. .9. Mugil cephalzs) and minnow (Gambusia species) -,..rophyes species, and carp (e.g. Carassius carrasius) and :h Plecoglossus altiyelis in the case of Metagonimas species. ::s are infected after ingestion of inadequately cooked fish -..'rng metacercariae, which mature in the flesh or scales of ..-' . :du1t worms attach to or invade the mucosa of the upper :orvel where they may cause granulomatous inflammation !.'i.3 Famtlies of intestinal trematodes containing species that are uncommon human pathogens i:ig":-.!1"+.i+ EggotMetagonimusyokogawai.A[L heterophyideggslooksimilar,as do those of Clonorchis stnensis and Optsthorchts vtverrint. (Courtesy of P Radomyos.) and erosion. Light infections are generaliy asymptomatic but hear,7 worm burdens may be associated with anorexia, nausea, abdominal discomfort and mucous diarrhoea. Occasionally ova deposited in the bowel wa11 enter blood vessels and embolize to other tissues. Eggs have been found in the heart and central nervous system and rarely in the b1ood. In cases of heterophyiasis described in the Philippines, cardiac failure was associated with subepicardial haemorrhages, myocardial damage caused by occlusion of vessels by ova, and eggs stuck to a thickened, calcified mitral valve. Neurological features include focal cerebral disturbances and transverse myelitis. Eggs (20-40 x 10-20pm in size) are passed in the stools (!,i;,:. ,:. I i. 1..;). They are yeliow-brown, elongated, operculate, and contain a miracidium. Eggs of members of the family Heterophyidae cannot be reliably differentiated from each other. Furthermore, they are extremely difficult to differentiate from eggs of Clonorchis sinensis and Opisthorcftls species although heterophyids tend to have a smoother egg shell and a less prominent shoulder at the operculum, and the abopercular knob may be absent. 7"1-1.4 INTESTINAL TREMATODE INFECTIONS 1223 r.rlllxi:tittlutrr:rr::rrirra luq: :S Geographical