EN
The detection of coronaviruses in calf faeces by the haemadsorption-elution-haemagglutination assay (HE-HA), described by van Balken et al. (1), may be employed in different laboratory procedures. The experiments were done with coronavirus 800 (11), propagated in faetal lung cells of the calf (10), and rat erythrocytes. There were determined: a) the influence of erythrocyte concentrations on the effectiveness of the haemadsorption-elution assay (Table 1), b) the receptor capacity of erythrocytes assessed in suspensions of a different concentration (Table 2), c) the conditions of the effective elution assay after prior repeated adsorption to erythrocytes (Table 3, 4), d) the possibility of the eluted coronavirus to bind to new erythrocytes, e) the influence of temperature (37—70°C) on the activity of coronavirus haemagglutinin. The usefulness of the obtained parameters was checked using gut washings from diarrhoeic calves. Virions of the virus following the haemadsorption procedure to the surface of rat erythrocytes have been presented (Fig. 1, 2).