EQUINE POTOMAVAC® (EHRLICHIA RISTICII BACTERIN)\ Size 5 single doses - $ 90.74 3ml X 10 Dose - $ 473.46 $ 90.74 Qty: Add to Cart Recommended for the vaccination of healthy horses as an aid in the prevention of Potomac Horse Fever (equine monocytic ehrlichiosis) caused by E. risticii.