The transmission of louping ill by ticks (Rhipicephalus appendiculatus)

Abstract

1. Experiments conducted to demonstrate the susceptibility of horses and cattle are described. 2. The appearance of virucidal antibodies in the serum of these animals after infection is demonstrated by a technique of in vitro neutralization of virus. 3. The technique of tick feeding investigations is briefly described. 4. It is shown that- (a) larvae of R. appendiculatus will pick up infection for transmission as nymphae; (b) nymphae will pick up infection for transmission as adults; (c) the virus does not pass through the egg to the next generation; (d) infective nymphae tend to lose their infection after feeding on immune animals though some of the resulting adults may still be infective ; (e) the same occurrence was noted after feeding infective nymphae on susceptible animals but, particularly if sheep are the hosts, there is a danger of the nymphae reacquiring infection before detachment; (f) clean ticks do not acquire infection when feeding on an immune animal simultaneously with infective ticks. 5. The significance of the work is discussed.