Maternal transfer of protection from Echinococcus granulosus infection in sheep.

Although passive immunity against larval metacestodes of the genus Taenia is well established, the transfer of immunity against Echinococcus granulosus infection has not been demonstrated convincingly. The immune status of newborn lambs born to ewes that had been infected or immunised with E granulosus eggs or oncospheres was investigated. The ewes and their six- to eight-day-old lambs were subsequently challenged. Lambs born to triply infected ewes were 80 per cent protected from a challenge infection whereas lambs born to simply infected ewes were only 45 per cent protected. Lambs born to ewes that had been immunised with preparations of sonicated oncospheres had the lowest levels of immunity. The infected ewes were challenged intramuscularly with activated oncospheres and showed some degree of immunity. Ewes which had received oncospheres solubilised in sodium dodecylsulphate or sonicated oncospheres were protected from subsequent oral challenge by 60 to 66 per cent. Radial immunodiffusion revealed that lambs with statistically significantly lower levels of IgG were more susceptible to challenge. However, the degree of protection did not show a simple relationship to the titre of antibody, as determined by an ELISA using a solubilised antigen.