Transmission of pathogens byStomoxysflies (Diptera, Muscidae): a review

Abstract

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.

Characterization of tabanid flies (Diptera: Tabanidae) in South Africa and Zambia and detection of protozoan parasites they are harbouring

“…On the oher hand T. evansi is well known to be mechanically transmitted by biting flies including Stomoxys and tabanid flies (Sumba et al 1998;Gutierrez et al 2010;Desquesnes et al 2013). It has been reported that trypanosomes can also develop within the midgut and hindgut of tabanid flies (Krinsky and Pechuman, 1975;Bose and Heister, 1993).…”

“…Secondly, there must be a high density of potential mechanical vectors and close contact between the host animals and the vector flies (Desquesnes et al 2009). Thirdly, the biology of the flies is another contributing factor, for instance, the size of the fly mouthparts, whereby larger mouthparts of flies mechanically transmit more parasites (Sumba et al 1998;Baldacchino et al 2013). Lastly, the duration of parasite survival on the mouthparts is shorter (24 hours) as compared to inside the crop and the gut (5 to 7 days) and this would allow delayed transmission as the flies can regurgitate infected blood into the host (Baldacchino et al 2013).…”

“…Thirdly, the biology of the flies is another contributing factor, for instance, the size of the fly mouthparts, whereby larger mouthparts of flies mechanically transmit more parasites (Sumba et al 1998;Baldacchino et al 2013). Lastly, the duration of parasite survival on the mouthparts is shorter (24 hours) as compared to inside the crop and the gut (5 to 7 days) and this would allow delayed transmission as the flies can regurgitate infected blood into the host (Baldacchino et al 2013). * Indicates the average prevalence of the tested pathogens from the positively tested tabanid flies **Indicates the significance for the prevalence of the detected pathogens at p<0.05 calculated using Fisher's Exact Test by comparing the positively tested flies per pathogen detected…”

Molecular detection of Anaplasma marginale in stable flies Stomoxys calcitrans (Diptera: Muscidae) feeding on a tick-free bovine herd

“…In fact, outbreaks of bovine anaplasmosis have been documented in some geographical areas where there are no ticks. 11 S. calcitrans, is one of the biting flies implicated in the mechanical transmission of A. marginale among bovines, 12 but there are not published reports that demonstrate this assumption. On this basis, the aim of this study was to detect DNA from A. marginale in S. calcitrans caught at 6 meters near a bovine herd, housed in pens with cement floors, which has been maintained free of ticks for 40 years, and occasionally experienced some cases of anaplasmosis.…”

Is the Oriental House Rat (Rattus tanezumi) a Potential Reservoir for Trypanosoma evansi in Thailand?

“…In large herbivores, mechanical transmission by biting insects such as tabanids (Tabanidae) or stomoxes (Stomoxys spp.) is considered the primary route of infection (Baldacchino et al 2013(Baldacchino et al , 2014. However, these insects are diurnal and are attracted by large animals (Foil et al 1994) while wild rodents are small and mostly nocturnal.…”