Natural control: ecology and biology

Abstract

In the Cevennes, the distribution of canine leishmaniasis and, therefore,of human visceral leishmaniasis is usually on the middle slopes ofhillsides. From previous work, it was assumed that the reason isthat the same places are the preferred habitats of the sandfly vector,Phlebotomus ariasi Tonnoir, 1921. An investigation was made throughoutone season (13.05.1977 to 7.10.1977) of the comparative densitiesof sandflies at different altitudes on two opposite sides of a selectedhill (le massif d'Oiselette) in the department of Gard. Oiled papers,changed every 15 days, were distributed at 22 points at altitudesfrom 165 to 600 m above sea level. A total of 5,050 sandflies werecollected and analysed according to altitude and time of year. Ofthe sandflies collected, 86,2% were P. ariasi, 0,3% were P. perniciosusNewstead, 1911, 0,1% were P. mascittii Grassi, 1908 and 13,4% wereSergentomyia minuta (Rondani, 1843). P. ariasi was present at allaltitudes with maximum densities between 300 and 500 m. This specieswas present from mid May until late September, with a maximum densityat the end of July. The results support the notion that, in the Cevennes,inhabitants of farms and villages on the slopes of hillsides at altitudesof 300-500 m are at the greatest risk of acquiring leishmaniasisbecause these places are the preferred habitat of the sandfly vector,P. ariasi.