Johne's disease impacts beef and dairy industries, has severe herd impacts
Johne’s is a sneaky disease that you don’t notice until it is already well established in a herd of cattle. It doesn’t show up until an animal has been infected for a long time and eventually shows clinical signs of illness, including diarrhea and weight loss.
For many years, beef producers were not aware of this disease, or thought it was only in dairy cows.
Nearly 70 percent of the beef producers surveyed in 1997 by the National Animal Health Monitoring System (NAHMS) had no idea what it is. About 23 percent of producers had heard of it, but only about 2.4 percent were knowledgeable about Johne’s disease.
Ten years later, a 2007-2008 NAHMS study of cow-calf producers in 24 states representing 79.6 percent of producers showed that only 45.7 percent had never heard of Johne’s, and 14.8 percent were fairly knowledgable.
The information gap is changing, but the U.S. beef industry is still a long way from having a handle on this devastating disease. In 1983 it was estimated that annual losses to the cattle industry in the U.S. were more than $1.5 billion, and these losses have probably increased since then.
Dale Grotelueschen, DVM, a technical services veterinarian with Pfizer Animal Health, works with preventative health strategies in the beef industry.
“Biosecurity measures to keep Johne’s out of herds and preventing infection of new herds is important to the beef industry,” he says.
He chairs a new working group of National Cattlemen's Beef Association (NCBA) called Herd Health Security, which was formed at the NCBA meeting in February 2012.
“We will be working on herd health security issues and focusing on biosecurity and bio-containment strategies. The data show that a minority of herds are infected with Johne’s, which may lead to some perception that it is not an important issue,” he adds.
“We are currently in a period where we are likely to be rebuilding beef herds, with more females retained or purchased – with more animals introduced into herds, and therefore more risk for introduction of diseases like Johne’s,” he says.
The bacteria that cause Johne’s disease are shed in the feces of an infected cow, and picked up by susceptible animals ingesting contaminated feed or water or by a calf nursing a dirty udder, etc. The incubation period – or the time between the time of infection and when clinical signs appear – is relatively long.
Cattle generally do not show signs until they are at least two to five years old. Someone buying heifers or young cows may inadvertently bring home Johne’s disease.
Calves can be infected before birth if the dam has Johne’s.
“If a person purchased an infected pregnant female, there is a risk for the offspring to be infected. Colostrum from an infected cow may also occasionally contain the bacteria,” says Grotelueschen.
Thus, there is a risk if you use colostrum from an infected dairy or buy a dairy calf that may be infected.
Introducing new animals
There is always risk associated with introducing new animals into the herd, and producers need to consider this, because veterinarians still don’t have a good way to detect this disease in young animals. Infection is thought to occur quite early in life. The animals that break with clinical Johne’s disease as adults probably became infected as very young calves.
“Producers should consult with their herd health veterinarians to become more aware of their best options for their own herds, when trying to reduce risks for introducing Johne’s,” says Grotelueschen. “Some herds that have established levels of confidence through testing that Johne’s is not an issue. Information about the herd you are considering purchasing from can often be very valuable.”
Even knowledge there have been no animals that have had clinical signs of Johne’s is better than nothing when evaluating risk. It may be wise to do some checking before buying.
“In spite of risks, there will always be cattle purchased and introduced with no conversations about Johne’s, and the purchaser is just assuming whatever level of risk there might be,” says Grotelueschen.
Thus it’s important that stockmen learn more about Johne’s and the fact there could be some risk.
Getting rid of Johne’s
The next question is what should producers do when they discover that their herd is infected.
“There are protocols designed to address bio-containment within herds. This takes a team effort to address effectively. It will involve the local beef cattle veterinarian and a diagnostic laboratory. There must be a plan and some goals set for dealing with an infected herd,” he says.
“There are choices to make and some options. The best option, practically speaking, may not the same for everybody. It can be eradicated from a herd, but takes a good plan and diligent execution of that plan to accomplish it,” he says.