It is an infection of the small intestine caused by a bacteria (Mycobacterium avium subspecies paratuberculosis - or MAP for short). It is found most often in farmed ruminants but can occassionally be found in other species too. Infection generally occurs when the animal is very young but does not become a full-blown disease until some time later, often when the animal comes under stress.
Animals developing Johne's disease pass through a range of worsening clinical signs. The signs are usually a rapid loss of weight, often with scouring, leading to severe emaciation and eventually death.
They can go from healthy looking animals to severely ill, in only a month or two.
In weaner and yearling deer outbreaks of Johne's disease are occassionally severe, affecting around 20 - 30% of a mob. In adult deer the disease usually only causes sporadic cases.
It is a major cause of economic and productivity loss in deer at the farm and industry level and represents one of the most serious challenges facing the deer industry.
The disease is affecting more and more young deer every year.
It is difficult to control. The complex nature of the infection cycle means no single easy solution is effective on it's own.
It can cause false positive reactions to the Tb test and this leads to further unneccesary testing and costs.
If you see deer in your herd losing weight with diarrhoea JD needs to be ruled out as the cause, as these symptoms may be due to many things. To rule out JD, get your veterinarian to confirm a diagnosis. For Johne’s disease the diagnosis is based on a combination of the following tools:
Johne’s Management Limited has established a network of veterinarians with specialist training in Johne’s disease to help. [link to JCN]
Avoid purchasing deer if at all possible. If deer must be purchased, ensure they test negative for Johne's disease before being brought on to your farm.
If the disease is already present, contact your local Johne's Consultant Network member, veterinarian or Johne's Management Limited. Johne's Management Limited and the JCN can tailor-make an on-farm disease control programme for you.
Yes.
Johne’s disease can be successfully and cost effectively controlled.
Experience with the Deer Industry ‘Making a DIFFerence’ Focus Farms has demonstrated successful control and a cost-benefit analysis has shown it’s well worth the relatively low costs involved (see the Deer Industry News, issues 46 and 49).
Controlling JD is not as simple as giving an injection or a pill so JML has established a network of veterinarians with specialist training in JD to help make an on-farm control programmes [link].
Controlling JD will take a small but firm commitment on the farmer’s part to stick with the programme. But the programme will work. And the solution is achievable.
A control programme will involve the following steps:
It will take a little work each year for several years to really minimise JD but after that, vigilance and some targeted monitoring are all that is required to ensure it stays minimised.
The bottom line is more animals, heavier sooner and better which is exactly the aim for the New Zealand Deer Industry.
The main way that JD spreads between farms is through the trading of healthy looking but infected deer.
The main way that JD is transmitted between individual animals is when young calves ingest infected faeces or milk. This is most likely when it is suckling from an infected hind (calves may suckle from hinds other than their mother) but can also happen when grazing contaminated pasture or eating contaminated supplementary feeds. The calf’s gut system matures in the months post birth and this process is likely to make it particularly susceptible to infection by MAP.
Calves may also be infected before birth in the uterus.
Drinking water contaminated with MAP infected faeces is another potential source of infection.
There is no transmission risk through nose-to-nose contact through fences.
Wildlife are not considered a major source of transmission of JD. It’s true that the bacteria can be found in multiple wildlife species in New Zealand including rabbits, hedgehogs, ferrets, cats and gulls but the realistic chances of transmission from them to young calves is low compared to transmission from infected hinds or contaminated feed or water.
The importance of transmission of JD between deer and other species of livestock is not yet well understood.