Natural arbovirus infection rate and detectability of indoor female Aedes aegypti from Mérida, Yucatán, Mexico

Abstract

Arbovirus infection in Aedes aegypti has historically been quantified from a sample of the adult population by pooling collected mosquitoes to increase detectability. However, there is a significant knowledge gap about the magnitude of natural arbovirus infection within areas of active transmission, as well as the sensitivity of detection of such an approach. We used indoor Ae. aegypti sequential sampling with Prokopack aspirators to collect all mosquitoes inside 200 houses with suspected active ABV transmission from the city of Mérida, Mexico, and tested all collected specimens by RT-PCR to quantify: a) the absolute arbovirus infection rate in individually tested Ae. aegypti females; b) the sensitivity of using Prokopack aspirators in detecting ABV-infected mosquitoes; and c) the sensitivity of entomological inoculation rate (EIR) and vectorial capacity (VC), two measures ABV transmission potential, to different estimates of indoor Ae. aegypti abundance. The total number of Ae. aegypti (total catch, the sum of all Ae. aegypti across all collection intervals) as well as the number on the first 10-min of collection (sample, equivalent to a routine adult aspiration session) were calculated. We individually tested by RT-PCR 2,161 Aedes aegypti females and found that 7.7% of them were positive to any ABV. Most infections were CHIKV (77.7%), followed by DENV (11.4%) and ZIKV (9.0%). The distribution of infected Aedes aegypti was overdispersed; 33% houses contributed 81% of the infected mosquitoes. A significant association between ABV infection and Ae. aegypti total catch indoors was found (binomial GLMM, Odds Ratio > 1). A 10-min indoor Prokopack collection led to a low sensitivity of detecting ABV infection (16.3% for detecting infected mosquitoes and 23.4% for detecting infected houses). When averaged across all infested houses, mean EIR ranged between 0.04 and 0.06 infective bites per person per day, and mean VC was 0.6 infectious vectors generated from a population feeding on a single infected host per house/day. Both measures were significantly and positively associated with Ae. aegypti total catch indoors. Our findings provide evidence that the accurate estimation and quantification of arbovirus infection rate and transmission risk is a function of the sampling effort, the local abundance of Aedes aegypti and the intensity of arbovirus circulation.

Pilot trial using mass field-releases of sterile males produced with the incompatible and sterile insect techniques as part of integrated Aedes aegypti control in Mexico

“…Indoor female Ae . aegypti density is considered one of the closest entomological measures of arbovirus transmission risk [ 60 , 61 ]. Indoor female Ae .…”

“…Ovitraps represent an economic and simple method for monitoring Aedes mosquito populations which is already in use by the Mexican MoH [ 31 , 41 ], and an established infrastructure to monitor egg hatch rates after Wolbachia release. Adult collections are not systematically done as part of routine activities, although “entomo-virological surveillance” (adult collections and arbovirus detection) is currently being conducted with portable aspirators such as Prokopack aspirators in a few Mexican States to determine the prevalence and abundance of female mosquitoes and infection with DENV, CHIKV and now ZIKV [ 61 , 63 – 65 ]. Therefore, indoor adult female collections, which represent the epidemiologically important target [ 17 , 18 , 33 , 66 ], can be more feasible to implement than outdoors collections (with BG traps or others).…”

Protective effect of house screening against indoor Aedes aegypti in Mérida, Mexico: A cluster randomised controlled trial

“…Both indoor adult Ae . aegypti density and ATV infection in mosquitoes are considered the closest entomological measures to transmission risk [ 44 , 45 ]. The detection of positive houses in 10‐minute sampling rounds with Prokopack aspirators has shown high levels of sensitivity for Ae .…”

“…Although the ability of Ae . aegypti to breed around human habitats is considered an important risk factor for transmission of ATVs [ 44 , 56 , 57 ], because of the nature of the intervention our results were mainly driven by the collection of adult Ae . aegypti mosquitoes, which unfortunately left the peridomestic areas of the enrolled households out of immature‐based entomological information.…”

Influence of Host Blood Meal Source on Gut Microbiota of Wild Caught Aedes aegypti, a Dominant Arboviral Disease Vector

“…Given that gut microbiota can also modulate the pathogen infection status in mosquitoes [11,31], we screened the collected Ae. aegypti mosquitoes for prevalent arbovirus (DENV, CHIKV and ZIKV) infection using real-time PCR-based method [32]. RNA extracted from individual head-thorax was used for this purpose.…”