Johne's Disease: Going, Going Gone?25 February 2014
In the absence of a Johne's vaccine, producers should focus on management practices to limit the disease, urges a Pennsylvania Extension veterinarian.
In this article by the National Johne's Disease Education Initiative, Dr Hovingh states that calves must be kept away from manure. He also recommends regular ELISA tests on milk to monitor the farm's Johne's burden.
Federal funding has disappeared, but Johne’s disease has not gone away. This money-robbing disease is present in a significant number of dairy herds. A recent publication estimates that between 82 percent and 99 percent of all dairy farms in the United States with 30 or more cows are infected with the bacteria that causes Johne’s disease—Mycobacterium avium ssp. Paratuberculosis, commonly referred to as MAP.
Dr. Ernest Hovingh, extension veterinarian, Pennsylvania State University, says the news about vaccines to help control JD is not “overly promising” at this time. He adds that, although efforts are being made to develop better and more effective vaccines, the availability of any such vaccine is most likely several years away.
But does this mean that we should give up on Johne’s disease? “Not at all,” Dr Hovingh states. “The goal for most infected herds should be to eliminate virtually all clinical Johne’s disease animals and achieve and/or maintain only a very low level of infection.
"The good news is that it appears that this is quite doable.” A number of recent studies have examined the effi cacy of various management practices at reducing the transmission of Johne’s disease within a dairy herd. “Studies from Minnesota, Wisconsin and Canada suggest that implementing management factors to reduce calf hood exposure to the MAP bacteria is crucial to reducing Johne’s disease,” Dr Hovingh states.
“Our experience working with a number of infected herds over multiple years here in Pennsylvania is consistent with these studies.” Dr Hovingh and Dave Wolfgang, senior research associate, Pennsylvania State University, offer several relatively easy and inexpensive management practices that you can use to minimize the level of infection and the impact of this disease in your herd.
Critical Management Practices
One highly important management practice is to reduce the exposure of calves to manure in the calving area by ensuring that the pen is kept extremely clean at all times. Ideally, you should have only one cow in a maternity pen at a time.
Another practice is to remove the newborn calf from the maternity area immediately to avoid contact with adult cows or their manure. Although this can usually happen more quickly (< 30 minutes) in large herds with roundthe- clock maternity area personnel, Dr Hovingh and Wolfgang emphasize that—if they want to reduce a newborn’s potential exposure to MAP— this practice should also be standard in small- and medium-sized herds.
The goal should be to remove a newborn calf within one to two hours of birth. They add that, if MAP testing is routinely carried out such as via milk ELISA testing, calving pens can also be designated for test-positive and testnegative animals.
“What the calves are fed is also very important,” Dr Hovingh notes. “Colostrum should be fed from cows that have at least one negative MAP test, and/or the colostrum should be properly heat-treated prior to feeding. Excess colostrum from testnegative animals can be frozen for later feeding to calves born to test-positive dams.”
Johne’s disease experts discourage the pooling of fresh or frozen colostrum from multiple cows. “In extreme situations feeding of colostrum replacers might be justifi ed,” Dr Hovingh elaborates. “Similarly, if milk replacer is not being fed after colostrum, pasteurized whole milk should be offered.
Manure contamination of colostrum or milk should be carefully avoided.” Dr Hovingh and Wolfgang point out that testing of cows using milk, blood or manure MAP tests can be a useful addition to a herd management program. They add, however, that such tests should not be considered as the fi rst, or only, practice to be implemented.
“Simply removing test-positive animals without implementing other management practices is a very, very slow—and usually ineffective—way to make progress at controlling Johne’s disease in a herd!,” Dr Hovingh stresses.
Dr Hovingh and Wolfgang say, in general, animals that have a “high-positive” test result are much more likely to develop clinical disease than lowpositive or negative animals, and are much more likely to have their offspring test positive later in life. Their advice is that these animals should be sold for slaughter rather than be allowed to calve again on the farm.
“Although it is probably most economical not to cull cows just because they are ‘low’ or ‘moderate’ positives, these animals need to be handled as ‘more infectious’ than their test-negative herdmates.” Dr Hovingh tells. “And remember, some infected, MAP-shedding cows will test negative, so don’t let your guard down with testnegative animals!” To learn more about Johne’s disease, Dr Hovingh suggests visiting www.jdrap.org to try out an online, interactive Johne’s risk assessment tool.
“You should also discuss your Johne’s program with a knowledgeable veterinarian who knows your farm and management practices and can offer some tailored, professional advice and suggestions,” he summarizes.