Serum complement and blood platelet adhesiveness in acute canine ehrlichiosis.

Three dogs inoculated with Ehrlichia canis served as infected controls (group I), 3 dogs treated with cobra venom factor (CVF) after inoculation with E canis were the principals (group II), 3 noninfected dogs were the noninfected controls (group III), and 1 noninfected dog given CVF was the noninfected, decomplemented control (group IV). Thrombocytopenia occurred in all E. canis-inoculated dogs (groups I and II) within 3 weeks after they were inoculated. However, the severity of the thrombocytopenia was moderated in the group II dogs (decomplemented E canis-inoculated). Hypocomplementemia occurred in the CVF-treated dogs (groups II and IV) immediately and persisted for up to 5 days after administration of CVF. Hypocomplementamia also occurred in all E canis-infected dogs (groups I and II) during the period of maximal thrombocytopenia. The mean platelet retention was significantly decreased in all E canis-inoculated dogs and in the CVF-control dog (groups I, II, and IV). There was no correlation between platelet retention and the number of platelets in group III (nontreated, noninoculated) controls. The correlation between the decrease in platelet retention and the number of platelets was significant in the complement-intact infected dogs, yet was not significant in the decomplemented infected dogs. Data indicated that complement consumption occurred in acute canine ehrlichiosis and coincided, to a degree, with the development of thrombocytopenia. Decomplementation of inoculated dogs moderated the severity of the thrombocytopenia. Platelet function is also altered in acute stages of the disease.