A question I am asked often by media & public. Assuming they are actually referring to Periplaneta and Musca, what scientific evidence exists to indicate that either Periplaneta or Musca have ever SPREAD disease to humans? Yes, both may have E.coli on body surface, in gut, or in faeces, but in concentrations to be an issue to a human? Or is this a rumor to aid in the sales of insecticides, bacterial wipes, disinfectants etc?
As far as Musca is concerned there is plenty of evidence.
Early literature includes. Hewitt, G.C. 1912. House-Flies and How They Spread Disease and Howard, L.O. 1923. The House Fly, Disease Carrier: An Account of Its Dangerous Activities and of the Means of Destroying It.
Of greater significance, 1971 Prof. Bernard Greenberg listed the disease organisms carried by Diptera, devoting 50 pages in volume one (Flies and Disease Volume 1 & 2, Princeton University Press) to Musca domestica alone (67 pages to the genus Musca) setting this species in context with other disease transmitting flies.
Being coprophagous and synanthropic places Musca domestica in direct contact with humans as a vector of pathogens picked up while feeding. Feeding habits result in direct transmission of pathogens from the fly crop to food stuffs and domestic surfaces. Further trophic adaptation to the food stuffs and waste of humans and broad thermophilous habits enables this species to co-associate with humans all year around in all stages of development.
Greenberg skims over more detailed discussion of but refers the reader to West, L.S. 1951 The Housefly. Its Natural History, Medical Importance, and Control.
Pont (1973, Ch.5b Muscidae, in Insects and other Arthropods of Medical Importance, Trustees of te British Museum), provides a shorter and perhaps more accessible list of pathogens carried by Musca (pg. 263), including many diarrhoeal and enteric conditions through to more serious cholera, poliomyelitis, Q fever and tuberculosis).
Personally, I would discount the conspiracy theory "sales gimmick" idea. As early as 1923, Chinese public health noted the high concentration of pathogens on Musca bodies corresponded to the incidence of gastrointestinal disease outbreaks, confirmed by similar work in Egypt in the 1950. In an Annual Review of Entomology (1: 323 - 346) Lindsay and Scudder (1956) conclude that transmission by non-biting flies is as effective as the spread by other unhygienic practices, such as not washing hands and using dirty kitchen utensils.
More recently, Nichols, G.L. Disease transmission by non-biting flies, Ch.40 in Environmental Medicine by Jon G. Ayres et al gives a more modern perspective, but nonetheless based preceding knowledge of the early 1900s.
As far as Musca is concerned there is plenty of evidence.
Early literature includes. Hewitt, G.C. 1912. House-Flies and How They Spread Disease and Howard, L.O. 1923. The House Fly, Disease Carrier: An Account of Its Dangerous Activities and of the Means of Destroying It.
Of greater significance, 1971 Prof. Bernard Greenberg listed the disease organisms carried by Diptera, devoting 50 pages in volume one (Flies and Disease Volume 1 & 2, Princeton University Press) to Musca domestica alone (67 pages to the genus Musca) setting this species in context with other disease transmitting flies.
Being coprophagous and synanthropic places Musca domestica in direct contact with humans as a vector of pathogens picked up while feeding. Feeding habits result in direct transmission of pathogens from the fly crop to food stuffs and domestic surfaces. Further trophic adaptation to the food stuffs and waste of humans and broad thermophilous habits enables this species to co-associate with humans all year around in all stages of development.
Greenberg skims over more detailed discussion of but refers the reader to West, L.S. 1951 The Housefly. Its Natural History, Medical Importance, and Control.
Pont (1973, Ch.5b Muscidae, in Insects and other Arthropods of Medical Importance, Trustees of te British Museum), provides a shorter and perhaps more accessible list of pathogens carried by Musca (pg. 263), including many diarrhoeal and enteric conditions through to more serious cholera, poliomyelitis, Q fever and tuberculosis).
Personally, I would discount the conspiracy theory "sales gimmick" idea. As early as 1923, Chinese public health noted the high concentration of pathogens on Musca bodies corresponded to the incidence of gastrointestinal disease outbreaks, confirmed by similar work in Egypt in the 1950. In an Annual Review of Entomology (1: 323 - 346) Lindsay and Scudder (1956) conclude that transmission by non-biting flies is as effective as the spread by other unhygienic practices, such as not washing hands and using dirty kitchen utensils.
More recently, Nichols, G.L. Disease transmission by non-biting flies, Ch.40 in Environmental Medicine by Jon G. Ayres et al gives a more modern perspective, but nonetheless based preceding knowledge of the early 1900s.
I also would estimate nuisance flies as "germier" for several reasons:
Nuisance flies spit salvia on the food and then suck up the more or less liquefied food items (cockroaches feed more on solid food parts using mandibles etc).
Some fly species visit faeces, human food and human skins/eyes (among many other surfaces).
Visits of flies on human food can be unobserved and clandestine, whereas cockroaches often leave clear signs of the visits (faeces, parts are eaten away etc), therefore you anyway won't eat this anymore.
All increases the chance of contamination by nuisance flies and ingestion by humans.
But in my opinion this is especially true for warmer regions with very high population densities of nuisance flies increasing the likeliness that the densities of transferred bacteria will be high enough and that there are pathogenic strains among them, compared to temperate and cold regions. Also the higher temperatures and humidity and therefore faster development of the bacteria on the contaminated stuff might add to this. Therefore it also depends on where you are based.
There is a lot of work published on filth-feeding flies as "mechanical vectors" and/or dispersal agents for human and zoonotic pathogens. We have worked some with the role of muscids, sarcophagids, and calliphorids in agricultural and sylvatic ecosystems here in our One Health Center at Berry College. Our own work has looked only at contamination by viable infective pathogens, especially diarrhea-causing species. Also, we have worked with protists and microsporidians, which do not grow on the insects but simply are transported in their spore, cyst, or oocyst stages. (See link to ResearchGate full text below). The work done by others on these, and on bacterial pathogens, is rather extensive. The role of flies in transmitting trachoma is especially well established, as this is a disease affecting millions, especially children, and is a leading cause of blindness. Trachoma is also among the "neglected tropical diseases" that is now receiving high-priority attention from several global health groups. This is a great question that needs much more study; thanks for bringing up the issue.
Article Synanthropic Flies as Vectors of Cryptosporidium and Giardia...
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