Editor's note: the following study was presented at the 2024 Western Poultry Disease Conference. 

Avian reovirus (ARV) is a non-enveloped double stranded RNA virus that causes disease in chickens leading to significant economic losses to the poultry industry. ARV infection in broilers can be characterized by malabsorption, runting-stunting syndrome, myocarditis, arthritis and tenosynovitis.

Due to its RNA nature and segmented genome, the virus is prone to mutations, reassortments and recombination’s that result in the emergence of ARV variants.

To date, many laboratories use phylogenetic strategies to classify these variants reporting different genotypes (from 1 to 7) and some even sub-genotypes, noted Bilal Abdul Rehman, DVM, PhD, University of California, Davis.

Applied vs theoretical research

Rodrigo Gallard, DVM, PhD, researcher at the University of California, Davis, presented a study he conducted along with colleagues at the University of California, Davis and the University of Maryland.

While science training encourages investigating basic mechanisms and gathering information to understand a particular problem, veterinary science is usually focused on the fast resolution of complex issues through applied research. This is fundamentally wrong and perpetuates pathology and losses in modern production systems.

In avian reovirus, the nature of its genome plus inadequate management practices stimulates virus evolution, increasing the generation of variants and complicating control and prevention.

While currently used typing methods help understand virus epidemiology (Sigma C typing) or just partially inform antigenicity through virus neutralization, the information these methods generate is poor and does not allow the design of new vaccines or the improvement of the currently used autogenous vaccines.

Avian reovirus case data and viral isolates have been collected since 2016. Viruses were typed using Sigma C sequences and phylogenetic trees constructed. Autogenous vaccine actualization was periodical using the surveillance information generated.

Due to the inaccuracy and complexity of keeping a successful antigenic typing system, several plaque purified viruses were studied, looking for antigenic determinants through full genome sequencing and data analysis and through serum neutralization and antigenic mapping.

While some success was noticed when vaccines were periodically serviced, no effect on reduction of the virus variability was noticed. In addition, four main genes were associated with increased avian reovirus variability.

Finally, antigenic cartography demonstrated the potential to be added to current methods for virus selection in autogenous vaccine production.