A retrospective study of anopheles larval habitats in different ecological environments of northwestern Argentina

Abstract

Anthropogenic activities cause changes in natural environments, affecting the ecology of Anopheles mosquitoes and, therefore, increasing the potential for malaria transmission. Immature Anopheles were collected from different larval habitats in 3 geographical localities of northwestern Argentina: El Oculto, where the wild habitat included a mountain river; Aguas Blancas, where the peri-rural habitat consisted of stream ravines; and San Ramón de la Nueva Orán, where the peri-urban habitat comprised puddles, ponds, and irrigation and drainage channels. The incidencerate of each anopheline species was calculated according to the larval habitat. Additionally, to analyze the effect of environmental variables, the mean of each variable in each larval habitat was determined and related to the incidence of each anopheline species through Pearson’s correlation coefficient. A total of 5,553 larvae belonging to the genus Anopheles were collected. The most abundant species was Anopheles pseudopunctipennis (33.35%), followed by An.(Nyssorhynchus) argyritarsis (28.47%), An. (Nys.) evansae (16.64%), and An. (Nys.) strodei (14.62%). Both An. pseudopunctipennis and An. argyritarsis were present across all larval habitats. Considering the larval habitats separately, An. argyritarsis emerged as the most abundant species in both the mountain river (wild habitat) and stream ravines (perirural habitat), while An. evansae and An. strodei predominated in the irrigation and drainage channels (peri-urban habitat).In the peri-rural habitat, mean water temperature was positively associated with the presence of An. argyritarsis. In the peri-urban habitat, mean temperature was positively associated with An. strodei and An. evansae, while a strong negative relationship between these 2 species and water pH was also observed. This study showed the importance of longitudinal entomological surveillance, not only in wild and peri-rural environments due to the abundance of main malaria vectors, An. pseudopunctipennis and An. argyritarsis, but also in peri-urban areas. Considering that both vector species can transition to urban sites, as observed in other countries, current and future changes in these habitats require further studies. Consequently, research should focus on the emergence of new larval habitats that could favor a higher abundance of these malaria vector species.