An experimental study of East Coast fever in Ugand II. The durability of immunity in East Coast fever

Abstract

Confusion exists as to whether the immunity produced by one attack of East Coast fever is absolute or whether it requires to be maintained by reinfection.During the present experiments mild transient infections have been produced in six calves, and in five cases the immunity has been incomplete and second attacks have followed reinfestation by infected ticks.The time interval between the attacks has varied from 1 to 16 months, and it is suggested that when the interval is prolonged the second attack will be severe and may be fatal.It is concluded that the durability of the immunity depends on the severity of the original attack, being durable when the attack is severe, and only transient and probably never solid when the attack is mild.The temperature reaction is at the moment the best indicator as to the severity of the attack and the type of immunity evolved.