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A morphological and experimental study of some new dermatitis producing cercariae from Cultus Lake, B.C. Edwards, Donald Keith

Abstract

Previous workers at Cultus Lake discovered a new species of Schistosome cercaria. In the present attempts to find this cercaria and to elucidate its life cycle, four completely different dermatitis-producing forms were discovered, two of which are considered new species. The other two may be new. Three of the cercariae are described in detail. These are the cercaria of Trichobilharzia adamsi n.sp., Cercaria chilliwackensis n.sp. and Cercaria 10 which may be a new species. The description includes morphology, behavior, snail hosts, dermatitis-producing ability, and observations on the sporocysts of these forms. All were found to be capable of producing Schistosome dermatitis. Therefore two and possibly three more cercariae have been added to the list of known dermatitis-producers. The three cercariae were found in specific areas along the north-west shoreline of Cultus Lake. Attempts were made to complete the life cycle of the three cercariae. Two approaches were adopted. Animals were trapped within the areas at which the cercariae were found, but examination showed that they did not possess adult Schistosomes. Laboratory experiments were carried out in which animals were subjected to the various cercariae and later examined for adult worms. An immature female worm was recovered from a domestic duck which had been exposed to cercariae. The worm, Trichobilharzia adamsi, is described as a new species. Part of the life cycle of this trematode is described. The domestic duck was established as a definitive host under experimental conditions. The specific definitive host of the trematode at Cultus Lake was not determined. The cercaria of T. adamsi is placed in the "ocellata group" on the basis of its morphology. Cercaria chilliwackensis is placed along with Cercaria douthitti in the "douthitti group". Cercaria 10 is very similar to the cercaria of Gigantobilharzia huronensis, and is placed with the latter in the "spindalis group". All three of the cercariae described possess papillar spination. These spines have been described only once in the past as occuring on a dermatitis-producing cercaria. The papillar supination is described in detail. The spines are located in similar patterns on the bodies of the three cercariae. This pattern is carried through to the adult of T. adamsi. Evidence is given of the occurance of papillar spination on cercariae elsewhere in the Province. A modification of the perfusion technique of Yolles et al is described. This was used for the investigation of the experimental animals for adult worms. Further, a new technique using the side-arm flask of McMullen and Beaver is described. The apparatus concentrates Schistosome cercariae in large numbers in a relatively small area.

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