Paragonimus heterotremus Chen and Hsia, 1964
ETYMOLOGY:Para = side-by-side and gonimus = gonads along with heterotremus = referring to the different sized oral and ventral suckers.
SYNONYMS:Paragonimus tuanshanensis Chung, Ho, Cheng, and Tsao, 1964
HISTORY: This fluke was first found in rats in China. That same year, another group of workers described Paragonimus tuanshanensis.
GEOGRAPHIC DISTRIBUTION: China, Thailand, and Laos.
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. Paragonimus heterotremus differs from other species of Paragonimus in Asia in that the oral sucker is larger than the ventral sucker.
The eggs have a brown shell, a distinct operculum, and occasionally a knob on the abopercular end; eggs are about 86 µm in length by 48 µm in width.
LIFE CYCLE: The life cycle is basically the same as that of Paragonimus westermani. A snail intermediate host identified in China is Tricula gregoriana. The crab hosts that are used are Ranguna smithiana and Parathelphus dugasti in Thailand and Sinopotamon in China. The metacercariae are found in the liver, muscles, and gill of these crabs and are rather small, i.e., about 0.25 mm in diameter.
CLINICAL PRESENTATION AND PATHOGENESIS: Probably similar to the other species of Paragonimus. The death of a cat naturally infected with 13 of these flukes has been reported (Miyazaki and Vahrasthira, 1967).
TREATMENT: Probably praziquantel.
EPIZOOTIOLOGY: Hosts include cats, dogs, leopards, rats, and bandicoots.
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 beings have been infected with this trematode. Besides the typical pulmonary lesions, flukes have been recovered from subcutaneous tissues (Miyazaki and Harinasuta, 1966).
Miyazaki I, Harinasuta T. 1966. The first case of human paragonimiasis caused by Paragonimusheterotremus Chen et Hsia, 1964. Ann Trop Med Parasitol 60:509-514.
Miyazaki I, Vajrasthira S. 1967. Occurrence of the lung fluke Paragonimusheterotremus Chen et Hsiua, 1964, in Thailand. J Parasitol 53:207.
Figure 2-43.Paragonimusheterotremus from the lung of a cat in Thailand. Note the large oral sucker.