Changes in Hemostatic Indices in Foals Naturally Infected With Strongylus vulgaris

Abstract

Strongylus vulgaris has been found endemic in equine populations subject to parasite control by targeted selective anthelmintic therapy. This study investigated hemostasis in foals naturally infected with S. vulgaris and monitored this response over the course of progressing infection stages. The hemostatic indices D-dimer, antithrombin III (ATIII), fibrinogen, prothrombin time (PT), and activated partial thromboplastin time were evaluated in weekly blood samples for up to 50 weeks in 12 foals born into a herd with high prevalence of S. vulgaris. Results were compared with weekly S. vulgaris antibody enzyme-linked immunosorbent assay values in all foals using a linear mixed effects model with repeated measures and to total numbers of S. vulgaris larvae in nine foals at necropsy with Pearson linear correlation. In the first week of life, all evaluated indices of hemostasis were significantly different from those observed in the rest of the study weeks, corresponding to previously demonstrated aberrancies in neonates. Significant changes were seen for D-dimer in weeks 11–24, 26–27, 30, and 39 compared with week 2, for PT in weeks 12–13 compared with week 6, and for ATIII in week 15 compared with week 4. Strongylus vulgaris antibody levels were statistically associated with D-dimer (P = .0076) and fibrinogen (P = .0004) concentrations. Naturally acquired infection with S. vulgaris was associated with changes suggestive of mild activation of coagulation, fibrinolysis, and inflammation. The results of this study may help elucidate the pathogenesis of the endarteritis, thromboembolism, and nonstrangulating intestinal ischemia that is observed in horses with S. vulgaris infection.