Infectious coryza due to Haemophilus paragallinarum serovar B in China

Abstract

Infectious coryza, a disease of the upper respiratory tract of chickens, is caused by Haemophilus paragallinarum. The clinical signs of the disease include nasal discharge, facial swelling and a reduction in food and water consumption. Infectious coryza in poultry is a disease of economic significance in many parts of the world with the greatest economic losses resulting from an increased number of culls and marked reduction (10 to 40%) in egg production. The most widely used serological classification scheme for H paragallinarum is the Page scheme which recognises three different serovars, termed A, B and C. The importance of the Page scheme is that inactivated vaccines protect only against those serovars present in the vaccine.

There have been few studies performed in China on the serological characterisation of H paragallinarum isolates. All 29 Chinese isolates of H paragallinarum that have been examined to date have been shown to be serovar A. We report the first isolation of H paragallinarum serovar B from and outbreak of infectious coryza in China.