Anopheline and human drivers of malaria risk in northern coastal, Ecuador: a pilot study

• Published in: Malaria Journal
• Main Authors: James A. Martin, Allison L. Hendershot, Iván Alejandro Saá Portilla, Daniel J. English, Madeline Woodruff, Claudia A. Vera-Arias, Bibiana E. Salazar-Costa, Juan José Bustillos, Fabián E. Saénz, Sofía Ocaña-Mayorga, Cristian Koepfli, Neil F. Lobo
• Format: Article in Journal/Newspaper
• Language: English
• Published: BMC 2020
• Subjects: Nyssorhynchus albimanus; Anopheles calderoni; Plasmodium falciparum; Bionomics; Malaria; Long-lasting insecticide-treated nets (LLINs); Arctic medicine. Tropical medicine; RC955-962; Infectious and parasitic diseases; RC109-216; Arctic; Pacific; San Jose
• Online Access: https://doi.org/10.1186/s12936-020-03426-y; https://doaj.org/article/c1d257183c83474189d12c6e285edb06

Abstract Background Understanding local anopheline vector species and their bionomic traits, as well as related human factors, can help combat gaps in protection. Methods In San José de Chamanga, Esmeraldas, at the Ecuadorian Pacific coast, anopheline mosquitoes were sampled by both human landing collections (HLCs) and indoor-resting aspirations (IAs) and identified using both morphological and molecular methods. Human behaviour observations (HBOs) (including temporal location and bed net use) were documented during HLCs as well as through community surveys to determine exposure to mosquito bites. A cross-sectional evaluation of Plasmodium falciparum and Plasmodium vivax infections was conducted alongside a malaria questionnaire. Results Among 222 anopheline specimens captured, based on molecular analysis, 218 were Nyssorhynchus albimanus, 3 Anopheles calderoni (n = 3), and one remains unidentified. Anopheline mean human-biting rate (HBR) outdoors was (13.69), and indoors (3.38) (p = 0.006). No anophelines were documented resting on walls during IAs. HBO-adjusted human landing rates suggested that the highest risk of being bitten was outdoors between 18.00 and 20.00 h. Human behaviour-adjusted biting rates suggest that overall, long-lasting insecticidal bed nets (LLINs) only protected against 13.2% of exposure to bites, with 86.8% of exposure during the night spent outside of bed net protection. The malaria survey found 2/398 individuals positive for asymptomatic P. falciparum infections. The questionnaire reported high (73.4%) bed net use, with low knowledge of malaria. Conclusion The exophagic feeding of anopheline vectors in San Jose de Chamanga, when analysed in conjunction with human behaviour, indicates a clear gap in protection even with high LLIN coverage. The lack of indoor-resting anophelines suggests that indoor residual spraying (IRS) may have limited effect. The presence of asymptomatic infections implies the presence of a human reservoir that may maintain transmission.