How many clinically distinct forms of AHS exist, and what are they?

How many clinically distinct forms of AHS exist, and what are they?

• A. 3 forms: Pulmonary, Cardiac, and Fever
• B. 4 forms: Pulmonary, Cardiac, Fever, and Mixed
• C. 4 forms: Pulmonary, Cardiac, Fever, and Neurologic
• D. 5 forms: Pulmonary, Cardiac, Fever, Mixed, and Neurologic

Answer: (B)

AHS in horses presents with syndromes defined by which organ system bears the major burden, because the virus damages vascular endothelium and leads to organ-specific edema and dysfunction. The four clinically distinct forms most commonly recognized are the pulmonary form, which shows rapid, severe respiratory distress due to pulmonary edema; the cardiac form, marked by edema of the head and neck and often fluid in body cavities (hydrothorax) from cardiac failure; the fever form, where the horse runs a fever with little or no edema or major respiratory signs; and the mixed form, where features of both pulmonary and cardiac involvement are present. A neurologic form is described in some discussions but is not consistently treated as a separate, routinely recognized clinical form, so it’s not counted here. Thus, the standard four clinically distinct forms are pulmonary, cardiac, fever, and mixed.

AHS in horses presents with syndromes defined by which organ system bears the major burden, because the virus damages vascular endothelium and leads to organ-specific edema and dysfunction. The four clinically distinct forms most commonly recognized are the pulmonary form, which shows rapid, severe respiratory distress due to pulmonary edema; the cardiac form, marked by edema of the head and neck and often fluid in body cavities (hydrothorax) from cardiac failure; the fever form, where the horse runs a fever with little or no edema or major respiratory signs; and the mixed form, where features of both pulmonary and cardiac involvement are present. A neurologic form is described in some discussions but is not consistently treated as a separate, routinely recognized clinical form, so it’s not counted here. Thus, the standard four clinically distinct forms are pulmonary, cardiac, fever, and mixed.