Study of diagnosis and spatial epidemiology on paragonimiasis in Lao PDR.

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In spite of lack of information on paragonimiasis in Laos since 1973, eight districts in 5 provinces; Attopeu, Champasak, Savannakhet, Vientiane, and Luangnamtha, which exist and/or possible risk of the disease were clarified through our research. Around 700 metacercariae were collected from 2 species of the river crabs (7 Potamon lipkei and 5 Chulathelphusa brandti) obtained in Hinheup district which was especially investigated as a dense infested area in Vientiane province, where is 80 km north from Vientiane Capital in Lao PDR. Though the numbers were smaller, Paragonimus heterotremus, a known causative species of human parogonimiasis in Indochina region, and P. westermani were identified at the metacercariae population. On the major population, 2 unreported Paragonimus species of harinastai and bankokensis were identified and clarified using adult worms obtained from experimental infections of dogs in the laboratory. Among various experimental animals, adult worms of P. harinastai never survive after 3 month of the experimental infections in rats, which was demonstrated for the first time. Furthermore, dog is a suitable host for P. bankokensis was confirmed by recovery (80%) of the adult worms at the experimental infections. And the established PCR technology was used. To identify the actual causative species of human paragonimiasis in Hinheup, 6 samples of the parasite eggs from the sputa of dwellers were collected, and the established PCR technique; using primers of species specific region (ITS2) of the 4 parasites, was performed. All these samples resulted in P. heterotremus, thus the causative parasite of human paragonimiasis was strongly suggested as this species in the region.