Myths & Truths about Leptospirosis

 

Myths Truths
Leptospirosis in humans is caused only by direct contact with the secretions of wild animals like rodents. Many animal species like cattle, sheep, horses and dogs can be infected by leptospires. The organism settles in the kidneys and is excreted with their secretions (mainly urine). Transmission of leptospires takes place through direct contact with urine or tissue from an infected animal, or through indirect contact with an environment contaminated with urine or secretions.
Owners who have their pets vaccinated are not at risk of being infected by them.

 

The lack of antigenic relatedness between serotypes of leptospires means the vaccines are not able to protect the animals against serotypes not included in them. Moreover, vaccines may prevent the manifestation of clinical disease but they cannot prevent the installation of leptospires in the kidneys of the animal. Therefore, it is possible that vaccinated animals may excrete both homologous and heterologous serotypes of leptospires.
All serotypes of leptospires are pathogenic. There is a large number of serotypes of genus Leptospira that are non-pathogenic to humans. These serotypes are saprophytic, abundant in the environment, and create problems in the laboratory diagnosis of the disease.
Symptoms of leptospirosis are characteristic of the disease and the diagnosis based on these is relatively easy. Leptospirosis occurs in humans in a mild or severe form, causing a wide range of symptoms. Therefore, many of the symptoms associated with leptospirosis can be attributed to other diseases, indicating possible under-diagnosis of the disease.
Serotyping of leptospires which are detected in humans and animals has no practical value. The identification of the serotype of leptospires responsible for clinical disease of a patient/animal has great epidemiological importance. In animals, the epidemiological picture is very complex, and the co-existence of different animal species implies the co-existence of different natural and accidental hosts, which can lead to different disease states. The above demonstrates the need for constant and thorough monitoring of circulating serotypes of leptospires in animals which come into direct or indirect contact with humans, in order to reflect clearly the current epidemiological situation, and recognize early each new possible source of infection in humans and animals. Additionally, developing and using vaccines requires the identification of serotypes in each case, as the vaccines stimulate an immune response only against serotypes contained in them.

G. Valiakos, C. Billinis, Laboratory of Microbiology & Parasitology, Faculty of Veterinary Medicine,
School of Health Sciences, University of Thessaly