Controlling losses due to PI-BVD, Johne’s, Neospora infections
“Good biosecurity is a very cost effective strategy, resulting in less cost and more revenue.”
Producers who ignore production issues that result in easily avoidable losses are passing up ways to lessen costs, increase productivity and enhance profitability.
Trying to increase breed-up rates, selecting for heavier weaning rates, buying cows or heifers with better genetic merit, or buying superior bulls are all goals for many cattle producers. Just as importantly, ignoring herd health issues that may take a heavy toll on production is unwise, unnecessary, and possibly very expensive.
A good biosecurity plan is the basis for good results in the cow calf business. Vaccinations, worming programs, and external parasite control are all part of it, and a good testing plan is the next step in being confident your herd is as efficient as possible.
Herds that harbor problems like Persistently Infected BVD virus animals, or animals infected with Johne’s Disease, or animals infected with the parasite Neospora often suffer losses the producers don’t see, and probably are not aware of. These diseases are seldom obvious. A good testing program is necessary to detect these problems, and is the first step in eliminating them.
If you are not familiar with all three of the diseases just mentioned, you are not alone. Most producers are not. Persistently Infected BVD virus animals (PI-BVD) probably have the most visibility in the cattle business, since these animals shed massive amounts of BVD virus continuously, and are a constant threat to their herd mates. BVD virus is an important component of the BRD (bovine respiratory disease) complex that plagues the stocker industry. BVD virus is also a serious threat to the cow calf industry since it causes abortions in unprotected cows. Vaccination programs can help with BVD Virus control, but PI BVD animals can be an overwhelming challenge to even well-vaccinated cows. PI BVD animals are typically younger animals. Since BVD is a strong immune system suppressor, PI BVD animals often don’t live long enough to reach productive adulthood, though some certainly do. Because PI BVD animals become infected while still fetuses inside the cow, PI’s are born PI’s and they stay that way. They can’t get over it, they shed virus to their herd mates constantly, and they cause disease and losses (pneumonia, abortions, etc.) as long as they are present.
Control of PI BVD in your herd depends on a good vaccination program, and a testing program. While the incidence of PI BVD animals is low (about four) animals testing positive out of every 1,000 animals tested), the damage they do when present is very significant.
Johne’s disease, the second disease mentioned, is an insidious problem in many beef herds, and increasingly becoming recognized as a serious threat. Purebred and breeding stock producer’s programs can be devastated by this problem. Producing and selling infected Johne’s animals to customers and clients will rapidly destroy a seed stock producer’s reputation.
Johne’s disease is caused by Mycobacterium paratuberculosis, and is a difficult disease to deal with since animals can be exposed to the organism and become infected while very young, but not show clinical signs or test positive until much older, usually years later. Animals with Johne’s disease will at some point develop clinical disease, if they live long enough. Persistent diarrhea, marked weight loss, and eventually death is the hallmark of this disease. Large amounts of the disease causing agent is shed in the feces, contaminating the lots and pastures where the affected animal is housed. This contamination of the environment allows herd mates to come into contact with the disease agent, resulting in ingestion and more infection. Younger animals are more prone to infection than older herd mates.
Animals affected with Johne’s disease turn into “racks of bones” in the later stages of the disease. The weight loss can be quite pronounced and rapid, even though they usually have a good appetite. Producers who suspect they might have or have had this problem should test their herd, usually concentrating on older animals showing clinical signs. Should these animals test positive, then the herd owner should work with his veterinarian to develop a testing program to clear his herd of this problem. This will take several years to accomplish, since the mycobacterium can and does persist in the environment for months or even years, and currently infected animals may not show positive for years.
The last of the three problems mentioned, Neospoara infections and abortions, is far and away the most common. Neospora infected cows and heifers are a real financial drain on cow calf herds, because Neospora infected females are much more likely to spontaneously abort pregnancies mid- to late-term in gestation. Neospora is a parasite common to dogs, foxes and coyotes (the definitive hosts) and deer, sheep, goats, cattle and other herbivores are the intermediate hosts. The canines that are infected with Neospora shed infective eggs in their feces, and cattle can ingest these infective eggs when grazing, or eating contaminated hay or silage. Neospora infected cows and heifers are much more likely to abort pregnancies, but many of the infected animals will give birth to live, apparently normal calves. The problem is that a very large percentage of these live calves will be born already infected with Neospora. When these calves grow up to be heifers/cows, they will in turn be much more likely to lose pregnancies.
Since there is no wormer that will treat and remove this parasite from cows, I strongly recommend producers screen their replacement heifers for this infection. There is an excellent blood test that will detect Neospora infected heifers, and allow producers to select against them.
Neospora infected cattle are not contagious to each other, unlike PI BVD and Johne’s infected animals. However, Neospora infected cows, as mentioned above, will produce calves that are infected with Neospora if the calves are not aborted and are born alive. This occurs in about 85 to 90 percent of the live births. When screening/testing home-raised heifers for Neospora infection, realize that the positive heifers probably came out of positive cows.
I seldom test females in my herd for Neospora more than once, and usually never test bull/steer calves. Since males are not contagious, and since there seems to be no production issues with Neospora infected males, there seems to be no reason to test males. I will test cows for Neospora infection a second time, if the cow aborts a pregnancy. (By the way, Neospora was the second most commonly diagnosed cause of cattle pregnancy loss at the Kansas State University Veterinary School Diagnostic Lab in 2019.)
So, after all that, what are my usual recommendations for herd testing if producers are trying to have a really cost effective, useful biosecurity plan? I suggest testing your entire calf crop for PI BVD problems. You should test your calves prior to turning in bulls or prior to AI activity. A single positive calf or animal is cause for real alarm. PI BVD calves shed massive amounts of virus, and are a very serious threat to herd mates, breeding programs and general herd health. If you go to the trouble of testing your calf crop for PI BVD, make sure you advertise this when marketing your calves. Order buyers are very well aware of the destruction and problems PI BVD causes in light calves, and will pay more for calves that are well managed — and this part of managing well. Incidence of PI BVD is only four positives out of every 1,000 tested animals — but if you have one, it is a very serious problem.
Regarding Johne’s disease, I suggest producers monitor their herds for this problem. In closed herds with little to no new animal additions, the risk of infection is low, if the herd is clean to start with. I would, however, test any new additions that have any age to them. If I saw an animal wasting away without any obvious reason, I would draw a blood sample, or a stool sample, and test for Johne’s disease. New bulls are always a concern, so buy replacement bulls from a reliable source. A single positive Johne’s test animal is cause for real concern, since this is a problem that is very expensive and difficult to deal with once it gets out of hand. Incidence of Johne’s disease is hard to pin down — but some studies suggest 8 to 10 percent of beef herds have infected animals. The incidence is probably much higher. In dairy herds, it approaches 100 percent, believe it or not.
The incidence of Neospora is much higher in beef herds than is generally recognized. SEK Genetics did a 5,300 cow survey several years ago, and the criteria for inclusion in the study was the cow had to be within 300 miles of Galesburg, Kan. We found 8.9 percent (or about one out of each 11 cows tested) of the test subjects were positive. A more recent study (not yet published) found 9.6 percent of 500 animals tested positive. I have no systematically collected data to show what the average pregnancy loss is among test positive cows, but my clinical impression is about one-third of the infected cows abort each year. I am sure it is very cost effective to screen replacement heifers for infection prior to selection. Producers have testing tools to monitor herd health that are much better than just a few years ago. Using them wisely can make a real difference in the financial returns from your cattle operation. If you want more information, contact your veterinarian, or contact us at SEK Genetics. ❖
— Coover, DVM, along with Dr. Clem Neely, DVM, owns and runs SEK Genetics, specializing in herd health and advanced reproduction technologies in the cattle and small ruminant industries. Contact them at (800) 443-6389, or http://www.sekgenetics.com.
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