Use of Chicks in Eastern and Western Equine Encephalitis Studies

The use of ½-day-old chicks for virus titrations and serum neutralization tests against both Eastern and Western equine encephalitis is described. Chicks inoculated subcutaneously were 1 to 3 log units more sensitive in quantitating low-passage strains of these viruses and their antisera than were 3-week-old mice inoculated by the intracerebral route. They were also more sensitive in detecting these viruses than suckling mice or chick embryos. Chicks over one day of age did not give reliable results. The chick did not prove to be a satisfactory laboratory animal for the detection of St. Louis encephalitis virus.