Two experiments were carried out to identify the target population of @entity291 for immunisation against @entity12110 ( @entity12110 ) using the infection-and-treatment method. Firstly, a sentinel- @entity291 study was used to determine the age window for @entity12110 immunisation by determining ages at clinical detection of infection with @entity11250 . Six groups of five naive cross-bred ( @entity291 / @entity7040 ) male @entity291 , introduced at intervals of 2 months at a mean age of 26 days, were exposed to natural tick challenge on a high @entity12110 -risk, small-holder farm in the coastal lowland, coconut- @entity7243 agro-ecological zone of coastal Kenya. Secondly, a challenge study evaluated the relationship between the presence of T. parva antibodies and immunity. Ten indigenous adult @entity7040 and nine @entity7040 young stock purchased from farmers in the same zone, and eight cross-bred @entity291 (survivors of the sentinel- @entity291 study) were challenged with 10 times the immunising dose of @entity11250 Marikebuni stock. Twenty-four of these 27 @entity291 had high antibody titres before challenge. Two cross-bred @entity291 , obtained from an @entity12110 -free area and seronegative to T. parva schizont antigen, also were challenged and used as susceptible controls. Twenty-five (83%) of the 30 sentinel @entity291 contracted @entity12110 over an age range of 36-116 days (mean 72 days). The remaining five @entity291 died of other causes within 2 months of arrival on the farm. Fourteen of the 25 @entity291 survived the infection and developed antibodies to @entity11250 . Despite tick control, seven of these 14 @entity291 had a second episode of @entity12110 and two died. In total, 13 of the 25 @entity291 that contracted @entity12110 died. Only one of 19 indigenous @entity7040 animals developed clinical @entity12110 when challenged with @entity11250 Marikebuni (mild clinical signs with spontaneous recovery). Of the eight cross-bred survivors from the first experiment, only one succumbed to @entity12110 when challenged and it died. Both susceptible cross-bred @entity291 developed severe clinical signs of @entity12110 and one died. The experimental studies show that in the high @entity12110 -risk areas of the coconut- @entity7243 zone of coastal Kenya, immunisation against @entity12110 in cross-bred ( @entity291 / @entity7040 ) @entity291 should be targeted at an early age (preferably within 1-2 months of birth).

Identification of a target population for immunisation against XXXX in coastal Kenya.

@entity12110 :: ('MESH:D013801', 'Disease') :: ['East Coast fever', 'ECF'] @entity7243 :: ('3983', 'Species') :: ['cassava'] @entity11250 :: ('5875', 'Species') :: ['Theileria parva', 'T. parva'] @entity7040 :: ('9915', 'Species') :: ['Zebu cattle', 'B. indicus', 'Zebu', 'Bos indicus'] @entity291 :: ('9913', 'Species') :: ['calf', 'B. taurus', 'cattle', 'Bos taurus', 'calves']
@entity12110 :: (MESH:D013801,Disease) :: ['East Coast fever']
