Characterization of the putative haemagglutinin in haemophilus paragallinarum
Barnard, Tobias George
MetadataShow full item record
Haemophilus paragallinarum , the causative agent of infectious coryza (IC), an acute respiratory disease in chickens and fowl, was first isolated in 1931 by De Blieck (1932). The first serious, documented outbreak in South Africa occurred in 1968 (Buys, 1982) on a multi-age layer-farm, soon the bacterium spread to most large production sites and established itself as the most common bacterial infection in layers (Bragg, 1995). The disease has a low mortality rate but leads to a drop in egg production of up to 40 % in layer hens and increased culling in broilers and thus poses significant financial liability to chicken farmers (Arzay, 1987; Bragg, 1995). One of the reasons for the success of survival for this bacterium is that after recovering from infection, birds become carriers of the bacterium, therefore aiding the spread of H. paragallinarum (De Blieck, 1948). Secondly, the bacterial strain belongs to one of nine serovars, which makes combating the spread of the disease through inactivated vaccination ineffective especially due to low cross protection among these serovars. (Rimler et al., 1977; Kume et al., 1980a). Various potential factors have been identified as potential virulence factors, e.g. the haemagglutinin protein. This protein plays a crucial role in adherence of the bacteria to the host's cells and is considered a possible virulence factor (Sawata et al., 1982; Yamaguchi et al., 1989). Sawata and co-workers (1982) reported at least three different haemagglutinins from H. paragallinarum strain 221 with one, HA-L, being serovar specific with the other common types shared by the different serovars in one serogroup.It would therefore be important to understand the working and interaction of the various virulence factors of H. paragallinarum, especially the haemagglutinins, in order to combat this bacterium.