The Life History of the Salmon-Poisoning Fluke, Nanophyetus salmincola (Chapin)

Abstract

The life history of Nanophyetus (= Troglotrema) salmincola (Chapin) has been studied by several workers who were interested chiefly in a disease of canines transmitted by this trematode (Simms, Donham and Shaw, 1931; Cordy and Gorham, 1950; and Philip et al, 1954). The etiologic agent has been considered by various workers to be distemper virus (Suckley, 1855), a bacterium (Bonebrake, 1925), an ameba (Pernot, 1911), mechanical destruction (Hoeppli, 1926), a haemosporidian or rickettsia (Simms and Muth, 1933), a rickettsia (Cordy and Gorham, 1950), and Neorickettsia helmintheca, Philip, Hadlow and Hughes, 1953. The role of the fluke is still not clear, but its association with salmon-poisoning disease was established in 1925 by C. R. Donham (see Donham, 1928). Donham's fluke was named Nanophyes salmincola by E. A. Chapin (1926), who (1928) amended the generic name to Nanophyetus. This animal, along with Nanophyetus schikhobalowi Skrjabin and Podjapolskaja, 1931, from Siberian aborigines, was subsequently transferred to Troglotrema Odhner, 1914, by Witenberg (1932) who believed T. schikhobalowi to be conspecific with T. salmincola. Wallace (1933) considered Troglotrema for a related fluke, Sellacotyle mustelae Wallace, 1935, and retained the genus Nanophyetus for salmincola. The molluscan host was believed (Simms, Donham and Shaw, 1931) to be Oxytrema (= Goniobasis) silicula (Gould) as a result of work and unpublished drawings of Sinitsin (Wallace, 1935). There was confusion (Donham, 1928) as to which of several cercariae was that of N. salmincola. Sinitsin's (1930) descriptions of the larval forms are indeed confused. The important fish hosts were known to be species of Salvelinus, Salmo, and Onchorhynchus. Distomulum oregonensis, proposed for the metacercariae by Ward and Mueller (1926) who believed them to cause pop-eye disease of trout, was relegated to synonymy (Price, 1929). The purpose of this research was to complete the life history of Nanophyetus salmincola and to illustrate the various stages.