Experimental infection with African Horse Sickness Virus in horses induces only mild temporal hematologic changes and acute phase reactant response

Abstract

OBJECTIVE African Horse Sickness (AHS) is a vector-borne disease endemic to sub-Saharan Africa caused by African Horse Sickness Virus (AHVS). Infections in naïve horses have high morbidity and mortality rates. AHS pathogenesis is not well understood; neither the hematologic changes nor acute phase response occurring during infection has been fully evaluated. The study’s objective was to characterize the hematologic changes and acute phase response during experimental infection with AHSV. ANIMALS 4 horses negative for AHSV group-specific antibodies. PROCEDURES In this prospective, longitudinal study conducted between November 23 and December 2, 2020, horses were experimentally infected with AHSV, and blood samples were obtained before inoculation and then every 12 hours until euthanasia. Hematologic changes and changes for serum amyloid A (SAA) and iron concentration were evaluated over time using a general linear model including natural logarithm of sampling time. RESULTS All horses were humanely euthanized due to severe clinical signs typical of AHS. Median Hct increased significantly, and the median WBC count, monocyte count, eosinophil count, and myeloperoxidase index changed significantly in all horses over time. Horses developed marked thrombocytopenia (median, 48 X 103 cells/µL; range, 21 X 103 to 58 X 103 cells/µL) while markers of platelet activation also changed significantly. Median SAA increased and serum iron concentration decreased significantly over time. CLINICAL RELEVANCE Results indicated severe thrombocytopenia with platelet activation occurs during infection with AHSV. Changes in acute phase reactants SAA and iron, while significant, were unexpectedly mild and might not be useful clinical markers.

African Horse Sickness Characteristic Features of the Pathogen, Epizootiology, Clinical Signs, Diagnosis, and Monitoring Measures (Review Article)

“…Virions are adsorbed on erythrocytes and monocytes (an insignificant amount of the virus is present in the plasma) and are transported by the blood to endothelial cells of the lungs, spleen, and other tissues, which are the main sites of secondary replication. Despite the relatively low level of replication in these organs, the virus seriously damages endothelial cells and shows signs of edema and pleural effusion, which characterize the severe form of AHS believed to be the result of increased vascular permeability and impaired circulatory and respiratory function (Scacchia et al, 2015;Schliewert et al, 2022).…”

“…Replication in endothelial cells resulted in cell damage with changes in intercellular connections, endothelial loss, increased capillary permeability, and subendothelial deposition of cell debris and fibrin. In many organs, especially in the myocardium and lungs, swelling, hemorrhage, and microthrombi can be observed (Scacchia et al, 2015;Schliewert et al, 2022).…”