Procerovum varium Onji and Nishio, 1916

ETYMOLOGY:Procer = stretched out and ovum = uterus along with varium = varied

SYNONYMS:Haplorchis sisoni Africa, 1938; Haplorchis minutus Kobayashi, 1942; Haplorchis macrovesica Kobayashi, 1942; Haplorchis hoihowensis Kobayashi, 1942; Haplorchis cordatus Kobayashi, 1942;

HISTORY: This species was originally recovered from a cat that was experimentally infected with metacercariae from infected fish (Onji and Nishio, 1916).

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

LOCATION IN HOST: Small intestine.

PARASITE IDENTIFICATION:Procerovum specimens differ from those of Haplorchis is that they possess a highly muscular ejaculatory duct called an "expulsor." The species Procerovum varium can be differentiated from Procerovum calderoni by the presence of a much longer expulsor in the latter and by having small spines on the gonotyle.

This small pyriform trematode is 0.26 to 0.38 mm long and 0.13 to 0.16 mm wide. The eggs are 25 to 29 µm long by 12 to 14 µm wide.

LIFE CYCLE: The life cycle has elucidated by the feeding of infected brackish-water mullet (Mugil spp.) to dogs and cats.

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, pelicans (Pelecanus conspicillatus), egrets (Egretta alba and Egretta intermedia), the water rat (Hydromys chyrsogaster), herons (Notophoyx novaehollandiae and 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 probably could be infected by the ingestion of the infected fish intermediate hosts.

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


Onji Y, Nishio T. 1924. On the intestinal distomes. Chiba Igakki Zasshi 2:352-399.

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