Dirofilaria ursi-like parasites acquired by humans in the northern United States and Canada: report of two cases and brief review
Beaver, P.C.; Wolfson, J.S.; Waldron, M.A.; Swartz, M.N.; Evans, G.W.; Adler, J.
American Journal of Tropical Medicine and Hygiene 37(2): 357-362
1987
ISSN/ISBN: 0002-9637 PMID: 3310687 Document Number: 291009
2 cases of subcutaneous dirofilariasis acquired in Ontario and Vermont are reported. The parasites in these and 8 cases previously reported from the northern USA and Canada resemble D. ursi, a primarily subcutaneous parasite of bears, or D. subdermata from porcupines, in the same region. A distinguishing morphological feature of the D. ursi-like group is the presence of distinct longitudinal circular ridges regularly and widely spaced on the outer surface, and usually evident even when the worms are necrotic. In the 10 known cases, all patients were women, and the usual location of nodules containing the worms was the scalp or a covered part of the upper body where blackflies, the intermediate hosts of D. ursi usually feed. Two cases of subcutaneous infections with filarial worms acquired in Ontario (Canada) and Vermont (USA) are reported, in women aged 46 and 21. The parasites had some morphological similarities to Dirofilaria ursi of bears and D. subdermata of porcupines, but the specimens found were necrotic and could not be definitely identified. There have been 8 previous records of human infections with D. ursi-like parasites in the northern USA and Canada, all in women. The usual location of the subcutaneous nodules was on the head or upper part of the body, where blackflies normally feed.Sheila M. Crewe.