Larval cold tolerance as a possible explanation for the range expansion and increasing abundance of Aedes aegypti in temperate South America (Buenos Aires, Argentina)

GABRIELA ZANOTTI; SYLVIA FISCHER; RAÚL ERNESTO CAMPOS; MARÍA SOL DE MAJO

Palma de Mallorca, España

Congreso; 7th International Congress of the Society for Vector Ecology; 2017

Aedes aegypti is the main vector of dengue in the Americas. Despite its tropical origin, this species has successfully established in temperate regions during the last decades. In Buenos Aires province (Argentina), at the boundary of this species in South America, more than twenty new cities have been colonized by Ae. aegypti in recent years, expanding the distribution to colder climates. In Buenos Aires city (the largest urban area within this region), the abundance of Ae. aegypti increased steadily during the past twenty years. Since low temperatures are the main limiting factor for Ae. aegypti populations in temperate regions, we studied the tolerance (development time and survival) of immature stages to low temperatures trough: a) a field experiment during the winter season in Buenos Aires city; b) a study under constant temperatures within the range of 12-25ºC. The results showed that all cohorts initiated during the winter season were able to complete larval development. Cohorts initiated in early winter (experiencing average temperatures of 13-14ºC), exhibited a lower survival (30%) and longer development time (50 days) than those initiated in early spring (survival of 90% and development time of 18 days at average temperatures of 20-21ºC). Under constant temperatures 20% of individuals completed development in 48 days at 12ºC, and from 14ºC onwards survival exceeded 80% and development time decreased with higher temperatures. The comparison of our results with previous studies from other regions suggest an increased cold tolerance of immature stages of the Buenos Aires Ae. aegypti population.