Venereal disease often linked to open cows but tricky to diagnose

I recently had discussions with a cow-calf rancher and his veterinarian about a significant open cow problem.

The herd had a group of cows with close to 40 percent of the group diagnosed as open at pregnancy checking. The veterinarian and the producer tried to diagnose the problem without much success.

The problem did not appear to be nutritional and many of the common infectious causes of abortion and infertility were ruled out.

Ultimately, the most likely culprit was a venereal disease known as Campylobacter fetus subspecies venerealis, which is also known as vibrio or vibriosis.

This disease is caused by a bacterial infection sexual transmitted from bull to cow and from cow to bull. Bulls are usually asymptomatic carriers of the infection, which means they will appear normal and even have a normal breeding soundness examination with no adverse effects on their semen, yet they can harbour the bacteria within the folds of their prepuce. These infected bulls can spread the infection to cows at breeding.

The bacteria cause an inflammation of the cow’s reproductive tract, which usually results in early embryonic death. The cows often show up as repeat breeders, resulting in a high percentage of open or late cows at pregnancy checking and sometimes the occasional abortion will be seen. Infected cows can also spread the infection to clean bulls at breeding, causing multiple bulls to be infected in the same pasture.

Campylobacter fetus or vibriosis has an almost identical pattern of disease and symptoms to the disease known as trich or trichomoniasis. Trichomoniasis is also a venereal disease of cattle but it is a microscopic parasite, not a bacteria. Both diseases cause early embryonic death, repeat breeders and open cows.

Campylobacter fetus is also similar to trichomoniasis in one other fashion: the diagnosis is somewhat difficult to confirm because multiple tests are sometimes necessary to find infected bulls. It is also similar to trichomoniasis in that both diseases are usually more likely to be seen in herds that have used community pastures or been exposed to other breeding animals from multiple herds.

In the case of Campylobacter fetus, herd bulls provide the most likely candidates from which to isolate the bacteria.

Bulls are usually infected for life, but some can occasionally spontaneously clear the infection, making the diagnosis even more difficult. They are much more likely to maintain the infection within the herd compared to cows so diagnostic efforts are usually targeted at the bull.

The method of diagnosis is also similar to trichomoniasis. Veterinarians take a preputial scraping from the bull and submit it to the diagnostic laboratory for culture or for a newer PCR test that isolates the DNA from the Campylobacter bacteria.

Recent research carried out by Dr. Cheryl Waldner and her colleagues at the Western College of Veterinary Medicine has suggested that the PCR method is better at finding the bacteria with a slightly higher sensitivity of about 85 percent. That means only 85 percent of infected bulls will be identified as positive with a single culture.

The other major advantage of the PCR method is that it is easier to perform in the lab. Transporting the samples promptly to the diagnostic lab is important for both techniques but especially for the traditional culture method. As a result, researchers have recommended that to have the best chance of diagnosing Campylobacter, three sequential samples should be collected from each bull and submitted to the lab.

This is not logistically easy to do in most herds and can also be expensive. As a result, Campylobacter fetus can be difficult to diagnose, even though it may be a potential cause of major infertility problems.

We have recent data from the Western Canadian Cow-Calf Surveillance Network that also shed light on how commonly bulls are infected. In that study, Waldner and her colleagues had local veterinarians submit preputial samples from the herd bulls of many of the herds that were enrolled in the Cow-Calf Surveillance Network. Only eight of the 735 bulls sampled tested positive for Campylobacter fetus (1.1 percent) and only two of the 78 herds had positive bulls identified (2.6 percent of herds).

However, the study showed that if a positive bull was identified in a herd, the cows were almost 2.4 times more likely to be open in those herds.

The good news is that we have vaccines available for Campylobacter that are fairly effective. There are not a lot of clinical trials that have assessed the efficacy of these vaccines, but anecdotal reports from veterinarians and producers would suggest that these vaccines work reasonably well in protecting cows from disease.

Herds exposed to breeding animals from other herds, such as community pasture patrons, should have this vaccine given to their cow herd before the breeding season.

The herd owner I talked to about the infertility problem in his herd was doing most things well in his herd. The herd would probably be considered a low risk herd because it did not use community pastures. The producer had unfortunately been dealt a major economic loss with all of the open cows and was frustrated because the problem couldn’t be conclusively diagnosed.

We suspected vibrio, but it was never isolated from any bulls.

However, a vibrio vaccine will now be included in their future vaccination program. The additional small expense of including that vaccine to prevent the chance of future infertility problems was an easy decision.

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