Histopathological Findings in Snakes, Elaphe quadrivirgata (Reptilia; Colubridae), Infected with Plerocercoids of Spirometra erinacei (Cestoda; Diphyllobothriidae)

Abstract

The incidence and burden of plerocercoids of Spirometra erinacei (Cestoda; Diphyllobothriidae) were examined in 12 Elaphe quadrivirgata (Reptilia; Colubridae) captured in Okayama Prefecture, Japan, in the summer of 1984. Plerocercoids were obtained from all of the snakes examined, and the worm burden ranged from 63 to 486 with an average of 323. This great worm burden in snakes results from “biological concentration” due to their predation on infected frogs. Plerocercoids were observed at many sites in snake tissues, especially in the subcutis, muscle, and serosa. In histological examination, cell reaction against plerocercoids was not very severe in general and infiltration by aletocytes was seldom observed around the parasites in the subcutis. But a marked migration of eosinophilic cells was sometimes observed around the parasites near the stomach wall, and compression and histolysis of muscles were observed in some histological preparations. Therefore, a snake infected with a large number of plerocercoids will be severely damaged as a whole. Since many plerocercoids and damage caused by them were chiefly observed in the muscles, the locomotor ability of snakes will decline to the point that they are readily caught by the final carnivorous hosts. This phenomenon is considered to be one of the strategies of the parasites for survival.