Paragonimiasis in the Philippines: current status

Paragonimiasis in the Philippines was first reported in 1907. The first attempt to study its life cycle was made in 1941 when metacercariae of Paragonimus were found in fresh-water mountain crabs. At present the causative agent of human paragonimiasis in this country is Paragonimus westermani, although the new name, Paragonimus philippinensis, has been proposed instead. The second species of Paragonimus, Paragonimus siamensis, was reported in cats in 1973. The prevalence of disease in two endemic areas ranges from 0.5 to 12%. Transmission to man is attributed to the preparation of local delicacies using raw crab juice, eating of undercooked roasted crabs by children and eating of raw crabs by adult males with local alcoholic drinks. Microscopic examination of sedimented sputum collected over 24 h and dissolved in 3% sodium hydroxide appears to be the best diagnostic technique when performed twice. Intradermal testing followed by sputum examination is recommended in paragonimiasis surveys. Bithionol and probably praziquantel (2-cyclohexylcarbonyl-1,2,3,6,7,11b-hexahydro-4H-pyrazino[2,1-a]++ +isoquinolin- 4-one, EMBAY 8440, Biltricide) are drugs of choice for treatment. The first intermediate hosts are Antemelania asperata and Antemelania dactylus, formerly Brotia asperata, with an infection rate of less than 1%, while the second intermediate crustacean host is Sundathelphusa philippina, formerly Parathelphusa grapsoides, with an infection rate ranging from 50 to 100%. So far, the natural animal reservoir hosts are cats, dogs and field rats.