Efficacy of a new tetravalent coryza vaccine against emerging variant type B strains

Abstract

Outbreaks of infectious coryza have been reported in vaccinated flocks in different countries, indicating that new serotype(s) of Haemophilus paragallinarum may have evolved. Several field isolates from vaccinated flocks in the US, Ecuador, Argentina and Zimbabwe were examined and, apart from one serotype C strain, all were typed as serotype B. An inactivated commercial trivalent vaccine, containing serotypes A, B and C, protected against challenge with the serotype C isolate but protection against challenge with serotype B isolates was weaker, suggesting that they might represent a new variant immunotype. An experimental tetravalent oil adjuvant vaccine, containing one of the serotype B isolates, appeared immunogenic against all isolates after one vaccination. Its efficacy and safety were further tested in layer chickens housed under field conditions. Chickens were vaccinated at 8 and 16 weeks of age while controls were unvaccinated. Vaccinates and controls were challenged with type A, B, C and variant type B at 25, 45 or 65 weeks of age. There was good protection (PB/ 0.05) against all four immunotypes after all challenges. No systemic reactions were observed and local reactions were similar to those found with the commercial trivalent vaccine. The tetravalent vaccine may therefore be a good choice for control of new field isolates.

Cross-protection study of the nine serovars ofHaemophilus paragallinarumin the Kume haemagglutinin scheme

“…This evidence of antigenic diversity within Page serovar B/Kume serogroup B is further supported by the recent report that a standard commercial A, B, C trivalent infectious coryza vaccine provided a weaker level of protection against so-called 'variant' Page serovar B field isolates (Jacobs et al, 2003). Indeed, Jacobs et al (2003) reported that the inclusion of one of the 'variant' Page serovar B isolates, resulting in a tetravalent vaccine, was necessary to achieve good protection.…”

Infectious Coryza in Jimma Backyard Chicken Farms: Clinical and Bacteriological Investigation

“…Naturally male chickens are more susceptible too A. paragallinarum than females [38]. The present study result was in line with this fat in that the prevalence was 30.2% in males and 20.5% in females.…”

“…Erythromycin, Tetracycline, Fluoroquinolones, Sulphadimetoxine, and Sulphamethazine can be used as treatment medication. Although treatment may result in improvement, the disease may recur when medication is discontinued [3,12,[21][22][23][24]38].…”

The vaccination-challenge trial: the gold standard test to evaluate the protective efficacy of infectious coryza vaccines

“…As all controls were fully susceptible to challenge and as no antibodies to infectious coryza were detected in any chicken prior to vaccination, there is good evidence that the chickens used in this work were fully susceptible to infectious coryza. Our use of commercial chickens is a practice that has been adopted by other infectious coryza vaccine researchers (Terzolo et al, 1997;Jacobs et al, 2003;Bragg, 2004;Soriano et al, 2004).…”