An Experimental Study of the Sheep-Trypanosome (T. melophagium Flu, 1908), and its Transmission by the Sheep-Ked (Melophagus ovinus L.)

Abstract

Trypanosoma melophagium Flu, 1908, is a parasite of European domestic sheep (Ovis aries L.), in the blood of which it occurs in very scanty numbers and can be detected by the cultural method. In England it has been found in 80 per cent, of sheep examined.The infection is of fairly short duration and does not produce an immunity in sheep, since the latter can easily be re-infected. In all probability T. melophagium produces no pathological effect in sheep, and is incapable of infecting laboratory animals.Morphologically the sheep-trypanosome is closely allied to the cattle-trypanosome, T. theileri.The intermediate host of T. melophagium is the sheep-ked, Melophagus ovinus L., in the alimentary canal of which it passes through a definite cycle of development ending in the production of infective forms (metacyclic trypanosomes) in the hind-gut of the insect.The mode of transmission is contammative, the sheep acquiring an infection by ingesting the ked. Infection of sheep did not result from the bite of the ked, through abrasions of the skin, or from inoculation of cultures of the trypanosome.T. melophagium is easily cultivated at 30° C. Its evolution in cultures is similar to that in the invertebrate host.