East Coast Fever: 3. Chemoprophylactic Immunization of Cattle using Oxytetracycline and a Combination of Theilerial Strains

Abstract

In the first of two experiments performed, 29 animals were immunized by chemoprophylaxis against either a combination of three theilerial strains, Theileria parva (Muguga), T. parva (Kiambu 5) and T. lawrencei (Serengeti transformed), or against one or two elements of the combination separately, and then challenged with either T. parva (Kiambu 1) or T. lawrencei (Solio KB1), both of which were known to be heterologous to T. parva (Muguga). The animals immunized against the combination had mild or inapparent reactions to challenge, whilst the susceptible control cattle and many of those immunized against one or two strains either had severe reactions of died. In the second experiment, 17 cattle immunized by chemoprophylaxis against the combination were challenged with lethal doses of three theilerial strains, T. parva (Entebbe 1), T. parva (Entebbe 2) and T. parva (Ukunda), recently isolated from two widely separated areas of East Africa. They had mild or inapparent reactions whilst 13 of 15 susceptible control cattle died. Chemoprophylaxis using a combination of theilerial strains and a limited oxytetracycline regimen was shown to be an effective means of immunizing cattle against East African theilerioses. The use of this technique as a method of immunizing cattle before exposure in the field is proposed.