Genetic Diversity and Gene Flow among Stable Fly Populations, Stomoxys calcitrans (L.) in Thailand

ABSTRACT Isozymes from five wild-caught Stomoxys calcitrans (L.) were compared using starch gel electrophoresis to estimate the rates of gene flow between and among S. calcitrans populations from five different geographic regions of Thailand. Among ten enzyme systems, 13 putative loci and 10 polymorphisms were detected. Limited genetic differentiation among the five populations was observed as indicated by the low F ST (0.078). The highest percentage of polymorphic loci was observed in eastern Trat province and northern Chiang Mai province (69.2%), whereas the lowest percent polymorphism was seen in south-central Saraburi province (23.1%). Gene flow between populations varied from 6.16 to 15.38 reproductive migrants per generation with no fixed genetic differences detected. Among the five population samples, no correlation was seen between genetic and geographical distances showing that sampled S. calcitrans fit closely in the same cluster taxa. The genetic and epidemiological ramifications of these findings are discussed

Diversity of Anopheles species and trophic behavior of putative malaria vectors in two malaria endemic areas of northwestern Thailand

ABSTRACT: We determined the species diversity, blood-feeding behavior, and host preference of Anopheles mosquitoes in two malaria endemic areas of Tak (Mae Sot District) and Mae Hong Son (Sop Moei District) Provinces, located along the Thai border with Myanmar, during a consecutive two-year period. Anopheline mosquitoes were collected using indoor and outdoor human-landing captures and outdoor cow-baited collections. Mosquitoes were initially identified using morphological characters, followed by the appropriate multiplex AS-PCR assay for the identification of sibling species within Anopheles (Cellia) complexes and groups present. Real-time PCR was performed for parasite-specific detection in mosquitoes (Plasmodium spp. and Wuchereria bancrofti)

Pyrethroid Susceptibility in <i>Stomoxys calcitrans</i> and <i>Stomoxys indicus</i> (Diptera: Muscidae) Collected from Cattle Farms in Southern Thailand

The susceptibility to six pyrethroid insecticides (permethrin, deltamethrin, alpha-cypermethrin, cypermethrin, lambda-cyhalothrin, and bifenthrin), each at the recommended concentration, was evaluated for two stable fly species—Stomoxys calcitrans (Linnaeus, 1758) and Stomoxys indicus Picard, 1908 (Diptera: Muscidae)—through tarsal contact using a World Health Organization (WHO) cone bioassay procedure. The field populations of S. calcitrans were collected from the Songkhla and Phattalung provinces, while S. indicus were collected from the Phattalung and Satun provinces in Thailand. The stable flies were exposed to insecticide-treated filter paper for 30 min, and their knockdown counts at 30 min and 60 min and mortality counts at 12 h and 24 h were recorded. The S. calcitrans and S. indicus Songkhla and Phattalung populations were moderately susceptible to pyrethroids, as indicated by the 24 h mortality. Nonetheless, the Satun population of S. indicus was completely susceptible to permethrin, with 100% mortality, and showed the lowest susceptibility to deltamethrin and bifenthrin. The results indicate the generally low susceptibility of stable flies to pyrethroids in the southern provinces of Thailand

Phenotypic susceptibility to pyrethroids and organophosphate of wild Stomoxys calcitrans (Diptera: Muscidae) populations in southwestern France.

International audienceStomoxys calcitrans (Diptera: Muscidae), is an important vector of lumpy skin disease and bovine besnoitiosis in Europe. Control of this biting fly could represent a keystone in the containment of this emerging disease. Reports of insecticide resistance in S. calcitrans are scarce in Europe. Therefore, the purpose of this study was to evaluate the phenotypic susceptibility to deltamethrin, cypermethrin and phoxim of five wild S. calcitrans populations from southwestern France, where transmission of bovine besnoitiosis is very prevalent. Adult S. calcitrans were caught at each study site and exposed to insecticide-impregnated filter papers under laboratory conditions. Quantities of active ingredients on filter papers corresponded to the recommended doses proposed by the manufacturers (37.5 mg a.i./m2 of cattle's skin, 125 mg a.i./m2 and 750 mg a.i./m2 for deltamethrin, cypermethrin and phoxim respectively) were tested. Knock-down effects (KD) (1 h after the onset of exposure) and mortality rates (24 h and 48 h after exposure) were evaluated. Phoxim showed a rapid and full efficacy in all populations. However, the KD effects (37.5 to 97.5%) and the mortality rates at 48 h (10 to 91.25%) induced by the exposure to pyrethroids varied greatly according to the study site but none of the populations showed full susceptibility. Therefore, the current recommended doses of these pyrethroids are probably less efficient than expected in the field and should be considered with caution in the control of bovine besnoitiosis in France

Population Structure of Stomoxys calcitrans (Diptera: Muscidae) From Nine Regions of Thailand

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Bacterial Microbiome in Wild-Caught Anopheles Mosquitoes in Western Thailand

International audienceAmong the complex microbial community living in the mosquito midgut, some bacteria (e.g., Enterobacter spp.) can deliver effector molecules with anti-Plasmodium effects suppressing the development of malaria parasites (Plasmodium falciparum) before the öokinete can penetrate the mosquito midgut epithelium. Despite knowledge of this phenomenon, only a few studies have defined the diversity of microbiota in wild-caught adult Anopheles species. The objective of this study was to analyze and compare the bacterial microbiota in different Anopheles species, including representatives of the primary malaria vectors in western Thailand. Wild female Anopheles species were sampled from malaria-endemic areas in Tak and Mae Hong Son provinces near the Thai-Myanmar border. Midgut/abdominal bacterial diversity was assessed by examining the 16S rRNA gene, V3 hypervariable region, using PCR-Temporal Temperature Gel Electrophoresis (PCR-TTGE) profiling and sequence analysis. A total of 24 bacterial genera were identified from eight Anopheles species. Five bacterial genera were newly reported in Anopheles mosquitoes (Ferrimonas, Megasphaera, Pectobacterium, Shimwellia, and Trabulsiella). Five genera, including Megasphaera, were detected exclusively in a single-malaria (Plasmodium vivax) infected Anopheles minimus and not observed in other non-infected mosquitoes. The use of PCR-TTGE provides the first characterization of the midgut bacterial microbiome present in wild adult Anopheles in Thailand. Evidence that microbiota might impact pathogen development (suppression) in Anopheles and thereby reduce the risk of pathogen transmission deserves more studies to describe the presence and better understand the biological role of bacteria in natural mosquito populations

Geographic Distribution of Stomoxyine Flies (Diptera: Muscidae) and Diurnal Activity of Stomoxys calcitrans in Thailand

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