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A number of immuno-competent Blackface lambs were infected with 10,000 Haemonchus contortus third stage larvae and were later challenged with a second dose of 10,000 H. contortus third stage larvae. One group of lambs was treated with dialysed transfer factor prior to the second challenge dose. Histological changes in the abomasal wall, reductions in abomasal worm burdens at slaughter and faecal egg counts monitored throughout the experiment suggested the presence in some animals of (1) an innate resistance, (2) a 'self curing' effect, (3) an enhancement of this 'self curing' effect in the transfer factor treated group and (4) a response in one transfer factor treated animal comparable to 'classical self cure'. [ABSTRACT FROM AUTHOR]

Significant reductions in worm burdens were achieved in lambs treated with dialysed transfer factor and challenged with 10,000 Haemonchus contortus larvae, when compared with challenged control animals. Non-dialysed transfer factor, from the same leucocyte pool, produced no protection, but was successful in reducing worm burdens when given after a primary infection of 1,000 H. contortus larvae with subsequent challenge of 10,000 larvae. While the results confirmed the previously reported inconsistencies of transfer factor activity, the histological abomasla changes in all the dialysed and non-dialysed transfer factor treated groups, irrespective of measurable effects on worm burdens, were consistent and corresponded to immediate type hypersensitivity responses. The similarity of these responses with self cure in haemonchosis and the possibility of genetic factors influencing the quantitative expression of protection to the effects of transfer factor treatments is discussed. [ABSTRACT FROM AUTHOR]