Paramphistomosis in sheep; natural infection of lambs by Calicophoron daubneyi

SUMMARY In order to follow the course of natural infection by Calicophoron daubneyi in sheep, fourteen naive lambs were allowed to graze a known infected pasture. Repeated blood and faeces samples were taken and every two weeks two lambs were necropsied. Tissue samples from the abomasum, duodenum and local lymph nodes were obtained for histological examination. During the follow up, a softening of the faeces from D38 to D52 was the unique clinical sign observed. Significant hematological changes were noted in red blood cell, eosinophil, basophil and lymphocyte counts. Haemorrhagic lesions evident on D9 in the abomasum and duodenum were more marked on Days 38 and 52; varying numbers of immature paramphistomes were found during necropsies from D9 onwards. Histological examination revealed oedema and haemorrhages in the abomasum and duodenum, with infiltration by lymphocytes and eosinophils. During the course of the natural infection by C. daubneyi in lambs, three phases were observed: firstly, an early eosinophilic non-specific reaction, secondly, an extension of parasite-induced lesions with a significant inflammatory reaction and thirdly a healing phase associated with parasite maturation. Unfortunately, the follow-up (80 days) was too short for determination of the prepatent period.