We struggle in veterinary practice in Western Canada to make sense of the leptospirosis disease complex, as it can be hard to substantially diagnose. Leptospirosis is caused by spirochete bacteria that infect lots of different animal species but only certain serovars (variations within bacteria) are really pathogenic to cattle. Pomona and Hardjo are two variations of species believed to be the main causes.
It is important to understand some aspects of the disease complex when we see or suspect it, and the potential need to vaccinate. In breeding stock, leptospirosis comes up often as a barrier to exporting cattle or even entry into AI studs. That is when I have most often seen its significance in purebred cattle in the West. It may be spread by being excreted in an animal’s urine and can spread in water sources from wildlife.
Leptospirosis clinical signs involve a sick beef animal, often with bloody-looking urine, and they may appear icteric (yellow on the mucous membranes). The organism is pretty fragile so even when samples are taken post-mortem, a definitive diagnosis can be difficult. Trying to culture the organism is often futile.
Response to treatment with antibiotics such as tetracyclines may give us some clue but often it is a guess. Among bred cattle, leptospirosis can often cause reproductive failure, often in the form of abortions in the last trimester. At birth, it can often result in weak or premature calves. Usually, if there is a reproductive problem or abortions submitted for examination and no other common causes are detected, this is when leptospirosis is considered the cause.
Impacts reproduction plans
Where we often see leptospirosis in clinical practice is among top genetic AI sires destined for stud. In most countries other than Canada, bulls need a negative/marginal test for many different types of leptospirosis in order to get into a stud facility. They do allow some tolerances but if they exceed a specific limit on titres they are disallowed from having semen collected.
Depending on the degree of titre, it may just mean allowing some time before retesting to see if the titre has dropped. For Canadian semen collection, the lepto requirement was deemed unnecessary and smartly dropped several years ago.
Sometimes antibiotics or corticosteroids (can be used on bulls but never on breeding females) are administered to bring the titres down. For live cattle being exported into Mexico, for example, there is the option of vaccinating with an approved leptospirosis vaccine or giving a shot of streptomycin.
Most producers and veterinarians favour the vaccination route as it makes much more sense. If titres get above the 1/400 rate, in my experience, it never comes down. This high titres rate has been a trade barrier on bulls all over the country.
Oddly enough, the disease is very sporadic. It can be more frequent on some farms one year and nonexistent the next. It can occur in very healthy bulls that are not clinically sick, going to be entered into stud service and to our surprise, a high-lepto titre comes back on one or several of the serotypes.
Leptospirosis will continue to be an elusive disease and one that does create certain trade issues when it comes to collecting semen for export. Very few herds have undiagnosed reproductive issues so very little of the vaccines are used in Western Canada except where it is endemic or the veterinarian feels it may be of help. If it becomes easier to diagnose leptospirosis, perhaps usage will increase. Abortion rates above two to three per cent total or abortion storms should be checked. Anytime you see bloody urine is a definite need to get an individual animal checked. Causes are varied and all have much different treatments but most have relevance or can have an impact on the entire herd including leptospirosis.