First Reported Case of Accidental Gastric Myiasis Caused by Gasterophilus Larvae in a Gray Wolf

Abstract

Background: Myiasis is the infestation of living vertebrates by larvae (“maggots”) of dipterous flies. These include the Gasterophilus species (Oestridae). Their larvae are obligate endoparasites of equids, and their third instar larvae remain in specific areas of the gastrointestinal tract for many months. Non-equids are unsuitable hosts for Gasterophilus spp. However, their larvae have occasionally been found in the digestive tracts of carnivores and scavengers; this is known as accidental myiasis. Methods: A gray wolf (Canis lupus) hunted near a settlement in northern Kazakhstan in February 2023 was necropsied. Its stomach, which was otherwise empty, contained four cylindrical, cream-coloured maggots, approximately 15 mm long, attached to the gastric mucosa. Results: The maggots were identified morphologically as second and third instar Gasterophilus larvae and molecularly as Gasterophilus pecorum. Conclusion: This is the first reported case of accidental gastric myiasis in wolves. The causative species, Gasterophilus pecorum, is a common parasite of equids in Asian countries. The larvae must have survived the ingestion process intact and remained attached to the wolf’s stomach wall with cephalopharyngeal hooks for a prolonged period of time, lasting from more than half a day to several days.