Abstract: The objective of the study was to verify the migration routes in the horse body about Gasterophilus and describe the damage caused by its parasitic via autopsy examination. The results showed that with the growth of age, larvas gradually migrate towards the end of the digestive tract, and no inverse movements were found. The longest stage of third instars were selective in the parasitic locations, and G. nigricornis and G. nasalis were located in the anterior duodenum, while G. pecorum and G. haemovrhoidalis are in stomach. Study of individuals infected by Gasterophilus proverd an absence of relationship between quantity of Gasterophilus larvas and age (P=0.320) or gender (P=0.665) of the horses. Myiasis was prominent among local equid animals. Wild horses had the highest infection rate, which followed by wild donkeys and domestic horses. A damage of 60% to 80% on total surface area in stomach was found. The results helped to better understand of the harm caused by Gasterophilus and strongly supported the follow-up monitoring and protection on Przewalski horses.

Key words: injury; Gasterophilius; parasitic; migration