Biliary Fever

Biliaty Fever:
Babesiosis in the horse is caused by two protozoal piroplasms, Babesia equi and Babesia caballi. These organisms currently are the only erythroparasites of clinical significance in North American horses. B. caballi is a relatively large member of the genus and its appearance has been likened to B. bigemina, the species responsible for Texas Cattle Fever. The development of B. caballi in the host occurs exclusively in erythrocytes. The trophozoites appear as round, oval, or elliptical basophilic structures that measure 1.5 to 3µm in diameter. The organisms are intraerythrocytic within the cytoplasm of erythrocytes (Fig.1). Pairs of organisms are commonly found in a single erythrocyte oriented such that they form an acute angle. Babesia equi, in contrast, is a smaller member of the genus and has been found to have an extraerythrocytic stage of shizogony occurring in host lymphocytes. Similarities to the bovine pathogen Theileria have stimulated debate over the rightful taxonomic classification of this organism. Trophozoites of B. equi appear as oval, round, elliptical, or spindle-shaped basophilic structures that measure up to 3µm in diameter (Fig. 2). The merozoite stage appears as two or four pyriform parasites together within the erythrocyte, each with a length of only 1.5 µm on average. When four Babesia equi merozoites are present together in one cell, they frequently form a characteristic "Maltese cross"

Clinal Signs
Rarely, a peracute form of the disease occurs in which horses die within 24-48 hours of the onset of clinical signs. Clinical signs of equine babesiosis generally follow a variable incubation period of 5 to 21 days.
The acute form of the disease usually involves fever, malaise, anorexia, depression, icterus, hemoglobinemia / hemoglobinuria, pale mucous membranes, tachycardia, and tachypnea. Additional features that may or may not be seen include sweating, colic, lacrimation, incoordination, cardiac murmurs, and subcutaneous edema around the head and eyelids.
Subacute cases are characterized by intermittent fever, anorexia, weight loss, tachycardia, tachypnea, with variable degrees of icterus, hemoglobinuria, and bilirubinuria.