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

Abstract

Background Aedes aegypti is an efficient vector of several arboviruses of public health importance, including Zika and dengue. Currently vector management is the only available avenue for disease control. Development of efficient vector control strategies requires a thorough understanding of vector ecology. In this study, we identified households that are consistently productive for Ae. aegypti pupae and determined the ecological and socio-demographic factors associated with the persistence and abundance of pupae in households in rural and urban Kenya. Methods We collected socio-demographic, environmental and entomological data monthly from July 2014 to June 2018 from 80 households across four sites in Kenya. Pupae count data were collected via entomological surveillance of households and paired with socio-demographic and environmental data. We calculated pupal persistence within a household as the number of months of pupal presence within a year. We used spatially explicit generalized additive mixed models (GAMMs) to identify the risk factors for pupal abundance, and a logistic regression to identify the risk factors for pupal persistence in households. Results The median number of months of pupal presence observed in households was 4 and ranged from 0 to 35 months. We identified pupal persistence in 85 house-years. The strongest risk factors for high pupal abundance were the presence of bushes or tall grass in the peri-domicile area (OR: 1.60, 95% CI: 1.13–2.28), open eaves (OR: 2.57, 95% CI: 1.33–4.95) and high habitat counts (OR: 1.42, 95% CI: 1.21–1.66). The main risk factors for pupal persistence were the presence of bushes or tall grass in the peri-domicile (OR: 4.20, 95% CI: 1.42–12.46) and high number of breeding sites (OR: 2.17, 95% CI: 1.03–4.58). Conclusions We observed Ae. aegypti pupal persistence at the household level in urban and rural and in coastal and inland Kenya. High counts of potential breeding containers, vegetation in the peri-domicile area and the presence of eaves were strongly associated with increased risk of pupal persistence and abundance. Targeting households that exhibit pupal persistence alongside the risk factors for pupal abundance in vector control interventions may result in more efficient use of limited resources.

Spatio-Temporal Modelling Informing Wolbachia Replacement Releases in a Low Rainfall Climate

“…Typically, there are local areas where mosquitoes are abundant, interspersed with other areas where numbers are lower at fine spatial scales [ 13 ]. Local high-density areas may be identifiable through specific environmental factors to some extent (e.g., [ 4 , 14 , 15 , 16 ]). Trap catches can be relatively stable across time in some areas [ 17 ], but this is not always the case with high mosquito counts for a period in one area being replaced by other local areas even within the same village or suburb.…”

Human IgG responses to Aedes mosquito salivary peptide Nterm-34kDa and its comparison to Anopheles salivary antigen (gSG6-P1) IgG responses measured among individuals living in Lower Moshi, Tanzania

“…Furthermore, a study conducted in an urban setting in Zanzibar found that the presence of vegetation was significantly associated with the presence of immature stages of Aedes aegypti [ 52 ]. Another study conducted in both rural and urban Kenyan setting also reported the strongest risk factor for Aedes pupa abundance were the presence of bushes, tall around the houses [ 53 ]. Thus, the combined effect of rains and more dense vegetation cover may be the probable reason for the significant increase in Aedes mosquitoes’ abundance and thus exposure to Aedes mosquito bites in Oria village, in particular.…”

Dengue Virus Surveillance and Blood Safety: A One Health Perspective

“…Instead, it can be saved for special studies or used twice in each locality, once during the wet season and once during the dry season, to identify the most productive containers. For practical purposes, the Pupal index has been the most widely used strategy [84,86]. The basis for making the greatest use of a few resources can be laid by identifying the classes of containers in the neighborhood that have the highest rates of adult emergence.…”

“…Put every pupa in a vial with a label. Large containers provide a great challenge in pupal/ demographic surveys, as it is difficult to identify the precise number of pupae in them [86,90,91].…”