Serological responses to bovine anaplasmosis following treatment with gloxazone

Groups of unsplenectomised steers and calves were infected with either the Onderstepoort or Sukari 1 strain of Anaplasma marginale by the injection of infected blood. The infections were treated with gloxazone (2.5 – 25 mg/kg). The serological response of the animals was monitored by the complement fixation (CF) and capillary tube agglutination (CA) tests, using antigens prepared from the Onderstepoort strain. CF antibody responses were alike in both strains. The titre rose rapidly from four days after infection to a peak around the time of the initial crisis. These high titres were maintained, and generally did not rise further at the time of recrudescence of parasitaemia. CA antibody appeared 7–10 days after infection and reached a peak shortly after the initial crisis. Titres fell as parasitaemia was reduced following gloxazone treatment, then rose as parasitaemia recrudesced. There was a close correlation between the effectiveness of gloxazone treatment and changes in CA antibody titre.