Pseudomyiasis in Animals

In pseudomyiasis, dipteran larvae have been accidentally ingested and are found within an animal’s GI tract, where they are not able to continue their development. Dogs and cats infested with larvae of the facultative myiasis-producing flies in wounds or in the hair often ingest larvae while licking or grooming. These larvae pass through the GI tract and appear in the feces undigested. Dipteran larvae can also be passed in the feces when a roaming dog or cat ingests carrion that contains maggots; these maggots pass to the external environment undigested.

Pseudomyiasis can also occur if feces submitted for parasitological examination are not fresh. Adult facultative-myiasis flies might have laid their eggs in these feces, and larval development might have begun.

Eristalis tenax, the rat-tailed maggot, is found in the gutter behind cows in dairy barns. These maggots are associated with liquid feces and with feces that have not been removed from the environment. The larvae are known as rat-tailed maggots because their breathing pores are found at the tip of a long, siphon-like breathing tube on their caudal end. Many farmers erroneously assume that the cows defecated these maggots. The adults are nonparasitic, free-living flies.