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Stomoxys flies are mechanical vectors of pathogens present in the blood and skin of their animal hosts, especially livestock, but occasionally humans. In livestock, their direct effects are disturbance, skin lesions, reduction of food intake, stress, blood loss, and a global immunosuppressive effect. They also induce the gathering of animals for mutual protection; meanwhile they favor development of pathogens in the hosts and their transmission. Their indirect effect is the mechanical transmission of pathogens. In case of interrupted feeding, Stomoxys can re-start their blood meal on another host. When injecting saliva prior to blood-sucking, they can inoculate some infected blood remaining on their mouthparts. Beside this immediate transmission, it was observed that Stomoxys may keep some blood in their crop, which offers a friendly environment for pathogens that could be regurgitated during the next blood meal; thus a delayed transmission by Stomoxys seems possible. Such a mechanism has a considerable epidemiological impact since it allows inter-herd transmission of pathogens. Equine infectious anemia, African swine fever, West Nile, and Rift Valley viruses are known to be transmitted by Stomoxys, while others are suspected. Rickettsia (Anaplasma, Coxiella), other bacteria and parasites (Trypanosoma spp., Besnoitia spp.) are also transmitted by Stomoxys. Finally, Stomoxys was also found to act as an intermediate host of the helminth Habronema microstoma and may be involved in the transmission of some Onchocerca and Dirofilaria species. Being cosmopolite, Stomoxys calcitrans might have a worldwide and greater impact than previously thought on animal and human pathogen transmission. 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.

Stomoxys flies are widely distributed and economically significant vectors of various livestock pathogens of veterinary importance. However, the role of Stomoxys spp. in pathogen transmission is poorly understood. Therefore, we studied the feeding patterns of these blood feeders collected from specific locations in Kenya to identify various vertebrate hosts they fed on, the livestock hemopathogens they carried, and to elucidate their role in pathogens transmission. Our findings show that field-collected Stomoxys flies carried several pathogens, including Trypanosoma spp., Anaplasma spp., and Theileria spp., which were also detected in the blood of sampled livestock, namely camels and cattle. The findings on blood meal analysis show that Stomoxys flies fed on various domestic and wild vertebrate hosts. We further determined whether Stomoxys spp. are vectors of hemopathogens they harbored by studying the vector competence of Stomoxys calcitrans, S. niger niger, and S. boueti species complex, through laboratory and natural experimental in vivo studies. We show that in the process of blood feeding Stomoxys spp. complexes can transmit Trypanosoma evansi (8.3%) and T. vivax (30%) to Swiss white mice. In addition, field-collected Stomoxys spp. were exposed to healthy mice for blood meal acquisition, and in the process of feeding, they transmitted Theileria mutans and Anaplasma spp. to Swiss white mice (100% infection in the test mice group). All mice infected with trypanosomes via Stomoxys bite died while those infected with Theileria and Anaplasma species did not, demonstrating the virulence difference between pathogens. The key finding of this study showing the wide distribution, broad feeding host range, plethora of pathogens harbored, and efficient vector competence in spreading multiple pathogens suggests the significant role of Stomoxys on pathogen transmission and infection prevalence in livestock.

BackgroundHaematophagous Diptera can transmit a wide range of diseases to both humans and animals. Some species of the Trypanosoma genus rely on these vectors for transmission, either cyclically or mechanically. Trypanosoma evansi, the causative agent of Surra, is the only African-origin trypanosome species detected in Spain to date, which is mechanically transmitted.MethodsTo assess the occurrence and distribution of potential mechanical vectors at the national level, a systematic review was conducted on the Hippoboscidae, Muscidae and Tabanidae families. The review followed the methodology established by the Food and Agriculture Organization of the United Nations (FAO) and adhered to PRISMA guidelines. Data were compiled from 43 peer-reviewed scientific publications and four citizen science digital databases.ResultsThe review identified three genera belonging to the Hippoboscidae, two of the Muscidae and ten of the Tabanidae families. Genus-level distribution maps were generated for each group.ConclusionsThis atlas serves as a valuable tool for the prevention and control of vector-borne animal trypanosomosis in Spain. Nonetheless, further studies on the distribution, ecology and behaviour of haematophagous dipterans are essential to better understand their role in disease transmission and their potential impact on future outbreaks.

Colonies of house flies (Musca domestica L. [Diptera: Muscidae]) and four species of parasitoids (Muscidifurax raptor Girault and Sanders, Muscidifurax zaraptor Kogan and Legner, Spalangia cameroni Perkins and Spalangia endius Walker) were established by making collections from dairy farms near Bell, FL, Beatrice, NE, Minneapolis, MN, and San Jacinto, CA. Colonies were assessed for heat tolerance by comparing life history parameters at 25–27°C and fluctuating hot (26.7–41.7°C) temperatures. Muscidifurax raptor, S. cameroni, and S. endius produced 24–28% as many progeny under hot conditions as at 25°C. Colonies of M. zaraptor were more heat-tolerant and produced an average 46.9% as many progeny under the hot regime compared with moderate conditions. There was little evidence for higher heat tolerance in parasitoid populations from historically hot locations (CA desert and FL). Colonies of M. raptor and S. endius that had been in culture for 24 yr were the least heat-tolerant with regard to progeny production. House flies collected from the same locations varied little in longevity, fecundity, or egg-to-adult survival under either hot or moderate regimes. Flies reared under hot conditions laid about half as many eggs (89/female) and had about half the egg–adult survival rate (47.3%) under hot compared with moderate conditions, indicating that heat stress had less effect on flies than on all of the parasitoids except M. zaraptor. An attempt to select for heat tolerance in flies by subjecting them to incremental increases in rearing temperatures for 20 generations resulted in little change in tolerance among the selected flies.

Taeniid eggs may be transmitted either abi-otically by e.g. sewage disposal, rainfall and water streams or biotically by vectors as her-bivores, birds and insects. Among the insects especially the flies may play an important role as shown in New Zealand by Lawson & Gemmell (1983, 1985). The fly-borne trans-mission may take place over long distances. Lawson & Gemmell (1983) evaluated that the majority of eggs would be deposited within 1.6 km from their point of origin, but some eggs might be spread even longer.

Parabronema skrjabini is one of the most harmful nematodes to camels and is responsible for economic losses in animal husbandry industry. There is an urgent need for in-depth studies of potential vectors of the nematode due to its scant regarding information. As previous studies indicated that flies may be the vectors of P. skrjabini, we captured flies in the main camel-producing areas of Inner Mongolia. After autopsy of the specimens of two species of horn flies, we observed the morphology of the suspected nematode larvae found in them. Internal transcribed spacer ribosomal-DNA gene sequences were considered the best candidate to confirm the species of the larvae found. Our results showed that the homology compared with P. skrjabini was 99.5% in GenBank. Subsequently, we preliminarily identified two species of horn flies through morphological observation and then sequenced the mitochondrial-DNA-gene cytochrome oxidase subunit I obtained from two species of horn flies, with 100 and 99.2% similarity to sequences deposited in GenBank, respectively. Thus, we identified Haematobia titillans and Haematobia irritans and provided evidence for their potential role as vectors of parabronemosis. Our study provides reference for future research on the life history of the nematode and the vectors of parabronemosis.

Synthesiomyia nudiseta (Wulp) (Diptera: Muscidae) was identified during the course of three indoor medicolegal forensic entomology investigations in the state of Texas, one in 2011 from Hayes County, TX, and two in 2015 from Harris County, TX. In all cases, mites were found in association with the sample and subsequently identified as Myianoetus muscarum (L., 1758) (Acariformes: Histiostomatidae). This report represents the first records of a mite associated with S. nudiseta in the continental United States. In particular, this association is believed to be of potential future value in forensic investigations, as it lends new insight into the community structure of colonizers on human remains in indoor environments.

A prevailing hypothesis for the evolution of parasitism posits that the fitness benefits gained from parasitic activity results in selection for and fixation of parasitic strategies. Despite the potential fitness advantage of parasitism, facultative parasites continue to exhibit genetic variation in parasitic behaviour in nature. We hypothesized that evolutionary trade-offs associated with parasitic host-attachment behaviour maintain natural variation observed in attachment behaviour. In this study, we used replicate lines of a facultatively parasitic mite, previously selected for increased host-attachment behaviour to test whether increased attachment trades off with mite fecundity and longevity, as well as the phenotypic plasticity of attachment. We also tested for potential correlated changes in mite morphology. To test for context-dependent trade-offs, mite fecundity and longevity were assayed in the presence or absence of a host. Our results show that selected and control mites exhibited similar fecundities, longevities, attachment plasticities and morphologies, which did not provide evidence for life history trade-offs associated with increased attachment. Surprisingly, phenotypic plasticity in attachment was maintained despite directional selection on the trait, which suggests that phenotypic plasticity likely plays an important role in maintaining attachment variation in natural populations of this facultative parasite.

Release of parasitic wasps (Hymenoptera: Pteromalidae) as biological control agents for house flies and stable flies in livestock confinements has had variable success. In part, this may reflect a lack of knowledge regarding the optimal distance to be used between parasitoid release stations. In the current study, we assessed the effect of linear distance on host parasitism by the wasp Spalangia cameroni Perkins. In open fields at distances ranging from 1 m to 60 m from a central point, house fly puparia were placed in a mixture of pine shavings soiled with equine manure, urine, and alfalfa hay. Releases of S. cameroni then were made using a 5:1 host: parasitoid ratio. Host pupae were parasitized at all distances, with the highest rate of total parasitism (68.9%) recorded ≤ 5 m from the release site. Analyses of results using non-linear and linear models suggest that S. cameroni should be released in close proximity to host development areas. Additionally, releases may not be suitable in pasture situations where long-distance flight is required for control. However, further testing is needed to examine the effect of density-dependent dispersal and diffusion of S. cameroni.

Parasitoids are important natural enemies of house flies and other muscoid flies. The two most commonly used methods for collecting fly parasitoids from the field have distinct advantages and disadvantages. Collections of wild puparia depend on the ability to find puparia in sufficient numbers and are prone to localized distortions in relative species abundance because of the overrepresentation of samples from hot spots of fly larval activity. Placement and retrieval of sentinel puparia is convenient and allows consistent sampling over time but is strongly biased in favor of Muscidifurax spp. over Spalangia spp. An improved sentinel method is described that combines some of the advantages of these two methods. Fly medium containing larvae is placed in containers, topped with a screen mesh bag of puparia, and placed in vertebrate-proof wire cages. Cages are placed at sites of actual or potential fly breeding and retrieved 3–7 d later. The modified method collected species profiles that more closely resembled those of collections of wild puparia than those from sentinel pupal bags. A method is also described for isolating puparia individually in 96-well tissue culture plates for parasitoid emergence. Use of the plate method provided a substantial saving of time and labor over the use of individual gelatin capsules for pupal isolation. Puparia from the collections that were housed individually in the wells of tissue culture plates had a higher proportion of emerged Spalangia species than puparia that were held in groups.