Good herd management and a regular testing program will control Johne's disease.		Control of Johne's disease in beef cattle takes patience and consistency. The good news is that management changes recommended for Johne's disease control will also help control many other infectious diseases.

There are three reasons why the beef industry should be aggressive about Johne's disease control:

	1.	Prevent spread to the non-infected herds: the herd prevalence of Johne's disease in cow-calf operations is low and action now can eliminate the infection before it becomes endemic.
	2.	Preserve genetics: the infection spreads along family lines and valuable breeding stock will be lost unless infection prevention measures are taken for registered herds.
	3.	Protect product image: medical evidence suggests that M. paratuberculosis may cause Crohn's disease and control of this infection may be necessary to insure consumer confidence in their products.

Control or even eradication of Johne's disease takes several years. The challenge for practitioners and herd owners is to gauge what industry / public perception of the importance of this infectious disease will be in 3 to 6 years. If the decision is that Johne's disease will be important, then herd management and control programs must be instituted now to establish that the herd is free of Johne's or the infection is at very low prevalence when the market demands it.

Control programs are largely built on what is known about the epidemiology of Johne's disease and assessment of risk factors. In other words, control programs are largely theoretical. Field trials to test the success of such programs or to evaluate which techniques are most cost-effective are lacking due to a paucity of research funding. Consequently, the control methods I outline in this paper are scientifically well grounded but largely untested. Research data and clinical experience used to support these recommendations come primarily from work on dairy cattle. In spite of this disclaimer, experts agree on these recommendations and I am confident they will work. The single most important factor governing the success of Johne's disease control programs is consistent application of controls over an extended period of time, that is 5 to 8 years.

Five techniques or critical points for paratuberculosis control will be discussed beginning with the most effective and feasible and ending with the more difficult to implement.

Two basic types of tests are available for Johne's disease: tests to find the bacterium (M. paratuberculosis) in manure and tests for antibodies in blood (the ELISA being the most common). Culture is somewhat more sensitive than ELISA at detecting infected cattle, but the ELISA is faster and cheaper. The false-positive rate for culture is virtually zero while the ELISA has a false-positive rate that is low but can vary among herds. For a comprehensive discussion of diagnostic tests readers should go to the diagnostics section of this site.

Annual herd testing of the herd is necessary for culling the subclinical carriers of M. paratuberculosis. Annually repeated negative tests increases the confidence owners can place in the non-infected status of individual cows. Quantitative interpretation of the ELISA can be used to create ranked culling lists: from cows most likely to be infected and shedding M. paratuberculosis to those less likely to be infected or less likely to be fecal shedders. The test can be applied to cattle 2 years and older, however, restricting the test to cattle over 3 years old or over 4 years old is rational for beef herds and will decrease herd testing costs without seriously decreasing the rate of infection detection.

Transmission of M. paratuberculosis in beef cattle herds is most likely to occur from dam to off-spring rather than to other calves and herdmates. This bacterial infection becomes disseminated in the latter stages and M. paratuberculosis bacteria are excreted not only in feces but also directly into colostrum and milk, and can also infect the unborn fetus. Consequently, the highest risk of infection follows family lines: daughters of infected cows have a greater likelihood of being infected than do daughters of non-infected cows. However, the calf rearing environment and management will greatly influence risk of infection. On operations where young calves are more confined for longer times with infected adult cattle shedding M. paratuberculosis in their feces, the risk of random transmission from adults to calves is greater. This also occurs with cross fostering of calves or in the face of heavy environmental exposure with M. paratuberculosis and substandard hygiene . Nevertheless, herd owners wishing to make most rapid progress toward elimination of Johne's disease from their herd will be well advised to cull daughters of ELISA- or culture-positive cows starting with the last daughter born and working backwards in calving history.

. . . transmission at breeding

Bulls -

Infected bulls are frequently responsible for introduction of Johne's disease to herds. It is unclear whether the infection spreads from these animals through semen to the conceptus or simply by fecal contamination of the environment. Regardless, purchase of infected bulls should be avoided by requesting the Johne's disease herd test history from bull owners, ie. rational biosecurity. Exclusive use of artificial insemination is the only alternative.

Cows -

To "rescue" the genetics of valuable cows, embryo transfer is considered a safe means of producing non-infected calves from infected cows. Thorough embryo washing is required and careful selection of paratuberculosis-free recipients is a must.

...conditions that facilitate infection spread

a) Ponds that drain contaminated pastures will harbor M. paratuberculosis for over a year and are very potent means of infection spread and so should be fenced off. Clean well water in clean stock tanks should be provided.

b) Over-crowding in wet muddy lots should be avoided, particularly during calving season. If cattle are gathered up for calving, the pasture, calving pens and the cows should be kept as clean and dry as possible. Dam and newborn calf should be removed from the calving area to a lower risk environment as soon as possible.

c) Hay bales/rolls for winter feeding should be placed in different sites to prevent accumulation of contaminated feces in one area (areas which are often congregation sites for susceptible calves).

d) Grazing contaminated pastures is a possible means of infection transmission and pastures can remain contaminated for over a year. However, the risk of infection transmission from grazing is likely low and control efforts such as pasture rest or tilling and re-seeding are too expensive to be warranted for most producers.

For dairy herds, artificial rearing of calves is one of the most effective paratuberculosis control methods. While this technique is out of the question for most cow-calf operators, in some small herds for a few select cows, "rescue" of calves born to infected cowboy hand rearing with clean colostrum and milk replacer could be considered.

In closing, I reiterate that prevention is far more cost-effective than control after infection. If herds are infected, a steady consistently applied control program will succeed and potentially eradicate the M. paratuberculosis infection. The foundation of a Johne's control program in cow-calf operations is a test-and-cull plan.

More information...

For information on the frequency of Johne's disease in U.S. beef cow-calf herds and recommendations from other experts on how to control Johne's disease, readers should go to the articles section of this site and print the article by Geni Wren in the February 2000 issue of Bovine Veterinarian.