Leptospira and rodents in Cambodia: environmental determinants of infection

Abstract

We investigated infection of rodents and shrews by Leptospira spp. in two localities of Cambodia (Veal Renh, Kaev Seima) and in four types of habitat (forests, non-flooded lands, lowland rain-fed paddy fields, houses) during the wet and the dry seasons. Habitat preference was common, and rodent and shrew species were found only in houses or in rain-fed paddy fields or in forests. Among 649 small mammals trapped belonging to 12 rodent species and 1 shrew species, 71 of 642 animals tested were carriers of Leptospira according to the 16S ribosomal RNA marker used. Rodent infection was higher in low-slope locations, corresponding to rain-fed paddy fields, especially in the rainy season and in Kaev Seima. Rodents (Rattus exulans) and shrews (Suncus murinus) inhabiting households showed significantly low levels of infections, whereas rodents living in and near to forests (shrubby wasteland, orchards) showed high levels of infection.

Figure 1.

Normalized Difference Vegetation Index (NDVI) and slope maps with location of trap lines in the two study sites, Veal Renh and Kaev Seima, Cambodia.

Figure 2.

Distribution of rodent species in Cambodia according to habitat types: paddy fields (lowland rain-fed), non-flooded lands, forests, houses on the two first axes of principal component analysis. The factor 1 and 2 accounted for 85% of the variance.