Heterophyes aequalis Looss, 1902
ETYMOLOGY:Hetero = different and phyes = form (named to distinguish it from along with aequalis = equal, referring to the equivalent sizes of the ventral and oral suckers when compared to Heterophyes dispar which was named at the same time and which supposedly had a ventral sucker much larger in diameter than the oral sucker.
SYNONYMS:Heterophyes dispar Looss, 1902 (according to Kuntz and Chandler, 1956).
HISTORY: This species was originally described from naturally infected cats in Egypt.
GEOGRAPHIC DISTRIBUTION: Egypt and Israel.
LOCATION IN HOST: Small intestine, mainly the terminal portion of the intestinal tract (Taraschewski, 1987).
PARASITE IDENTIFICATION: Specimens of Heterophyes aequalis are characterized by having a few, 15 to 35, rodlets surrounding the genital sucker versus the 50 to 80 digitate rodlets present on that of Heterophyesheterophyes. The flukes from cats range in size from 0.5 to 1.4 (rarely 1.6) mm with a width of 0.25 to 0.5 mm. The ventral sucker is typically 0.06 to 0.18 mm in diameter. The yellowish-brown shelled eggs are 23-25 µm long by 14-16 µm wide.
LIFE CYCLE: The life cycle involves metacercariae encysted in Mugil, Epinephelus, Tapia, Lichia, and Barbus fish. Cats become infected by the ingestion of these marine, brackish-water, or fresh-water fish.
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 host that has been described for this parasite is the cat with adults sometimes being found in dogs.
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.
Figure 2-26.Heterophyesaequalis recovered from a cat in Cairo, Egypt. The separate genital sucker on this species is more apparent than in the figure showing Heterophyesheterophyes.