Behavior and abundance of Anopheles darlingi in communities living in the Colombian Amazon riverside

Abstract

In the past few years, relative frequencies of malaria parasite species in communities living in the Colombian Amazon riverside have changed, being Plasmodium vivax (61.4%) and Plasmodium malariae (43.8%) the most frequent. Given this epidemiological scenario, it is important to determine the species of anophelines involved in these parasites’ transmission. This study was carried out in June 2016 in two indigenous communities living close to the tributaries of the Amazon River using protected human bait. The results of this study showed a total abundance of 1,085 mosquitos, of which 99.2% corresponded to Anopheles darlingi . Additionally, only two anopheline species were found, showing low diversity in the study areas. Molecular confirmation of some individuals was then followed by evolutionary analysis by using the COI gene. Nested PCR was used for identifying the three Plasmodium species circulating in the study areas. Of the two species collected in this study, 21.0% of the An . darlingi mosquitoes were infected with P . malariae , 21.9% with P . vivax and 10.3% with Plasmodium falciparum . It exhibited exophilic and exophagic behavior in both study areas, having marked differences regarding its abundance in each community (Tipisca first sampling 49.4%, Tipisca second sampling 39.6% and Doce de Octubre 10.9%). Interestingly, An . mattogrossensis infected by P . vivax was found for the first time in Colombia (in 50% of the four females collected). Analysis of An . darlingi COI gene diversity indicated a single population maintaining a high gene flow between the study areas. The An . darlingi behavior pattern found in both communities represents a risk factor for the region’s inhabitants living/working near these sites. This highlights the need for vector control efforts such as the use of personal repellents and insecticides for use on cattle, which must be made available in order to reduce this Anopheline’s abundance.

Evidence for family-level variation of phenotypic traits in response to temperature of Brazilian Nyssorhynchus darlingi

“…Vector control interventions need to consider variation in life history traits [7], behaviors [5], and habitats [21]. At a high nutrition diet, low temperature treatment Anopheles were found to be larger and more likely to survive exposure to a LC 50 dose of permethrin [60].…”

“…Field studies of Ny. darlingi reveal endophagy and exophagy at different times throughout the night [5], and there is no evidence for a genetic basis of these behaviors [41]. Ivermectin treatment of cattle was shown to reduce An.…”

“…The plasticity of Ny. darlingi, including biting behavior [5,41], host [12,63] and breeding site [19][20][21] preferences, coupled with the potential of families within certain populations to withstand changing environments, help explain its status as the major malaria vector in South America. The present study contributes to the growing body of evidence of high levels of plasticity in Ny.…”

“…The Americas is the only region to have an increase in malaria mortality in 2017 compared to 2010, with a greater number of malaria cases reported in Venezuela, Brazil, and Nicaragua during this period [2]. The main vector and driver of this disease in South America is Nysorrhynchus darlingi (also known as Anopheles darlingi [3]), that exhibits significant geographical variation in behavior [4,5] and in phenotypic plasticity [6][7][8]. This species has a natural infection rate by Plasmodium of up to 20% [5,9], though a more common rate is 1-5% [10][11][12].…”

“…The main vector and driver of this disease in South America is Nysorrhynchus darlingi (also known as Anopheles darlingi [3]), that exhibits significant geographical variation in behavior [4,5] and in phenotypic plasticity [6][7][8]. This species has a natural infection rate by Plasmodium of up to 20% [5,9], though a more common rate is 1-5% [10][11][12]. Adult vector traits relevant to disease transmission, such as adult life span and body size [13], can vary between populations [6,7] and are influenced by larval development conditions such as food quantity [14] and temperature [15].…”