# What is the optimal In2Care stations density to achieve Aedes aegypti population reduction in a dengue endemic setting?

## TL;DR

This study shows that a high density of In2Care stations can significantly reduce Aedes aegypti mosquito populations in a dengue-endemic city.

## Contribution

The study provides empirical evidence that a lower-than-recommended In2Care station density can still effectively suppress Ae. aegypti populations.

## Key findings

- A high-density area with ~555 In2Care stations per km² saw a 56% reduction in Ae. aegypti egg counts.
- Low- and medium-density areas showed no significant reduction in mosquito breeding.
- The study suggests that ~555 stations per km² may be effective, though further testing is needed in other regions.

## Abstract

Autodissemination traps are among the most innovative strategies for suppressing mosquito vector populations. These traps are particularly effective against Aedes aegypti due to the species’ skip oviposition behavior, where eggs from a single clutch are distributed across multiple breeding sites. Evaluating the efficacy of different densities of In2Care stations under large-scale field conditions is crucial for understanding their potential impact on Ae. aegypti populations.

A total of 3,250 In2Care stations were deployed in Goiânia, the 10th largest city in Brazil, with an estimated population of 1.45 million. The field study lasted 14 months, with each station serviced bi-monthly. To assess the impact of In2Care, ovitraps were installed and inspected weekly to measure changes in the number of positive ovitraps and the average number of eggs laid by Ae. aegypti females in intervention areas compared to control neighborhoods. Over the course of the study, 666,204 eggs were sampled. The density of In2Care stations varied across neighborhoods, ranging from 220 to 555 stations per km2. In the high-density area (~555 stations per km2), the Ovitrap Positivity Index (OPI) decreased from 56.9% to 31.5%, while the average number of eggs per positive paddle dropped from 41.2 to 18.1—representing a 56% reduction in egg counts. Conversely, in the low- and medium-density, no significant effect was observed.

The recommended density of In2Care is about 2500 stations per Km2. Our results demonstrated stations density 4.5 times lower than the recommended density is able to reduce the frequency of positive ovitraps and the number of eggs collected on them. entomological indexes. Additional fieldwork in other entomological and epidemiological settings are needed to evaluate whether the In2Care density of ~555 units/Km2 observed for Goiânia was site-dependent or if it has borader applicability. Our results show that In2Care stations can effectively suppress Ae. aegypti populations over large geographic areas, with efficacy likely influenced by trap density.

Autodissemination traps are an exciting new approach to controlling mosquito populations. These traps are especially useful for fighting Aedes aegypti mosquitoes because of their unique egg-laying behavior, where they spread their eggs across multiple sites. Testing the effectiveness of In2Care stations, a type of autodissemination trap, in real-world conditions in areas with high dengue transmission is important for understanding their potential. A total of 3,250 In2Care stations were set up in Goiânia, one of Brazil’s largest cities with a population of 1.45 million people. The fieldwork lasted for 14 months, and each trap was serviced every two months. To monitor the results, small egg traps called ovitraps were installed and checked weekly. This helped measure how effective the In2Care stations were in reducing mosquito breeding compared to areas without them. Over the course of the study, 666,204 mosquito eggs were collected. The number of In2Care stations varied by neighborhood, with densities ranging from 220 to 555 stations per square kilometer. The area with the highest number of stations saw a big drop in mosquito breeding: the number of positive ovitraps fell from 56.9% to 31.5%, and the number of eggs per trap dropped by 56%, from 41.2 to 18.1. However, in the other three sites, with In2Care density ranging between 220–340, no significant changes were seen. Overall, these findings suggest that In2Care stations can significantly reduce mosquito populations over large areas, especially when enough traps are in place.