Herd prevalence studies in North America found 40%-45% of beef herds infected with L. hardjo. “We suspect 50% of herds are infected or have at least one animal carrying L. hardjo. One study found higher rates of infection in southern vs. northern states. The most obvious difference is climate,” Grooms says.

“The northern U.S. or Canada may not have as much, but the prevalence can vary with cattle management. For instance, prevalence in dairy cattle is generally higher because they’re more confined,” he says.

What’s new in vaccines

“Until 10 years ago, we only had multivalent, five-way lepto vaccines that were whole-cell bacterins,” Grooms says. “They stimulated humoral immune response, and probably provided protection against pomona, grippotyphosa, etc., but weren’t effective against L. hardjo, which is host-adapted and carried by cattle. Thus, for many years, we found problems with lepto even in vaccinated animals. In the last 10 years, new vaccines appear to do a much better job of protecting against L. hardjo,” he says.

Newer vaccines also reduce the risk of renal colonization and kidney infection, he adds. When the first L. hardjo vaccines debuted, they were given in addition to the five-way vaccine. Today, several companies combine the serovars in one vaccine.

“The host-adapted serovar in the U.S. in cattle is L. borgpetersenii serovar Hardjo [type hardjo-bovis],” Anderson says. “The new vaccines — by Zoetis and Schering-Plough — have focused on this species.” 

Some producers don’t vaccinate young animals for lepto, believing only cows need protection to prevent reproductive loss and abortion. This can leave younger cattle vulnerable, Carter says.

“Lepto vaccine is inexpensive. We also must remember that lepto is a zoonotic disease. If you have kids out there helping, or handling a 4-H calf, potential risk to human health raises the importance of preventing it in cattle,” Carter says.

Vaccination timing

As lepto vaccines are administered primarily to prevent reproductive losses, they should be given before breeding. Cows should be vaccinated twice a year, especially if likelihood of exposure is high. Grooms advises against vaccinating only at weaning. “The cows may be pregnant for several months at this point, with little protection.”

The important thing with any vaccine program for the breeding herd is establishing good immunity in replacement heifers, to build the foundation for future immunity, he says. Lepto vaccines require two initial doses (a booster 4-6 weeks after the first vaccination). “Make sure heifers get both doses prior to breeding to establish that foundation,” Grooms says.

Heather Smith Thomas is a rancher and freelance writer based in Salmon, ID.

 

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