While
prevention is far more cost-effective than control after infection,
good herd management and a regular testing program can control Johne's disease.
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 6 years.
The broad goals for the elk industry regarding Johne's disease are to:
| 1. | Prevent further spread to the non-infected herds: the herd prevalence of Johne's disease in farmed elk herds operations is currently low and action now can eliminate the infection before it becomes endemic in the industry. |
| 2. | Preserve genetics: the infection spreads along family lines and valuable breeding stock will be lost unless infection prevention measures are taken. |
There are many factors affecting the design of a farm control program:
- The reason the elk are being raised
- The estimated herd prevalence of Johne's disease,
- The owner's perception of the importance of Johne's disease control relative to other husbandry/health issues
- The capacity of the owner to pay for diagnostic tests and make management changes to limit the spread of the infection
- The speed with which the owner wants to achieve control of Johne's disease, and
- Whether the goal is to control or to eradicate the infection.
1. Test and cull
If
M. paratuberculosis infection has been confirmed in one
elk in a herd, it is likely that other animals are infected as well. The
next step should be to decide how aggressive the herd manager needs/wants
to be to address these other potential cases and prevent the spread of
the infection in the herd. To do so, s/he needs to assess whether and
when (at what age) other elk were exposed to the infected animal(s) and
if there were other cases in the recent past that fit a Johne's disease
profile but may not have been assessed for the infection. To control or
eradicate the infection, it will be necessary to identify and test these
elk. Test-positive animals should be culled or segregated from the herd.
Since a single round of testing may not identify all infected animals due to the biology of the disease, the manager should begin longer term surveillance of the herd to include if feasible:
| 1. | Regular assessment and recording of body condition to monitor weight loss. |
| 2. | Annual AGID or fecal culture of the elk exposed to manure from the confirmed case. |
| 3. | More frequent testing for any offspring of the confirmed case(s) and animals exhibiting weight loss or diarrhea. These animals should be segregated until a diagnosis explaining the clinical signs is reached (remember, there may be more than one health problem - for instance, elk can have a parasite problem and still have Johne's disease!). |
2. Cull recent off-spring of test-positive cows
Transmission of
M. paratuberculosis in elk herds is most likely to occur from dam to offspring
rather than to other calves and herdmates. In cattle, this bacterial infection
becomes disseminated throughout the body in later stages. M. paratuberculosis
bacteria are excreted not only in manure 
but
also directly into colostrum and milk, and can also infect the unborn fetus. This
is likely to occur in elk as well. Consequently, the highest risk of infection
follows family lines: offspring of infected cows have a greater likelihood of
being infected than do offspring of non-infected cows since they are more directly
exposed to manure and milk from an infected dam. Herd owners wishing to make most
rapid progress toward elimination of Johne's disease from their herd are advised
to cull calves from or infected cows starting with the last born and working backwards
in calving history.
3. Correct herd / environment management
Here are conditions
that facilitate the spread of this infection:
a)
Standing water that drains contaminated pastures can concentrate and harbor M.
paratuberculosis for over a year and are very potent means of spreading the
infection, especially when used as wallows by adult and young elk. Ponds should
be fenced off. Shown here is a muddy wallow in an elk pen. This wallow
is believed to have contributed to an outbreak of Johne's disease .
b) Over-crowding in wet muddy lots should be avoided, particularly during calving season. If elk are gathered up for calving, the pasture, calving pens and the cows should be kept as clean and dry as possible. The 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.
4. Protect calves from infection!
It is important
to block the spread of the infection by keeping calves away from potentially contaminated
manure. Ways to help accomplish this include:
| 1. | Segregating the herd by level of infection risk so that likely-uninfected calves are not exposed to adults with a higher risk of infection |
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| 3. | Conducting calving in clean, manure-free areas |
| 4. | Cleaning with a phenolic-based disinfectant since M. paratuberculosis is believed resistant to many of the commonly available disinfectants |
| 5. | Hand-rearing calves if particularly valuable (be sure to use milk from a goat/cow free of M. paratuberculosis infection). |
Preventing
fecal pellets from contaminating waterers and feeders. Examples of good waterer
and feeder designs are shown here:
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