Aedes aegypti surveillance under the International Health Regulations - experience at Madeira Island

Abstract Problem Aedes aegypti was first identified on Madeira Island in 2005, persisting since then. This mosquito transmits various haemorrhagic diseases and caused a Dengue outbreak in 2012-2013. The island has two seaports and one airport 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 and airport during 2023. Description Data was collected from 52 entomological panels produced by the Regional Health Department throughout 2023. This data is publicly available on the Institute of Health Administration’s website. Ovitraps capture eggs, larvae, and pupae of Ae. aegypti, and BGtraps capture adult mosquitos. Positivity refers to the proportion of times an ovitrap recorded eggs in the entomological cycle. Results In 2023, there were 204 active ovitraps at the island (17 at the airport, 9 at Funchal’s seaport 8 at Caniçal’s seaport) and 24 BGtraps (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, ovitraps’ positivity at the airport (avg 6.4%; 0-59%) and 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%). Per-ovitrap, the average weekly positivity rate rose by 15%, 10% and 5% at Caniçal’s port, airport and Funchal’s port, respectively, compared to 2012-2022. Lessons Ae. aegypti’s eggs prevalence increased in 2023. The high positivity of eggs suggests an increased likelihood of mosquitos nearby. The detection of immature forms 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. This is particularly important at high-traffic areas such as seaports and airports. Key messages • The increase in Ae. aegypti egg positivity in 2023 on Madeira Island suggests a higher risk of disease transmission. • It is essential to prioritize vector control measures at seaports and the airport in Madeira Island.