RECOVERY OF A SECOND INSTAR GASTEROPHILUS LARVA IN A HUMAN INFANT:

Abstract. We report a case in an infant of horse bot fly myiasis that was unusual because the maggot had developed to the second instar (of three potential instars). This represents the first report of such late development in a human. The case occurred in a rural area of the Pacific northwest (Washington) in late summer. Human cutaneous myiasis caused by Gasterophilus hae-morrhoidalis (Gasterophilidae: Diptera), a horse bot com-monly known as the nose fly, has been reported on a few occasions. Larvae burrow just beneath the skin of human hosts producing a visible tortuous path and may cause severe itching.1,2 Previous reports end with removal of first-instar larvae, but second and third instars have not been reported on human hosts. This is probably because the first-instar lar-vae are either killed by scratching3 or removed before they can grow to the next instar. It is unknown if the larva could develop past the second instar in a cutaneous situation since the third (final) instar in the normal host, such as horses