Controlling Leptospirosis in Cattle
US - Scientists are constantly looking for effective vaccines that reduce the spread of leptospirosis in cattle. They recently evaluated a commercial vaccine for its ability to provide short- and long-term protection against experimental infection with L. borgpetersenii serovar Hardjo, the main cause of bovine leptospirosis.
19 April 2012
2 minute read
In the study, cattle were vaccinated twice with the commercial vaccine, a standard vaccine, or a control vaccine. Animals were challenged with serovar Hardjo a year after the second vaccination. To test the vaccine's ability to induce short-term immunity to infection, cattle were challenged three months after a second vaccination.
"The commercial vaccine induced greater immunologic responses than the standard vaccine and greater protection against shedding after challenge," David Alt, a veterinary medical officer in National Animal Disease Centre's (NADC) Infectious Bacterial Diseases Research Unit, says. "However, it did not provide complete protection from shedding."
With the commercial vaccine, scientists were not able to detect any bacteria in either the urine or the kidney at the end of the short-term study. Cattle vaccinated and then challenged with the live bacteria cleared the bacterial infection of the kidney more efficiently, Richard Zuerner, a retired microbiologist who worked at the Agricultural Research Service (ARS) NADC in Ames, Iowa says. Results of the year-long study indicated that only one animal had bacteria in the kidney.
Results showed that the immune system of vaccinated animals was exhibiting a recall response and naturally eliciting an appropriate reaction against the bacteria, he says.
Despite the success with the commercial vaccine, it's not always easy to find the right vaccine. It all depends on the infecting serovar, Alt says. More than 200 serovars can cause leptospirosis, and it's difficult to identify differences within the genus.
Leptospirosis is a contagious disease caused by Leptospira bacteria. It's transmitted naturally from infected domestic animals and wildlife to humans through urine-contaminated water, food or soil.
In livestock such as cattle, leptospirosis can cause abortions, stillbirths, lower fertility and reduced milk production, Dr Zuerner says. It can also result in uveitis, a potential cause of blindness in horses.
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