Gasterophilus (Diptera, Gasterophilidae) infestation of equids in the Kalamaili Nature Reserve, China.

We investigated infections with Gasterophilus spp. in three equids within the Kalamaili Nature Reserve (northern China). We conducted necropsies on 6 Przewalski's horses (Equus ferus przewalskii) and 6 Mongolian wild asses (Equus hemionus) and administered ivermectin to 10 overwintering domestic horses to expel parasites during winter periods. All 22 equids studied (100%) were infested with Gasterophilus spp. and a total of 17,225 larvae were collected. These included six species: G. haemorrhoidalis, G. inermis, G. intestinalis, G. nasalis, G. nigricornis, and G. pecorum. The mean intensity of Gasterophilus spp. larvae was 1904 in Przewalski's horses, 780 in Mongolian wild asses, and 113 in domestic horses. Gasterophilus pecorum was the most abundant species in all three equids. Przewalski's horses, a reintroduced species, had a significantly higher intensity of Gasterophilus spp. than the Mongolian wild ass, indicating greater susceptibility to parasites in its ancestral home.