Cold Hemagglutinin Associated with Leptospiral Hemolytic Anemia in the Sheep 1

Abstract

Leptospirosis is a zoonotic disease which affects many species of animals as well as man. In ruminants, Leptospira pomona is frequently the etiologic agent. The clinical signs of infection in sheep include fever, icterus, and a hemolytic anemia. Several investigations have failed to elucidate conclusively the mechanism of this anemia (1–4). The detection of a transiently occurring cold-hemagglutinin (CHAn) associated with the hemolytic crisis in the plasma of experimentally infected anemic sheep, has recently been reported (5). Some characteristics of this CHAn are reported here.

Materials and Methods. A total of 15 sheep free of lepotospiral agglutinins was used in three separate experiments. All sheep were housed in isolation units, provided with hay and a complete pelleted ration and water ad libitum. One noninfected control was maintained in contact with the infected sheep in each experiment. The sheep were infected with Leptospira pomona by subcutaneous inoculation with 2.5 ml of a 10% emulsion, in 0.85% NaCl solution, of liver and spleen obtained from leptospiremic, moribund hamsters.

The microscopic agglutination test employing live L. pomona as antigen, using 7- to 10-day cultures in Stuarts' fluid medium (Difco Laboratories, Detroit, Mich.) with 10% rabbit serum, was used for the detection of leptospiral agglutinins (6) in the serum of the experimental sheep. Rectal temperatures and packed RBC volumes and hemoglobin values were determined daily to define the development of the infection and the anemia which has been described in detail elsewhere (5).

For the isolation of CHAn, large volumes of blood were obtained from normal control sheep or experimentally infected sheep during the hemolytic crisis in either Alsever's (7), ACD (8) or citrate (1 vol of 0.5 M na citrate for 5 vol of blood) anticoagulant solution. Plasma was separated at 25° and its globulin fraction concentrated by precipitation at 40% saturation with ammonium sulfate.