PLATELET DYSFUNCTION ASSOCIATED WITH EXPERIMENTAL ACUTE CANINE EHRLICHIOSIS

To determine whether platelet dysfunction occurs in canine ehrlichiosi s, platelet aggregation studies in response to collagen/epinephrine, t hrombin and adenosine diphosphate (ADP) were carried out by the indire ct method, using sera from six dogs experimentally infected with Ehrli chia canis, Samples of serum taken before infection and four and 20 da ys after infection were tested by incubation with platelet-rich plasma from a seronegative healthy dog, Platelet aggregation was significant ly inhibited in five of six infected dogs in response to at least one of the agonists used, A significant increase in pre-aggregation lag ti me was recorded in response to collagen/ epinephrine in sera taken 20 days after infection from three of five dogs (P<0.05). When compared w ith the preinfection values, a significant increase of 45 per cent in the mean pre-aggregation lag time was detected (P<0.05). Maximal relat ive aggregation responses to ADP decreased significantly in one serum sample taken four days and one taken 20 days after infection (P<0.01) and there was a significantly lower relative slope for one serum sampl e 20 days after infection (P<0.05). Maximal relative aggregation respo nses to thrombin were significantly decreased together with their rela tive slopes in serum samples from two of four dogs four days after inf ection (P<0.05). The results suggest that platelet dysfunction may occ ur in the acute stage of canine ehrlichiosis, and may be a contributin g factor to the tendency to bleed commonly observed in this disease, A ntiplatelet antibodies directed against platelet glycoproteins may pla y a role in the inhibition of platelet aggregation.