Development of Spirometra and Paragonimus Eggs in Harada-Mori Cultures

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Abstract
The Harada-Mori type of hookworm culture which consists of a thin film of feces on a strip of filter paper in an upright test tube containing a shallow reservoir of water was found to be a simple and effective medium for incubating Spirometra and Paragonimus eggs. When the eggs of S. mansonoides in feces of experimentally infected cats were cultured by this method, essentially all of the eggs contained coracidia in 2 weeks at room temperature (22 to 26 C). When the feces-smeared filter paper from the culture was placed in water, there usually was prompt hatching and swarming of coracidia into the water. Eggs of P. kellicotti similarly incubated in feces of an experimentally infected cat contained fully developed miracidia in 17 to 20 days and these remained viable in cultures for 3 months. When placed in water, a high proportion of the miracidia hatched, especially if subjected to a sudden change of temperature. Hatching in water possibly was not necessary for infecting snails, however, for of 67 Pomatiopsis lapidaria allowed to feed directly on the leached culture feces, six became infected and shed cercariae in 60 to 68 days. The observations suggest that development of the eggs of these helminths may occur under nonaquatic natural conditions similar to those provided by the Harada-Mori culture.