Get Up to Speed on Johne's
Often known as the silent disease, beef producers are money-ahead to not turn a deaf ear to Johne’s.
When cattle producers talk about diseases and health issues within their herds, Johne’s disease is very seldom discussed or mentioned. It’s true that Johne’s is a disease commonly found in dairy herds. But beef producers are best served to be aware of Johne’s because it’s a silent disease that takes its toll over time. It’s not often identified until significant, irreversible damage has already been done.
Johne’s (pronounced Yo-knees) disease was identified as early as 1894, but even today many, if not most, beef producers are unfamiliar with it. In fact, the Beef ’97 Study, a project conducted by the USDA’s National Animal Health Monitoring System (NAHMS), showed that more than 92 percent of beef producers were either unaware of Johne’s disease or recognized the name, but had limited information. In the NAHMS’s 2007 study – which included 2,872 cow-calf operations representing 24 states – that percentage had lowered to only 68.7 percent, and highlights the lack of overall concern in the beef industry.
The Johne's Information Center estimates that 7.8 percent of the nation’s beef herds are infected. This figure may seem substantially less compared to the 68 percent of dairies nationwide that are known to have Johne’s, according to the 2007 NAHMS study. But there’s still cause for concern because Johne’s disease is infectious and costly to clean up in beef cow herds.
Get Up to Speed on Johne’s: What is Johne’s?
Johne’s is a contagious bacterial disease of the intestinal tract that affects cattle, sheep, goats, deer, and several species of wild ruminant animals. Mycobacterium paratuberculosis bacteria invade the walls of the small intestine for a prolonged period of time.Their invasion causes the walls to thicken to the point that the animal cannot absorb nutrients (see photo). The animal has severe diarrhea and progressive weight loss, but maintains a healthy appetite. The diarrhea often appears as "pea soup" with no blood or mucous; it may be intermittent at first, but is continuous as the disease progresses.
Accumulation of fluid under the jaw can also occur as a result of diarrhea and protein loss. In general, clinical Johne's is a wasting disease even though infected animals continue to eat well. These animals appear unthrifty, are often weak, and usually do not have a fever. The signs of Johne's disease can be confused with those for several other diseases. However Johne’s signs are not usually seen until 
animals are adults, often 2 to 10 years of age, because of the infection’s slow, progressive nature.
For beef producers, the disease causes lost revenue due to decreased milk production (thus lighter-weight calves), early culling of the cow, and decreased slaughter prices. However that’s just one part of the cost equation associated with Johne’s. Since most beef cattle go undiagnosed, the disease spreads to more cows, which affects revenue even more.
“Johne’s disease is much more common in beef herds than producers and most who are involved in the industry think. From my experiences, most of the cattle that have it will never show any clinical signs prior to being sold from the herd, thus some owners will not be aware of Johne’s in their herd. Once a herd is known to be infected, true eradication, based on current technology and studies, does not exist,” explains Robert H. Whitlock, DVM, PhD, DACVIM, associate professor of medicine at the University of Pennsylvania College of Veterinary Medicine. Whitlock was the former co-chair of the National Johne's Working Group for 12 years and is a former six-year chair of the United States Animal Health Association (USAHA) Johne's Committee.
What are its symptoms?
The USDA Animal and Plant Health Inspection Service (APHIS) reports that Johne’s signs are rarely evident until two or more years after the animal is initially infected, usually at birth. Young animals, which are most susceptible to infection, typically ingest the M. paratuberculosis bacterium from a contaminated teat or colostrum, milk, feed or water contaminated with feces. Specialized cells in the wall of the intestine take up the bacteria. Normally an invading bacterium would be killed, priming the
immune system to strengthen itself against future invasion. However, some of the organisms which cause Johne's disease are able to survive this process.
As time passes, more and more specialized cells are recruited to try and kill the bacteria. This causes a thickening of the intestinal wall which results in poor absorption of nutrients, and eventually diarrhea. Infected animals can't be cured of the disease, and most cases of Johne's disease progress to a terminal condition when the animal is 2 to 6 years of age.
Johne’s disease typically progresses in these four stages:
Stage 1: A silent, sub-clinical, nondetectable infection. At this early stage, infected animals cannot be detected with current diagnostic tests. The infection progresses slowly over several months or years
to Stage II. It is possible that some animals recover from this early infection.
Stage 2: Sub-clinical shedders typically include adults and older heifers that are likely to appear healthy. The M. paratuberculosis they are shedding in their manure can be detected with a fecal culture;
however, blood tests are not reliable at this stage. These animals are a major and hidden threat to herd infection through environmental contamination.
Stage 3: Clinical Johne’s disease includes any animal with advanced infection, often associated with a period of stress such as calving. Cattle in this stage have watery manure and will eat, but continue to lose weight. They shed millions of bacterium and will test positive for the disease with a fecal culture and many with a blood test.
Stage 4: At this final and terminal stage, an animal becomes emaciated with fluid diarrhea and develops a “bottle jaw” appearance. If harvested now, the carcass may not pass inspection for human
consumption.
How is Johne’s spread?
The most common source of Johne’s disease infection is the fecal material shed onto feed or grass from infected animals in the herd. Although the bacteria do not multiply, once outside the body they can
live up to a year in the environment. Some respected sources believe the bacteria also can live for an unknown amount of time in stock tanks.
“Calves less than six months of age are most susceptible to infection, and a calf can contract the disease in utero,” says Andy Schwarz, DVM. “Milk from infected dams can infect calves via excretion of the bacteria directly into the milk or by fecal contamination of the teats. If the mother is in the late stages of the disease, the calf has a 30 percent chance of being infected before it is born.” Schwarz is the designated Johne’s coordinator for the Texas Animal Health Commission and the current chair of the
USAHA Johne's Committee.
What educational efforts are underway?
Johne’s disease concerns have elevated the past 15 to 20 years, and scientific, academia, and governmental efforts have concentrated on making information available that can be used to reduce the incidences and cost of this disease. Some of these efforts include the USAHA.
In 1995 this group set up a Johne’s task force – the National Johne’s Working Group. From this evolved individual state working groups to educate beef and dairy producers about the disease and its impact, and to develop programs for testing and identifying Johne’s-free individual animals and herds. The Johne’s Disease Integrated Program (JDIP) was also formed to bring together scientists, universities, and related sources. Its mission is to promote animal biosecurity through the development and support
of projects that are designed specifically to enhance knowledge, promote education, develop real-world solutions, and mitigate losses associated with Johne's disease.
JDIP osted a conference this past August that highlighted on-going Johne’s research. Some of the current research outlined included determining ways to reduce the Johne’s bacteria in colostrum, reducing environmental factors, and how monensin sodium might reduce disease incidences.
“There are some advances as far as control of Johne’s, and the use of monensin is very promising,” explains Whitlock.
“Studies have shown that it can reduce the severity of disease; uptake of the Johne’s organism into an animal’s tissues is decreased and shedding of the Johne’s organism is reduced, which slows down the spread. Monensin is relatively inexpensive and can be added to feed or salt blocks, which makes
it easy to administer.”
The dairy industry itself has also ecome highly involved, and individual breed associations have enacted additional testing and biosecurity measures. There are also a number of programs in place for dairy
producers that allow for disease identification and tracking.
To help beef producers understand Johne’s and become further acquainted with all of its aspects, an online course has been developed by the University of Wisconsin-Madison School of Veterinary
Medicine through a USDA grant. The course covers the cause of Johne’s, how it’s spread, how to prevent it from entering a herd, how to test for it, and its related management practices. It is free and can be accessed through www.vetmedce.org; it takes about an hour to complete.
With education at the forefront, there are many sources that can help beef producers with Johne’s information. Start by contacting your local veterinarian, state Johne’s Working Group, and/or Animal Health Commission. Also visit online:
A check-off brochure that helps producers assess their risk for Johne’s disease and gives preventative measures can also be obtained from the National Institute for Animal Agriculture at www.animalagriculture.org, (719) 538-8843.
In the next issue we’ll look at how to recognize Johne’s in a herd, how to prevent and control the disease, biosecurity measures, testing options, and how to continue marketing cattle once a herd has contracted the disease.