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Leptospirosis

Cattle in areas with standing water most susceptible.

Leptospirosis in cattle occurs worldwide. Illness from this type of infection is usually mild (unless it causes renal damage), but this disease is sometimes economically significant because it can cause abortion.

“Lepto” is caused by spiral-shaped bacteria that affect many kinds of animals, including humans. It is often present in wildlife populations. The leptospires can survive in surface water, stagnant ponds, streams or moist soil for long periods at mild temperatures. It is thus more common in wet climates.

Shelie Laflin, clinical associate professor of agricultural practices at Kansas State University, says the pathogen resides in carrier (persistently infected) animals in their kidneys. “It can be shed in urine and picked up by other animals through mucous membranes. If an infected cow urinates in a pond and another cow gets her face in the pond, she could pick it up,” says Laflin.

From an abortion standpoint, it is hard to prove lepto to be the cause, in most cases.

“From an abortion standpoint, it is hard to prove lepto to be the cause, in most cases. With an abortion, we do serology to check titers on the dam and two weeks later check them again. We are looking for a fourfold increase or decrease in titers (making sure these are not influenced by previous vaccination). If they are increased, we know she was exposed to lepto and developed an immune response. This, in the face of not being able to find anything else as a cause — no other titers that have risen and we didn’t find anything conclusive in the fetus — is usually how we diagnose lepto as the cause of the abortion,” she says.

The presence of these organisms in the aborted fetus is conclusive, she says, but not finding them doesn’t rule out lepto. The organism is hard to culture, and staining of tissues is rarely successful. There are many abortions that are not conclusively diagnosed. In one survey, only 44.4% of abortion cases were diagnosed.

Stockmen often ask whether they should vaccinate for lepto. “In arid conditions where there are no ponds, such as western Nebraska where I grew up — where there is no groundwater at all — lepto is less of an issue than in a region where the climate is wet. I could probably go to any pond in Kansas and find lepto,” says Laflin.

“We don’t really know how effective vaccination is in preventing abortions. We know it can decrease shedding of the organisms and decrease carrier status. If a vaccinated cow is exposed to that organism she probably won’t become a carrier; she won’t shed leptospires in her urine. But reducing incidence of abortions in the herd has never been demonstrated very well in the scientific literature,” she says.

There are some serovars of lepto that appear in dogs and cats that don’t appear in cattle, and some that appear in cattle and cause disease that don’t manifest disease in other animals, she says. Several types are widespread in wildlife, so they might be a source of infection in a herd, rather than exposure to other cattle.

Most stockmen vaccinate just because it’s an inexpensive vaccine and a way to possibly provide some protection. A question often asked: Do we rarely see lepto as a cause of abortion because most stockmen do vaccinate their cows? Or do we rarely see it as a cause of abortion because it isn’t really much of a problem?

“We don’t know the answers to these questions, so many stockmen go ahead and vaccinate, to play it safe,” Laflin notes.

If a breeder is selling purebred stock and wanting value-added factors, having the cattle vaccinated for all common diseases is a good practice. Then those cattle can go into any herd and not bring a new disease, and will also be protected against a disease that might already be in that herd.

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Editor’s Note: Heather Smith Thomas is a cattlewoman and freelance writer from Salmon, Idaho.





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