Introduction:
Aedes aegypti was first identified on Madeira Island in 2005, persisting since then¹. This mosquito transmits various haemorrhagic diseases and caused a dengue outbreak in 2012-2013^1,2. The island has two seaports that may serve as points of entry or dissemination of these diseases, potentially leading to a new outbreak or international disease spread. We aimed to assess Ae. aegypti presence at the island’s seaports during 2023.

Methods:
Data was collected from 52 entomological surveillance reports produced by the Regional Health Department throughout 2023. This data is publicly available on the Institute of Health Administration’s website. Ovitraps captured Ae. aegypti eggs, larvae, and pupae, and BG-Sentinel 2 traps captured adult mosquitos. Positivity refers to the proportion of times an ovitrap recorded eggs during a defined period, usually a week.

Results:
Throughout 2023, there were 204 active ovitraps at the island (9 at Funchal’s seaport, 8 at Caniçal’s seaport) and 24 BG traps (2 at the airport, 2 at Funchal’s port and 1 at Caniçal’s port). Weekly reports revealed a median of 2243 (0-14448) eggs and 14 (0-234) mosquitos in all traps. Positivity was higher in the second semester. On average, ovitrap’s positivity at Caniçal’s port (avg 2.8%; 0-47%) were lower than the positivity of the island (avg 14.8%). Funchal’s port had a higher positivity than the island (avg 15.9%; 0-67%). The average weekly positivity rate per ovitrap rose by 15% and 5% at Caniçal’s port and Funchal’s port, respectively, compared to 2012-2022.

Conclusions:
Ovitrap positivity rate increased in 2023, indicating an increased likelihood of Ae. aegypti mosquitos nearby. The detection of immature stages triggers actions to prospect the surrounding area for identification and elimination of breeding grounds, as well as the placement of salt in water accumulation areas for mosquito control. This is particularly important at high-traffic areas such as seaports and airports.