Attempts to vaccinate ewes and their lambs against natural infection with Haemonchus contortus in a tropical environment

•A vaccine made from Haemonchus contortus was trialled in grazing sheep in Brazil.•Vaccination reduced worm burden and egg counts of H. contortus in lambs.•A small amount (5μg) of native vaccine antigen was required per dose.•Vaccination did not protect periparturient ewes.•This vaccine could be useful to control Haemonchus in tropical countries.