Life History, Morphology and Taxonomy of Atriotaenia (Ershovia) procyonis (Cestoda: Linstowiidae), a Parasite of the Raccoon

Abstract

While investigating the intestinal parasites of vertebrates from Franklin County, Ohio, a high level of tapeworm infection was encountered in the raccoon (Procyon lotor lotor). This tapeworm proved to be one of the linstowids originally described by Chandler (1942) as Oochoristica procyonis. Since these specimens seemed to disagree in some respects with the species description, an extensive study of the morphology was undertaken in order to define more completely the species limits. The clarification of the characteristics of this cestode brought up the problem of its proper taxonomic position. As a result of investigation into this problem, the author decided that this species should be referred to as Atriotaenia (Ershovia) procyonis (Chandler, 1942) Spassky, 1951. The reasons are presented in the discussion. Further investigation revealed that the life history was not known. With ample material readily available, the life history of this cestode was completed in the laboratory. Extensive trapping activities led to a survey of the incidence in feral raccoons. MATERIALS AND METHODS Cestodes were obtained by trapping raccoons with especially constructed live traps. Trapped animals were housed in outdoor pens and served as a source of gravid proglottids and eggs used in feeding experiments. Five suckling, 2-week-old raccoons were obtained for future use in life history experiments. These were subsequently weaned and maintained on a diet of fresh ground beef, dog chow checkers, and water. These animals were kept in indoor cages, well isolated from the adult, infected raccoons. Fecal examinations were made periodically to determine whether the animals were still uninfected. They all remained so until used for feeding experiments. Cultures of the flour beetle Tribolium castaneum (Hbst.), used as an experimental intermediate host, were maintained in large mason jars and fed on a mixture of wheat flour and brewers yeast. These cultures were kept at room temperatures which varied from 22? to 29? C. Gravid proglottids used in feeding experiments were obtained either from the feces of infected raccoons or from living worms recovered from sacrificed animals. Two proglottids were placed on a small piece of filter paper, moistened, and teased apart with two small needles. In each feeding experiment, 10 beetles, starved for the previous 48 hours, were allowed to feed on the proglottids for 24 hours. These beetles were then returned to culture jars and left undisturbed until they were examined for stages of cysticercoid development. When dissecting beetles, the body (after removal of head, elytra, wings and legs) was placed in a drop of insect saline solution, teased apart, and the larval stages removed. During these dissections, care was taken to keep the entire digestive tract of the insect intact so that examination for early larval stages penetrating the gut could be carried out. Cysticercoids recovered from beetles, when fed to uninfected raccoons, were embedded in small pieces of ground beef about the size of the human thumb. Daily fecal examinations for gravid proglottids were then carried out. Some of the raccoons infected in this manner were sacrificed, and both immature and adult worms were removed from the small intestine.