Physaloptera rara Hall & Wigdor, 1918

ETYMOLOGY:Physalis = bubble and ptero = wing, along with rara = rarus (thin)

SYNONYMS:Physalopterafelidis Ackert, 1936

HISTORY:Physalopterarara was originally described by Hall and Wigdor (1918) from the dog. This worm is now considered mainly a parasite of the coyote (Canislatrans) that has developed a domestic cycle in the cat, dog, and other wildlife species throughout the range of this host. Ackert (1936) found a parasite in the cat that he described as Physalopterafelidis, but the two descriptions of these parasites are very similar, and it would warrant additional work on the biology and taxonomy of these species to verify that they are actually distinct.

GEOGRAPHIC LOCATION: Hitchcock (1953) reported that she found Physalopterarara in kittens in Michigan. Baughn and Bliznick (1954) found it in cats in New York. Ackert (1936) recovered his specimens from cats in Kansas. Ackert and Furomoto (1959) also found it in cats in Kansas. Shoop et al. (1991) reported Physalopterarara from cats in Arkansas. Marchiondo and Sawyer (1978) recovered specimens from cats in Utah.

LOCATION IN HOST: The adult worms are found in the stomach and very anterior portion of the duodenum of the cat.

PARASITE IDENTIFICATION:Physalopterarara differs from Physalopterapraeputialis in that there is no sheath over the posterior portion of the body of the males and females. The males are 2.5 to 3 cm long; the females are 3 cm to 6 cm in length. These worms tend to be white in color. The male has caudal alae and pedunculate papillae on its tail. The vulva of the female is anterior to the middle of the body. The eggs are thick shelled, ellipsoid, 42 µm to 53 µm long, 29 µm to 35 µm wide, and contain a larva when passed in the feces. Like the eggs of Physalopterapraeputialis, the eggs of Physalopterarara are quite clear and difficult to see, especially in sugar flotations.

LIFE CYCLE: Petri (1950) showed that the German cockroach, Blatellagermanica, and grain beetles, Triboliumconfusum, could serve as intermediate hosts of Physalopterarara. Petri and Ameel (1950) added ground beetles, Harpalus sp., and crickets, Achetaassimilis, to the list of intermediate hosts. Olsen (1980) added grasshoppers, Melanoplusfemurrubrum, to the list of intermediate hosts. Widmer (1967) found larvae attached to the mucosa of the stomachs of rattlesnakes in Colorado, and he used these larvae to experimentally infect cats (Widmer, 1970). Olsen (1980) used larvae from rattlesnakes to infect cats and found the prepatent period to be 75 to 79 days. Olsen also showed that mice and frogs could served as paratenic hosts, with the larvae persisting attached to the mucosa of the gastro intestinal tract. Using larva recovered from frog feces 21 days after infection, a cat developed a patent infection 156 days after infection.

CLINICAL PRESENTATION AND PATHOGENESIS: Reports of clinical signs due to this parasite are rare. Santen et al. (1993) report on signs including vomiting and diarrhea in a seven-month-old cat that was infected with Physalopterarara and Toxocaracati.

TREATMENT: The only description of treatment in the cat is that of Santen et al. (1991) who treated an infected cat with pyrantel pamoate (5 mg/kg bodyweight pyrantel pamoate). Examination of the feces of the cat six weeks after treatment revealed the continued presence of eggs of Physalopterarara and Toxocaracati. The cat was then treated with 2 oral doses of pyrantel pamoate (5 mg/kg body weight) 3 weeks apart. Repeat fecal examinations revealed no additional eggs in the feces of this cat.

EPIZOOTIOLOGY: Cats apparently can become infected with Physalopterarara by the ingestion of the arthropod intermediate host or through the ingestion of paratenic hosts. The failure of Olsen (1980) to infect chickens with larvae suggest that birds may not be important as paratenic hosts of this parasite. The fact that German cockroaches could serve as intermediate hosts could mean that this parasite could become a problem in catteries with less than adequate cleanliness.

HAZARDS TO OTHER ANIMALS: The larvated eggs passed in the feces are not infectious unless ingested by arthropod intermediate hosts.

HAZARD TO HUMANS: Humans have been reported infected with Physaloptera spp., but it is unclear which species has been involved in these infections (Nicolaides et al., 1977). Infections are probably required by the accidental ingestion of arthropod hosts or by the ingestion of uncooked paratenic hosts.

CONTROL/PREVENTION: Control would involve preventing cats from hunting paratenic hosts or preying on the arthropod intermediate hosts.


Ackert JE. 1936. Physalopterafelidis n. sp., a nematode of the cat. Trans Am Microsc Soc 55:250-254.

Ackert JE, Furumoto. 1949. Helminths of cats in eastern Kansas. Trans Kans Acad Sci 52:449-453.

Baughn CO, Bliznick A. 1954. The incidence of certain helminth parasites of the cat. J Parasitol 40(suppl):19.

Hall MC, Wigdor M. 1918. A Physaloptera from the dog, with a note on the nematode parasites of the dog in North America. J Am Vet Med Assoc 53:6:733-744.

Hitchcock DJ. 1953. Incidence of gastrointestinal parasites in some Michigan kittens. N Am Vet 34:428-429.

Marchiondo AA, Sawyer TW. 1978. Scanning electron microscopy of the head region of Physalopterafelidis Ackert, 1936. Proc Helm Soc Wash 45:258-260.

Nicolaides NJ, Musgrave J, McGuckin D, Moorhouse DE. 1977. Nematode larvae (Spirurida: Physalopteridae) causing infarction of the bowel in an infant. Pathology 9:129-135.

Olsen JL. 1980. Life history of Physalopterarara Hall and Wigdor, 1918 (Nematoda: Physalopteroidea) of canids and felids in definitive, intermediate, and paratenic hosts. Rev Iberica Parasitol 40:489-525.

Petri LH. 1950. Life cycle of Physalopterarara Hall and Wigdor, 1918 (Nematoda: Spiruroidea) with the cockroach, Blatellagermanica serving as intermediate host. Trans Kans Acad Sci 53:331-337.

Petri LH, Ameel DJ. 1950. Studies on the life cycle of Physalopterarara Hall and Wigdor, 1918 and Physalopterapraeputialis Linstow, 1889. J Parasitol 36(suppl):40.

Power LA. 1971. Helminths of casts from the Midwest with a report of Ancylostomacaninum in this host. J Parasitol 57:610.

Santen DR, Chastain CB, Schmidt DA. 1993. Efficacy of pyrantel pamoate against Physaloptera in a cat. J Am Anim Hosp Assoc 29:53-55.

Shoop WL, Haines HW, Michael BF, Eary CH, Endris RG. 1991. Molineusbarbatus (Trichostrongylidae) and other helminthic infections of the cat in Arkansas. J Helm Soc Wash 58:227-230.

Widmer EA. 1967. Helminth parasites of the prairie rattlesnake, Crotalusviridis Rafinesque, 1818, in Weld Couty, Colorado. J Parasitol 53:362-363.

Widmer EA. 1970. Development of third-stage Physaloptera larvae from Crotalusviridis Rafinesque, 1818 in cats with notes on pathology of the larvae in the reptile (Nematoda, Spiruroidea). J Wildl Dis 6:89-93.