ABSTRACT
The incidence of infectious bronchitis (IB) in chickens has increased in Russian Federation during 2020- 2021 despite the widespread vaccination of the susceptible poultry. The effectiveness of vaccinations against IB virus and Newcastle disease can be significantly affected by vesicular enteritis (runting stunting syndrome) accompanied by malabsorption. The study presented demonstrated that virally induced malabsorption in broilers is accompanied by the synchronous decreases in the concentrations of magnesium and zinc in blood serum. Evaluation of the effectiveness of vaccination by RT-PCR for the presence of IB viral RNA in the intestine at day 2 after the vaccination indicates a sharp decrease in the PCR prevalence in individuals with vesicular enteritis and allows for the exclusion of possible population-wide decrease in post-vaccination immunity. When considering biochemical parameters as markers of organopathologies the population-based approach to data analysis should be applied.