To the Editor: Leptospirosis is a worldwide bacterial zoonosis caused by infection with pathogenic Leptospira spp. (Spirochaetales, Leptospiraceae). Most mammals can be infected, but rats are considered the main reservoir, maintaining Leptospira spirochetes in the lumen of renal tubules and contaminating the environment with bacteria-infected urine. Transmission to humans is accidental, occurring through contact with animal secretions or with contaminated environmental materials.
In temperate countries, human leptospirosis is a sporadic disease; incidence is much higher in the tropics because climate and environmental conditions are conducive to the survival of bacteria, resulting in increased exposure of humans to leptospirosiscausing pathogens (1). Among islands in the southwestern Indian Ocean, human leptospirosis is endemic to Mayotte, France, and La Reunion (2-4) and to the Seychelles, where the incidence of leptospirosis is one of the highest worldwide (5). Leptospirosis is poorly documented in other islands in the region, including Mauritius, Madagascar, and the Union of the Comoros (2,6-8). Whether the scant documentation indicates underdiagnosis or reflects local epidemiologic specificities is unknown. To improve knowledge of Leptospira infection in the region, we conducted a study in the Union of the Comoros to serologically assess the presence or absence of leptospirosis in humans. The Union of the Comoros consists of 3 islands: Grande-Comore, Moheli, and Anjouan. Together with a fourth, southern island, Mayotte, these islands form the Comoros Archipelago.
For feasibility reasons, we used excess serum samples. Seventy-six samples were from healthy volunteers who gave informed consent; 318 clinical blood samples from patients had been obtained by private laboratories and by the surveillance laboratory of the National Malaria Control Programme (PNLP) during August 1-October 8, 2011. The Ministere de la Sante, de la Solidarite et de la Promotion du Genre of the Union of the Comoros, authorized the serologic investigation (authorization no. 1175/ MSSPG/DNS).
We used the microscopic agglutination test (MAT) to test serum samples; the MAT was based on a panel of 15 Leptospira strains,...