[Production and titration of a vaccine against the infectious encephalomyelitis of poultry].

A vaccine was produced against infectious encephalomyelitis of day-old chicks infected cerebrally with strain Calnek 1143. It is a brain suspension from killed birds that have shown disease symptoms, treated with penicillin and streptomycin and stored at -20 degrees C. Experiments were carried out to titrate the vaccine through determining the minimum infective dose for day-old chicks treated with 0.1 cm3 each of it, orally, as obtained from tenfold dilutions. It was found that birds do not manifest clinically the disease, however, with birds killed 20--25 days following infection there have been characteristic histologic changes speaking of infectious encephalomyelitis. The minimum infective dose of the various batches of vaccine have been found to range from 10(-3) to 10(-5)/cm3. Applied under the conditions of the practice the vaccine has proved harmless, contributing to eradication of the disease on the infected farms.