Phenotypic variation and vector competence in Anopheles aquasalis: A comparative analysis of susceptibility to...

Malaria remains a major public health problem worldwide, with Plasmodium vivax being the predominant species in the Americas. Anopheles aquasalis is an important malaria vector in coastal Central and South America and the Caribbean Islands and exhibits distinct phenotypic variations-30BS (30 % black scales) and 50BS (50 % black scales). However, the influence of these phenotypes on P. vivax vector competence has not been systematically investigated. Laboratory-reared 30BS and 50BS An. aquasalis phenotypes were infected with blood from P. vivax-infected patients in Manaus, Brazil. Five independent experimental infections were performed using membrane feeding assays. Mosquito midguts were dissected 7-10 days post-infection, and oocyst counts were recorded. Prevalence and intensity were analyzed using a generalized linear model with a negative binomial distribution. A total of 286 mosquito midguts were examined (139 from 50BS and 147 from 30BS). Overall prevalences were 67.63 % for 50BS and 55.10 % for 30BS. Negative binomial regression showed no significant difference in prevalences between phenotypes (IRR = 1.11; 95 % CI: 0.67-1.84; p = 0.68). However, infection intensity was significantly higher in 30BS mosquitoes, with a mean oocyst count of 72.91, compared to 56.94 in 50BS (p = 0.042). Three of five experiments confirmed this trend, while one showed the opposite effect, and one showed no significant difference. Phenotypic variation in An. aquasalis influences susceptibility to P. vivax. Although prevalences were similar, 30BS mosquitoes harbored significantly higher parasite loads, suggesting greater permissiveness to parasite development. These findings highlight the importance of considering intraspecific variation in malaria vector competence and its potential implications for transmission dynamics and control strategies.