Leptospirosis


Leptospira bacteria in liver impression smear.
FA stain
This section provides information on one of the nine zoonotic diseases which have been identified by a experts in a national consultation organised by RCZI in June, 2008  as focus or priority diseases for the next five years.

Leptospirosis is a contagious disease of animals, occasionally communicable to humans, caused by a pathogenic spirochete of the genus Leptospira. All mammals appear to be susceptible to at least one species of Leptospira. Disease is rare in cats, and less common in sheep than cattle.

The primary reservoir hosts for most Leptospira serovars are wild mammals, particularly rodents. Reservoir hosts among domestic animals include cattle, pigs, sheep and dogs. The specific reservoir host(s) vary with the serovar and the geographic region.

Disease in reservoir hosts is more likely to be asymptomatic, mild or chronic. Leptospira infections may be asymptomatic, mild or severe, and acute or chronic. The clinical signs are often related to kidney disease, liver disease or reproductive dysfunction, including abortions. For instance, in newly infected cattle herds, up to 30% of the cows may abort, and overall calf production can decrease by up to 40%. In endemically infected herds, abortions are usually sporadic and occur mainly in younger animals. Infertility, with decreased pregnancy rates and increased culling, may also be noted. The estimated decrease in the first service conception rate is approximately 16-32%. Deaths can occur in calves. Chronically infected animals are often asymptomatic.

In humans, symptoms include high fever, severe headache, chills, muscle aches and vomiting and may include jaundice, red eyes, abdominal pain, diarrhea and/or rash. If the disease is not treated, the patient could develop kidney damage, meningitis, liver failure and respiratory distress. In rare cases death occurs. Many of these symptoms can be mistaken for other diseases. Leptospirosis is confirmed by laboratory testing of a blood or urine sample.

Leptospirosis is particularly prevalent in warm and humid climates, marshy or wet areas, and in regions with an alkaline soil pH; Gujarat with high alkalinity is an endemic focus of Leptospirosis in India. This disease is often seasonal: it is most common during the rainy season in the tropics (massive floods following Mumbai rains in 2005 led to large outbreak of Leptospirosis), and in the summer and fall in temperate regions.

In India, coastal states have reported sudden upsurge. From 5313 cases and 237 deaths in 2004 the numbers have gone down to 1879 cases and 86 deaths in 2009 in the six coastal states of Andamans, Maharashtra, Karnataka, Tamil Nadu, Kerala and Gujarat. Following massive rains in 2005, Mumbai witnessed one of the largest outbreaks of Leptospirosis in India with pulmonary form of disease as the predominant clinical presentation thus resulting high mortality. The disease is now also being reported from other parts of the country now such as Assam and Delhi, although the validity of these reports need to be established.

Regional/ India Situation

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Confirmed and Suspected Outbreaks of Leptospirosis