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Leptospiral infection among primitive tribes of Andaman and Nicobar Islands

Published online by Cambridge University Press:  01 June 1999

S. C. SEHGAL
Affiliation:
Regional Medical Research Centre (Indian Council of Medical Research), Post Bag No. 13, Port Blair 744 101, Andaman and Nicobar Islands, India
P. VIJAYACHARI
Affiliation:
Regional Medical Research Centre (Indian Council of Medical Research), Post Bag No. 13, Port Blair 744 101, Andaman and Nicobar Islands, India
M. V. MURHEKAR
Affiliation:
Regional Medical Research Centre (Indian Council of Medical Research), Post Bag No. 13, Port Blair 744 101, Andaman and Nicobar Islands, India
A. P. SUGUNAN
Affiliation:
Regional Medical Research Centre (Indian Council of Medical Research), Post Bag No. 13, Port Blair 744 101, Andaman and Nicobar Islands, India
S. SHARMA
Affiliation:
Regional Medical Research Centre (Indian Council of Medical Research), Post Bag No. 13, Port Blair 744 101, Andaman and Nicobar Islands, India
S. S. SINGH
Affiliation:
G.B. Pant Hospital, Port Blair
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Abstract

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The Andaman islands were known to be endemic for leptospirosis during the early part of the century. Later, for about six decades no information about the status of the disease in these islands was available. In the late 1980s leptospirosis reappeared among the settler population and several outbreaks have been reported with high case fatality rates. Besides settlers, these islands are the home of six primitive tribes of which two are still hostile. These tribes have ample exposure to environment conducive for transmission of leptospirosis. Since no information about the level of endemicity of the disease among the tribes is available, a seroprevalence study was carried out among all the accessible tribes of the islands. A total of 1557 serum samples from four of the tribes were collected and examined for presence of antileptospiral antibodies using Microscopic Agglutination Test (MAT) employing 10 serogroups as antigens. An overall seropositivity rate of 19·1% was observed with the highest rate of 53·5% among the Shompens. The seropositivity rates in the other tribes were 16·4% among Nicobarese, 22·2% among the Onges and 14·8% among the Great Andamanese. All of the tribes except the Onges showed a similar pattern of change in the seroprevalence rates with age. The prevalence rates were rising from low values among children to reach a peak in those aged 21–40 years and then declined. Among Onges the seroprevalence rates continued to rise beyond 40 years. In all the tribes, seroprevalence rates were found to be significantly higher among the males. The commonest serogroups encountered were Australis followed by Grippotyphosa, Icterohaemorrhagiae, Pomona and Canicola.

Type
Research Article
Copyright
© 1999 Cambridge University Press