Host-parasite relationships and morphologic characters of the larval and adult stages have been used to identify the hydatid worm which is the cause of hydatid disease in both swine and man in Mississippi. Attempts were made to infect the dog, fox, opossum, raccoon, and domestic cat with the adult stage of the hydatid worm present in Mississippi and to infect swine and rodents with the larval stage. Dogs were infected experimentally by being fed the larval stage found in the liver of naturally infected swine. The adult worms of known ages were recovered and studied in detail.
Host-parasite studies have shown that the hydatid worm present in Mississippi will readily infect dogs in the adult stage, but will not mature in the fox, opossum, raccoon, or domestic cat. It has also been shown that this worm in the larval stage will readily infect swine, thereby producing a unilocular hydatid cyst, but will not readily infect rodents. These results indicate the species of hydatid worm studied is Echinococcus granulosus.
On the basis of the number of proglottids in the gravid worm, the number of testes in the mature proglottid, the distribution of the testes in relation to the genital pore, and the position of the genital pore in the mature and gravid proglottids, the species of hydatid worm in this study was identified as E. granulosus. The length of the strobila and the size of the hooks are of limited value in the determination of the species of Echinococcus.