MATERNAL TRANSFER OF PROTECTION FROM ECHINOCOCCUS-GRANULOSUS INFECTION IN SHEEP

Although passive immunity against larval metacestodes of the genus Tae nia is well established, the transfer of immunity against Echinococcus granulosus infection has not been demonstrated convincingly. The immu ne status of newborn lambs born to ewes that had been infected or immu nised with E granulosus eggs or oncospheres was investigated. The ewes and their six- to eight-day-old lambs were subsequently challenged. L ambs born to triply infected ewes were 80 per cent protected from a ch allenge infection whereas lambs born to singly infected ewes were only 45 per cent protected. Lambs born to ewes that had been immunised wit h preparations of sonicated oncospheres had the lowest levels of immun ity. The infected ewes were challenged intramuscularly with activated oncospheres and showed some degree of immunity. Ewes which had receive d oncospheres solubilised in sodium dodecylsulphate or sonicated oncos pheres were protected from subsequent oral challenge by 60 to 66 per c ent. Radial immunodiffusion revealed that lambs with statistically sig nificantly lower levels of IgG were more susceptible to challenge. How ever, the degree of protection did not show a simple relationship to t he titre of antibody, as determined by an ELISA using a solubilised an tigen.