Fig. 3. Parasite ggs packed in the body of adult worm.
| Parasite | Didymozoidae trematode |
|---|---|
| Taxonomy | Plathyhelminthes, Trematoda, Didymozoidae |
| Host | Skipjack tuna (Katsuwonus pelamis) |
| Infection site | Trunk muscle |
| Clinical sign | A yellowish amorphous aggregation (ca. 1 cm) is observed in the trunk muscle (Fig. 1). The aggregation is a folded filamentous parasite. |
| Parasitology | The worm has elongated cylindrical body (ca. 0.5 mm in diameter) (Fig. 2) which is filled with oval eggs (ca. 20 mm in diameter) (Fig. 3). |
| Pathology | No report |
| Health hazard | Since this parasite is not infectious to human, it is harmless in food hygiene. |
| Diagnosis | Check the morphology of worm and parasite eggs in the trunk muscle. |
| Other information | Similar trematodes were reported in red sea bream (Nakajima, 1974) and crescent sweetlips (Momoyama and Tensha, 2006). |
| References | Nakajima, K., K.
Sugiyama and S. Egusa (1974) A trematode, Gonapodasmius
okushimai Ishii, found in the muscle of red sea bream, Pagrosomus major. Fish Pathol.,
8, 175-176. (In Japanese) Momoyama, K. and K. Tensha (2006): Ugly-looking parasitic infections and other abnormalities of wild fish and shellfish caught in the coastal or inland waters around or in Yamaguchi Prefecture. Bull. Yamaguchi Pref. Fish. Res. Ctr., 4, 143-161.(In Japanese) |
(Photos by J. Araki)
Fig. 2. Thread-like body of the parasite.
Fig. 1. Didymozoon found in the fillet of skipjack tuna.
