Evaluation of a vaccine against infectious bursal disease in field trials.

It has been established in field trials that the mutant strain Cu-1M of the infectious bursal disease virus can be used for vaccination against the disease. Vaccination does not cause clinical signs or significant pathological alterations in the Bursa of Fabricius, and consequently it is not accompanied by immunosuppressive effects. In the proposed vaccination scheme maternally derived antibodies do not interfere with the establishment of immune protection in young chickens.

Loss of virulence in a small plaque mutant of the infectious bursal disease virus.

A variant strain Cu-1 M was established from the infectious bursal disease virus strain Cu-1. This variant strain forms smaller plaques than the wild type; it has a retarded growth rate, does not lead to an overt disease in chickens and causes only minor lesions in the bursa of Fabricius. Infection with this strain induces solid protective immunity against infection with the virulent virus.

Structural and growth characteristics of infectious bursal disease virus.

The infectious bursal disease virus is not enveloped and has a diameter of 60 nm and a density of about 1.32 g/ml. It contains two pieces of single-stranded RNA with molecular weights close to 2 X 10(6).

Structural and growth characteristics of two avian reoviruses.

Two virus strains which had been suspected to be the etiological agents of infectious bursitis (Gumboro disease) and of inclusion body hepatitis of chickens were characterized by their morphology, their peptide composition and the segmented genome of their double-stranded RNA to be typical reoviruses. Although the 2 avian strains did not clearly differ in their serological behaviour, the size of some of their RNA segments were not identical. Both strains replicated in tissue cultures prepared from the chorioallantoic membrane of embryonated eggs with growth characteristics of reoviruses.

In vitro cultivation of cells from the chorioallantoic membrane of chick embryos.

By treatment of chorioallantoic membranes from embryonated eggs with collagenase and hyaluronidase before the conventional application of trypsin cells could be grown in culture which supported growth of a large variety of myxoviruses, herpesviruses, avian reoviruses and the infectious bronchitis virus of chickens. The cultures could be used for sensitive plaque assays and neutralization tests.