Identifying avian malaria vectors: sampling methods influence outcomes

Abstract

BackgroundThe role of vectors in the transmission of avian malaria parasites is currently understudied. Many studies that investigate parasite-vector relationships use limited trapping techniques and/or identify potential competent vectors in the field in such ways that cannot distinguish between an infected or infectious vector. Without the use of multiple trapping techniques that address the specific biology of diverse mosquito species, and without looking at the infection status of individual mosquitoes, it is not possible to make dependable conclusions on the role of mosquitoes in the transmission of avian malaria parasites.MethodsWe conducted two years of mosquito collections at a riparian preserve in California where a wide diversity of species were collected with multiple trap types. We hypothesized that competent mosquito species can influence the distribution and diversity of avian malaria parasites by acting as a compatibility filter for specific Plasmodium species. To determine the infection status of all individual mosquitoes for Plasmodium species/lineages, amplification within the cytochrome b gene was carried out on over 3000 individual mosquito thoraxes, and for those that tested positive we then repeated the same process for abdomens and salivary glands.ResultsOur data show heterogeneity in the transmissibility of Plasmodium among ornithophillic mosquito species. More specifically, Culex stigmatosoma appears to not be a vector of Plasmodium homopolare, a parasite that is prevalent in the avian population, but is a vector of multiple other Plasmodium species/lineages.ConclusionsOur results suggest that conclusions made on the role of vectors from studies that do not use different mosquito trapping methods should be re-evaluated with caution, as we documented the potential for trapping biases, which may cause studies to miss important roles of specific mosquito species in the transmission of avian malaria. Moreover, we document heterogeneity in the transmission of Plasmodium spp. by mosquitoes can influence Plasmodium diversity and prevalence in specific locations to Plasmodium-vector incompatibilities.

Overlap in the Seasonal Infection Patterns of Avian Malaria Parasites and West Nile Virus in Vectors and Hosts

“…56 Such studies could examine whether species of mosquito vectors that are known to share Plasmodium infections in nature 57 are equally effective at transmitting these parasites to hosts, and illuminate whether vector community structure can influence seasonal Plasmodium infection dynamics. 58,59 Seasonal variation in temperature may also influence patterns of Plasmodium transmission. The development rate of some Plasmodium parasites in mosquitoes is strongly linked to ambient temperature.…”

Searching for putative avian malaria vectors in a Seasonally Dry Tropical Forest in Brazil

“…Sampling methods can influence the community of collected mosquitoes and as a result, the prevalence of haemosporidian parasites [5]. Our trap system relied on LED lamps and human presence as baits, which may have attracted mostly anthropophilic mosquitoes, a result supported by the blood meal analysis of our samples.…”

“…Vector-parasite compatibility [5] and mosquito feeding patterns [6] also play a role in parasite distribution. Nevertheless, haemosporidian vectors have received less attention than their vertebrate hosts, and this is especially true for tropical latitudes.…”

Avian malaria co-infections confound infectivity and vector competence assays of Plasmodium homopolare

“…Prevalence studies conducted in 2011 and 2012 showed that China Creek Park harbored a rich diversity of avian Plasmodium species and lineages in birds (Walther et al 2016) and mosquitoes (Carlson et al 2015). However, there was some incongruence between the prevalence of Plasmodium species in resident birds and mosquitoes.…”