ARS | Publication request: Use of bioluminescent Escherichia coli to determine retention during the life cycle of the housefly, Musca domestica (Diptera: Muscidae, L)

Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 13, 2012
Publication Date: May 1, 2013
Citation: Schuster, G.L., Donaldson, J.R., Buntyn, J.O., Duoss, H.A., Callaway, T.R., Carroll, J.A., Falkenberg, S.M., Schmidt, T.B. 2013. Use of bioluminescent Escherichia coli to determine retention during the life cycle of the housefly, Musca domestica (Diptera: Muscidae, L). Foodborne Pathogens and Disease. 10:442-447.

Interpretive Summary: Adult flies have been shown to be able to carry pathogenic E. coli (such as O157:H7) on their bodies; however, no data has been presented on exposure of flies in other life stages to E. coli O157:H7. This study examined if the larvae of house flies could ingest E. coli in bovine manure, using a bioluminescent E. coli to track locations in the fly where it was primarily located. It was found that house fly larvae can ingest and retain large amounts of E. coli, potentially emerging as an immediate vector of pathogenic E. coli. Further research is needed to determine how easy it is for these larvae to spread E. coli in further contact.

Technical Abstract: Researchers have documented that the house fly (Musca domestica) can serve as a bio-enhanced vector for the spread of pathogens to livestock, food, and humans. However, current data has investigated Musca domestica as a vector only after contact with/consuming the pathogen after emerging as an adult. The objective of this study was to determine if the larvae of Musca domestica could ingest Escherichia coli from bovine manure and the E. coli survive the metamorphosis process. Larvae were incubated in sterilized bovine manure inoculated with 0, 3, 5, and 8 log10 CFU/mL of bioluminescent E. coli for 24 (larvae stage), 48 (larvae stage), 120 (pupae stage), and 192 h (adult stage). Larvae incubated for 24 h in bovine manure were able to ingest 0.0, 2.7, 2.9, and 3.5 log10 CFU/mL of E. coli from manure inoculated at a rate of 0, 3, 5, and 8 log10 CFU/mL, respectively. Larvae incubated for 48 h in bovine manure were able to ingest 0.0, 3.0, 3.3, and 3.9 log10 CFU/mL of E. coli from manure inoculated at a rate of 0, 3, 5, and 8 log10 CFU/mL, respectively. Concentrations of E. coli within the pupae were 0.0, 1.7, 1.9, and 2.2 log10 CFU/mL for 0, 3, 5, and 8 log10 CFU/mL, respectively. Flies that emerged from the pupae stage contained 0.0, 1.3, 2.2, and 1.7 log10 CFU/mL of E. coli from larvae incubated in manure inoculated with 0, 3, 5, and 8 log10 CFU/mL of E. coli, respectively. These results suggest the house fly can emerge with quantities of E. coli capable of initiating illness; however, further research is needed. Larvae were incubated in sterilized bovine manure and there was not bacterial competition for the E. coli, thus the rate of positive flies and concentrations present when flies emerged may vary.