The response of Nigerian West African Dwarf goats to experimental infections with Haemonchus contortus

One option for controlling haemonchosis in warm pastoral regions is improve ment of resistance by selective breeding. Variation in acquired immunity to H. contortus and immunological correlates of infection were studied in Wes t African Dwarf WAD) goats. Following exposure to 5000 L3, 63 per cent of t he inoculum established but 77 per cent of established worms were expelled by week 5. All infected animals were anaemic (day 14). When exposed to 2000 L3, 36 per cent of the inoculum was still present (day 35) with no loss by day 49. Persisting primary infection worms survived a superimposed challeng e (day 35), but their growth was slowed and resistance to challenge was sig nificant. Most goats showed eosinophilia and parasite-specific IgG response s to primary infection, but only eosinophilia increased after challenge. No consistent associations were found between parasite burden and any immunol ogical measures of infection, but parasite egg counts showed considerable v ariation. Overall, our results suggest that resistant genotypes exist among the WAD goat population.