Leptospirosis is a disease that can impact the bottom line of every dairy producer, mainly through lost reproductive efficiency. Leptospirosis is a zoonotic bacterial disease that affects mammals worldwide. The definition of a zoonosis is a disease that can be transmitted from animals to people. Leptospires are gram-negative bacteria that can survive for considerable periods of time in moist soil or standing water. Warm, moist conditions are ideal for the spread of leptospirosis.
Infection can occur through open wounds or penetration of mucosal surfaces of the eye, mouth and reproductive tract. Venereal transmission through semen from infected bulls is also possible.
Following infection, the leptospire organism enters the animal’s bloodstream, where it spreads throughout the body and invades many organs. After several days, the animal produces antibodies which may clear the infection from most sites.
However, the organism may become localized in the mammary gland, kidney or genital tract. Chronic infection in the kidney is important as the organism is shed in the urine, which contaminates the environment and spreads the disease. Urine contamination of the environment is the key to perpetuating the disease in susceptible animals.
There are many different serovars (or types) of leptospira. but the ones of most importance to cattle are as follows:
• Leptospira interrogans serovar hardjo (type hardjo-prajitno)
• Leptospira interrogans serovar pomona
• Leptospira interrogans serovar canicola
• Leptospira interrogans serovar icterohaemorrhagiae
• Leptospira kirschneri serovar grippotyphosa
• Leptospira borgpetersenii serovar hardjo (type hardjo-bovis)
Most of the five-way lepto vaccines are labeled for protection against the first five serovars: hardjo-prajitno, pomona, canicola, icterohaemorrhagiae, and grippotyphosa.
Previously, it was thought that the hardjo serovar in the U.S. was hardjo-prajitno, but it was then revealed that the hardjo-bovis serovar was much more common.
It is very difficult to distinguish these serovars, and it requires advanced techniques only available in special laboratories. The infection cannot be distinguished between these two serovars by examination of blood antibody responses.
Cross-protection between hardjo-prajitno and hardjo-bovis has been demonstrated in many of the leptospira vaccines from Boehringer Ingelheim Vetmedica Inc.
The role of maintenance hosts
Maintenance hosts are highly susceptible to infection with a specific serovar, but they do not show serious clinical signs of infection. Because maintenance hosts do not mount a strong antibody response to these serovars, the infection tends to persist in the kidney and sometimes the genital tract.
Chronic kidney infection is responsible for urine shedding of the organism into the environment and so “maintains” the infection cycle for the leptospira. The weak antibody response also makes disease difficult to diagnose by serological methods.
In contrast to maintenance hosts, when a leptospire infects an incidental or non-adapted host, clinical signs are much more severe and the disease tends to be acute rather than chronic. Incidental hosts also tend to have a strong antibody response to infection, which makes diagnosis much easier.
Cattle are maintenance hosts for hardjo-bovis. When hardjo-bovis infects a maintenance host, such as a cow, the organism causes a chronic infection in the kidney and is shed in high numbers in the urine. Hardjo-bovis also can persist in the genital tract and has been suspected of causing some degree of infertility.
Other common maintenance hosts for the different lepto serovars are listed in Table 1 .
Leptospira spp pomona and grippotyphosa are the most common non-adapted serovars causing serious clinical signs in cattle in the U.S.
Clinical signs
Both maintenance and incidental hosts can exhibit all the clinical signs of the disease listed below and the infection can be acute, sub-acute or chronic in nature. However, disease in maintenance hosts tends to be sub-acute and chronic, whereas in incidental hosts the disease is more likely to be acute.
• Acute: Clinical signs include fever, lethargy, septicemia, mastitis, abortion, hemoglobinuria (red urine), anemia and death. Abortions may be the only presenting clinical sign. Calves are also more likely to show acute clinical signs than adult cows.
• Sub-acute: Similar clinical signs but not as severe; abortions occur three to four weeks later than in an acute case of leptospirosis.
• Chronic: Chronic clinical signs are mild or don’t appear at all. Chronic leptospirosis is generally restricted to reproductive problems that occur weeks to months after initial infection.
Mastitis due to leptospirosis is distinguished from other forms of mastitis due to the udder being flaccid. The secretions from all four quarters are thick, yellow and generally blood-tinged.
Prevention of leptospirosis
Dairy producers are strongly advised to prevent leptospirosis in the dairy herd. Prevention of leptospirosis consists of breaking the infection cycle.
An initial step is to identify and eliminate those cows contaminating the environment through urine shedding of hardjo-bovis. A presumptive diagnosis of infection is made after laboratory analysis of both urine and blood samples.
Antibiotic treatments have been recommended to rid the kidney of the infection, but the efficacy is still controversial. Secondly, access to free-standing water should be eliminated if possible. Finally, an appropriate vaccination protocol should be implemented.
An effective vaccination protocol for leptospirosis should accomplish two objectives. First, to prevent the urinary shedding of hardjo-bovis so environmental contamination does not occur and, secondly, to protect against the devastating effects of the disease.
From a dairy’s perspective, this mainly pertains to lowered reproductive performance from poor fertility and abortions.
All lepto vaccine recommendations in female dairy animals should include protection against lepto hardjo-bovis urinary shedding.
The following is a suggested protocol for leptospira protection. Pay attention to the vaccine label, as the product may need to be boostered on the primary series.
• Pre-weaning: First vaccination with a product containing a five-way lepto that cross-protects against Lepto hardjo-bovis at approximately five weeks of age. The booster is given two to four weeks later.
• Six months old or older: If calves were vaccinated at younger than six months, they should receive a five-way lepto (with cross-protection against lepto hardjo-bovis) booster
• Pre-breeding: Heifers and lactating cows should be vaccinated at about one month prior to breeding
Pregnant animals can also be boostered with a lepto vaccination, provided the vaccine is labeled appropriately.
Leptospirosis is an important disease that can cause problems and economic loss on the dairy. Discuss preventive measures with your veterinarian to ensure you have the proper protection against this disease. PD
References omitted due to space but are available upon request to editor@progressivedairy.com .
Mark van der List
Professional Services
Veterinarian
Boehringer Ingelheim Vetmedica Inc.
mark.van_der_list@boehringer-ingelheim.com
