Alessandra da Silva Bastos

Anopheles darlingi mosquitoes are the main malaria vectors in the Amazon region and play a significant role in the high transmission cycle of Plasmodium vivax, particularly in areas undergoing degradation of the Amazon. Establishing an An. darlingi colony under laboratory conditions allows for critical studies on this vector, including insecticide resistance, vector competence, and the development of new tools for controlling vivax malaria. However, the establishment of mass-rearing mosquito colonies has proven challenging, with success being heavily dependent on supporting their reproduction. A key factor in this process is finding the most efficient blood source for feeding. Here, we evaluated the reproductive potential of An. darlingi using different blood feeding methods and sources. First, we assessed the effect of anesthesia on reproductive potential by comparing anesthetized mosquitoes with those that were physically restrained. Next, we assessed the best blood source using both direct and indirect blood feeding methods, the latter involving an artificial feeding system. The blood sources tested included from rabbits, chickens, mice, bovines, and humans. In the anesthesia tests, no significant differences in the evaluated biological parameters were observed between anesthetized or non-anesthetized groups. Similarly, no significant differences were detected in the biological parameters assessed for each blood source, regardless of whether the feeding was direct or indirect. Because all blood sources proved effective, the practicality of obtaining and maintaining blood becomes a crucial factor. In this regard, bovine blood emerged as an effective and practical alternative for maintaining an An. darlingi colony under laboratory conditions.

The maintenance of a highly productive colony of anopheline mosquitoes requires standardized methods in order to obtain a sufficient number of homogeneous individuals for malaria research. In this context, nutritional status may affect survival, fecundity, and the capacity to support pathogen development. Here we assess the effects of carbohydrate sources on fecundity, survival, and susceptibility to Plasmodium vivax infection in colonies of Anopheles darlingi and Anopheles deaneorum mosquitoes. Newly emerged females from each species were fed either 10% sugar or 15% honey solutions until the end of each experiment. The type of carbohydrate meal did not impact any entomological parameters for An. deaneorum, except for survival. For both species, honey meal significantly increased median survival post-emergence by three to four days, probably due to its nutritional value. For An. darlingi fed with honey, a higher mean frequency in stage 5 was observed at 48 h post-blood-meal, which could indicate a delay in the digestion process. However, no effects on fecundity parameters were observed. Regarding susceptibility, An. darlingi fed with sugar exhibited a low intensity of sporozoites, although any negative effects of sucrose on sporozoites invasions in the salivary glands are unknown. Based on the increase in mosquito survival, a carbohydrate source composed of 15% honey solution could be better for maintaining An. darlingi and An. deaneorum in the lab-rearing context.

: Anopheles darlingi is the primary malaria vector in the Amazon region and is highly susceptible to both Plasmodium vivax and Plasmodium falciparum parasites. Although anopheline mosquitoes may develop melanotic encapsulation in response to Plasmodium parasites, there is no record of An. darlingi exhibiting a melanization response to P. vivax, the main malaria parasite in the Americas. Here, we report the occurrence of P. vivax sporozoite melanization in An. darlingi mosquitoes.

Circadian behavioral patterns in mosquitoes can be observed through their locomotor activity, which includes fundamental behaviors such as foraging, mating, and oviposition. These habits, which are fundamental to the life cycle of Anopheles mosquitoes, are closely related to pathogen transmission to humans. While rhythmic cycles of locomotor activity have been described in Anopheles species, no studies have been conducted on Anopheles darlingi species, the main malaria vector in the Amazon region. The aim of this study was to investigate how insemination status, blood meal, and Plasmodium vivax infection affect the locomotor activity of An. darlingi. The experiments were performed with 3- to 10-day-old An. darlingi females, which had been fed with 15% honey solution. These mosquitoes were obtained from the Malaria Vector Production and Infection Platform (PIVEM)/FIOCRUZ–RO. The experimental groups were divided into four categories: virgin vs. inseminated, unfed virgin vs. blood-fed virgin, unfed inseminated vs. blood-fed inseminated, and infected blood vs. uninfected blood. Locomotor activity was monitored using the Flybox equipment, capturing images that were subsequently converted into video to measure the insect activity, using PySoLo software. The periodicity and rhythmicity of mosquito locomotor activity were analyzed using MatLab® software. The locomotor activity of An. darlingi females showed a nocturnal and bimodal pattern under LD conditions. When comparing the insemination states and blood meal, there was a reduction in the locomotor activity in inseminated and blood-fed females. However, the P. vivax⁺ infection did not increase locomotor activity of An. darlingi species.