Transmission of pathogens by "Stomoxys flies (Diptera, Muscidae): a review

Les stomoxes sont des vecteurs mécaniques de pathogènes présents dans le sang et les tissus cutanés de leurs hôtes, spécialement le bétail, mais aussi parfois les humains. Pour le bétail, leurs effets directs sont principalement la perturbation des animaux, les lésions de la peau, la réduction de l'alimentation, le stress, la spoliation sanguine et un effet immunosuppressif global. Ils entrainent aussi le regroupement des animaux pour une protection mutuelle ; tout cela favorise le développement des parasites chez les hôtes et leur transmission. Leur effet indirect est la transmission mécanique de pathogènes. En cas de repas interrompu, les stomoxes peuvent reprendre leur repas de sang sur un autre hôte. En injectant de la salive avant l'absorption de sang, ils peuvent inoculer du sang infecté qui restait sur leurs pièces buccales. En plus de cette transmission immédiate, il a été observé que les stomoxes pouvaient conserver du sang dans leur jabot, qui offre un meilleur environnement pour les pathogènes. Ces derniers peuvent être régurgités lors du prochain repas de sang. Ainsi, une transmission retardée semble possible par les stomoxes. Un tel mécanisme a une conséquence épidémiologique considérable, puisqu'il permet une transmission de pathogènes entre les troupeaux. Les virus de l'anémie infectieuse équine, de la fièvre porcine africaine, des fièvres à West Nile ou de la Vallée du Rift, sont connus pour être transmis par des stomoxes ; d'autres sont suspectés. Des rickettsies (Anaplasma, Coxiella), d'autres bactéries et des parasites (Trypanosoma spp., Besnoitia spp.) sont aussi transmis par les stomoxes. Enfin, les stomoxes sont aussi des hôtes intermédiaires de l'helminthe Habronema microstoma et pourraient être impliqués dans la transmission de certaines espèces d'Onchocerca et de Dirofilaria. En étant cosmopolite, Stomoxys calcitrans pourrait avoir un impact plus important qu'initialement imaginé sur la transmission de pathogènes aux animaux et aux humains. (Résumé d'auteur

Stable Fly (Diptera: Muscidae) Distribution in Thailand

ABSTRACT Diurnal sampling of stable flies (Stomoxys spp.) was carried out in ten localities throughout Thailand in 2007. Vavoua traps were used to lure and capture flies in ten provinces of the country, representing four major ecological settings: six small local dairy farms; two large industrial dairy farms; one national park; and one wildlife conservation area. Six species of stable flies were identified: Stomoxys calcitrans (91.5%), S. bengalensis (4.7%), S. uruma (2%), S. indicus (1%), S. sitiens (0.6%) and S. pullus (0.2%). The number of stable flies collected differed significantly among different collection sites, with greater numbers from dairy farms (χ 2 = 360.15, df = 3, P< 0.05)

The abundance and host-seeking behavior of culicine species (Diptera: Culicidae) and Anopheles sinensis in Yongcheng city, people's Republic of China

<p>Abstract</p> <p>Background</p> <p>The knowledge of mosquito species diversity and the level of anthropophily exhibited by each species in a region are of great importance to the integrated vector control. Culicine species are the primary vectors of Japanese encephalitis (JE) virus and filariasis in China. <it>Anopheles sinensis </it>plays a major role in the maintenance of <it>Plasmodium vivax </it>malaria transmission in China. The goal of this study was to compare the abundance and host-seeking behavior of culicine species and <it>An. sinensis </it>in Yongcheng city, a representative region of <it>P. vivax </it>malaria. Specifically, we wished to determine the relative attractiveness of different animal baits versus human bait to culicine species and <it>An. sinensis</it>.</p> <p>Results</p> <p><it>Culex tritaeniorhynchus </it>was the most prevalent mosquito species and <it>An. sinensis </it>was the sole potential vector of <it>P. vivax </it>malaria in Yongcheng city. There were significant differences (P < 0.01) in the abundance of both <it>An. sinensis </it>and <it>Cx. tritaeniorhynchus </it>collected in distinct baited traps. The relative attractiveness of animal versus human bait was similar towards both <it>An. sinensis </it>and <it>Cx. tritaeniorhynchus</it>. The ranking derived from the mean number of mosquitoes per bait indicated that pigs, goats and calves frequently attracted more mosquitoes than the other hosts tested (dogs, humans, and chickens). These trends were similar across all capture nights at three distinct villages. The human blood index (HBI) of female <it>An. sinensis </it>was 2.94% when computed with mixed meals while 3.70% computed with only the single meal. 19:00~21:00 was the primary peak of host-seeking female <it>An. sinensis </it>while 4:00~5:00 was the smaller peak at night. There was significant correlation between the density of female <it>An. sinensis </it>and the average relative humidity (P < 0.05) in Wangshanzhuang village.</p> <p>Conclusions</p> <p>Pigs, goats and calves were more attractive to <it>An. sinensis </it>and <it>Cx. tritaeniorhynchus </it>than dogs, humans, and chickens. Female <it>An. sinensis </it>host-seeking activity mainly occurred from 19:00 to 21:00. Thus, we propose that future vector control against <it>An. sinensis </it>and <it>Cx. tritaeniorhynchus </it>in the areas along the Huang-Huai River of central China should target the interface of human activity with domestic animals and adopt before human hosts go to bed at night.</p

Field evaluation of a spatial repellent emanation vest for personal protection against outdoor biting mosquitoes

Exophilic vectors are an important contributor to residual malaria transmission. Wearable spatial repellents (SR) can potentially provide personal protection in early evening hours before people retire indoors. An SR prototype for passive delivery of transfluthrin (TFT) for protecting humans against nocturnal mosquitoes in Kanchanaburi, western Thailand, is evaluated. A plastic polyethylene terephthalate (PET) sheet (676 cm2) treated with 55-mg TFT (TFT-PET), attached to the back of short-sleeve vest worn by human collector, was evaluated under semifield and outdoor conditions. Field-caught, nonblood-fed female Anopheles minimus s.l. were released in a 40 m length, semifield screened enclosure. Two collectors positioned at opposite ends conducted 12-h human-landing collections (HLC). The outdoor experiment was conducted between treatments among four collectors at four equidistant positions who performed HLC. Both trials were conducted for 30 consecutive nights. TFT-PET provided 67% greater protection (P < 0.001) for 12 h compared with unprotected control, a threefold reduction in the attack. In outdoor trials, TFT-PET provided only 16% protection against An. harrisoni Harbach & Manguin (Diptera: Culicidae) compared with unprotected collector (P = 0.0213). The TFT-PET vest reduced nonanophelines landing by 1.4-fold compared with the PET control with a 29% protective efficacy. These findings suggest that TFT-PET had diminished protective efficacy in an open field environment. Nonetheless, the concept of a wearable TFT emanatory device has the potential for protecting against outdoor biting mosquitoes. Further development of portable SR tools is required, active ingredient selection and dose optimization, and more suitable device design and materials for advancing product feasibility

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

International audienc

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

International audienc

Indoor resting behavior of Aedes aegypti (Diptera: Culicidae) in northeastern Thailand

BACKGROUND: Aedes aegypti is a vector of several arboviruses, notably dengue virus (DENV), which causes dengue fever and is often found resting indoors. Culex spp. are largely nuisance mosquitoes but can include species that are vectors of zoonotic pathogens. Vector control is currently the main method to control dengue outbreaks. Indoor residual spraying can be part of an effective vector control strategy but requires an understanding of the resting behavior. Here we focus on the indoor-resting behavior of Ae. aegypti and Culex spp. in northeastern Thailand. METHODS: Mosquitoes were collected in 240 houses in rural and urban settings from May to August 2019 at two collection times (morning/afternoon), in four room types (bedroom, bathroom, living room and kitchen) in each house and at three wall heights (&lt; 0.75 m, 0.75-1.5 m, &gt; 1.5 m) using a battery-driven aspirator and sticky traps. Household characteristics were ascertained. Mosquitoes were identified as Ae. aegypti, Aedes albopictus and Culex spp. Dengue virus was detected in Ae. aegypti. Association analyses between urban/rural and within-house location (wall height, room), household variables, geckos and mosquito abundance were performed. RESULTS: A total of 2874 mosquitoes were collected using aspirators and 1830 using sticky traps. Aedes aegypti and Culex spp. accounted for 44.78% and 53.17% of the specimens, respectively. Only 2.05% were Ae. albopictus. Aedes aegypti and Culex spp. rested most abundantly at intermediate and low heights in bedrooms or bathrooms (96.6% and 85.2% for each taxon of the total, respectively). Clothes hanging at intermediate heights were associated with higher mean numbers of Ae. aegypti in rural settings (0.81 [SEM: 0.08] vs. low: 0.61 [0.08] and high: 0.32 [0.09]). Use of larval control was associated with lower numbers of Ae. aegypti (yes: 0.61 [0.08]; no: 0.70 [0.07]). All DENV-positive Ae. aegypti (1.7%, 5 of 422) were collected in the rural areas and included specimens with single, double and even triple serotype infections. CONCLUSIONS: Knowledge of the indoor resting behavior of adult mosquitoes and associated environmental factors can guide the choice of the most appropriate and effective vector control method. Our work suggests that vector control using targeted indoor residual spraying and/or potentially spatial repellents focusing on walls at heights lower than 1.5 m in bedrooms and bathrooms could be part of an integrated effective strategy for dengue vector control