DEATH OF FASCIOLA HEPATICA L. WEAKENED BY X-IRRADIATION.

Abstract

MY work on Fasciola hepatica in mice1 has been advanced recently2 by a technique which a former pupil has used to assess possible acquired immunity in fascioliasis3. In 3 series of my experiments 32 mice were infected with cysts X-irradiated at 3 kr. In the first two series 8 and JO mice received respectively 20 and 40 cysts each to facilitate an examination of flukes weakened by X-irradiation alive and also in serial sections of the liver. Serial autopsies carried out 8–29 days after infection yielded 59 living flukes and 68 flukes in liver sections. The remaining 14 mice formed a third series for an, examination of possible immunity effects. These were given a ‘challenge’ infection of either 5 or 10 normal cysts 22 days after receiving the X4rradiated cysts, Serial autopsies carried out 8–39 days later yielded 62 flukes in groups of 1–8 per mouse, with mean yields of 4.4 flukes per mouse and 55.4 per cent of cysts producing flukes. One mature fluke had laid many eggs in the bile duct and gall bladder after 39 days and 3 flukes nearing maturity were recovered after 32 days. No evidence of protective immunity was forthcoming, however, in respect of either intensity of infection (fluke burden) or delayed maturation. At all stages of infection flukes were very similar to those of normal single infections, confirming the results of Hughes3; but they were of unusually small size.