Some Observations on the Effect of Digestive Juices on Scolices ofEchinococcus granulosus(Batsch).

Abstract

Experimentsin vivoandin vitroare reported on the action of digestive juices of various animals on the scolices ofE. granulosus. Inin vitrostudies, scolices ofE. granulosuswere placed in the digestive juices of different animals, incubated at 37°C., and the digestive action of the fluids was studied by examining portions of the material under the microscope.In vivoexperiments were carried out on kittens, rats and rabbits. These animals were fed large quantities of scolices of hydatid cyst membranes and they were killed at definite time intervals and their intestinal tract was carefully examined for scolices.Gastric juice of rats, dogs, cats, sheep and cattle did not digest scolices. The action of the gastric juice of rabbits begins late and proceeds slowly. Human gastric juice causes incomplete digestion and acts only on the evaginated scolices.The intestinal juices of man, rats, rabbits, sheep and cattle are able to digest scolices completely, whereas the intestinal juice of dogs and cats is inactive. In spite of the fact that cat intestinal juice is inactive, kittens are found to be slightly susceptible. Since they suffer only relatively light infestation and the rate of development is retarded, we would classify the cat as an “abnormal” host toE. granulosus.Time of evagination of scolices from a single cyst or from cysts from different animals is variable. Some scolices evaginate readily, others more slowly and still others fail to evaginate completely.