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Frequently Asked Questions on Johne's Disease in Deer and Elk


Murray Woodbury DVM, MSc.

Specialized Livestock Research and Development Program
Department of Large Animal Clinical Sciences
Western College of Veterinary Medicine
University of Saskatchewn
Saskatoon,Saskatchewan    S7N 5B4

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Contents

 

What is Johne's Disease? (Pronounced Yo-nees)

Johne's Disease is a chronic, debilitating, infection of the intestinal tract. It occurs primarily in cattle, sheep and goats but can affect other ruminant species. Medical researchers have associated the presence of Johne's organisms in intestinal tract tissues with Crohn's disease in humans but have not shown the association to be causative.

What causes Johne's Disease?

Johne's Disease results from a bacterial infection of the intestine by Mycobacterium avium, subspecies paratuberculosis. This bacterium is also called simply Mycobacterium paratuberculosis, or M. paratuberculosis.

What are the signs of Johne's Disease?

In cattle - chronic weight loss with diarrhea.

In sheep and goats - weight loss with or without diarrhea.

In deer and elk - weight loss, but sometimes with no diarrhea but pasty feces. In outbreak form can have severe, liquid, bloody diarrhea and rapid death. The point is that the chronic watery diarrhea usually seen in cattle may or not be present. Animals can maintain their appetite and appear normal except be losing condition because their damaged gut will not absorb nutrition.

In the intestine, the bacteria causes granulomatous inflammation. This type of inflammation thickens the intestinal wall, preventing it from functioning normally. This leads to diarrhea and poor absorption of nutrients. As a result, even though animals will seem to be feeling and eating well, they will rapidly lose weight.

In deer and elk, abscess formation in body lymph nodes and/or systemic (whole body) disease can occur. Outbreaks of Johne's with rapid progression of clinical signs to death have also been known to occur in young animals (9 - 15 mos).

How is the disease transmitted?

Because this is mostly a disease of the intestines, it is logical that infection begins by eating the Mycobacterium organism. Because the organism is shed into the feces of diseased animals, it follows that Johne's disease is contracted by eating food or water contaminated with feces. Pasture puddles or water sources affected by field drainage from contaminated pastures are typical sources of the Johne's organism. Oral contact with contaminated surfaces such as udders and teats also leads to infection.

The organism exists in the colostrum and milk of infected animals and there is evidence that it can survive the pasteurization process for milk.

The M. paratuberculosis organism can live in feces or standing water for months, and depending on the conditions perhaps more than a year, while remaining infective to animals.

Johne's disease organisms contaminate the pastures and environment of affected farms and persist for a long time. Uninfected animals placed into the contaminated environment soon become infected.

Are we giving our hand raised elk calves Johne's disease by using colostrum and milk from goats carrying M. paratuberculosis?

This route of transmission in elk or deer has not been tested or proven but yes, there is reason to believe that infection of hand raised elk calves could occur in this way. For this reason it is advisable to feed only pasteurized colostrum and milk, or colostrum and milk derived from Johne's tested goat herds.

How is Johne's disease treated?

There is no effective treatment for Johne's disease. Animals showing clinical Johne's disease go on to die of malnutrition and other secondary disease, or are humanely killed and disposed of.

How is Johne's disease in deer and elk different from the disease in cattle sheep or goats?

In most domestic species, the infection is frequently acquired early in life with the animal showing clinical symptoms much later. The clinical manifestations of disease therefore occur primarily in older animals. The most common age of onset is 2 to 4 years of age.

In deer and elk, the onset of disease symptoms happens earlier, at about 8 to 20 months. In older animals the period between infection and clinical signs is variable but is thought to be shorter than with cattle.

In other species Johne's disease tends to happen more sporadically (here and there in a few animals at a time) with low mortality until the late stages of disease. In deer and elk, Johne's disease can occur in outbreaks (suddenly, in many animals) with mortality as high as 50%.

In cattle the signs of Johne's disease are watery diarrhea and wasting away of the body. In deer and elk, there is muscle wasting but diarrhea is not a consistent feature of the disease. There can be abscess formation in multiple body lymph nodes in addition to those associated with the intestine. Animals can appear normal but have abscessed lymph nodes which are difficult to distinguish from tuberculosis lesions caused by Mycobacterium bovis, the agent of bovine TB in elk and deer.

Johne's disease is a potential human health hazard and is related to both bovine and human tuberculosis. Is Johne's disease reportable to the Canadian Agri-Food and Agriculture authorities?

No. It is not a "reportable disease" in Canada under the Health of Animals Act. There is no official requirement to report it's occurrence in any domestic animals.

How does this affect Canadian surveillance and control measures?

Agriculture Canada operated a voluntary program of reporting and testing for several years but does not currently maintain any control program or monitoring of Johne's disease in any species of livestock.

How widespread is Johne's disease in Canadian domestic livestock?

Nobody knows for sure. In the U.S. a national survey estimated that 1.4% of the nation's beef cattle and 2.6% of the country's dairy cattle are infected with M. paratuberculosis. Some areas of the country report much higher infection rates. Those figures are for individual cattle. An American Johne's disease research scientist (M. Collins DVM, PhD at U of Wisconsin) says that 41% of U.S. dairy herds have at least one cow that tests positive (but is not necessarily showing signs) for Johne's disease.

In Canada, we currently have no way of knowing the level of disease in the collective national cattle herd or in individual cattle herds. Likewise, there are no figures for sheep, goats or elk and deer. We can only make educated guesses using information from countries with similar agricultural systems.

Johne's disease has been around in cattle for a long time, why has it now become an issue for us in the deer and elk farming industry?

Johne's disease is not uncommon in domestic ruminants and we have accepted and learned to live with the economic consequences of the disease. Agri-Food and Agriculture Canada has not yet identified this disease as a large enough drain on agriculture to warrant the expense and effort required to eliminate it from Canadian animals.

On the other hand, it is important to realize that at present western Canadian elk and deer herds are likely free of significant levels Johne's disease. It is infinitely less expensive and easier to keep herds clean than to attempt eradication once the disease has become established.

Does Johne's disease occur in wildlife and is there a threat to wild elk and deer from infected farmed elk?

Yes, wild elk and deer can become infected with M. paratuberculosis and the infection has been shown to persist in wild herds.

However, an elk or deer specific strain of M. paratuberculosis has not been identified. Elk and deer are infected by cattle and sheep strains. Given the estimated prevalence of Johne's disease in domestic livestock versus specialized livestock, wildlife species are probably at greater risk from exposure to dairy cattle pastures than deer or elk farm pastures.

Why should we be worried about Johne's disease in farmed deer and elk in particular?

Reason #1- Given the close family relationship between Mycobacterium avium and Mycobacterium paratuberculosis, skin testing with M. avium antigen has been used as a surrogate test for M. paratuberculosis in red deer. Because of this, it is tempting to assume that "avian reactors" to TB tests are actually M. paratuberculosis infections. Will the presence of Johne's disease confuse the meaning of TB testing procedures?

Reason #2 - In deer and elk, this disease frequently does not merely cause a loss of production efficiency. In these species it can occur as expensive clinical outbreaks with a younger class affected after a shorter incubation time and with significant mortality.

Reason #3 - In deer and elk, Johne's disease may be unwittingly transmitted to animals (herds) by bottle raising elk with goat colostrum or milk; not an uncommon practice on deer and elk farms.

Reason #4 - The disease is a lot easier to prevent than to eradicate from herds. Efforts to rid an individual herd of Johne's are slow and expensive. Basically it's a test and slaughter affair.

Reason #5 - Diagnosis of Johne's disease in deer and elk is difficult. The suitability of existing tests is not established or well understood in deer and elk. Research is underway to adapt and refine domestic livestock tests for use in deer and elk.

How is the spread of Johne's disease controlled on a farm and how can a farm get rid of Johne's disease?

Johne's disease typically enters a herd when an infected but healthy looking animal is purchased. Because the disease frequently takes time to develop and become recognized the infection spreads to other animals without the owner's knowledge.

Methods for control of Johne's disease in animal herds or flocks depends on the management type. Currently, deer and elk farming could be considered cow-calf operations. In principle, two strategies must be employed at the same time:

Prevent new infections - Newborn animals must be protected from infection by being born and raised in a non contaminated environment, and fed colostrum and milk that is free of M. paratuberculosis. Except for hand raised animals like orphans, this is easier said than done on an elk or deer farm.

Adult animals carrying the M. paratuberculosis infection must be identified by laboratory tests and removed from the herd. In other words, test and cull. But then where would you sell a Johne's positive animal?

How is the spread of Johne's disease controlled between farms?

The best way to avoid the spread of Johne's disease to your farm is to be as certain as possible that animals brought into your herd are not infected with M. paratuberculosis. Laboratory tests for cattle are more widely available than for elk or deer but suitable tests can be performed by some laboratories. Ask your veterinarian to find one for you.

Screening tests performed on the whole herd from which you purchased the animal are more meaningful than tests done on only the animal you bought. Johne's tests are not 100% sensitive, meaning that tests done on individual animals might not detect every infected animals. It is better to rely on tests done on the herd of animals from which you want to buy. If a whole herd test is negative, then the probability the herd is free of M. paratuberculosis infection is very high. This means that any member of that herd is very likely to be free from M paratuberculosis infection. Johne's disease test-negative herds are the best sources of animals for purchase.

If I test my herd and find Johne's positive animals, nobody will buy my animals. Why would I create problems for myself by testing my animals?

Soon you may not have a choice. Nobody wants to buy or trade infected animals because they can cause economic loss through decreased production and animal death. Buying animals from test negative herds is the best way to insure that a farm remains free from Johne's disease. This means that herds with a negative Johne's status will probably enjoy a market advantage over untested herds.

Consider these facts:

Interprovincial trade may depend on test negative status as provinces that prove or perceive themselves to be free from Johne's disease try to remain that way.

International trade may also depend on test negative status as countries that have Johne's control programs seek to trade with other countries having similar programs to control the spread of this disease. The O.I.E. (Office International des Epizooties) classifies disease according to its global significance and makes recommendations for activities such as international importation of animals. The O.I.E. makes Johne's disease a "List B" disease along with tuberculosis and brucellosis and recommends a testing protocol prior to importation of animals from countries where these diseases exist.

Australia has a National Johne's Disease Market Assurance Program (1996) and the USDA has developed certification and control program guidelines. Presently there is no USDA trade restriction on Johne's positive animals but that could change at any time.