Abstract
It is well known that the guinea pig is the most suitable experimental host ofMetastrongylus apri. Many studies have been done on the migratory behavior of thisparasite in the definitive host. Tlae infectivity of M. apri to the guinea pig was differentin various reports. At present there are many unknown point sabout its migratorybehavior. Tlte purpose of this paper is to investigate the infectivity and migratory behaviorof M. apri in the guinea pig in more detail, ]) The infectivity and migratory behavior of M. apri in the guinea pig.Infective larvae were collected by the pepsin digestion method from earthworms, Eisenia foetida, which Jaad been artificially infected with the embryonated eggs of M. apri.Guinea pigs were inoculated orally with a dose of 1, ODD or 2, 000 larvae, and killed atWarious intervals after infection.Various tissues were collected from guinea pigs and examined for larvae by the pepsindigestion method and additionally by the microscopical method.All guinea pigs were infected with M. apri. The degree of infection was constant inthem. On the lst to 3rd days after inoculation, a large number of 3rd or 4th stagelarvae were recovered from the caecum or the omentum, and a small number from theperitoneal cavity, ileo-caecal or colic-ntesenteric Nymph nodes, and mesentery. On tlae4th to 6th days, larvae recovered in the tissues rapidly decreased in number, whereas theyincreased in the lungs and thoracic cavity. On the 9th day or later, 5th stage wormswere recovered almost exclusively from the lungs.It must be especially emphasized that 3rd or 4th stage larvae were found in theperitoneal cavity and omentum, and that many parasitic granulomas were observed micro-scopically in the extended samples of the omentum. These findings are new informationindicating the presence of a new migratory route in addition to the known routes.2) A new migratory route.In order to confirm this new migratory route, 4 guinea pigs were inoculated intra-peritoneally with 200 infective larvae. On the 9th day after infection, all
