Some physico‐chemical and biological properties of a Belgian strain (u 76/1035) of infectious laryngotracheitis virus

The physico-chemical and biological properties of a Belgian strain of infectious laryngotracheitis (ILT) virus (U 76/1035) have been investigated. Less than 1% of the virus was viable after 60 min at 56 degrees C. It was little affected by pH4 for 2 hours, but 90% of the virus was inactivated by pH9 treatment for 2 hours. The virus multiplied in eggs when inoculated either into the allantoic sac or onto the chorio-allantoic membrane. It did not grow in chick or duck embryo fibroblasts but replicated well in chick kidney cells. Differences in symptomatology and mortality were observed when chickens were infected by different routes; intratracheal inoculation of the virus caused the highest morbidity and mortality.