Leptospirosis is a potentially fatal and zoonotic bacterial disease caused by pathogenic bacterium Leptospira. There are over 200 serovars maintained in renal tubules of many domestic and wild animal species.
The organism is maintained in renal tubules without causing disease. The organisms are excreted through urine and can contaminate the environment or result in infection of susceptible animals and humans through contact with urine. Accidental/incidental hosts may be infected by accidental exposure, and infection may result in severe disease.
Leptospira are transmitted through contact with urine of infected animals or contaminated environment. The bacteria will enter the blood stream through the skin and mucosa and invade the tissues. If the host’s immune responses are adequate, the infection will be cleared. The organisms may persist in the kidneys and eyes for a period of time.
In acute leptospirosis, the disease has a protean manifestation, which will resemble many other bacterial and viral infections. Acute infections may result in renal and hepatic failure, cardiopulmonary failure, hemorrhage, jaundice, abortion and stillbirth. Recurrent uveitis is common in horses and humans as a result of Leptospira infection.
Cattle may drop in milk production, and early embryonic death or abortions are attributed to Leptospira infections.
For animals in early stages of infection, heparinized blood and urine for fluorescent antibody (FA) staining and polymerase chain reaction (PCR) are recommended. A paired serum sample is also recommended for serological testing. Antibodies appear five to 10 days after infection. Therefore, samples collected at the initial stage of infection and after 14 days of infection will give an accurate estimate. The microscopic agglutination test (MAT) is available for six serovars of Leptospira, which may provide information on the specific serovar involved.
In cattle, when reduced fertility is suspected due to leptospirosis, submit 10 ml of a midstream-collected urine sample for FA and/or PCR. Midstream urine (second or third void urine) collected after the administration of a diuretic such as furosemide (Lasix®) is ideal. Using a combination of PCR and FA is ideal to minimize false negative or false positive results.
Postmortem specimens of internal organs such as liver, kidney and heart blood, collected aseptically soon after death, should be transported immediately to the laboratory. If there is delay in transporting the specimens, samples should stored at 4oC.
FA, PCR and Immunohistochemistry are available for testing tissue specimens. Culture is available, but is not recommended due to low sensitivity resulting from contamination and a prolonged incubation period. All samples for PCR and FA should be shipped overnight with ice packs.
This bacterium is susceptible to a wide variety of antibiotics. Commonly used antibiotics are: penicillin G, amoxicillin, ampicillin, doxycycline and erythromycin. Vaccines containing some serovars are available for prevention.
Humans mainly acquire infection by occupational and recreational exposure to infected animals’ urine in a contaminated environment. Fatal disease may develop.
Through research at the TVDIL, we are attempting to isolate strains of Leptospira prevalent in animal populations from this geographic region. This is important for developing improved vaccines and control measures. We are also studying the association of Leptospira with reduced fertility in cattle. If you have a case or questions concerning leptospirosis, please contact Dr. Sree Rajeev at the TVDIL (229-386-3340).
