Johne's disease can be controlled and even eliminated from infected herds. However, it takes a thorough understanding of the disease by animal owners, consultation with a veterinarian, and requires use of one or more of the available cervid diagnostic tests. Half-hearted attempts to control Johne's disease will generally fail. [deer JD NZ.jpg] Control of Johne's disease also takes time and a strong commitment to management practices focused on keeping young animals away from contaminated manure, milk, water, etc. A typical herd clean-up program may take a number of years. Faster clean-up programs are possible, but they are usually more expensive. The basics of control are simple: new infections must be prevented, and animals with the infection must be identified and removed from the herd.
A computer simulation model illustrates that faster Johne's control can be accomplished by changing both deer or elk rearing procedures and testing the adult herd to identify and cull the infectious animals. Of these two basic strategies, changing hind/cow management to limit the chance of calves/fawns becoming infected (swallowing the organism) is the most important.
Prevent new infections in calves through:
. . . manure management
The most MAP bacteria excreted by infected ruminants are in the feces (manure). Farm sanitation and control over where manure goes on a farm are critical to control of Johne's disease. Because of the susceptibility of calves/fawns to MAP infection, it is important to keep them well away from adult deer or elk pellets that may harbor the infection at least for the first 6 months of life, the "window" of maximum susceptibility.
Calves/fawns should be born in a clean dry environment with minimal fecal contamination. Individual birthing pens or paddocks are optimal but if not feasible, you may establish test-negative and test-positive pens (you could test all your adult animals a few months ahead of time to have this test information available). Then try to establish an area outside the pen free of adult manure contamination (“the safe zone”) for calves/fawns from test-negative dams.
Manure contamination of water supplies, particularly ponds or streams that young animals can drink from, must be avoided to limit spread of the infection. If you use water troughs, when cleaning them remove the sediment at the bottom and dump it away from where animals might graze – MAP apparently survives for a long time in this substrate.
Pasture contamination with MAP is also important as means of infection transmission, but it is less so than other modes of transmission and far more difficult to control. Till contaminated pastures and wait for time and environmental conditions (repeated changes in temperature, minimize shaded soil by cutting grass/crops/shrubs) to kill off MAP on fields. While a majority of the organisms die within three months, a small population can remain for up to a year. Put off stocking contaminated pasture with young animals as long as feasible. Be aware of what the pasture was used for before putting your youngstock on the premises. Farmed elk or deer are often grazed on fields that had been used for dairy cattle - MAP infection is a common problem for dairies.
Read about survival of MAP in the environment in the "Biology of MAP" section of this site.
. . . milk and colostrum management
Many animals infected with MAP will excrete the bacterium in their milk. This happens most often in animals showing clinical signs of Johne's disease, but also occurs in infected animals that still appear healthy.
If you need to bottle-feed a fawn, use pasteurized milk or milk replacer. A recent study saw no difference in the number of new cases of Johne’s disease arising in dairy herds (cattle) between those that pasteurized and those that used milk replacer (Recommended protocols: 145°F (63°C) for 30 minutes for batch pasteurization, or 162°F (72°C) for 15 seconds for flash pasteurization. The milk should be stirred or otherwise in motion to ensure even heat distribution.) Pasteurization kills virtually all MAP that may contaminate raw milk as well as other viral and bacterial agents that could affect the fawn/calf’s health.
Colostrum, the antibody-rich milk produced in the first few days after giving birth, also can contain MAP. Because colostrum is critical to the health and survival of newborns, feeding colostrum must be done.
While these articles focus on cattle, they are excellent sources of information and can be found in the "Articles and Brochures" section of this website. Three articles in particular to read are:
- "Raising Calves - The 5Cs of a Healthy Start"
- "They Tackled Johne’s Heads-On"
- "Pasteurizers Become Part of Heifer Program"
. . . culling offspring
of infected mothers
MAP infections can be transmitted from mothers to offspring by contact with the mother's infected manure, through infected colostrum or milk from the dam, or across the placenta into the fetus even before the fawn/calf is born. Depending on the extent to which manure management and milk/colostrum management recommendations listed above can be implemented, there is a moderate to high probability that fawns/calves born to MAP-infected mothers will acquire the infection. Consequently, on a case by case basis, it may be wise to cull offspring born to infected dams. If not culled, it may take two or more years to determine if the young animal became infected, and she herself might have spread the infection to her own calf and to others on the farm. Time will be lost in pursuit of control or eradication of the MAP in the herd if daughters of infected hinds or cows are kept in the herd.
Identify and remove infected animals:
Test-and-cull program
The majority of MAP infections in a herd are "invisible". Deer or elk with clinical signs of Johne's disease (diarrhea and weight loss) are only a small fraction of the infected animals in a herd. The infection may silently spread from deer or elk to fawns/calves long before signs of illness in infected animals are evident. For this reason, laboratory tests are important to determine which deer or elk are infected. Test-positive deer or elk are generally those most likely to be infectious (excreting MAP in milk and manure) and so they should be removed, or at least isolated from, the herd.
Referred to as a test-and-cull program, this practice is essential to successful control of Johne's disease in herds in a reasonable period of time. Clearly, there are situations where alternatives must be considered: testing and culling of all test-positive animals is not necessarily always required. For instance, some control programs retain deer or elk with low or medium-level ELISA results to generate meat or velvet income but these deer or elk are clearly tagged and strictly managed to limit premise contamination. Decisions on how best to implement testing in a Johne's control program should be made in consultation with your veterinarian. For details about available laboratory tests for Johne's disease, see the deer or elk diagnosis section of this web site.
Disinfection
MAP is resistant to most disinfectants; washable tools, troughs, and feed dishes may be treated as directed on the bottle with a disinfectant labeled as “tuberculocidal”. Since organic material deactivates the disinfectant, items should thoroughly cleaned with soap and water, rinsed and dried before the disinfectant is applied. Tuberculocidal disinfectants usually contain strong chemical compounds and should be used carefully. The instructions provided on the label for proper use and safe handling should be followed precisely.
Vaccination
No Johne’s disease vaccines are available for deer or elk in the United States. In Europe and Australia a vaccine (Gudair) is used in small ruminants to reduce the amount of shedding and clinical disease in a flock or herd, but the vaccine has not been tested in cervid species. The vaccine is likely to trigger false-positive tuberculosis test results since the two organisms (Mycobacterium bovis and MAP) have many antigens in common.
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