Paragonimus and Paragonimiasis

Abstract

This chapter discusses the advancement of research into Paragonimus and paragonimiasis in the taxonomic, immunodiagnostic, and chemotherapeutic fields. New species of Paragonimus have been reported with regard to classification of the lung flukes. At present, the life cycles of four species— P. westermani, P. kellicotti, P. ohirai and P. iloktsuenensis —are fully known. The wide variation in the histopathological findings in the lungs of man with paragonimiasis is because of differences in the number of infecting worms, the duration varying from the onset of this disease to autopsy and the susceptibility of the individuals to the worms. At an early stage of paragonimiasis, almost all cases show pleurisy of varying severity and occasionally pneumothorax. The most remarkable symptom is cough and blood-stained sputum. Paragonimiasis in endemic areas can be diagnosed clinically by an occasional light cough and yellowish brown pus-like sputum in which bloody spots or lines can sometimes be seen. The diagnosis is confirmed by microscopic examinations of the sputum or stool in order to find the eggs of Paragonimus . Charcot-Leyden's crystals in sputum assist the diagnosis. The methods of breaking the life cycle of the lung fluke of man are (1) destruction of the adults in the human host by treatment; (2) killing of reservoir hosts to destroy the adults; (3) disinfection of sputum and faeces of infected individuals to kill the eggs; (4) destruction of snail intermediate hosts to kill the larval stages; (5) killing of second intermediate hosts to destroy the metacercariae; (6) prevention of human infection by the metacercariae freed from the second intermediate hosts; and (7) prevention of human infection through eating the second intermediate host raw or partially cooked.