Stellantchasmus falcatus

Stellantchasmus falcatus Onji & Nishio, 1916

(Figure 2-24)

ETYMOLOGY: Stella = star, ant = against and chasmus = hollow along with falcatus = hooked

SYNONYMS:Diorchitrema pseudocirrata Witenberg, 1929; Stellantchasmus formosanus Katsuta, 1931; Stellantchasmus amplicaecalis Katsuta, 1932; and Haplorchis pumilio of Odening, 1962.

HISTORY: This species was originally described from cats that were experimentally infected by the feeding of fish containing metacercariae (Onji and Nishio, 1916). This trematode has since been recovered from naturally infected cats and other hosts.

GEOGRAPHIC DISTRIBUTION: This trematode has been reported from Japan, Hawaii, China, the Philippines, Israel, Egypt, and Australia (Pearson, 1964).

LOCATION IN HOST: Small intestine, mainly 6 to 18 inches from the junction with the stomach.

PARASITE IDENTIFICATION:Stellantchasmus specimens differ from those of Haplorchis and Procerovum in that they possess two testes and possess an expulsor as in Procerovum.

This small pyriform trematode is 0.43 to 0.55 mm long and 0.19 to 0.34 mm wide. The eggs are 21 to 23 µm long by 12 to 13 µm wide.

LIFE CYCLE: The life cycle has elucidated by Martin (1958), Noda (1959), and Pearson (1960). The snail hosts include species of Stenomelania, Melanoides, and Tarebia. Fish that have been found to be infected include brackish and fresh-water fish, Mugil, Gavia, and Anabas spp; the larvae are found mainly within the skeletal muscle (Martin, 1958). The fully developed cysts are about 0.3 mm in diameter.

CLINICAL PRESENTATION AND PATHOGENESIS: Not reported but thought to be asymptomatic.

TREATMENT: Probably praziquantel, but not reported.

EPIZOOTIOLOGY: Cats become infected by eating raw fish. Other hosts that ingest infected raw fish are also likely to become infected. The normal natural hosts include cats, nankeen night herons (Nycticorax caledonicus) and a whistling eagle (Haliastur sphenurus).

HAZARD TO OTHER ANIMALS: None known; however, due to the requirements for two intermediate hosts, it is unlikely that an infected cat would pose a direct threat to other animals.

HAZARD TO HUMANS: Humans have been infected with this species in Hawaii.

CONTROL/PREVENTION: The prevention of the ingestion of raw fish.

REFERENCES:

Martin WE. 1958. The life histories of some Hawaiian Heterophyid trematodes. J Parasitol 44:305-323.

Noda K. 1959. THe larval development of Stellantchasmus falcatus (Trematoda: Heterophyidae) in the first intermediate host. J Parasitol 45:635-642.

Pearson JC. 1960. New records of trematodes from the cat. Aust Vet J 36:93.

Pearson JC. 1964. A revision of the subfamily Haplorchiinae Looss, 1899 (Trematoda: Heterophyidae). Parasitology 54:601-676.

Figure 2-24.Stellantchasmus falcatus from the small intestine of a domestic cat in Hawaii.

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