Leptospirosis vaccination is important for beef cattle
January 21, 2013
Leptospirosis is a worldwide bacterial disease that occurs in many species of mammals, including humans.
The spiral-shaped bacteria (spirochetes) are shed in the urine and other discharges/secretions from infected or carrier animals, and can survive in moist soil or surface water for long periods at mild temperatures. If a sick, or carrier animal, urinates on pasture or hay, or in a pond or stream, susceptible animals may pick up spirochetes when eating/drinking contaminated feed or water, or when walking through contaminated water or having it splash into the eyes, nose or mouth.
Daniel Grooms, Michigan State University, says there is always risk for exposure for beef cattle since the disease is carried by wildlife and rodents. "Studies have shown that about 50 percent of beef herds in the U.S. are infected, with at least one animal in the herd carrying Leptospirosis hardjo, the serovar that is host-adapted to cattle. We see more incidence of lepto (all types) in warm, moist climates," he said.
L. hardjo manages to survive in a cow for long periods of time, often without causing acute illness, living in the kidneys and shed in the urine. Even though adult cattle may not show signs of illness, this particular type of lepto may cause abortion or reproductive problems and a lower pregnancy rate.
The disease in cattle may be mild or severe, depending on the serovar encountered. There are more than 100 serotypes of leptospira, of which about 40 are pathogenic. About 10 pathogenic serovars have been
recognized in the U.S.
The disease may be acute, causing loss of appetite, high fever, anemia, labored breathing, jaundice (yellow tinge on mucous membranes such as the gums and whites of the eyes), and changes in the milk if the sick animal is lactating. A cow's milk production will suddenly drop, with milk becoming thick, yellow and sometimes blood-tinged. Sub-acute cases are milder, with intermittent fever. Sub-clinical (non-apparent) cases show very little signs of illness other than abortion and infertility, according to Grooms.
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Most adult cattle show very little evidence of sickness, but a few may have one or more symptoms of acute illness. In about 5 percent of cases the animal may die, due to septicemia, anemia or malfunction of liver and kidneys. Young cattle are often more severely affected than adults. After recovery from the acute period of illness, the leptospires localize in the kidneys and the animal continues to shed bacteria in the urine for several months, serving as a source of infection for other animals. With the host-adapted L. hardjo the cow may become a carrier and shed the bacteria for a much longer time.
Lepto infection in a pregnant cow may cause her to abort, even if she did not appear to be sick. Sometimes an infected cow will give birth to a live but weak calf that dies a few days later. "The non-adapted types are more likely to cause outright abortion (and abortion 'storms'), whereas hardjo may cause abortion or just infertility, depending on when the infection occurs. In most herds that are infected with hardjo, the most common thing we see is just infertility or early pregnancy losses rather than outright abortion," Grooms
Dr. David Steffen, University of Nebraska, says lepto is a disease that needs to be evaluated on a regional and herd basis. "These bacteria are present, and I expect that without vaccination we would see lepto emerge as a problem much more regularly. We are often asked about vaccines, but the producers who use vaccination rarely see any lepto problems in their herds. Vaccination is widely used and may be why reproductive losses are minimized,"
"Lepto abortions are very rare in my geographic area and I personally have only seen two cases here. I worked in Kansas for three years, North Dakota for four-and-a-half years, and have been in Nebraska for 16 years. Diagnosing the abortions we've seen here was fairly straightforward because we found spirochetes on 'dark field microsopy' and confirmed them by FA (fluorescent antibody stain). We also got paired serology on the cow serum to demonstrate rising antibody titers. Today we also have additional diagnostic tools of immunohistochemistry and PCR testing," Steffen explained.
"The L. hardjo serovar is host-adapted, however, and causes minimal serologic response (not much rise in titer). So looking for high titers is not the best diagnostic tool. The PCR test also has some limitations," he said.
"I had a visiting veterinarian here from Brazil a few years ago who indicated that lepto is one of the most common causes of abortion in that country. Their vaccination practices, topography and climate are much different than here on the Great Plains. In our semi-arid northern plains where vaccination is widespread, lepto abortions are fairly rare. The level of herd immunity from vaccination – along with climate conditions that do not favor easy transmission – all work against the disease here," Steffen explained.
Grooms says that up until about 10 years ago there was just the 5-way lepto vaccines. "These did a pretty good job of protecting against those species (pomona, grippotyphosa, etc.) but didn't give much protection against L. hardjo which is the one carried by cattle. The newer vaccines do a better job of protecting cows against infection and colonization with that one, and the cows don't become carriers," he said.
Timing of vaccination is important, for best protection against abortion or fertility problems. Grooms recommends giving lepto vaccine before breeding, to protect the cow during her pregnancy. He says the biggest mistake most ranchers make is giving the vaccine in the fall at weaning/preg-checking time, because at this point the cows have already gone through part of pregnancy with no protection. Since this vaccine may not give protection for a full year, he says it's best to do it in the spring before breeding if you only have one opportunity to vaccinate, or better yet, give it twice a year, in spring and fall.
It's also important to start building immunity in replacement heifers by vaccinating them for lepto before they are bred. "Lepto vaccines require 2 doses initially (a booster 4 to 6 weeks after the first shot). Make sure the heifers get both, before they become pregnant, to establish a good foundation for later immunity," Grooms added. F