# Wolbachia Screening in Aedes aegypti and Culex pipiens Mosquitoes from Madeira Island, Portugal

## TL;DR

This study found that Wolbachia, a bacterium used to control mosquitoes, is absent in Aedes aegypti but present in Culex pipiens mosquitoes on Madeira Island.

## Contribution

The study provides the first evidence of Wolbachia presence in Cx. pipiens and absence in Ae. aegypti on Madeira, informing future biocontrol strategies.

## Key findings

- Wolbachia was absent in all 100 Aedes aegypti mosquitoes tested.
- All 40 Culex pipiens mosquitoes tested were infected with Wolbachia of the wPip clade.
- Cx. pipiens included the molestus biotype and hybrids, the first such hybrids found in Madeira.

## Abstract

Mosquitoes can spread serious diseases like dengue and West Nile virus. On Madeira Island, two mosquito species—Aedes aegypti and Culex pipiens—are present and may pose a risk to public health. Scientists are exploring new ways to control these mosquitoes using a natural bacterium called Wolbachia, which can reduce a mosquito’s ability to transmit viruses and even lower mosquito populations. However, for these methods to work, it is important to know first if the mosquitoes in the area already carry this bacterium. In this study, we tested Ae. aegypti and Cx. pipiens from Madeira for Wolbachia. Wolbachia was absent in all 100 Ae. aegypti tested but present in all 40 Cx. pipiens. We also found that the Wolbachia in Cx. pipiens belonged to a group commonly seen in other parts of the world. These results are important because they help us understand which mosquito control strategies might work in Madeira. Specifically, if scientists want to use Wolbachia to control Ae. aegypti on the island, they would need to introduce it artificially. This information can help improve public health efforts and reduce the risk of mosquito-borne diseases in the region.

Mosquito-borne diseases such as dengue and West Nile virus pose serious public health risks. On Madeira Island, the presence of the mosquito species Aedes aegypti (Linnaeus, 1762) and Culex pipiens (Linnaeus, 1758) raises concerns about local transmission. In this study, we tested 100 Ae. aegypti and 40 Cx. pipiens mosquitoes collected exclusively in the municipality of Funchal, Madeira Island, to assess the presence and diversity of Wolbachia, a naturally occurring bacterium known to reduce mosquitos’ ability to transmit viruses. Molecular identification confirmed that all Cx. pipiens specimens belonged to the molestus biotype, with three individuals identified as hybrids between molestus and pipiens biotypes. This is the first evidence of such hybrids in Madeira. Wolbachia was not detected in any of the Ae. aegypti samples. In contrast, all Cx. pipiens mosquitoes were positive, showing a 100% prevalence. Genetic characterization placed these infections within the wPip clade, supergroup B, sequence type 9. These findings provide key baseline data to inform future mosquito control strategies on the island. As Ae. aegypti showed no natural Wolbachia infection, introducing Wolbachia-infected mosquitoes may be necessary to implement such biocontrol approaches in Madeira.