LeptospirosisWeil’s disease, an infection associated with jaundice and caused by invasion with Leptospira icterohaemorrhagiae, was the first leptospiral infection to be recognized in man. It was not long before it was discovered that the rat is the natural host and that the mode of spread is by contact with rat’s urine containing the organism, which can penetrate the skin or mucosae.
Subsequently over 100 serotypes of leptospires have been identified, many of which have been shown to cause disease in man. The natural hosts of most of these types are small wild rodents, but some may also occur in animals such as dogs and pigs. In Britain only two serotypes, namely L. icterohaemorrhagiae and L. canicola, have been shown to cause human disease, but other serotypes have been isolated from wild rodents. The spread of these infections is usually by contamination with infected animal urine, and fish cleaners, farm-workers, veterinarians and vagrants are those most at risk; immersion in canals or stagnant water may also result in sporadic infection and in such instances the disease may present as lymphocytic meningitis due, probably, to the entrance of the leptospires through the conjunctivae.