Critical Evaluation of Quantitative Sampling Methods for Aedes aegypti (Diptera: Culicidae) Immatures in Water Storage Containers in Vietnam

• Published in: Journal of medical entomology Vol. 44; no. 2; pp. 192 - 204
• Main Authors: Knox, T.B, Yen, N.T, Nam, V.S, Gatton, M.L, Kay, B.H, Ryan, P.A
• Format: Journal Article
• Language: English
• Published: England 01.03.2007
• Subjects: Aedes - physiology; Aedes aegypti; Animals; aquatic habitat; containers; Dengue - prevention & control; Environmental Monitoring - methods; estimation; immatures; insect vectors; Insect Vectors - physiology; Larva; larvae; methodology; Mosquito Control - methods; net sampling; Population Density; pumping/sieving technique; Pupa; pupae; sampling; Time Factors; vector surveillance; Vietnam; Water; water jars; water tanks; Vietnam
• ISSN: 0022-2585; 1938-2928
• DOI: 10.1603/0022-2585%282007%2944%5B192%3ACEOQSM%5D2.0.CO%3B2

In response to an identified paucity of information on the size and composition of immature Aedes aegypti (L.) (Diptera: Culicidae) populations in large field containers, we assessed net sampling and pumping/sieving methods for estimating and enumerating third (III)/fourth (IV) instar and pupal populations. Sweep net detection thresholds (number above which >or= 90% chance of a positive sample) were <or= 28 immatures for seven different container types (115-3000 liter jars and tanks) in the laboratory, and mean recovery percentages varied by container type (6.15-41.29 and 7.39-33.10% for III/IV instars and pupae, respectively). A pumping method or hand bailing was applied in the field for the collection of III/IV instars and pupae from 406 receptacles, of which 343 had been previously sampled via a five-sweep netting technique. Larvae were 9.30 times more prevalent than pupae, and abundance varied by container type with means of 36-537 III/IV instars and 6-53 pupae per receptacle. Sweep netting for III/IV instars effectively identified 86.2% of Ae. aegypti-positive containers, whereas sampling for pupae detected only 43.1% of positive containers. When conversion factors (inverse of laboratory recovery percentages) were applied to field net sampling data, estimates of container populations were more accurate for III/IV instars than pupae (maximum R2 = 0.610 and 0.328, respectively); however, the relationship between immature abundance and emergent adult populations remains to be defined.