A Comparison of Embryo and Bird Infectivity Using Five Strains of Laryngotracheitis Virus

Abstract

SINCE the early investigations of infectious laryngotracheitis (LT) from 1930 to 1940, relatively few basic studies have been made in this country on LT virus. This disease is still a problem in many localized poultry production areas. Occasional outbreaks in vaccinated flocks have raised the question as to whether these outbreaks are due to variant types of LT virus, misdiagnoses, deficiencies in the vaccines used, or failures to properly apply the vaccine. In order to determine possible reasons for these so-called failures of vaccines, better methods of diagnosis and characterization of the virus are needed. The purpose of this study was to investigate some of the current techniques used in virology that might be applied to LT virus. Fundamental to any work on viruses is a method of titration for assessing the virus content of suspensions used. Brandly (1935) estimated the virus content of preparations by inoculating varying dilutions on . . .