Attention is directed to the lack of a readily available small laboratory animal to replace the horse in evaluating the innocuity and antigenicity of strains of horsesickness virus attenuated for equines by serial intracerebral passage in mice.
In guinea-pigs the result of the intraperitoneal injection of vaccine virus strains may range from the absence of any clinical reaction to the production of 100 per cent mortality from specific aseptic viral encephalitis.
Guinea-pigs are susceptible to infection and the production of encephalitis by the intraperitoneal, subcutaneous, intramuscular and rectal routes of infection, but not per os or by supraconjunctival instillation.
The intranasal route appears to be the most constant one for the invasion of the central nervous system by virus.
Recovery from infection is followed by the appearance of serum virus neutralising antibodies in the serum, the titre varying with the antigenic potency of the particular attenuated virus strain. The value of the guinea-pig in future research into horsesickness is discussed.