbreak will often see up to 20% of a mob affected but those that appear unaffected may still be shedding high numbers of bacteria.


During an outbreak, vaccination is of little value, so the best option can be to treat all deer with antibiotics. Sick animals may also benefit from fluid treatment if given early enough. 


Management of young deer during and after weaning will determine whether they will succumb to disease. Aim to reduce stress levels as much as possible in young deer. Keep them well fed, watered and sheltered, and avoid long periods in the yards and try to avoid transport. Also ensure there is a parasite control plan in place and trace mineral levels are monitored.

Vaccination with Yersiniavax® is a good preventative approach, alongside the avoidance of stress factors as much as possible. Yersiniavax® has been available since the mid-90s and has shown good protection against outbreaks. Two shots, three to six weeks apart are required and the timing of the first dose is critical. Ideally it should be done in autumn, before the bad weather and the mobbing together of young deer. Weaning date has the greatest bearing on when to vaccinate. Vaccinating before weaning can be a challenge, but leaving deer unprotected until after the rut may be risky.

Vaccination will not stop all outbreaks but will decrease death rates in the event of there being one.