Novel strains of Culex flavivirus and Hubei chryso-like virus 1 from the Anopheles mosquito in western Kenya.

Surveillance of mosquito vectors is critical for early detection, prevention and control of vector borne diseases. In this study we used advanced molecular tools, such as DNA barcoding in combination with novel sequencing technologies to discover new and already known viruses in genetically identified mosquito species. Mosquitoes were captured using BG sentinel traps in Western Kenya during May and July 2019, and homogenized individually before pooled into groups of ten mosquitoes. The pools and individual samples were then used for molecular analysis and to infect cell cultures. Of a total of fifty-four (54) 10-pools, thirteen (13) showed cytopathic effect (CPE) on VeroB4 cells, eighteen (18) showed CPE on C6/36 cells. Eight (8) 10-pools out of the 31 CPE positive pools showed CPE on both VeroB4 and C6/36 cells. When using reverse transcriptase polymerase chain reaction (RT-PCR), Sanger sequencing and Twist Comprehensive Viral Research Panel (CVRP) (Twist Biosciences), all pools were found negative by RT-PCR when using genus specific primers targeting alphaviruses, orthobunyaviruses and virus specific primers towards o'nyong-nyong virus, chikungunya virus and Sindbis virus (previously reported to circulate in the region). Interestingly, five pools were RT-PCR positive for flavivirus. Two of the RT-PCR positive pools showed CPE on both VeroB4 and C6/36 cells, two pools showed CPE on C6/36 cells alone and one pool on VeroB4 cells only. Fifty individual mosquito homogenates from the five RT-PCR positive 10-pools were analyzed further for flavivirus RNA. Of these, 19 out of the 50 individual mosquito homogenates indicated the presence of flavivirus RNA. Barcoding of the flavivirus positive mosquitoes revealed the mosquito species as Aedes aegypti (1), Mansonia uniformis (6), Anopheles spp (3), Culex pipiens (5), Culex spp (1), Coquilletidia metallica (2) and Culex quinquefasciatus (1). Of the 19 flavivirus positive individual mosquitoes, five (5) virus positive homogenates were sequenced. Genome sequences of two viruses were completed. One was identified as the single-stranded RNA Culex flavivirus and the other as the double-stranded RNA Hubei chryso-like virus 1. Both viruses were found in the same Anopheles spp. homogenate extracted from a sample that showed CPE on both VeroB4 and C6/36 cells. The detection of both viruses in a single mosquito homogenate indicated coinfection. Phylogenetic analyses suggested that the Culex flavivirus sequence detected was closely related to a Culex flavivirus isolated from Uganda in 2008. All four Hubei chryso-like virus 1 segments clusters closely to Hubei chryso-like virus 1 strains isolated in Australia, China and USA. Two novel strains of insect-specific viruses in Anopheles mosquitoes were detected and characterized.

A Systematic Review of the Evidence on the Effectiveness and Cost-Effectiveness of Mass Screen-and-Treat Interventions for Malaria Control.

Malaria elimination and eradication efforts have stalled globally. Further, asymptomatic infections as silent transmission reservoirs are considered a major challenge to malaria elimination efforts. There is increased interest in a mass screen-and-treat (MSAT) strategy as an alternative to mass drug administration to reduce malaria burden and transmission in endemic settings. This study systematically synthesized the existing evidence on MSAT, from both epidemiological and economic perspectives. Searches were conducted on six databases (PubMed, EMBASE, CINALH, Web of Science, Global Health, and Google Scholar) between October and December 2020. Only experimental and quasi-experimental studies assessing the effectiveness and/or cost-effectiveness of MSAT in reducing malaria prevalence or incidence were included. Of the 2,424 citation hits, 14 studies based on 11 intervention trials were eligible. Eight trials were conducted in sub-Saharan Africa and three trials in Asia. While five trials targeted the community as a whole, pregnant women were targeted in five trials, and school children in one trial. Transmission setting, frequency, and timing of MSAT rounds, and measured outcomes varied across studies. The pooled effect size of MSAT in reducing malaria incidence and prevalence was marginal and statistically nonsignificant. Only one study conducted an economic evaluation of the intervention and found it to be cost-effective when compared with the standard of care of no MSAT. We concluded that the evidence for implementing MSAT as part of a routine malaria control program is growing but limited. More research is necessary on its short- and longer-term impacts on clinical malaria and malaria transmission and its economic value.

The Human Biting Culex pipiens Bioform molestus Detected in Several Areas in Southern Sweden.

Background: The mosquito species Culex pipiens is a known vector of several pathogens and occurs in two distinct bioforms, pipiens and molestus. The bioform molestus thrives in urban environments where there are below-ground habitats; it can mate in confined spaces and feed on mammals as well as birds. In contrast, the bioform pipiens is found above ground, is thought to require more space for mating, and mainly feeds on birds. The pipiens bioform is present in large parts of Sweden but the molestus bioform has previously only been found in major cities. Materials and Methods: People experiencing mosquito nuisance in southern Sweden submitted mosquito samples as part of a citizen science project, and these samples were analyzed to determine the geographical distribution of the molestus bioform of Cx. pipiens. Mosquito specimens were identified to the species level by DNA barcoding of the cytochrome C oxidase subunit I (COI) gene, and the bioforms were determined through the CQ11 microsatellite marker. Results:Culex pipiens f molestus was observed to be spread across large parts of Gothenburg as well as in the suburbs. This bioform was found both in urban and rural areas at several sites across southern Sweden. In one site, hybrids between the two bioforms were found. Conclusions: The detection of Cx. pipiens f molestus in several rural areas was surprising, indicating that it may be more widely spread than urban areas alone, where it has been previously reported.