Conserved virome diversity and structure in the mosquito vector Culex pipiens. P15

Recent epidemics caused by different mosquito‐borne viruses underline the viral diversity associated to mosquitoes. However, beyond human viral pathogens, we know little on other viruses of the mosquito virome. This unexplored diversity probably influences vector competence and other aspects of the mosquito biology, as shown for the mosquito bacteriome. We have analysed the virome of Culex pipiens, a mosquito vector of important arboviruses like Rift Valley fever virus or West Nile fever virus. To this end, we have coupled a metagenomics approach with a large sampling campaign involving different countries and habitats around the Mediterranean basin. Our results show for the first time conserved patterns in virus diversity among mosquito populations, as well as specificities probably linked to different environmental conditions. The discovery of a ubiquitous group of viruses strongly supports the existence of a core virome in Culex pipiens that is likely to influence mosquito physiology

Midgut microbiota of the malaria mosquito vector Anopheles gambiae and Interactions with plasmodium falciparum Infection

The susceptibility of Anopheles mosquitoes to Plasmodium infections relies on complex interactions between the insect vector and the malaria parasite. A number of studies have shown that the mosquito innate immune responses play an important role in controlling the malaria infection and that the strength of parasite clearance is under genetic control, but little is known about the influence of environmental factors on the transmission success. We present here evidence that the composition of the vector gut microbiota is one of the major components that determine the outcome of mosquito infections. A. gambiae mosquitoes collected in natural breeding sites from Cameroon were experimentally challenged with a wild P. falciparum isolate, and their gut bacterial content was submitted for pyrosequencing analysis. The meta-taxogenomic approach revealed a broader richness of the midgut bacterial flora than previously described. Unexpectedly, the majority of bacterial species were found in only a small proportion of mosquitoes, and only 20 genera were shared by 80% of individuals. We show that observed differences in gut bacterial flora of adult mosquitoes is a result of breeding in distinct sites, suggesting that the native aquatic source where larvae were grown determines the composition of the midgut microbiota. Importantly, the abundance of Enterobacteriaceae in the mosquito midgut correlates significantly with the Plasmodium infection status. This striking relationship highlights the role of natural gut environment in parasite transmission. Deciphering microbe-pathogen interactions offers new perspectives to control disease transmission.Institut de Recherche pour le Developpement (IRD); French Agence Nationale pour la Recherche [ANR-11-BSV7-009-01]; European Community [242095, 223601]info:eu-repo/semantics/publishedVersio

Conceptual model of salt marsh management on Merritt Island National Wildlife Refuge, Florida: final report

Diking and holding water on salt marshes ("impounding" the marsh) is a management technique used on Merritt Island National Wildlife Refuge (MINWR) and elsewhere in the Southeast to: a) prevent the reproduction of saltmarsh mosquitos, and b) attract wintertering waterfowl and other marsh, shore, and wading birds. Because of concern that diking and holding water may interfere with the production of estuarine fish and shellfish, impoundment managers are being asked to consider altering management protocol to reduce or eliminate any such negative influence. How to change protocol and preserve effective mosquito control and wildlife management is a decision of great complexity because: a) the relationships between estuarine organisms and the fringing salt marshes at the land-water interface are complex, and b) impounded marshes are currently good habitat for a variety of species of fish and wildlife. Most data collection by scientists and managers in the area has not been focused on this particular problem. Furthermore, collection of needed data may not be possible before changes in protocol are demanded. Therefore, the purpose of this document is two-fold: 1) to suggest management alternatives, given existing information, and 2) to help identify research needs that have a high probability of leading to improved simultaneous management of mosquitos, waterfowl, other wildlife, freshwater fish, and estuarine fish and shellfish on the marshland of the Merritt Island National Wildlife Refuge. (92 page document

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

Currently, there are very few studies of avian malaria that investigate relationships among the host-vector-parasite triad concomitantly. In the current study, we experimentally measured the vector competence of several Culex mosquitoes for a newly described avian malaria parasite, Plasmodium homopolare. Song sparrow (Melospiza melodia) blood infected with a low P. homopolare parasitemia was inoculated into a naïve domestic canary (Serinus canaria forma domestica). Within 5 to 10 days post infection (dpi), the canary unexpectedly developed a simultaneous high parasitemic infection of Plasmodium cathemerium (Pcat6) and a low parasitemic infection of P. homopolare, both of which were detected in blood smears. During this infection period, PCR detected Pcat6, but not P. homopolare in the canary. Between 10 and 60 dpi, Pcat6 blood stages were no longer visible and PCR no longer amplified Pcat6 parasite DNA from canary blood. However, P. homopolare blood stages remained visible, albeit still at very low parasitemias, and PCR was able to amplify P. homopolare DNA. This pattern of mixed Pcat6 and P. homopolare infection was repeated in three secondary infected canaries that were injected with blood from the first infected canary. Mosquitoes that blood-fed on the secondary infected canaries developed infections with Pcat6 as well as another P. cathemerium lineage (Pcat8); none developed PCR detectable P. homopolare infections. These observations suggest that the original P. homopolare-infected songbird also had two un-detectable P. cathemerium lineages/strains. The vector and host infectivity trials in this study demonstrated that current molecular assays may significantly underreport the extent of mixed avian malaria infections in vectors and hosts

Population genomics of the Asian tiger mosquito, Aedes albopictus. Insights into the recent worldwide invasion

Aedes albopictus, the “Asian tiger mosquito,” is an aggressive biting mosquito native to Asia that has colonized all continents except Antarctica during the last ~30–40 years. The species is of great public health concern as it can transmit at least 26 arboviruses, including dengue, chikungunya, and Zika viruses. In this study, using double- digest Restriction site-Associated DNA (ddRAD) sequencing, we developed a panel of ~58,000 single nucleotide polymorphisms (SNPs) based on 20 worldwide Ae. albopic-tus populations representing both the invasive and the native range. We used this genomic- based approach to study the genetic structure and the differentiation of Ae. albopictus populations and to understand origin(s) and dynamics of the recent inva-sions. Our analyses indicated the existence of two major genetically differentiated population clusters, each one including both native and invasive populations. The de-tection of additional genetic structure within each major cluster supports that these SNPs can detect differentiation at a global and local scale, while the similar levels of genomic diversity between native and invasive range populations support the scenario of multiple invasions or colonization by a large number of propagules. Finally, our re-sults revealed the possible source(s) of the recent invasion in Americas, Europe, and Africa, a finding with important implications for vector- control strategies

The Effect of Garden Plant Diversity on Mosquito Species that Act as Infectious Disease Vectors in Central Illinois

Urban landscaping plants provide many ecosystem benefits including increased biodiversity and habitat for many organisms including mosquitoes. However, the impact of urban landscaping plants on the behavior/ecology of mosquitoes that may transmit pathogenic diseases is relatively understudied. The aim of this study was to evaluate the presence of mosquito disease vector species (e.g., West Nile virus-transmitting Culex pipiens & Culex restuans) and other local mosquito species in gardens with high versus low plant diversity in Champaign-Urbana. From August to October 2015, two types of mosquito traps (light and gravid) were placed weekly at twelve local garden sites; six sites were selected as Master Garden sites, chosen for their high plant diversity, and six were paired control sites selected for low plant species diversity. Traps were placed at each site for 24 hours and after collection, mosquitoes were identified and quantified in the lab. A plant list was generated for each site to characterize plant species richness. In total, 25 mosquito species were observed, with the most abundant occurrences being Aedes albopictus, Aedes japonicus, Aedes vexans, Culex pipiens, and Culex spp. A significant difference was found for the total number of mosquitoes collected using light versus gravid traps after accounting for site diversity, but not between master garden sites (with high plant diversity and abundance) versus low diversity control sites. Significant differences were found at the genus level with both Aedes and Anopheles mosquitoes having higher abundance at sites with low plant diversity. However, at the species level non-significant differences were found for mosquito abundance between high and low plant species diversity sites. Lastly, it was found that two Anopheles species are significantly correlated with trap collection date. The findings of this study suggest that local gardens with high plant diversity do not provide additional resources that result in a higher quantity of mosquitoes carrying West Nile virus and other diseases.LAS Preble Research Grant fall 2015Ope

The impact of conservation translocations on vector-borne parasites : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Ecology at Massey University, Palmerston North, New Zealand

Wildlife conservation in New Zealand relies on translocations of endangered species to safe sites. While knowledge of the biology and behaviour of translocated hosts has steadily increased, the role of parasites in wildlife translocations has been largely overlooked. Parasites can affect their host’s survivorship during translocations by causing disease. However, failure to translocate or reintroduce a host specific parasite with its endangered host can contribute to the extinction of the parasite with unforeseen consequences for the future of the host or even the whole ecosystem. The main aims of this study were to establish baseline data on the impact of North Island saddleback translocations on their avian malaria (Plasmodium spp.) parasites as well as gaining further insight into potential vectors in New Zealand. The study was also intended to contribute to the development of recommendations for future parasite screening programmes for native passerine translocations. Saddlebacks and Plasmodium were chosen because of the detailed saddleback translocation history and its known relationship with the parasite. As a result of this study, several Plasmodium lineages previously unrecorded in saddlebacks and New Zealand were identified, for example, the native Kokako01 and one lineage closest related to two lineages from the Americas. Nonetheless, the most frequent lineages found were the cosmopolitan P. elongatum GRW6 and LINN1, and P. vaughani SYAT05, common in birds introduced to New Zealand. This finding suggests that endemic parasites may have already become rare or extinct. In addition, Plasmodium DNA was detected in both native and introduced mosquitoes that may act as vectors. A qPCR assay was developed that was found to be a cost effective and rapid screening tool for the detection of Plasmodium in native birds suffering from acute infection, presenting with clinical symptoms, and in birds that were found dead. . I conclude that future translocations should consider the movement of endemic parasites with their hosts. How this should happen is open for future studies. However, I urge managers to start considering this issue now as New Zealand has already recorded the extinction of one endemic parasite and many more may have already been lost without knowledge

Genomic signatures of population decline in the malaria mosquito Anopheles gambiae

Population genomic features such as nucleotide diversity and linkage disequilibrium are expected to be strongly shaped by changes in population size, and might therefore be useful for monitoring the success of a control campaign. In the Kilifi district of Kenya, there has been a marked decline in the abundance of the malaria vector Anopheles gambiae subsequent to the rollout of insecticide-treated bed nets. To investigate whether this decline left a detectable population genomic signature, simulations were performed to compare the effect of population crashes on nucleotide diversity, Tajima's D, and linkage disequilibrium (as measured by the population recombination parameter ρ). Linkage disequilibrium and ρ were estimated for An. gambiae from Kilifi, and compared them to values for Anopheles arabiensis and Anopheles merus at the same location, and for An. gambiae in a location 200 km from Kilifi. In the first simulations ρ changed more rapidly after a population crash than the other statistics, and therefore is a more sensitive indicator of recent population decline. In the empirical data, linkage disequilibrium extends 100-1000 times further, and ρ is 100-1000 times smaller, for the Kilifi population of An. gambiae than for any of the other populations. There were also significant runs of homozygosity in many of the individual An. gambiae mosquitoes from Kilifi. These results support the hypothesis that the recent decline in An. gambiae was driven by the rollout of bed nets. Measuring population genomic parameters in a small sample of individuals before, during and after vector or pest control may be a valuable method of tracking the effectiveness of interventions