Ron P Marchand | PubMed Health

PubMed2005

First record of Anopheles minimus C and significant decrease of An. minimus A in central Vietnam.

Before August 1998, in the Khanh Phu commune (central Vietnam), Anopheles minimus s.l. individuals were identified as species A and showed the typical species A wing form. After a significant decrease over the 3 years 1999-2001, an increase in 2002 of An. minimus s.l. possessing a different wing pattern was observed. To determine the specific status of the An. minimus species collected in 2002 and to follow changes in the species composition, an allele-specific polymerase chain reaction was applied to samples collected from 1993 to 2002. This study reports the first record of An. minimus C in central Vietnam and, since 1998, a significant reduction of An. minimus A that coincided with the wide use of permethrin-treated bednets. This change in anopheline composition may have important consequences on malaria transmission. This work shows that the geographic distribution of malaria vectors in southeast Asia is only partially known and highlights the importance of species identification for understanding changes in the vector composition as a result of selective vector control.

Animals↗

PubMed2003

Quantitative evaluation of funnel traps for sampling immature Aedes aegypti from water storage jars.

The trend is increasing to incorporate assessments of abundance into surveys for immature Aedes aegypti to identify the most important types of containers that should be targeted for control. In this study, we examined whether funnel traps could be used to sample immature Ae. aegypti from water storage jars ranging in size from 0.28-m diameter (30 liters) to 0.52-m diameter (150 liters). The effects of jar size and duration of funnel trap sampling were investigated and a set of calibration factors was developed to convert funnel trap numbers to absolute population estimates (0.28-m diameter = 2.5, 0.38-m diameter = 3.0, 0.48-m diameter = 4.6, and 0.52-m diameter = 7.4). Although the funnel traps were highly sensitive (90-100%) for detecting immature Ae. aegypti at densities as low as 25 3rd and 4th instars per jar, the large variation in funnel trap recapture rates meant that absolute population estimates based on a single funnel trap sample were inaccurate. However, by using a computer simulation, estimates of the total overall numbers of larvae from multiple jars were reasonably accurate (+/- 20%), if more than 50 positive jars were surveyed. For example, 95% confidence intervals for the percentage error in estimated numbers of immatures from a series of 50 0.38-m-diameter and 50 0.52-m-diameter jars, were -10.0% to +10.2% and -19.9% to +17.8%, respectively. Although we generally recommend the use of nets to sample immature Ae. aegypti in jars, under some conditions funnel traps may be more acceptable than nets, because some householders object to the increased turbidity associated with net sampling in jars.

Aedes↗