Leptospirosis in Cattle

Also known as

Weil's disease, autumn fever, French disease in humans

Description

Several bacterial infections in cattle occur worldwide, and one of the most common is leptospirosis. Illness from this type of infection is usually mild, but this disease is economically significant because it is a common cause of infectious abortion in unvaccinated cattle.

“Lepto” is caused by spiral-shaped bacteria (spirochetes) that affect many kinds of animals, including humans. It is often present in wildlife populations, including rats and mice. The leptospires can survive in surface water, stagnant ponds, streams, or moist soil for long periods at mild temperatures. There is more incidence of lepto (all types) in warm, moist climates than dry climates.  

Leptospirosis is a common cause of infertility, delayed breeding and early embryonic death, as well as abortions or birth of premature and weak calves.

There are many types of leptospires and some cause more severe illness than others. 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 lower pregnancy rate.

The incubation period for leptospirosis is 3 to 7 days or longer after coming into contact with the bacteria. The disease in cattle may be mild or severe, depending on the type encountered (there are more than 100 serotypes of leptospira, of which there are about 40 types that can cause illness, but less than 10 of those have been recognized in the U.S.). Signs of illness last 3 to 5 days.

The disease may be acute and deadly with a toxic blood infection, or mild. After recovery from the acute 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 bacteria in her urine for a much longer time, serving as a source of infection for other animals.

Most adult cattle show very little evidence of sickness, but about 30% may have one or more signs of acute illness. In about 5 percent of cases the animals die, due to septicemia, anemia or malfunction of the liver and kidneys. Young cattle are often more severely affected than adults.

Lepto infection in a pregnant cow may cause her to abort, usually 1 to 3 weeks after recovering from the acute stage of the disease. Even if she did not appear to be sick, she may abort. Sometimes an infected cow will give birth to a live but weak calf that dies a few days later. Abortion outbreaks from lepto are thought to be most common in the last trimester of gestation, but this is generally because aborted fetuses are most likely to be seen at that stage; a cow may abort from lepto at any stage of gestation.

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.

Diagnosis is not always easy in an individual animal since signs can vary so much, but the presence of lepto in a herd can usually be detected by taking blood samples from about 10% of the animals. Whenever there’s a higher than normal number of abortions, lepto could be a possible cause.

Signs

Acute cases

• Loss of appetite
• high fever
• anemia
• labored breathing
• jaundice (yellow tinge on mucous membranes--gums and whites of the eyes) drop in milk production
• milk becomes thick and yellow and sometimes blood-tinged.
• Sub-acute cases
• Intermittent fever

Sub-acute cases

• Intermittent fever.

Sub-clinical (non-apparent)

• Very little sign of illness other than abortion and infertility

Causes

Lepto is caused by spiral shaped bacteria (spirochetes) that affect many kinds of animals. This disease is spread by discharges and secretions (especially urine) of sick and carrier animals, which often contaminate feed and water. Some infected animals, particularly with certain strains of lepto, appear to be healthy, yet harbor bacteria in their kidneys and reproductive tract, shedding the bacteria in urine or reproductive fluids.

Bacteria may enter a susceptible animal via the nose, mouth or eyes by contact with contaminated feed, water or urine, or through breaks in the skin on feet and legs when walking through contaminated water. Urine or contaminated water splashing into the eyes of susceptible animals can spread the disease, as can breeding.

Calves infected before birth (in the uterus) may shed the bacteria. Once the leptospires enter an animal, they multiply in the liver and migrate through the bloodstream to the kidneys; they release toxins that damage red blood cells, liver and kidneys.

There is always risk for exposure for beef cattle since the disease is carried by wildlife and rodents. Studies have shown that about 50% 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.

Prevention

Recovered animals are generally immune to the type of lepto they encountered, but still susceptible to infection from other types. There is vaccine available against the most common kinds of lepto (Leptospira pomona, L. grippotyphosa  L. hardjo, L. canicola and L. icterohaemorrhagiae), giving immunity for about 6 months.

The other serotype, hardjo-bovis, was not covered in the earlier 5-way vaccines, but a specific vaccine could be given for this one.

The 5-way lepto vaccines did a pretty good job of protecting against those species 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.

Unlike the other types of lepto, hardjo-bovis infects animals for a longer period of time (sometimes for life), residing in the kidneys and reproductive tract of cattle that may not show any signs of disease. These bacteria are continually shed in urine or any discharges from the reproductive tract, serving as a continual source of infection in the herd. This type of lepto can also be passed from the dam to her fetus.

For best protection against the various strains of lepto, calves should be vaccinated at about 4 to 6 months of age, and cows should be vaccinated twice a year.

Timing of vaccination is important for best protection against abortion or fertility problems. Recommendations are to give lepto vaccine before breeding, to protect the cow during pregnancy.

The 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 early pregnancy with no protection. Since the vaccine may not give protection for a full year, 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 heifers get both, before they become pregnant, to establish a good foundation for later immunity.

Leptospirosis can be introduced to a herd by purchasing an infected cow, from pigs or wildlife mingling with cattle, or rodent urine (contaminating feed or water). Even if your cows never come into contact with other cattle, they can get lepto from dogs, mice, wild animals such as raccoons, skunks, foxes, deer, elk, antelope, etc. or other carrier animals urinating on a feed ground or into a water source.

Deer eating with cattle, or in haystacks can spread lepto. Thus the best protection is semi-annual vaccination.  

It also helps to limit the access of rodents and wildlife to cattle feed and eliminate cattle access to surface water used by other livestock. Draining or fencing off swampy areas that might harbor leptospires is another good preventative measure. Infected or recovered bulls should never be used for breeding until they have been treated to reduce shedding of leptospires.

Treatment

Treatment is most effective if given early in the course of the acute disease, before serious or irreversible damage is done to liver and kidneys. Treatment in later stages of chronic infections can be helpful, however, to reduce shedding of bacteria and shorten the carrier stage. Several antibiotics are effective but may not completely resolve the carrier state in certain animals; consult your veterinarian regarding choice of antibiotic and duration of treatment.