peak of frequency 60 for infected non vaccinated animals was in the range of 21 30 worms in contrast the peak of frequency 64 5 for mice vaccinated with either se or sm 14 fell within the range of 0 10 worms mouse as can be seen according to the present invention it is of particular interest that essentially the whole of the protective effect of the complex se mixture can be reproduced with this single antigen trials with other defined antigens derived from se glutathione s transferase and paramyosin did not result in the same high level of protection as mentioned above sm 14 also has a significant level of homology with various fatty acid binding proteins the results shown in table iii of experiments 1 to 4 are demonstrated graphically in fig3 3a 3b 3c and 3d 6 6a 6b and 6c fig3 3a 3b 3c and 3d to 6 6a 6b and 6c correspond to experiments 1 to 4 in these figures it is possible to evaluate the protection through the analysis of the population profiles of the worm burden of vaccinated versus non vaccinated groups in this example vaccinated mice were challenged with 500 and 1000 cer animal or challenged 2 or 3 times 100 cerc animal infection with one week.