Lutzomyia longipalpis (Diptera: Psychodidae) at a suburban focus of visceral leishmaniasis in the Chicamocha Canyon, Santander, Colombia.

Abstract

Introduction. Between 1998 and 2000, the occurrence of 8 cases of American visceral leishmaniasis in children from a recently established human settlement in Guatiguará, in the municipality of Piedecuesta (Santander, Colombia) indicated the possible presence of Leishmania transmission in this locality. This observation motivated the current entomological investigation.

Objectives. To determine the relative frequency of Lutzomyia longipalpis inside houses and outdoors, and the natural infection of this vector with Leishmania spp.

Materials and methods. CDC light traps were used for sampling inside houses and outdoors, and sand flies were collected on human volunteers and domestic animals, and in resting places, during the period from May 1999 through September 2000. Natural infection was determined by PCR, in pools of female Lutzomyia longipalpis.

Results: A total of 7,391 phlebotomine sand flies were collected. The predominant species was Lutzomyia longipalpis (Lutz & Neiva), representing 99.5% of captures. In the sand flies collected with CDC light traps, L. longipalpis was more frequently collected indoors than outdoors ( p=0.0001). The total rate of natural infection was 1.93% and a positive correlation was observed between months with higher abundance and the number of infected females entering human dwellings.

Conclusions: The results indicate that in Guatiguará Lutzomyia longipalpis, shows marked tendency for the indoors, which has important implications for leishmaniasis transmission.

Furthermore, transmission risk is increased during the months of higher abundance due to the entry of a higher number of infected females. From the standpoint of control, this behaviour permits the design of strategies to reduce indoor transmission.