Pupal productivity in rainy and dry seasons: findings from the impact survey of a randomised controlled trial of dengue prevention in Guerrero, Mexico

Abstract

BackgroundThe follow-up survey of a cluster-randomised controlled trial of evidence-based community mobilisation for dengue control in Nicaragua and Mexico included entomological information from the 2012 rainy and dry seasons. We used data from the Mexican arm of the trial to assess the impact of the community action on pupal production of the dengue vector Aedes aegypti in both rainy and dry seasons.MethodsTrained field workers inspected household water containers in 90 clusters and collected any pupae or larvae present for entomological examination. We calculated indices of pupae per person and pupae per household, and traditional entomological indices of container index, household index and Breteau index, and compared these between rainy and dry seasons and between intervention and control clusters, using a cluster t-test to test significance of differences.ResultsIn 11,933 houses in the rainy season, we inspected 40,323 containers and found 7070 Aedes aegypti pupae. In the dry season, we inspected 43,461 containers and counted 6552 pupae. All pupae and entomological indices were lower in the intervention clusters (IC) than in control clusters (CC) in both the rainy season (RS) and the dry season (DS): pupae per container 0.12 IC and 0.24 CC in RS, and 0.10 IC and 0.20 CC in DS; pupae per household 0.46 IC and 0.82 CC in RS, and 0.41 IC and 0.83 CC in DS; pupae per person 0.11 IC and 0.19 CC in RS, and 0.10 IC and 0.20 CC in DS; household index 16% IC and 21% CC in RS, and 12.1% IC and 17.9% CC in DS; container index 7.5% IC and 11.5% CC in RS, and 4.6% IC and 7.1% CC in DS; Breteau index 27% IC and 36% CC in RS, and 19% IC and 29% CC in DS. All differences between the intervention and control clusters were statistically significant, taking into account clustering.ConclusionsThe trial intervention led to significant decreases in pupal and conventional entomological indices in both rainy and dry seasons.Trial registration ISRCTN27581154.

Relationships between traditional larval indices and meteorological factors with the adult density of Aedes albopictus captured by BG-mosquito trap

“…As the Ae. albopictus generally breed in artificial water containers, any type of water-holding container with clean water would be a good larval habitat [3,8]. The two villages investigated in this study had good sanitation conditions, and vegetation was abundant in and around the villages.…”

“…Precipitation played a crucial role in the transmission of mosquito borne diseases, due to the fact that mosquito required water for the aquatic larval and pupal breeding stages. Higher pupal productivity and entomological indices was found in the rainy season than dry season [3,16,26], and the effect of the precipitation to the larval density may have a time lag from 2 months to 1 month [33]. Precipitation could also influence the adult mosquito capturing.…”

“…aegypti and Ae. albopictus [3][4]. It is estimated that there are 390 million dengue infections each year globally, and among which, 96 million can produce clinical disease, leading to heavy disease burden [5].…”

Utility of entomological indices for predicting transmission of dengue virus: secondary analysis of data from the Camino Verde trial in Mexico and Nicaragua

“…The entomological data were stable between measurement points with respect to season and type of hatcheries. In our clusters, 99% and 98% of pupal productivity came from conventionally used water storage containers [ 50 ]. Barrera reported similar results in Puerto Rico[ 51 ].…”

Risk factors for Aedes aegypti household pupal persistence in longitudinal entomological household surveys in urban and rural Kenya

“…However, recent studies have shifted focus to include pupae in the surveillance of Aedes spp. immatures as a measure of disease outbreak risk [18][19][20] as pupae are a reliable proxy for adult mosquito abundance [21][22][23][24]. Lack of viable vaccines and effective therapies for dengue and other emerging arboviral infections leaves vector control as the only known disease control measure [25][26][27].…”