Genetic resistance to helminths. Comparison of the development of Ostertagia circumcincta infections in Scottish Blackface sheep of different haemoglobin type.

Over the years a number of investigators have reported that sheep with haemoglobin A are more resistant to Haemonchus contortus than animals of the same breed with haemoglobin B. The experiment described here was an attempt to ascertain whether a similar association might exist between haemoglobin type and resistance to non-haematophagic parasites. The results indicate that such a relationship might exist, since Scottish Blackface sheep with HbA showed milder biochemical and pathophysiological changes than their HbB counterparts and at the same time harboured smaller numbers of adult worms and more inhibited larvae when necropsied 16 days after a primary infection with 100,000 Ostertagia circumcincta third-stage larvae.