The Role of the Earthworm, Eisenia foetida, in the Transmission of Stephanurus dentatus

Abstract

unbroken skin. Following entry into the body of the pig, the majority of the larvae reaches the liver where they undergo a long period of development. This culminates in escape of the worms into the peritoneal cavity and their migration to the perirenal area. The sexually mature kidney worms are found in cysts in the walls of the ureters, the cysts being connected to the lumen through fistulae. The pre-patent period is usually considered to be about 6 months. Spindler (personal communication) was unable to produce patent infections in swine experimentally infected and kept under conditions designed to preclude extraneous infections with these parasites even when these animals were kept under observation for a year or longer. I was unable to demonstrate patency in experimentally infected swine after 9 months. The unusually lengthy pre-patent period and the difficulty of securing patent experimental infections in swine indicate perhaps the existence of some hitherto unelucidated phase of the life cycle. The present investigation was undertaken to explore the possibility of an intermediate or transport host in the life cycle of S. dentatus. Earthworms of the family LUMBRICIDAE were chosen as possible vectors because they are known to serve both as obligate and transport hosts for a number of nematodes. After some preliminary observations, Eisenia foetida, known to be an intermediate host of various nematode parasites, was selected. This earthworm is commonly found in soil contaminated with feces and is therefore naturally available as an intermediate host. Furthermore, these annelids may be collected in large numbers from situations uncontaminated by swine, such as compost heaps of cow manure, are rarely infected with Rhabditis pellio according to Otter (1933) and Clapham (1934), and are easily maintained in the laboratory. MATERIALS AND METHODS Technique of infecting earthworms. Large numbers of E. foetida were obtained from a compost heap of cow manure. Stock cultures of the annelids were maintained in terraria one-third full of compost covered with moist burlap. The earthworms were infected by placing them in large staining dishes containing a mixture of autoclaved compost and a charcoal culture containing infective third stage S. dentatus larvae. The surface of the material was covered with moist burlap and a glass lid was placed on the dish to conserve moisture. Frequent moistening