Monthly variation and natural infection in Lutzomyia umbratilis Fraiha & Ward, 1977, Lutzomyia anduzei Rozeboom, 1942, Lutzomyia flaviscutellata Mangabeira, 1942 and Lutzomyia olmeca nociva Young & Arias, 1982 (Diptera: Psychodidae) with trypanosomatids (

Abstract

INTRODUCTION: In the military reserve area located between kilometers 54 and 70 of the AM-010 Highway (Manaus-Itacoatiara) in Amazonas State, there are five military training bases (BIBR, BI1, BI2, BI3 and BI4) where cases of American tegumentary leishmaniasis (ATL) have been reported.
OBJECTIVES: The aims of this study were as follows: i) to determine the monthly variation in the frequency and distribution of Lutzomyia umbratilis, L. anduzei, L. flaviscutellata and L. olmeca nociva, vectors of ATL, at training bases in the military reserve; and ii) to assess the natural infection rate of these phlebotomine sandfly species by trypanosomatids at the affected military bases.
MATERIAL AND METHODS: The study was conducted between March 2002 and February 2003. Phlebotomine sandflies were captured using CDC light traps, sucking aspirators placed at the base of trees and animal bait. Parasites were isolated from the sandflies using NNN medium (agar-blood) and susceptible laboratory animals (hamsters).
RESULTS: A total of 11,583 phlebotomine sandflies, comprising 58 species, were captured. The four vector species accounted for 6,182 (53.3%) of these flies; L. umbratilis was the most abundant species collected (4,293; 69.4%), followed by L. anduzei (890; 14.4%), L. olmeca nociva (668; 10.8%) and L. flaviscutellata (331; 5.4%). The only species that was collected during each of the study months was L. flaviscutellata. The greatest number of phlebotomine sandflies was captured at the BI1 base (2,573; 47.6%), followed by the BIBR base (1,496; 27.6%), the BI2 base (899; 16.6%), the BI3 base (366; 6.8%) and the BI4 base (73; 1.4%). Of the 821 females that were dissected, 15 (1.96%) specimens of L. umbratilis from military bases BI1 and BIBR were found to be naturally infected by trypanosomatids. It was not possible to transport experimental animals to the sampling sites (military bases), which hindered the direct isolation of flagellates. Isolation of promastigotes from the guts of insects was not performed because contamination of the culture media prevented their inoculation into experimental animals.
CONCLUSION: The monthly variation in the frequency of the four vector species in the military training areas showed no regular pattern, and L. umbratilis was identified as the species that was likely to be responsible for the transmission of ATL in this military reserve.