Prevention of Johne’s Disease in Dairy Cattle

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Introduction
Many animals in the early stages of Johne's disease may not be seen. Therefore, it is a herd problem, not just an individual animal problem. Johne's disease can be prevented, controlled and even eliminated from infected herds, based on a thorough understanding of the disease. Half-hearted attempts to prevent or control Johne's disease will generally fail. Once a herd becomes infected, control of Johne's disease takes time. Usually, the infection has been spreading through the herd for a few years before clinical cases are noticed. A typical herd control program may take five years or longer. Faster programs are possible, but may be more expensive. Prevention is cheaper than control.

Prevention Recent surveys show that 60 percent to 80 percent of U.S. dairy herds do not have Johne's disease. Therefore, prevention should be the goal of every farm that is currently free of the disease. It is encouraging to note that management practices directed at preventing Johne's disease, an intestinal infection, will also reduce the risk for other important cattle diseases as well.

Many viral, bacterial and parasitic intestinal diseases that affect dairy herds are also transmitted from infected animals excreting or shedding the pathogen in their feces. A potential list of these pathogens includes calf scour microbes like BVD, Corona and Rota viruses, E. coli, and Salmonella bacteria. Also intestinal parasites like Coccidia and Crypto plus nematodes or worms are transmitted through manure.

The basics of prevention are straight forward. Prevent infections by closing the herd from animal additions or securing additions or replacements from Johne's free or Johne's test-negative herds. In herds where infection is already present additional steps are required for control. These include identification manure management, colostrum or milk management, of infected animals and their removal or separation from the herd and by culling offspring of known infected mothers.

I. Prevention Practices

A. Prevent infections by closing the herd or securing additions or replacements from Johne's-free or Johne's test-negative herds.

1. Purchase replacements from a herd that has individual cow/offspring records, good management practices and is currently herd-test-negative.

2. A second choice may be purchasing replacements from an owner who will sign a statement with the veterinarian of record that states, to the best of their knowledge, Johne's disease has not been in the herd for the past 5 years.

II. Control Practices for an Infected Herd

A. Reduce infections by manure management; all manure is suspect.

Calves should be born in a clean environment with minimal fecal contamination. Separate new calves from their mothers within 6 hours.

Reduce exposure to calves of manure from adult animals that may be shedding the microbe by keeping them isolated and in facilities separate from adults. Avoid manure contamination of feed by using feed bunks and by not using the same equipment to handle feed and move manure.

Avoid manure contamination of water supplies, i.e., ponds or troughs where animals drink. For maximum risk reduction, till infected pastures or graze with non-replacement feeder cattle until environmental conditions cause destruction of Johne's bacteria. This can take up to a year.

B. Reduce infections by colostrum and milk management.

For natural colostrum needs of newborn calves, use the colostrum from Johne's- negative animals.

Do not pool the colostrum.

Avoid natural nursing and milk feeding whenever possible.

Thoroughly clean the udder and teats before collection of the colostrum to avoid manure contamination.

Feed an artificial milk replacer instead of raw milk to supply nutritional needs of new calves.

C. Identify and remove infected animals and their offspring to minimize disease spread.

Consult with your veterinarian for decisions on how best to use and interpret tests used for diagnosis of Johne's disease.

Use a test-certified diagnostic laboratory for running your tests.

Identify all females and their daughters remaining in the herd.

Remove, or keep separate, all test-positive animals.

Prevent infection spread by culling, or separating, offspring of infected mothers.

Note: Information in this section has been reviewed by the National Johne's Working Group, a subcommittee of the U.S. Animal Health Association

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Some Johne's Disease Prevention or Control Plan Options for Dairy Herds
1. Management changes only

It should be noted that these management practices are essential to the success of other program options. Management changes should include:

Calving cows in a clean, sanitary environment separate from the rest of the herd and free from any possible contamination from dairy barn waste or runoff from possible infected corrals;
Allowing a maximum of 12 hours before the calf is removed from the cow (ideally a calf should be removed immediately and fed the colostrum from Johne's-negative cows).

Further, one should always feed calves a high quality milk replacer and never use milk from medicated or sick animals. Isolate calves from each other until at least 30 days old (e.g., calf hutches). Minimize exposure of a calf to manure from adult cattle. The facilities for young replacement stock should be clean, free from feces, mud holes, effluent drains, and other sources of contamination. Separate boots, and perhaps clothes, should be used for working in calf areas.

Plan for dedicated low-risk pastures (e.g., hay pastures) and raise replacement heifers in these areas, ensuring no contact with adult cattle manure, until calves are 1 year old. Do not use bulls or dry cows to clean up excess feed in heifer pastures; cut this pasture for hay or silage. Only use fresh manure on pasture grazed by adult animals and do not spray effluent on heifer pastures.

Some final points include:

immediate isolation of any scouring or unthrifty animals;
taking samples to diagnose the condition;
culling of any animal with diarrhea that is unresponsive to therapy and of an unknown cause;
culling offspring of infected cattle.

Further management recommendations are to restrict access of susceptible stock to high-risk areas (including swamps and ponds) where infected animals are known or highly suspected to have been recently.

Recommend use of AI rather than natural service. Finally, keep a closed herd or purchase only from test-negative herds.

A management only choice is generally more affordable than other choices. Most often it will likely reduce the prevalence of infection in the herd and incidence of clinical cases to a steady state. In some herds, of low risk and low prevalence, management only may eliminate Johne's infection from the herd.

A disadvantage may be that costs will not always be evident. These methods are unlikely to work in heavily infected herds or unsuitable environments. This management only option is ongoing, and must become a permanent part the operation. One final note; if the prevalence of infection in the herd is not known, an initial screening test is advised to establish a baseline for the herd. Test-positive animals should be considered for culling.

2. Test and cull

This option requires adoption of the improved management practices as described above. Whole-herd tests are recommended at least once per year, preferably in mid-late lactation. Keep records that allow indentification of infected family lines and introduced Johne's cases. Cull confirmed test-positive cattle when possible or at the end of their lactation. Cull the offspring of infected cattle and sell to feeder/slaughter channels only. In herds with a low prevalence of infection, ELISA test results should be confirmed with a culture test or with appropriate samples collected at slaughter.

This option permits assessment of the herd status, identification of high-risk groups, and ongoing monitoring of progress. Another advantage is the ability to have an objective assessment of herd status for selling breeding stock purposes or herd classification. Managed well, a rapid reduction in herd prevalence of infection and clinical disease will be likely. The herd owner may progress toward a test-negative status, if those are goals.

A disadvantage is the cost associated with the testing regime and culling reactors. Further, since some infected cattle will not be detected by the diagnostic tests early in their disease course, the option requires a long-term commitment.

Expected outcomes include a rapid reduction in the prevalence of Johne's disease and a reduction of environmental loads of Johne's microbes. Finally, it can help eradicate infection from most herds. This may be an option for purebred herds, commercial herds selling breeding stock, and some self-replacing herds.

3. Partial depopulation

This option requires sending all calves from infected dams for slaughter only. Cull normally for 5 years, selling all home-bred cattle to feeder/slaughter channels only. Producers must buy replacement cattle from low- risk or test-negative herds. Another option may be to obtain a written statement from both the herd owner and the veterinarian of record that, to the best of their knowledge, Johne's disease has not been in the herd for the past 5 years. Over the longer term, management should progressively create low-risk pastures, e.g., using cropping and grazing with low-risk terminal stock. Manage herds as described above emphasizing animal identification, record-keeping, whole-farm planning and risk assessment of operation.

This option generally incurs lower expenditures compared with other options and will improve the prospects for success. It is to be considered a long-term program. As with other options, good management skills and planning are essential for success.

One disadvantage may be that low-risk replacement stock may be difficult to obtain until herd certification programs are more widely used. However, eradication of infection is possible in some herds. This may be an option for a herd where high-risk groups or areas with a high risk of infection are well defined.

4. Embryo transfer There is minimal risk of embryos being contaminated, but as a precaution, it is recommended that embryos come from Johne's-negative dams. However, embryos from infected dams may also be harvested with limited risk. Regardless, all embryos must be implanted into non-infected recipients. This option provides a means of saving herds of high genetic merit. However, there may be difficulty in obtaining uninfected recipients and success will depend on risk and disease freedom of recipients.

5. Vaccination Vaccination reduces clinical disease but, without strict management, infection in herds continues and is maintained at an unknown level. Vaccination may be an option for any heavily infected herds with high rates of clinical disease to reduce the economic impact of the disease. However, vaccination alone is not a way to eliminate the disease.

As with all other options, producers will need to adopt improved management as described. Use of the vaccine requires approval from the State Veterinarian. Every year, all calves must be vaccinated within 35 days of birth. Some states require permanent identification of all vaccinated cattle. Check with your State Veterinarian for specific requirements in your state.

Vaccination usually results in a reduction of clinical disease in herds. It also reduces the number of cows shedding bacteria. Therefore, the environmental load of M. paratuberculosis is also diminished, thus reducing the overall risk for new infections.

The expense of vaccination may be a disadvantage for some. The per-dose cost of vaccine may be high as it must be administered by a veterinarian. Further, vaccinated herds remain infected. Vaccinated cattle may be sensitized to the tuberculin (TB) tests. Vaccinates will be false-positive reactors to serological Johne's tests. Large injection-site lesions are common.

Note: Information in this section has been reviewed by the National Johne's Working Group, a subcommittee of the U.S. Animal Health Association.

Some material has been adapted with kind permission from CSL Limited, Parkville, Australia.