Extraintestinal migration of Pharyngostomum cordatum metacercariae in experimental rodents

Extraintestinal migration patterns of Pharyngostomum cordatum (Digenea: Neo diplostomidae) were studied in experimental rodents such as mice, rats, and hamsters. When metacercariae isolated from grass snakes were infected oral ly to rodents, they penetrated the intestinal wall at days 2-3 post-infecti on (p.i.) and were discovered mainly in the diaphragm, intercostal muscles, and vital organ such as the lungs at days 7-28 p.i., without morphological changes. Interestingly, from several rodents which died suddenly at days 2 -9 p.i., small to considerable numbers of metacercariae were found, not onl y in the lungs, but also in the heart and brain. Within the tissues, worms were freely motile until day 7 p.i., but later they were surrounded by host cells, and finally tissue cysts were formed. When metacercariae harvested from the snakes and intercostal muscles of rodents were infected orally to cats, they developed into adult flukes in the small intestine. The results show that P. cordatum undergoes considerable extraintestinal migration incl uding the vital organs of its rodent hosts.