Dose-dependent pathophysiological changes in cattle experimentally infected Dictyocaulus viviparus.

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In two trials five calves were each experimentally infected on three consecutive days with a total number of either 30 Dictyocaulus viviparus larvae per kg body weight (trial A) or 3 larvae/kg body weight (trial B). Five calves served as non-infected controls. Infected cattle in trial A developed severe clinical signs of dictyocaulosis and one calf died 37 days post infection (p.i.), whereas all cattle in trial B remained clinically healthy. Weight gains in both trials were not statistically different. Haemoglobin concentrations, packed cell volume (PCV), number of erythrocytes and leucocytes, blood pH and albumin concentrations were in the physiological range in all groups. Infected cattle in trial A showed increases in respiratory rates, body temperature, serum protein concentrations, and blood eosinophil counts and decreases in oxygen partial pressure. Infected cattle in trial B showed increased blood eosinophil counts. Antibody formation in infected cattle of both trials showed a similar pattern. Excretion of larvae from infected cattle reflected the different infection doses. Microbiological examinations showed an increase of facultatively pathogenic bacteria in the lung fluid.