The Paragonimus westermani Group in India -Systematics and Genetic Variation

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The present study is to make clear what Paragonimus westermani is which was described by Kerbert in 1878 as a new species, Distoma Westermani on the basis of the specimens from a Bengal tiger, together with the systematic and genetic relations as well as their life histories of Paragonimus species occurring in some endemic areas of paragonimiasis, north-eastern India.During the period of September 23, 1993 - October 16, 1993, the field investigation was carried out in Manipur, north-eastern India. A total of 894 freshwater crabs belonging to two species ; 678 Potamiscus manipurensis and 216 Barytelphusa lugbris were collected from 12 localities of 7 areas in Manipur and examined for Paragonimus infection. Eight hundred and twenty-seven Paragonimus metaceracriae were isolated from P. manipurensis and one was from Barytelphusa lugbris. The former species was proved to be an important crab host and source of human Paragonimus infection in this area. The metacercariae obtained were provisionally classified into 4 groups : "Large P. westermani type", "Small P. westermani type", "Excysted type" and "P. heterotremus type". The number of respective type of Paragonimus metacercariae obtained was as follows : 401, 31, 383 and 13. They were inoculated into dogs, cats and rats, respectively.The morphology of adult flukes, originating from the metacercariae of Large and Small P. westermani types was in good agreement with the description of P. westermani by Vevers(1923), but not by Kerbert(1878).Further systematic, genetic and molecular biological studies on Indian Paragonimus are now in progress.