Background: Flies are natural carriers of pathogens and play a considerable role in the mechanical transmission of many pathogens, such as viruses, fungi, bacteria, and parasites, in various regions of the world.
Objective: To investigate the existence of Toxocara spp. eggs on two types of flies, the Oriental latrine fly, Chrysomya megacephala, and the house fly, Musca domestica, in Ubon Ratchathani, Northeast Thailand.
Material and Method: Flies were collected by the use of sterilized insect sweeping nets at five types of sites, fresh-food markets, garbage piles, restaurants, school cafeterias, and paddy fields from September 2010 to October 2011. After centrifugation, sediments from each fly species were examined for parasites under a light microscope.
Results: From the analysis of 555 C. megacephala and 439 M. domestica adult samples, Toxocara eggs were isolated from only the former species in all sites except for the restaurants in the Warinchamrap. No other helminthes and protozoa were found on the body surfaces of both fly species.
Conclusion: The data suggest that C. megacephala is more likely to be a potential carrier of Toxocara eggs than M. domestica in areas frequented by humans in this region of Thailand.

Keywords: Toxocara spp., Chrysomya megacephala, Musca domestica, Mechanical vector, Thailand