Association of Escherichia coli O157:H7 with Houseflies on a Cattle Farm

Abstract

The ecology of Escherichia coli O157:H7 is not well understood. The aims of this study were to determine the prevalence of and characterize E. coli O157:H7 associated with houseflies (HF). Musca domestica L. HF (n ‫؍‬ 3,440) were collected from two sites on a cattle farm over a 4-month period and processed individually for E. coli O157:H7 isolation and quantification. The prevalence of E. coli O157:H7 was 2.9 and 1.4% in HF collected from feed bunks and a cattle feed storage shed, respectively. E. coli O157:H7 counts ranged from 3.0 ؋ 10 1 to 1.5 ؋ 10 5 CFU among the positive HF. PCR analysis of the E. coli O157:H7 isolates revealed that 90.4, 99.2, 99.2, and 100% of them (n ‫؍‬ 125) possessed the stx1, stx2, eaeA, and fliC genes, respectively. Large populations of HF on cattle farms may play a role in the dissemination of E. coli O157:H7 among animals and to the surrounding environment.Enterohemorrhagic Escherichia coli O157:H7 is a wellknown causative agent of hemorrhagic colitis and hemolytic uremic syndrome in humans. Outbreaks of the food-borne illness caused by E. coli O157:H7 have been reported throughout the northern hemisphere, most frequently in the United States, Canada, Japan, and the United Kingdom. In the United States alone, E. coli O157:H7 causes more than 73,000 cases of human infection every year (11). E. coli O157:H7 strains commonly carry verotoxins (encoded by the stx1 and stx2 genes) and factors for the attachment to the host mucosa, including intimin (encoded by the eaeA gene) (11). The low infectious dose and high virulence of E. coli O157:H7 make infections severe and life-threatening, particularly for young children, the elderly, and those with weakened immune systems (11). The main reservoir for E. coli O157:H7 is the intestinal tracts of healthy cattle. Individual cattle are transiently colonized and shed E. coli O157:H7 in their feces (1). The sources of E. coli O157:H7, which colonizes cattle, are not well understood, and little is known about the ecology of E. coli O157:H7 in the environment (1). Additionally, the high variability in the prevalence of E. coli O157:H7 among cattle suggests the possibility of a reservoir of E. coli O157:H7 external to cattle. However, other than the detection of E. coli O157:H7 in nonbovine animals, including sheep, horses, dogs, and wild birds (1), the ecology of this pathogen has not been extensively studied.One of the potential modes of dissemination of this pathogen in the environment is by insects that are associated with animal feces and manure, primarily houseflies (HF; Musca domestica L.). HF larvae develop in animal feces, including cattle manure. Consequently, HF commonly build up very large populations on cattle farms and in other animal facilities. Previously, a laboratory-based study demonstrated that E. coli O157:H7 ingested by HF remained viable in the fly excreta and that the HF were able to carry and disseminate E. coli for several days (9). In Japan, HF were implicated in the transmission of E. coli O157:H7 from reservoir animals to...

Study of pathogenic bacteria detected in fly samples using universal primer-multiplex PCR

“…All detected bacteria from M. domestica in the current study are pathogenic. These findings agree with the previous reports of Alam & Zurek (2004), in which E. coli O157:H7 was detected in both farm and urban environments and Greenburg (1965), Kobayashi et al, (1999) and Moriya et al, (1999). In conclusion, we developed an easy and rapid Universal Primer-Multiplex PCR showing high specificity capable of detecting three bacteria.…”

Animal Reservoirs of Shiga Toxin-ProducingEscherichia coli

“…STEC O157:H7 has been recovered from houseflies (Musca domestica), dump flies (Hydrotaea aenescens), and dung beetles (Catharsius molossus) residing on animal farms and at animal fairs (155)(156)(157)(158). Houseflies, in addition to being a mechanical vector, may also be involved in bioenhanced transmission (159).…”

Assessment of Hygiene Practices and Identification of Critical Control Points Relating to the Production of Skewered Meat Sold in N’Djamena-Chad

“…In addition, the analysis showed that these flies carry many different bacteria and thus are vectors. Musca domestica, each time landing on the surface of the food, leaving a large number of pathogenic bacteria (de Jesus et al, 2004) and is recognized as a vector responsible for several diseases in all continents (Allan & Zurek, 2004). The importance of the fly population on sites of preparation and sale of food indicates the presence or proximity of an unhealthy environment so favorable to the living conditions of these insects (Barro et al, 2006).…”