Paragonimus miyazakii

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Paragonimus miyazakii Kamo, Nishida, Hatsushika, and Tomimura, 1961

ETYMOLOGY:Para = side-by-side and gonimus = gonads along with miyazakii = for Dr. Miyazaki’s lifelong efforts in the study of paragonimiasis.


HISTORY:Paragonimus miyazakii was described based on specimens recovered from a weasel in Japan and initially considered to possibly be Paragonimus kellicotti. Kamo et al. (1961) found a different metacercaria of a Paragonimus type and after growing the flukes to maturity experimentally showed that it was a new species.


LOCATION IN HOST: In cysts in the lungs.

PARASITE IDENTIFICATION: Species of Paragonimus are 7 to 12 mm long, 4 to 8 mm wide, and quite thick, i.e., 4 to 6 mm. For differentiation of the Asian species see Paragonimus westermani.

The eggs have a thin brown shell, a distinct operculum, and occasionally a knob on the abopercular end; eggs range from 75 µm in length by 43 µm in width and tend to be larger on the whole than those of Paragonimus westermani.

LIFE CYCLE: The life cycle is similar to that of Paragonimus westermani. The first intermediate host is the snail Bithynella nipponica. The second intermediate host is a fresh-water crab, Geothelphusa dehaani, in which the metacercariae are found in blood vessels around the heart. The metacercariae of Paragonimus miyazakii are larger than those of the other asian species of Paragonimus, being about 0.5 mm in diameter. In cats fed 40 to 50 metacercariae, patent infections developed 51 to 52 days after infection (Tomimura et al., 1964).

CLINICAL PRESENTATION AND PATHOGENESIS: The presentation of infection in cats appears similar to that of Paragonimus westermani. In human hosts, outbreaks have tended induce pleural rather than pulmonary manifestations.

TREATMENT: Probably praziquantel.

EPIZOOTIOLOGY: Infected mammalian hosts other than the cat include dogs, weasels, sables, pigs, raccoon dogs, and badgers. These hosts are becoming infected by the ingestion of infected crabs.

HAZARD TO OTHER ANIMALS: If mammals ingest the infected crab, there is a possibility that larval flukes will penetrate the intestinal wall and migrate into the abdominal cavity. In permissive hosts, the flukes will go onto develop in the lungs while in some hosts the flukes will persist as in the swine paratenic host. In all these hosts, there is the possibility for associated pathology.

HAZARD TO HUMANS: Human outbreaks have occurred with this infection due to the ingestion of raw or inadequately cooked crabs. The first known outbreak of infection with this parasite occurred in 1974 and was characterized by a large number of patients who had signs of fluke infection within the pleural cavity without eggs being present in the sputum.


Kamo H, Nishida H, Hatsushika R, Tomimura T. 1961. On the occurrence of a new lung fluke, Paragonimusmiyazakii n.sp. in Japan. (Trematoda: Troglotrematidae). Yonago Acta Medica 5:43-52.

Tomimura et al., 1964 NEED REFERENCE

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