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

Abstract

Infectious coryza is an upper respiratory tract disease of chickens with the major impact occurring in multiage flocks. We investigated the relationship between the level of antibodies, as detected by a haemagglutination-inhibition (HI) assay, in infectious coryza-vaccinated chickens and the protection against challenge in those chickens. In one experiment, chickens given a single dose of either of two infectious coryza vaccines lacked a detectable HI response to vaccination but showed significant levels of protection 11 weeks after vaccination. In contrast, in chickens given two doses of an infectious coryza vaccine and challenged 3 weeks after the second vaccine dose, there was a strong serological response with 36/40 birds having a HI titre of 1/20 or greater. In this trial there was an apparent relationship between titre and subsequent protection, with none of the 32 chickens with a titre of 1/40 or 1/80 showing any clinical signs and only one of the same group yielding the challenge organism on culture. In contrast, three of the four vaccinated chickens with a HI titre less than 1/5 developed the typical clinical signs of coryza and yielded the challenge organism on culture. Overall, our results suggest that HI titres cannot be regarded as a definitive predictor of vaccine efficacy. We suggest that the vaccination-challenge trial is the gold standard for the evaluation of the immune response to infectious coryza vaccines.

Differential susceptibility and immune response in chicken and Japanese quail towards Avibacterium paragallinarum

“…paragallinarum in poultry indicated a significant induction of immune responses to the HA antigen (Iritani et al 1980;Kume et al 1980;Sawata et al 1980) that were correlated with protection in birds and correspondingly the host response against a particular antigenic epitope of Av. parallinarum has been largely utilized for the estimation of vaccine-mediated efficacy (Takagi et al 1991;Hsu et al 2007;Garcia et al 2008). In the present study, a similar immune-protection due to the presence of circulatory HI antibodies was noted in Japanese quail as evident by lack of clinical sign development.…”

An Update on Avian Infectious Coryza: It’s Re-Emerging Trends on Epidemiology, Etiologic Characterization, Diagnostics, Therapeutic and Prophylactic Advancements

“…15,16 It is further important to note that during course of such vaccine development and in other subsequent studies particularly, it was observed that single shot immunization of tetravalent vaccine does not yield appreciable immune response, but evoked good protection in host in terms of survivality/life expectancy and clinical sign development, while double shot immunization at 8 weeks apart yielded both relevant immune response and protection against the diseases, therefore questioned definitive predictor for vaccine efficacy in future. 49 Having such inconclusive insight on protective efficacy of several developed vaccines, some researcher considered certain factors as a hindrance to evaluate the vaccine efficacy and they are as infection dosage, individual differences of the host's (chicken) and choice of infection model, besides non-standardisation of pathogenicity effects on host which is otherwise markedly complicated. 50 Their studies also suggested that natural way of disease transmission phenomenon or simulated manner of disease transmission during experimentation could reflect valuable information on natural process of spreading, sticking and proliferation of germs among hosts (birds) and may evaluate the definite understanding to pathopoietic mechanism of Avibacterium paragallinarum to suggest variance seen in vaccine efficacy study.…”

Efficacy of tetravalent coryza vaccine against the challenge of Avibacterium paragallinarum serovars A and B isolates from Indonesia in chickens

“…Garcia et al . [20] demonstrated that over 90% of vaccinated chickens have titers more than 5 HI if the chickens receive more than one vaccination.…”

“…Research conducted by Garcia et al . [20] mentions that the challenge test is the gold standard to determine the immunological response in chickens that have been vaccinated with a double dose of A. paragallinarum . Based on the challenge test, both the severity of symptoms and pathological changes will be known.…”