Inhibition of Babesia divergens in cattle by oxytetracycline
Taylor, S.M.; Elliott, C.T.; Kenny, J.
Veterinary Record 118(4): 98-102
1986
ISSN/ISBN: 0042-4900 PMID: 3952967 Document Number: 270646
The effects of continuous oxytetracycline administration on the development of parasitaemia of B. divergens during both natural and artificial infections were studied. During natural exposure on pasture heavily infested with Ixodes ricinus, 7 of 42 cattle with no previous exposure to tick-borne diseases were injected every four days with a long-acting preparation of oxytetracycline at a dose rate of 20 mg/kg. During the 6-week grazing period 21 untreated cattle developed a patent parasitaemia of B. divergens and all became seropositive by the fluorescent antibody test. In contrast, no parasites were observed in treated cattle and antibody titres remained low. Artificial infections were studied with different dose levels of oxytetracycline and their effects on antibody stimulation noted. First, four groups of cows were infected with 108 erythrocytes infected with B. divergens, three groups being injected every four days with the long-acting oxytetracycline formulation at dose levels of 20, 10 and 5 mg/kg, respectively. The highest level completely inhibited parasite replication and antibody formation; the same was observed in one animal dosed at 10 mg/kg but the remainder, plus those treated at 5 mg/kg, developed both low parasitaemia and high antibody titres. The untreated cows developed severe babesiosis. A further untreated control group was added, and three weeks after cessation of oxytetracycline treatment all were infected with 109 erythrocytes infected with a homologous isolate of B. divergens. The controls, plus those in which the previous infection had been completely inhibited, developed severe clinical babesiosis, but the remainder were refractory to parasite development.