Responses to a vaccine trial for East Coast fever in two cattle herds at the Kenyan coast

Abstract

A total of 373 cattle (271 Zebu-European crosses and 102 pedigree Jerseys) were immunized against East Coast fever on two farms in the Kilifi District of Coast Province, Kenya. The cross breeds and the Jersey cattle received I ml of either 10-01 or 10-' dilution of Thellena parva parva Marikebuni stock, respectively and simultaneous treatment with a long-acting formulation of oxytetracycline. Following immunization, 362 cattle (96.5%) showed Theileria parva antibodies; 346 cattle (92.7%) seroconverted without clinical reactions. The Jersey cattle developed a higher proportion of clinical East Coast fever reactors (14.7%) following the immunization than the cross breeds (0.6%). All the calves immunized (37) on both farms seroconverted to Theileria parva antigen without any theilerial clinical reactions. The development of a serological response to East Coast fever was independent of the route of stabilate inoculation and was unaffected by concurrent infections such as trypanosomiasis and foot and mouth disease. Following immunization, no discernable effects on milk production were recorded, except from cattle undergoing a clinical reaction, where a transient reduction in milk production was seen. Thirty months later, the immunized cattle are reported to have withstood the disease challenge presented to them naturally on the farms without any breakdown in immunity to East Coast fever.