Physaloptera species

Physaloptera spp. are spiruroid stomach nematodes that occur primarily in cats, wild felids and occasionally dogs in North America, including Canada, as well as in South America, China, and Africa. In Western Canada the parasite has been reported in cats, badgers, bobcats, raccoons, foxes, lizards, toads, skunks and coyotes, and also in a dog in BC. Elsewhere in Canada, Physaloptera has been reported in coyotes in Newfoundland, lynx and black bears in Ontario, and wolverines in the NWT. Adult Physaloptera are larger than most spiruroids and resemble ascarids, with males measuring 2.5-4.5 cm and females 3-6 cm.  Spirurid nematodes are thus named because of the spiral posterior of the male nematode. Females pass larvated eggs which are ellipsoidal, have a thick, clear shell, measure 42-58 µm by 30-42 µm, and each contains a first-stage larva. 

Along with other spirurid nematodes (like Dirofilaria, Draschia, Habronema, Stephanofilaria, and Setaria), Physaloptera spp. have an indirect life cycle involving an arthropod intermediate hosts, in this case a beetle, cockroach or cricket.  The intermediate host ingests the parasite’s eggs from the feces of the definitive host. The egg hatches in the gut of the intermediate host, migrates into the tissues and develops to the third-stage infective larva. Infection of the feline or canine definitive host follows ingestion of an infected intermediate host. 

Animals infected with Physaloptera spp. are usually asymptomatic. Gastric ulceration and hemorrhage can result from lesions caused when the adults attach to the mucosa. Heavy infections can result in catarrhal gastritis with emesis, blood in the feces, vomiting, anorexia, and weight loss. Diagnosis can be made by recovery and identification of larvated eggs in a direct fecal smear or fecal sediment. Fecal flotations are unreliable for this parasite as the eggs do not float well.  Adult parasites may also be observed on gastroscopy; a differential diagnosis would be Ollulanus tricuspis, but Physaloptera is much larger. Physaloptera spp. can be effectively treated using fenbendazole, ivermectin or pyrantel.

Although the species of Physaloptera that causes infection in monkeys is known to cause infection in people, there are no reports of human infection with the species from dogs and cats.