A Clinical, Histopathological, And Immunofluorescent Study of Babesia spp. Infection In White-Tailed Deer

Thesis, 1966-1968, Harold Ray Emerson, D.V.M., Department of Veterinary Pathology, College of Veterinary Medicine, Texas A&M University, College Station, Texas 

Introduction

The Babesia spp. are present in many countries of the world and produce diseases in many wild and domestic animals.  Babesia bigemina cause extensive economic losses in the southern United States in the nineteenth and twentieth centuries and was finally eliminated by the eradication of its tick vector, Boophhilus annulatus.  Babesia canis, which produces a disease in dogs, and Babesia cabelli, which produces diseases in horses in Florida, are the only members of the genus now reported consistently in the United States. 

Spindler, in 1958, reported a Babesia-like organism which was found in blood smears from white-tailed deer, Odocoileus virginianus, in New Mexico.  Attempts to isolate and propagate the organism were unsuccessful.  Isolation of a Babesia spp. which morphologically resembled Babesia divergens from white-tailed deer in Tyler County, Texas indicated the possible presence of an unreported disease in East Texas deer herds.  A study was initiated to determine the clinical signs, gross and microscopic lesions in deer infected with this Babesia spp; to determine the site of reproduction of this Babesia during the prepatent period by use of serial sacrifice of deer and fluorescent antibody techniques; and to identify this Babesia by comparison with other Babesia spp. 

Summary

Babesia odocoilei produced a fulminant, hemolytic disease in splenectomized deer and a chronic disease, characterized by emaciation and anemia after 6 to 12 months in intact deer, which apparently were the primary hosts for this hemoprotozoan.  Splenectomized deer had a febrile response and a 3 to 9% parasitemia 2 days after intravenous inoculation of 10 ml. of blood in which 1% of the erythrocytes contained Babesia.  Anemia and erythrocytic lysis resulted in pallor and icterus of mucous membranes, increased respiratory rate and weakness.  Hemoglobinuria was a prominent sign.  Intact deer also had a febrile response that accompanied the development of a 0.5 to 1.5% parasitemia, although no other signs occurred.  Gross lesions observed during necropsy of of the splenectomized deer were subendocardial and subepicardial hemorrhages; thin, watery blood; edematous iliac, prefemoral, prescapular, and renal lymph nodes; icterus; and dark red urine in the urinary bladders.  The only lesions found in the intact deer at necropsy were edematous lymph nodes and unusually prominent lymphoid follicles in the hepatic and renal lymph nodes. 

Microscopic lesions in the splenectomized deer consisted of small, focal areas of centrolobular necrosis; diffuse hepatocellular vacuolation and periglomerular, lymphocytic accumulations in the kidneys; regeneration of the epithelial cells of the proximal convoluted tubules in the kidneys of an animal that lived 3 weeks post-innoculation; perivascular hemorrhages in the myocardium; edema in the lymph nodes; and petechial hemorrhages and lymphocytic accumulations in the submucosa of the urinary bladder.  Changes in the blood consisted of parasitism of erythrocytes with Babesia; anisocytosis, and poikilocytosis.  Nucleated erythrocytes were present in the peripheral circulatory systems of some deer.  Active hemopoietic centers were present in the bone marrow.  Babesia were observed in the erythrocytes of intact deer during the early stages of the infection.  Lesions in the liver, lymph nodes, and urinary bladder were were similar to those seen in splenectomized deer. 

Babesia reproduction occurred only within erythrocytes as demonstrated with fluorescent antibody technique.  There was an 18 to 24 hour prepatent period. 

Babesia odocoilei was characterized as a mononucleated hemoprotozoan that reproduced by binary fission or budding with a single organism producing the paired, divergent, club-shaped bodies averaging 1.9 x 0.75 microns which were located peripherally in the parasitized erythrocytes from white-tailed deer.  A comparison of Babesia odocoilei with Babesia divergens indicated that they should be considered as different species.