Parametorchis complexum (Stiles and Hassall, 1894) Skrjabin, 1913

(Figure 2-41)

ETYMOLOGY:Para = near, meta = posterior and orchis = testis [thus, near Metorchis] along with complexum = for the complex coiling of the uterus at the level of the acetabulum.

SYNONYMS:Distoma complexum Stiles and Hassal, 1894.

HISTORY:Parametorchis complexum was described from trematodes collected from cats in New York, Baltimore, and Washington, D.C., USA. (Stiles and Hassall, 1894).

GEOGRAPHIC DISTRIBUTION: Northeastern USA; it was reported in 1965 from two cats in New Jersey (Burrows and Lillis, 1965).


PARASITE IDENTIFICATION: Specimens of Parametorchis differ from those of Metorchis in that the vitelline glands on both sides of the body become confluent anterior to the ventral sucker.

Adult flukes measure from 5 to 7 mm in length with widths of 1.5 to 2.0 mm. The oral sucker is about the same size as the ventral sucker. The testes are situated in the third quarter of the body, tandem or slightly oblique, and tend to be lobate (3 to 8 lobes) in outline. The eggs measure 24 µm long by 12 µm wide.

LIFE CYCLE: Not described.


TREATMENT: Praziquantel is likely to prove successful in eliminating these trematodes from many treated cases.

EPIZOOTIOLOGY: Other hosts have not been described as infected with this parasite, including raccoons. It would appear that carnivores in Russia are infected with a related species.


HAZARD TO HUMANS: It is possible that humans could become infected if they were to ingest the infected intermediate host.


Burrows RB, Lillis WG. 1965. Trematodes of New Jersey dogs and cats. J Parasitol 51:570-574.

Stiles CW, Hassall A. 1894. Notes on parasites - 21. A new species of fluke (Distoma [Dicrocoelium] complexum) found in cats in the United States, with bibliographic and diagnoses of allied forms. Vet Mag 1:413-432.

Figure 2-41.Parametorchiscomplexum collected from a raccoon in Virginia, USA. Although the vitellaria are rather light in this preparation, they can be observed to extend along the lateral sides of the trematode and to come together anterior to the dark, egg-filled uterus that fills the middle of the second fourth of the body.

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