Natural and Experimental Infections of THELAZIA CALIFORNIENSIS Price (1930, Nematoda: Thelaziidae) with Descriptions of the Adult and Larval Parasites

The purpose of this work was to determine the extent and effects of infestation of the eye worm of mammals, Thelazia californiensis, and to elucidate through experimentation or observation the mode of transmission. A survey of literature revealed that thelaziasie (infestation by Thelazia species) may cause serious pathological changes in the eye and its adnexa, sometimes resulting in blindness. It was found that reports of thelaziasis in the United States were (with two exceptions) of cases in California. It was further found that T. californiensis has been reported in a wider variety of host than has any of other thelazias. The hosts were found to include many wild animals, most of the domestic animals, and men. From Russian literature it was learned that muscid flies were intermediate hosts of the thelazias found in that country. A detailed description of the viviparous worm (male and female) and the larva is given. One phase of the work is concerned with observing the conduct of muscid files in the vicinity of infested dogs in areas endemic for the eye worm. The flies, Fannis canicularis and F. benhamini, were observed to manifest a marked avidity for the eyes of dogs and other mammals. Information was gained through laboratory experiments and field observations strongly suggest that the latter is the intermediate host of the parasite. A second phase of work is concerned with reservoir host studies. Animals found involved were dogs, domestic silver fox, deer, coyotes, and jack rabbits. Information gained during this phase of work suggests that the jack rabbit may be the optimal host, and that during years when these animals are plentiful, they may constitute a large portion of the reservoir. During this part of the study it was learned that the endemic areas are in mountainous or hilly regions which are amply shaded and supplied with moisture. On the basis of these studies it was concluded that thelaziasis is an serious infestation, endangering the sight of the host, that it has infested a wider variety of animals than has any other members of the genus, and that transmission is probably thought the fly, F. benjamini