DEVELOPMENT OF PROTECTIVE IMMUNITY AGAINS T LUNGWORMS AFTER ADMINISTRATION OF THE IVOMEC SR BOLUS OR PANACUR SR BOLUS IN CATTLE

Two groups of first-year grazing cattle were treated at turnout with e ither an Ivomec SR Bolus or a Panacur SR Bolus, A third group remained as untreated control. Experimentally lungworm infected control animal s guaranteed that all animals were continuously exposed to lungworm la rvae during the whole grazing season. At the end of the grazing period all animals were dewormed and challenged four weeks later with 1 000 infective lungworm larvae to test, whether a protective immunity had b een stimulated in spite of the bolus treatment. Single animals in both bolus-groups shed low numbers of gastrointestinal nematode eggs or lu ngworm larvae already during the efficacy of the boil, After the chall enge infection only one animal of each bolus-group shed low numbers of lungworm larvae with the faeces. The control animals remained negativ e. No clinical symptoms were seen in either group. It was shown that i n spite of the application of either an Ivomec SR bolus or a Panacur S R bolus the uptake of lungworm larvae stimulates an immune response.