How many steps of AHS pathogenesis are described and what are they?

How many steps of AHS pathogenesis are described and what are they?

• A. Initial replication site unknown; hematogenous spread; secondary replication in endothelial cells
• B. Initial replication site known; rapid systemic spread; replication in myocardium
• C. Entry via respiratory tract; localized infection; no systemic spread
• D. Initial replication site unknown; lymphatic spread; replication in muscle cells

Answer: (A)

The key idea is that African horse sickness progresses from a local entry point to systemic disease through the bloodstream, with the main pathological effect coming from infection of vascular endothelial cells. After the virus enters, it replicates at the inoculation site, then spreads through the blood (hematogenous spread) to reach tissues throughout the body. The crucial step that drives the disease’s severe signs is the replication in endothelial cells lining blood vessels, leading to vasculitis, edema, and hemorrhages. This sequence—local replication, viremia, and endothelial cell infection—best describes the pathogenesis and why the described three-step pattern is correct.

The key idea is that African horse sickness progresses from a local entry point to systemic disease through the bloodstream, with the main pathological effect coming from infection of vascular endothelial cells. After the virus enters, it replicates at the inoculation site, then spreads through the blood (hematogenous spread) to reach tissues throughout the body. The crucial step that drives the disease’s severe signs is the replication in endothelial cells lining blood vessels, leading to vasculitis, edema, and hemorrhages. This sequence—local replication, viremia, and endothelial cell infection—best describes the pathogenesis and why the described three-step pattern is correct.