As Yersinia is everywhere it is not possible to eradicate – so we must manage around it.
Yersiniosis is a bacterial disease that can cause severe scouring and death in young deer. Yersinia bacteria are carried in the faeces of many animals and survive well in soil and on pasture, especially in the cooler months.
When young deer are under stress their gut slows down which can allow proliferation of the Yersinia bacteria to massive numbers. The bacterial toxins damage the intestines leading to diarrhoea. The resulting dehydration and toxin absorption into the bloodstream frequently result in death unless picked up and treated early. Mass medication with injectable antibiotics usually puts the brakes on an outbreak most reliably. This is very expensive and time consuming, plus you have usually lost a fair number of fawns before taking this step – so prevention is much better than cure!
As mentioned above Yersiniosis outbreaks are precipitated by stress, and common tipping points are:
Obviously, you have no control over the weather, and fawns must be weaned at some point, so it’s difficult to eliminate these stressors, but the others are manageable.
A really good tool for reducing the risk of Yersiniosis is the Yersiniavax® vaccine. However, it does require some attention to detail to get the most out of it.
The first point to be made is that the vaccine will not prevent 100% of fawn deaths from Yersiniosis. In the original field trial work (which was carried out on ‘high risk’ farms) around 20-30% of unvaccinated animals developed Yersiniosis, whereas in the vaccinated animals this was reduced to 4-8%. We often quote 5% as a loss rate in vaccinated animals where other stressors are at play. Five dead weaners in a mob of 100 can seem like a lot when you have gone to the effort of vaccinating. Read on, as timing of this vaccine is critical. On many farms, this could be improved.
Yersiniavax® is quite sensitive to the presence of antibodies that the fawn may still carry from its mum’s colostrum. If Yersiniavax ® is administered too early, the colostral antibodies can remove the vaccine before the animal’s own immune system recognises it as something it should be responding to. In this case, the fawn does not produce its own antibodies in response to the first shot of vaccine. Come the second dose of vaccine these young fawns will only be partially protected and can be more susceptible to Yersiniosis than they should be.
This effect of colostral antibodies has normally worn off by 10-12 weeks of age. If you read the packet it does say not to administer until after 12 weeks but 10 is probably OK. Thus, if you are vaccinating pre-rut in mid-February, anything born after the end of November will be too young to respond properly to the first shot of Yersiniavax®.
Solutions to this issue include:
And of course, work to keep fawns well fed and healthy, with minimal changes to routine, to minimise stress and reduce the underlying risk.