Intensive trapping of blood-fed Anopheles darlingi in Amazonian Peru reveals unexpectedly high proportions of avian blood-meals

Abstract

Anopheles darlingi, the main malaria vector in the Neotropics, has been considered to be highly anthropophilic. However, many behavioral aspects of this species remain unknown, such as the range of blood-meal sources. Barrier screens were used to collect resting Anopheles darlingi mosquitoes from 2013 to 2015 in three riverine localities (Lupuna, Cahuide and Santa Emilia) in Amazonian Peru. Overall, the Human Blood Index (HBI) ranged from 0.58–0.87, with no significant variation among years or sites. Blood-meal analysis revealed that humans are the most common blood source, followed by avian hosts (Galliformes-chickens and turkeys), and human/Galliforme mixed-meals. The Forage Ratio and Selection Index both show a strong preference for Galliformes over humans in blood-fed mosquitoes. Our data show that 30% of An. darlingi fed on more than one host, including combinations of dogs, pigs, goats and rats. There appears to be a pattern of host choice in An. darlingi, with varying proportions of mosquitoes feeding only on humans, only on Galliformes and some taking mixed-meals of blood (human plus Galliforme), which was detected in the three sites in different years, indicating that there could be a structure to these populations based on blood-feeding preferences. Mosquito age, estimated in two localities, Lupuna and Cahuide, ranged widely between sites and years. This variation may reflect the range of local environmental factors that influence longevity or possibly potential changes in the ability of the mosquito to transmit the parasite. Of 6,204 resting An. darlingi tested for Plasmodium infection, 0.42% were infected with P. vivax. This study provides evidence for the first time of the usefulness of barrier screens for the collection of blood-fed resting mosquitoes to calculate the Human Blood Index (HBI) and other blood-meal sources in a neotropical malaria endemic setting.

Spatio-temporal dynamics of Plasmodium falciparum transmission within a spatial unit on the Colombian Pacific Coast

“…We assessed the population structure of P. falciparum populations circulating in the area using a SNP barcode corresponding to 49 independent loci (see Methods), taking advantage of the long term persistence of clonal lineages in South American populations of P. falciparum 28 which allows tracking parasite populations in time and space. Long term persistance of clonal lineages is probably due to the low diversity of P. falciparum populations in the Americas 27 as a consequence of the bottleneck resulting from its relatively recent introduction during the slave trade 45,46 , the strong selective pressure by antimalarials 47,48 and the relatively low mosquito Blood Index Feeding rates in South American anophelines as compared to high transmission areas in Africa [49][50][51][52][53] . This results in a low proportion (8% in this study) of polyclonal infections, low MOIs and highly clonal lineage infections persisting over time 28 .…”

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

“…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.…”

“…Details of the collection site criteria for paired sites are found in [7]. Mosquitoes were collected in the evening for 5 hours (17:00-22:00 h) using barrier screens as described in Moreno et al [12] for 1-5 days, depending on locality and successful collection of the target species, Ny. darlingi.…”

“…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].…”

Sistema ecológico da malária

“…Many factors contribute to the challenge of malaria control, for instance, there are other vector species competent to transmit Plasmodium and adapted to deposit eggs in open areas with partial shade, such as Ny. marajoara (Galvão & Damasceno) 50,64,65 , 66 . These species have distinctive ecologies compared with Ny.…”