House Flies Are Underappreciated Yet Important Reservoirs and Vectors of Microbial Threats to Animal and Human Health

Abstract

House flies are well recognized as filth-associated organisms and public nuisances. House flies create sanitation issues when they bridge the gap between microbe-rich breeding environments and animal/human habitations. Numerous scientific surveys have demonstrated that house flies harbor bacterial pathogens that pose a threat to humans and animals. More extensive and informative surveys incorporating next-generation sequencing technologies have shown that house fly carriage of pathogens and harmful genetic elements, such as antimicrobial resistance genes, is more widespread and dangerous than previously thought. Further, there is a strong body of research confirming that flies not only harbor but also transmit viable, and presumably infectious, bacterial pathogens. Some pathogens replicate and persist in the fly, permitting prolonged shedding and dissemination. Finally, although the drivers still have yet to be firmly determined, the potential range of dissemination of flies and their associated pathogens can be extensive. Despite this evidence, the house flies’ role as reservoirs, disseminators, and true, yet facultative, vectors for pathogens have been greatly underestimated and underappreciated. In this review, we present key studies that bolster the house fly’s role both an important player in microbial ecology and population biology and as transmitters of microbial threats to animal and human health.

Bacterial communities and prevalence of antibiotic resistance genes carried within house flies (Diptera: Muscidae) associated with beef and dairy cattle farms

“…House flies are well known carriers of hundreds of species of human and animal pathogens. Their close association with animal and human habitats as well as their feeding and reproductive behaviors make them efficient vectors to spread disease-causing microbes among various environmental niches (Nayduch and Burrus 2017, Onwugamba et al 2018, Geden et al 2021, Nayduch et al 2023). In this study, we observed a high abundance and prevalence of several potential pathogenic bacterial taxa such as Corynebacterium , Staphylococcus , Streptococcus , Enterococcus , Enterobacteriaceae, Providencia , Acinetobacter , Dietzia , Bacillus , Turicibacter , Clostridium , and Pseudomonas from all farms.…”

“…Although both male and female flies forage on animal waste, female house flies have closer associations than males with microbe-rich substrates such as manure, upon which they feed and potentially oviposit (Thomson et al 2017). Flies acquire and harbor microbial communities residing in habitats where they feed and take refuge, and can potentially disseminate microbes to neighboring farms or communities (Nayduch and Burrus 2017, Nayduch et al 2023).…”

“…Moreover, house flies also harbor and disseminate antimicrobial resistant (AMR) pathogenic and nonpathogenic bacteria, containing antimicrobial resistance genes (ARGs) that can be horizontally transferred among bacteria (Xu et al 2018, Zhang et al 2018, Neupane et al 2020, Poudel et al 2020, Stelder et al 2021). Flies may play a major role in spreading AMR bacteria from animal production operations to human habitats (Zurek and Ghosh 2014), causing major concerns to public and animal health (Onwugamba et al 2018, Nayduch et al 2023).…”

Evaluation of the stability of physiological and behavioral resistance to imidacloprid in the house fly (Musca domestica L.) (Diptera: Muscidae)

“…1,2 These facilities produce large amounts of microbe-rich materials, which are ideal for larval fly development. 3,4 The house fly has adapted to living in almost every environment, is known worldwide as a serious nuisance pest species, and has been implicated in the transmission of >200 different pathogens. 4,5 Under optimal environmental conditions large numbers of flies can be produced in a short period of time, with flies developing from egg to adult in as little as 7 days.…”

“…3,4 The house fly has adapted to living in almost every environment, is known worldwide as a serious nuisance pest species, and has been implicated in the transmission of >200 different pathogens. 4,5 Under optimal environmental conditions large numbers of flies can be produced in a short period of time, with flies developing from egg to adult in as little as 7 days. 6 Although most house flies will remain on or near animal production facilities from which they developed, 7 house flies also are known to readily disperse from development sites.…”