The diverse pathologies of infected lung with paragonimus heterotremus

Abstract

Pheterotremus (lung fluke) is one of the causative agent of food-borne parasitic zoonoses which infects animals and humans. More than 40 species of Paragonimus have been identified so far. Paragonimiasis is found mainly in Asia, part of West Africa and Central America. In Thailand, the first case of human paragonimiasis was reported from Petchaboo Province in 1928. Since then, the studies on paragonimiasis both epidemiological and taxonomic aspects have been carried out continuously. Six species of Paragonimus were found, among with P.heterotremus is of the etiologic significant in man. We performed an experimental study to examine the diverse pathologies of cat lung which was infected with P.heterotremus by feeding with infected mountain crab, harboring metacercaria. By gross examination, the cat lung appeared with small hemorrhagic spots. The worms were ably seen in the pleural cavity together with turbid pleural serosanguinous effusion. In the parenchyma were found military lung abscesses and cytic lesions containing adult worms with dense fibrous connective tissue around the cysts. The visceral pleura covering the cyst was thicked and inflamed. By microscopic examination, cross sections of the worm were located in the dilated bronchus which had already undergone squamous metaplasia. Surrounding the worm was a large granulomatous tissue containing yellowish brown operculated eggs with and without miracidium. The cystic lesions were surrounded by bands of thick fibroconnective tissue. The adjacent lung tissue showed marked diapedesis, congestion, atelectasis and pneumonia. Paragonimus can infect various kinds of mammalian hosts but the infection rate, the development of the worms and the pathology in their hosts may differ. In this study, we found the pathologies associated not only with the adult worms but also with the eggs. The irritation from the motility of the worms caused disruption of the bronchiolar mucosa which brought about the leakage of the eggs into the adjacent alveolar spaces and may form thereby granulomatous lesions.