Leptospiroses

acute infectious diseases caused by leptospira.

More than ten serological types of leptospira are known to be capable of causing leptospiroses in man. Leptospiral jaundice and anicteric leptospirosis have been studied in the most detail.

Leptospiral jaundice, or Weil-Vasil’ev’s disease (named after the German scientist A. Weil, who described it in 1886, and the Russian scientist N. P. Vasil’ev, who did so in 1888), is caused by Leptospira icterohaemorrhagiae. The disease sets in acutely, with chills, general weakness, and elevated temperatures of about 39°-40°C. The victim suffers headaches; pains in the small of the back, in the muscles and joints, and, often, in the right hypochondrium and the epigastric region; and nausea and vomiting. Jaundice appears on about the fourth day. Rats are the natural reservoir of the disease and the source of infection for man, the causative agent being excreted with the urine of the diseased rats. Human beings become infected by drinking water contaminated by these excretions or by eating contaminated foods. Extermination of rats is the best preventive.

Epidemics of anicteric leptospirosis were first described by the Soviet scientist V. L. Bashenin in 1928, and the causative agent Leptospira grippotyphosa was discovered by the Soviet scientist S. I. Tarasov the same year. The incubation period lasts from three to 14 days. The disease sets in with chills and weakness. Headaches and pain in the small of the back, leg, and thoracic muscles develop. The temperature rises to 39°-40°C. The main sources of infection and the natural reservoirs of the leptospira are rats and mice, sheep, goats, swine, and cattle. The diseased animals excrete the causative agent with the urine and feces for three to six months. Human beings become infected by drinking contaminated water or eating food contaminated by the excretions. The disease can also be transmitted by contaminated hands. Major epidemics have been described, and the morbidity appears markedly seasonal (high in summer and fall). Anicteric leptospirosis is prevented by exterminating rodents, draining swampy meadows, and prohibiting bathing in and downstream of cattle watering places. Seven-day fever and canine fever are leptospiroses that have not been thoroughly studied.

Among the animals susceptible to leptospiroses are cattle, sheep, goats, swine, horses, arctic foxes, chickens, ducks, and rodents, such as mice, rats, and susliks. The natural nidi of leptospiroses are the wet habitats (bogs, low-lying areas, river floodplains) of the rodent-carriers of the causative agents of the disease. The main factor in the transmission of the causative agents is stagnant water contaminated by the excretions of diseased animals. The activity of the affected animals is inhibited, and the animals’ productivity decreases sharply as body temperature rises. In acute cases, the animals often die. A serum proposed by S. Ia. Liubashenko is used for treatment. The diseases are prevented by quarantining animals newly arriving at a farm, exterminating rodents, observing sanitary regulations at animal watering places, and vaccinating domestic animals.

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