Which organism causes heartwater?

• A. Ehrlichia ruminantium
• B. Anaplasma phagocytophilum
• C. Borrelia burgdorferi
• D. Rickettsia rickettsii

Answer: (A)

Heartwater is caused by Ehrlichia ruminantium, an intracellular bacterium that infects the lining of blood vessels in ruminants. This endothelial infection leads to vascular leakage and fluid buildup around the heart (hydropericardium, and other serous cavities), causing rapid deterioration and often death in susceptible animals like cattle, sheep, and goats. The organism is transmitted by Amblyomma ticks, making it a tick-borne disease typical of certain regions in Africa and nearby areas. Other listed organisms are associated with different diseases—Anaplasma phagocytophilum with granulocytic anaplasmosis, Borrelia burgdorferi with Lyme disease, and Rickettsia rickettsii with Rocky Mountain spotted fever—so they do not cause heartwater.