Dairy Quality University Beef Industry Brings Johne's Disease Into Open in Calls for Prevention, Research to Disarm 'Bomb'

DENVER, COLO. It's a disease that "has historically been pushed under the rug," according to beef cattle producer Gary Wilson, and it's "a sleeping time bond," according to veterinarian Dr. Robert Whitlock.

It's Johne's disease (pronounced "yo-knees"), a chronic mycobacterial infection that affects most ruminant animals¾including beef and dairy cattle, goats, sheep, bison, antelope, deer and elk, but rarely hogs and horses¾and it's a disease for which there is no cure or vaccine and, in a cattle herd, only 40-50% of all infected animals can be detected even using the most sensitive testing techniques, they said during a special symposium on the disease at the annual meeting of the National Cattlemen's Beef Assn. (NCBA) here.

It's also linked to Crohn's disease in humans, the incidence of which is increasing, they said.

Wilson, a producer from New Concord, Ohio, and chair of NCBA's emerging cattle health issues unit, said while there are arguments the disease should be kept off the public screen, it needs "to be talked about and worked on." Wilson moderated the symposium.

NCBA's board of directors supported Wilson's charge that the issue needs to be addressed, passing two resolutions seeking education and surveillance as well as "adequately funded" research in Johne's and Crohn's diseases.

Steel-Belted Phenomenon

Whitlock, a member of the School of Veterinary Medicine at the New Bolton Center of the University of Pennsylvania and co-chair of the National Johne's Working Group, explained Johne's normally refers to the clinical condition of the disease, the causative organism for which is Mycobacterium paratuberculosis. He said the term "paratuberculosis" is sometimes used to describe animals that are infected but not showing the clinical signs of the disease itself.

The clinical signs include diarrhea with a normal appetite and weight loss, and animals in the advanced stages become emaciated and die quickly, within a few weeks, he said. Infection normally occurs soon after birth, but clinical signs usually do not appear until 2-10 years after infection, he said.

M. paratuberculosis, first isolated by Dr. Heinrich Johne in 1895 is an acid-fast bacterium related to tuberculosis organisms, he reported. It is exceptionally hardy and resistant, surviving for more than one year in manure and water, even in freezing temperatures, he said, comparing it to "a steel-belted tire."

It is also extremely slow growing, requiring 10-14 weeks to grow in the laboratory, he said.

It affects all beef and dairy breeds.

Whitlock said infection occurs at or soon after birth as baby calves ingest infected manure from the calving environment or from the mother's teat or udder, although infection also can occur in the uterus or pass through colostrum or milk. He said the more advanced the stage of the disease in the mother, the more at risk the calf will be.

He emphasized that infection occurs through fecal-oral transmission, and reported that 1g of infected manure can contain 10,000 organisms, pointing to how a cow can deposit 22,700g of manure per day, or an infected cow 227 million organisms per day, in clinical cases as many as 1 billion - 2 billion per day. Quoting a colleague, he said "all manure should be assumed guilty unless proven otherwise."

He said calves and other young animals are most susceptible to infection but cautioned that, although animals do develop resistance over time, animals of any age can be infected if introduced into an infective environment, especially where animal density is high or feed or water have been contaminated with infected manure.

After infection, the bacteria grow slowly in the intestinal wall, gradually thickening the wall, impairing normal functioning and leading to the malabsorption syndrome where an animal is hungry, eats well but loses weight, he said.

Even following infection at the youngest ages, infected animals do not usually exhibit clinical Johne's until at least two years of age, and some individuals do not show signs for 10 years or longer, he said. Age at exposure and the dosage or number of organisms ingested are critical factors in determining when clinical disease develops, he said.

Iceberg phenomenon

Whitlock said there are four stages in the development of paratuberculosis and then Johne's disease. In the first stage, the infection is non-detectable and subclinical and typically occurring in animals less than two years of age or older stock that are exposed to very small amounts of the organisms. Infection can not be detected with current tests, including fecal culture or new serologic tests.

The first stage, develops slowly over months and years, and it is possible "some animals recover, or resolve," from this early phase of the infection, he said.

In the second stage, the infection remains subclinical but shedding starts, and older animals shed enough organisms in their manure for paratuberculosis to be detected through fecal cultures. These animals pose a hidden but major threat to other animals through contamination of the environment, he said.

In stage three, clinical Johne's materializes, often after an extended period of stress. Animals continue to eat but milk production and weight decline, and animals demonstrate intermittent, watery pea-soup manure, shedding billions of organisms for Johne's to be detected in fecal cultures and serologic tests. Some animals appear to recover but relapse again in the next period of stress.

The fourth stage is a fatal or terminal stage.

Whitlock said the clinical stages are "an iceberg phenomenon" in which, for every fourth-stage infection, there are 15-25 other animals in the herd that are likely to be infected. Indeed, he suggested that the appropriate assumption is that for each fourth-stage infection, there are 1-2 clinically diseased cows in the herd in the third stage, 6-8 inapparent carriers in the second stage, and 10-15 calves in the first stages.

He said the iceberg parallel is a central concept in recognizing the potential impact of Johne's on a herd and the beef cattle and dairy industries. In a herd of 100 cows, for instance, two clinical cases occurring at the same time would indicate 20-30 members are infected and half of those are not detectable by fecal culture, he said. Furthermore, if infection remains unchecked, the number and rate of infected animals increases progressively over time, he said.

According to an outline provided the symposium, the economic impact of Johne's may include:

However, there is no treatment or vaccine for paratuberculosis or Johne's, Whitlock said, and "the outlook for treatments or vaccines is not good."

There are control measures, but even there, early diagnosis to affect control steps is also difficult because of the cost and time fecal culture require, he said.

The key to preventing, controlling and eliminating Johne's is management, Whitlock said. He said testing, once infection reaches suspect subclinical and clinical levels, is an important tool for identifying infected animals, determining necessary control intensity, and monitoring control progress. "The general strategy" to consequently control infection is to adopt good management and sanitation procedures that will accomplish three goals, he said:

All animals should be managed as if they are infected. Whitlock said. "The most effective and simplest approach is to manage all animals as if they are infected and all manure as if it's guilty," he said, and "sanitation has no substitute."

Whitlock said control and prevention are possible on any operation from farms to large ranches "if producers are willing to put in place a solid commitment." He suggested that the wise application of testing, culling and management can eliminate "most infection" in 7-10 years, and he urged producers to "do the things that you can do," whether it's just not using the same loader to remove manure and then transport silage to testing.

Crohn's link

Beyond cattle and other animals, Whitlock said Johne's is becoming a public health issue because of a link to Crohn's disease, an inflammatory bowel disease marked by abdominal pain, diarrhea and hemorrhaging that occurs in 2-10 of every 100,000 people in the population per year, but is increasing. He said it can be controlled with anti-inflammatory drugs and/or surgery and appears to be higher in women than men, ethnic populations and urban populations, suggesting a genetic predisposition.

However, he said because Johne's has similar effects on cattle and because M. paratuberculosis organisms are so hardy in water, there are activist groups making a connection between agriculture runoff and Crohn's.

NCBA's resolutions added Johne's to the industry's animal health strategies. The first said that as Johne's is an infectious disease in cattle and other ruminants that is difficult to diagnose until late-expressed clinical signs and as its spread is most effectively prevented by early detection and application of control strategies combining management, sanitation and surveillance, NCBA encourages industry education about Johne's.

The resolution also called for states to develop a Johne's prevention and management program that would be supported by accurate and relevant information to guide education and management programs for the state beef councils.

The second requested that NCBA and the U.S. Animal Health Assn. Conduct a future symposium on the diagnosis, control and prevention of Johne's for beef cattle producers, veterinarians and Johne's advisory committees. The resolution also called for the U.S. Department of Agriculture to formalize a laboratory certification program and set proficiency standards for private and public diagnostic laboratories for testing for paratuberculosis and Johne's in cattle.

The resolution also called for USDA to establish Johne's as "a high priority" for research grants and other resources.

Reprinted with permission from FEEDSTUFFS, June 15, 1998.
Written by Rod Smith, FEEDSTUFFS Staff Editor