Immunization of day-old chicks having maternally derived antibodies against infectious bronchitis: degree of protection as monitored by ciliary activity after intratracheal challenge.

One-day-old chicks with maternally derived antibodies were vaccinated against infectious bronchitis (IB) with 3000 EID50 of the IB vaccine virus designated H120. The degree of protection induced by intranasal-eye drop (IE) vaccination was compared to that achieved by spray (S) vaccination. The protection afforded by vaccination was monitored by intratracheal challenge with IBV strain M-41 (clinical signs, ciliary activity in tracheal explants, virus isolation) and by serological tests (ovoneutralization, microneutralization in cell culture, haemagglutination inhibition (HI) test, ELISA).

Isolation and characterization of new infectious bronchitis virus variants in Hungary.

Two agents not agglutinating chicken erythrocytes were isolated, one in each of two flocks, from organ samples and tracheal swabs taken from 4- to 7-week-old chicks of 8 broiler flocks experiencing respiratory signs. Virus isolation was done in embryonated SPF hen's eggs. Morphological changes of the embryos, appearing as dwarfing or curling into a spherical form, usually occurred in the 3rd or 4th passage on postinoculation (PI) days 5-9.

[Requirements of rabbit-adapted swine fever vaccine].

Studies were conducted into the demands made on both harmlessness and effectiveness of SUVAC, a swine fever vaccine prepared from strain "C", a rabbit-adapted Chinese virus strain. The following findings were obtained: --The vaccine strain was attenuated to an extent by which it could be used without serum. --The vaccine was harmless even with immunodepressor action.