Managing Johne's disease in deer
Johne's disease (JD) is an intestinal disease causing progressive weight loss, sometimes with scouring, leading to emaciation and eventual death.
Johne's disease affects any age of deer from weaning through to adulthood. Unlike Johne's disease in other species, young deer may suffer severe disease which is rapid in onset (up to 25% losses) whereas in adult deer, cases tend to be more sporadic and slowly progressive. The latter is more typical of the disease in cattle, sheep and goats.
Johne's disease is an emerging threat to the New Zealand deer industry. It is estimated that approximately 62% of New Zealand deer farms are infected.
Financial losses on individual farms can be very high. For example, it has been estimated that a deer farm with 1000 hinds, and a medium prevalence of JD, could be expected to lose $35,000 per annum. This estimate takes into account deaths in young deer (8% prevalence), deaths in adults (2% prevalence), detained and downgraded carcasses at deer slaughter premises and tuberculosis-testing losses. Johne's disease can cause false test positive reactions at the time of reading a TB test and can also show lesions similar to TB at post-mortem examination.
Additional costs may be associated with slower weaner growth rates, poor reproductive performance in infected hinds, lighter weaners, reduced velvet productivity, farmer's time and veterinary/laboratory costs for diagnosis and control.
The first step in control of the disease on an individual farm is to determine your herd status. The Johne's research group defines a herd's status as either low risk, confirmed infected or unconfirmed. Totally Vets can help you to establish an appropriate cost-effective testing programme.
- A low-risk herd means JD has not been diagnosed on or off the farm (at deer slaughter premises). For these herds, it is important to put measures in place to prevent the introduction of JD.
- Confirmed infected herds will require control procedures to be put in place. It is important to get a handle on how prevalent JD is in these herds before an effective control programme can be established. This is based on historical evidence of JD, TB-testing results and any carcass lesions. A control programme is likely to involve culling of infected animals, identifying and culling sub-clinically infected deer and managing other farm species (like cattle, sheep, goats, alpaca, llama and wildlife) which may also be shedding the bacteria.
- Unconfirmed status means that the herd has not had an appropriate testing programme.
Once your herd status has been established, then a programme for your farm can be tailored to either keep JD out, or where already established, minimise infection. These programmes may require ongoing status monitoring (e.g. once a year where JD is of significant concern).
Please contact Totally Vets for more information about prevention and control of Johne's disease.