Recently there has been increased emphasis on controlling leptospirosis in cattle with special consideration for the serovar Leptospira Hardjo-bovis.
Leptospirosis involves infection with one of several strains of leptospira bacteria. This can be manifested in many different ways in the animal. Most producers are likely familiar with late-term abortion as a consequence of infection with Lepto. Other manifestations are also possible. Young calves with leptospirosis often run a high fever, show signs of kidney and/or liver infection and frequently die despite treatment. Occasionally, adult cows may manifest with systemic illness similar to calves, however, chronic infection and poor reproductive performance is more common when affected by Hardjo-bovis. Transmission of the organism is primarily by contact with infected bodily fluids such as urine or placental fluid.
Two basic classifications of Lepto. exist and are important for understanding infection and control measures. These classifications are ‘host-adapted’ and ‘non host-adapted.’ Most strains of Lepto. are non host-adapted in regards to cattle, meaning that the organism is maintained in another species of animal such as raccoons or dogs. Infection in cattle occurs when a cow or calf is exposed to the organism in an environment contaminated by an alternate species. This type of exposure generally results in a more severe, acute infection with the animal becoming significantly ill. In contrast, Lepto. Hardjo-bovis is host-adapted to cattle and is maintained in the bovine and transmitted from cow to cow. Because of the organism’s adaptation to the cow as the primary host, illness is often less severe and frequently goes unnoticed. Reproductive failure in the form of a failure to conceive or early embryonic loss is a frequent manifestation but the cow may appear otherwise normal and the Lepto. may not be readily identified as the cause. Stillbirths, weak calves and slowly progressive, chronic kidney disease are other potential manifestations of Hardjo-bovis. Infected cows or even calves may carry the Hardjo-bovis organism in the kidney or reproductive tract for long periods of time shedding the organism into the environment and serving as a significant source of infection to other individuals in the herd.
The host-adaptation of the Hardjo-bovis strain makes diagnosis challenging. Because animals may shed the organism in low levels and because the immune response is often mild, detecting infection is unreliable. Therefore, efforts to control infection revolve around culling open cows, instituting an effective vaccination protocol and implementing a biosecurity plan to minimize new introductions of infected animals to the herd. Maintaining a closed herd or avoiding the introduction of non-pregnant females to the herd is a good first step towards biosecurity. Finally, using a vaccine specifically with the Hardjo-bovis serovar can aid significantly in reducing kidney infection and urinary shedding as well as reproductive losses associated with infection.
Dr. Darren Loula, DVM, is owner of Christian County Veterinary Service, LLC, a mobile large animal vet clinic.