The incidence and species composition of Gasterophilus (Diptera, Gasterophilidae) causing equine myiasis in northern Xinjiang, China.

A survey was conducted on the detection of the larval Gasterophilus species in 90 equines via necropsy or after administering oral ivermectin in Xinjian, China, from 2008 to 2013. All 90 (100%) equines were infested by larval Gasterophilus, and 3723second instar larvae (L2) and 63,778 third instar larvae (L3) were collected from faecal samples and the digestive tract, a ratio of L2:L3=1:17. Over 84.45% of the animals contained ≤1500 larvae and 7.78% had >2000 larvae. The highest totals of L2 and L 3 larvae in any one animal were 1208 in Mongolian wild ass (Equus hemionus hemionus), 2491 in Przewalski's horse (Equus ferus przewalskii), and 1785 in the domestic horse (Equus ferus caballus). Six species of Gasterophilus were identified, with the following proportions of overall parasite abundance: Gasterophilus pecorum 88.94%, Gasterophilus nigricornis 4.94%, Gasterophilus nasalis 3.93%, Gasterophilus haemorrhoidalis 1.91%, Gasterophilus intestinalis 0.19%, and Gasterophilus inermis 0.087%. A majority of equines (n=32, 35.57%) was infested with five Gasterophilus species, while 29 animals (32.22%) harboured four species, 13 animals (14.44%) had six, 12 animals (13.33%) had three, three (3.33%) had two, and one (1.11%) had only one species. The percentage of Przewalski's horses infested was higher than local domestic horse or Mongolian wild ass.