BLOOD-CLOTTING DISORDERS DURING EXPERIMENTAL SARCOCYSTIOSIS IN CALVES

The effects of experimental infection of calves with Sarcocystis cruzi on the blood coagulation cascade were investigated. Calves were inocu lated orally with 1 x 10(5) sporocysts (group S1, n = 6) or with 5 x 1 0(5) sporocysts of S. cruzi (group S2, n = 3). A. group of eight calve s served as non-infected controls (group C). The animals were bled onc e during the first 4 weeks of infection and twice a week thereafter un til day 40 p.i. The following parameters were measured: activated part ial thromboplastin time, prothrombin time, thrombin time, reptilase ti me, thrombin coagulase time: factors XII, XI, X, IX, VIII:C, VII, V, p rekallikrein, fibrinogen, alpha 2-antiplasmin, antithrombin III, alpha 1-antitrypsin, alpha 2-macroglobulin, haematocrit, haemoglobin, numbe rs of erythrocytes and thrombocytes. The infected calves developed acu te sarcocystiosis from 25 (S1) or 29 (S2) days p.i. onwards. During th e acute disease, antiproteases tended to elevated values and thrombocy te counts were generally reduced. In group S1 prolonged prothrombin ti me and reduced activities of factors VII or V were found. In group S2 accelerated prothrombin time and activated partial thromboplastin time , as well as elevated factor X activities, were recorded even before t he onset of clinical disease at 19 days p.i. While prothrombin time re turned to normal levels thereafter, activated partial thromboplastin t ime remained short. Activities of factor V, factor VII and factor X we re significantly reduced in group S2 at the onset of acute sarcocystio sis, and one of the three calves died at 29 days p.i. The other parame ters were not significantly affected by either dose of infection. No e vidence for a classical disseminated intravascular coagulation syndrom e could be found; however, it was demonstrated that S. cruzi alters pl asma coagulation in a dose-dependent way. (C) 1998 Australian Society for Parasitology. Published by Elsevier Science Ltd.