Cow milk was experimentally contaminated with a vaccine strain of poliovirus type I. A concentration procedure was utilized to assay for the virus in a milk sample using adsorption on aluminium sulphate at pH 4.5-5.5, aluminium sulphate concentration being 0.15 g. 1(-1), followed by elution with 0.1 M Na2HPO4 pH 9.5 and subsequent detection in cultured VERO cells (kidney cells from the monkey Cercopithecus aethiops). The yield of the virus ranged from 14 to 58% of the inoculated amount, the mean value being 27%.

Research Institute of Preventive Medicine Bratislava Czechoslovakia