Fighting a mobile menace
Joe Itle, VMD, is convinced that, above anything else, cattle movement has contributed to the rising incidence of Johne’s disease in his area of south-central
“We have high animal density here, and, like almost everywhere else, we’ve had a good deal of expansion,” says Itle, of Dairyside Veterinary Service,
Control or coast?
Itle says the severity of the disease ranges from occasional deaths in older animals who break with diarrhea and clinical Johne’s, to 2-year-old heifers that simply lie down and die. Unfortunately, many producers are willing to accept losing a cow to Johne’s disease every now and then. “I have some
clients who are fully aware that they have Johne’s and are willing to live with it,” he explains. “Until their problem affects them more profoundly, there’s not much I can do for them. I can educate them about the disease, but ultimately, it has to be their decision to make changes in their management.”
On the other hand, Itle has several herds that have achieved Level 4 (certified Johne’s-free) status in the Voluntary Johne’s Disease Herd Status Program for Cattle. He has found that the herd managers who have become accredited and certified in brucellosis and tuberculosis (TB) eradication programs are the ones who are most receptive to Johne’s control. Those programs have exposed them to the tandem concepts of testing and controlling disease via management, both of which also are needed for Johne’s eradication. Another one of Itle’s client herds is enrolled in the Pennsylvania Johne’s Disease Herd Demonstration Project and is making good progress following the program’s management protocol.
“A big part of my job is helping those who want the help and protecting them from those who don’t,” says Itle. “Unfortunately, choosing to ignore Johne’s can hurt more than you -- it can hurt your neighbors, as well.”
If Itle has a herd with a serious clinical Johne’s outbreak, he recommends that cattle traffic stops on and off that dairy until the problem is under control. If replacements are needed in those herds, he encourages sourcing them from Level 4 certified herds.
Eradication reaps rewards
For herds intent on addressing their Johne’s problem, Itle has found the use of likelihood ratios assigned to serum ELISA results to be extremely helpful. His basic protocol for large herds is to run a serum ELISA on every cow at dry-off, then confirm the positives with a fecal culture. “Of course we’d like to get rid of every Johne’s-positive cow, but that’s just not economically practical for most of my clients,” Itle relates. “The ratios help us classify the severity of the disease in individual animals
and manage them accordingly. If we get one with a very high S/P (sample positive) ratio, she may not even be allowed to freshen, and under no circumstances -- including pasteurization -- is her colostrum or milk allowed to be fed to calves.”
In smaller herds, Itle performs a once-a-year, whole-herd check of second-lactation and older animals. This often is done when he is drawing blood for other disease certification programs.
Itle says many management steps can help prevent Johne’s spread, including:
Remove calves from dams immediately after birth.
Do not pool colostrum.
Feed milk replacer instead of waste milk.
Send calves off-site to be raised by a custom grower from newborns to springer stage. Ideally, the grower would raise calves only for one dairy.
For herds that have achieved Level 4 status or are working toward it, Itle counsels them to be extremely cautious when adding new animals to the herd or sending animals to a new facility, such as a newly rented pasture. “One of the problems in this area is manure -- there just aren’t enough places to go with it,” Itle explains. “So even though it is recommended to only spread manure on ground that will be tilled, it hits a lot of pasture ground, too.” If a dairy is renting a new pasture or putting animals into a new barn, Itle suggests collecting environmental samples and running Johne’s cultures on them, just as a fecal culture would be performed.
Communication between Johne’s-free herds is a role that Itle facilitates with pleasure. “It is very gratifying to put like-minded people together so they can help each other out,” he says. “Growing herds need to find sources of clean replacements and herd bulls and are usually willing to pay a premium price for animals that are less likely to be infected.” Itle says the sale of bulls has become an additional profit center for many Level 4 herds.
Down the road, the
“I’ve seen this disease put some herds out of business, and I’ve seen its positive control actually improve the business of others,” says Itle. “It’s an issue of awareness and attitude.”
The National Johne's Working Group
In 1986, Johne’s disease was moved from a subcommittee of the Tuberculosis Committee of the United States Animal Health Association (USAHA) to its own standing committee. The committee determined that more in-depth efforts were needed to study the zoonotic potential of M. paratuberculosis and its possible relation to human Crohn’s disease, and to develop a uniform approach for control, herd certification and eventual eradication of Johne’s disease. Thus, the National Johne’s Working Group (NJWG) was born in 1994.
More than 40 constituent groups, associations and corporations comprise the NJWG. It is a completely unfunded entity. NJWG co-chair Robert Whitlock, DVM, PhD, University of Pennsylvania College of Veterinary Medicine, says, “The NJWG is truly a grassroots effort. At the 2005 NJWG meeting during the USAHA meeting, more than 160 people participated and were not reimbursed by the NJWG or USAHA. That demonstrates the deep level of commitment they have to conquering this disease.”
The NJWG’s current priorities fall under six active subcommittees:
Program Standards. Responsible for developing the standards that became the framework for the U.S. Voluntary Johne’s Disease Herd Status Program for Cattle, a national herd-certification program; a risk assessment model for initial herd investigations; and Minimum Recommendations for Administering and Instituting State Voluntary Johne’s Disease Programs for Cattle. Currently, it is evaluating the impact of a model of contract heifer rearing and the transmission of Johne’s disease.
Education. Informs producers, veterinarians and agricultural leaders about Johne’s disease. Materials are available to help veterinarians, Extension agents and others serve as multipliers of Johne’s education. Many are free-of-charge at www.jd-rom.com/main.asp.
Knowledge Gaps. “Helps define and prioritize the knowledge gaps that are perceived to impede the full development of the national Johne’s disease program.” These include animal level, bacterial and cellular level, economics, national policy, transmission/effectiveness of control and diagnostic tests.
Budget and Strategic Planning. NJWG provides input on allocation of federal Johne’s disease funds. It has strongly recommended that the largest proportion of funds possible goes to the states for veterinarian education and certification, state producer education and control programs, and demonstration herd projects.
Laboratory Standards. The necessity to have laboratories approved to conduct both Johne’s enzyme-linked immunosorbent assay (ELISA) tests and Johne’s fecal cultures was recognized early by the USAHA Johne’s committee, and was emphasized to the USDA. The first national Johne’s check tests are now an annual effort. A list of certified labs can be found at www.johnesdisease.org/Labs/certifiedlabs.htm.
Demonstration Herds. The number one priority of the NJWG, demonstration herd projects are underway in 15 states, monitored by the USDA/ARS.
Whitlock adds that a group of NJWG volunteers maintains an ongoing effort in the area of Johne’s disease in small ruminants and cervids. Judy Stabel, scientist at the
The vaccination debate
Vaccinating for Johne’s disease is not an exact science. A vaccine containing a mixture of killed mycobacteria and oil has been available in the
At a symposium during the 2005 United States Animal Health Association’s annual meeting, vaccination advocates assert that, particularly in herds with a high level of infection, vaccination used in conjunction with proactive management changes may be the only option to salvage the farm’s viability. They argue that more aggressive use of the vaccine in more herds could lesson the overall environmental load of M. paratuberculosis and slow the disease’s transmission within herds and from herd to herd.
The vaccine does not prevent infection, but it can reduce the shedding of the organism later in the animal’s life. Many advocates theorize that herds may be able to work themselves into a completely Johne’s-free status after several of years of vaccinating.
There are also well-documented drawbacks to the vaccine, including:
Vaccinated animals will test positive on blood tests for both Johne’s disease and tuberculosis (TB). The true presence of Johne’s disease can be confirmed only with a more expensive fecal culture. Confirmation for TB must be performed with a comparative cervical skin test, which may be administered only by a state or federal veterinarian. Given the recent resurgence in bovine TB cases in some parts of the country and the great concern about bringing it under control, this factor alone makes the vaccine a controversial tool.
The adjuvant in the vaccine is highly irritating and can cause severe tissue reactions when accidental administration to humans occurs. For this reason, many veterinarians simply choose not to handle it.
Administration of the vaccine also can cause large lumps -- sometimes as big as a grapefruit or a soccer ball -- to develop at the injection site, usually in the brisket region, which may remain throughout the animal’s lifetime. Occasionally, they will become draining, abscess-like lesions.
As with any vaccine, there also is the risk that perceived protection via the vaccine will create a false sense of security, lessening the priority placed on day-to-day disease management. The two camps also debate the vaccine’s efficacy and whether or not vaccinated animals can actively shed M. paratuberculosis in their manure.
The Johne’s vaccine is widely used in
Visit the following websites to learn more about Johne’s disease.
Designated Johne’s Disease Coordinators, by state: www.johnesdisease.org/State/StatePrograms.htm
Johne’s Disease Information Center at the University of Wisconsin School of Veterinary Medicine: www.johnes.org
Johne’s information website by the National Institute for Animal Agriculture: www.johnesdisease.org
United States Department of Agriculture Johne’s information page: www.aphis.usda.gov/vs/nahps/johnes
National Johne’s Working Group educational materials: www.jd-rom.com/main.asp
National Veterinary Service Laboratory approved laboratories for Johne’s serology tests: www.johnesdisease.org/Labs/certifiedlabs.htm