[Corona- and rotavirus enteritis in newborn calves in Bulgaria].

In the course of investigations into enteritis enzootics in newly-born calves, 55 fecal samples have been studied through direct electron microscopy by the negative contrast method. Rota viruses were found in eight of them, corona viruses in 38.2 per cent of the cases, and both rota- and corona viruses in 49.1 per cent of the cases. Two types of rota-viral particles were observed: with and without supercapsids. Also two types of corona-viral particles were established. The first type was relatively monomorphic, having an average diameter of 120 nm, and length of the surface spikes of 20 nm. The second type was pleomorphic with length of the spikes of 11 nm. Most of the fecal samples, containing corona viruses, agglutinate mice, rat and hamster erythrocytes. On studying the physical and chemical properties of the hemagglutinine, ist gradient density and antigenic patterns it was shown that it is related to the intact corona-virions. With the hemagglutination-inhibition test developed, antibodies against corona-viruses in the sera of a considerable number of the cows have been demonstrated. A precipitating antigen has been shown in a part of the fecal samples, containing rota-viruses. By studying the physical and chemical properties, its gradient density and its comparison with a refernce antigen, it has been shown that the antigen was conditioned by degraded fragments of rota-viruses. With the aid of the immunodiffusion method with a fecal antigen evolved, precipitating antibodies have been shown in 18 to 46 per cent of the cows and calves.