Human Tracheopulmonary Myiasis

Ed. Note: This letter clarifies some of the information presented in a previously published article (reference 4).

Regarding the recent report (4) by Cornet et al., I would like to provide additional information about human tracheopulmonary myiasis and a few comments from a veterinary perspective.

The authors reported that only four cases of human tracheopulmonary myiasis have been reported to date. At least two more cases have been reported: one, from Brazil, caused by the primate parasite Alouattamyia baeri (Diptera: Cuterebridae) (7), and another, from Japan, caused by Megaselia spicularis (Diptera: Phoridae) (11). Other, nonpulmonary human infestations by Megaselia sp. have also been reported (1, 3, 12).

Tracheopulmonary myiasis appears to be equally rare in animals, despite the existence of many bot fly species whose larvae normally migrate into the upper respiratory tracts of their respective animal hosts (2). Even those bot fly species whose larvae routinely penetrate the upper respiratory tract and migrate into adjacent tissues rarely cause tracheopulmonary myiasis. For example, dogs and cats in North America are frequently infested during the late summer months with Cuterebra sp. larvae (2). Although pharyngeal myiasis is occasionally reported (10), as well as aberrant migration into other locations such as the eye (9) or central nervous system (8), the migration of the larvae through the pharyngeal tissues rarely causes harm. Despite the proximity of the migrating larvae to the lower respiratory tract, only three cases of tracheal, though not pulmonary, cuterebriasis have been described (5, 6).

Finally, two minor corrections should be made to the authors' statement that “only one genus of botfly is currently recognized as occurring in North America… .”. First, because these insects are members of the order Diptera, or true flies, “botfly” should be written as two words (1a). Second, several other bot fly genera certainly occur in North America, and veterinarians are quite familiar with their larvae: Gasterophilus (affecting horses), Hypoderma (cattle), Oestrus (sheep), and Cephenomyia (deer, elk, caribou, and other cervids) (2).