Evolution of equine influenza virus between epizootics

Abstract

Abstract New field strains of equid influenza virus isolated in different countries belong to independent branches in the Florida lineage, clade 2 – European and Asian. Asian viral isolates were akin to American evolutionary ancestors. Recently, there were local outbreaks of the disease with atypical symptoms among livestock. The initial diagnosis often meant a non-infectious problem. Throughout the year, horses of several equestrian bases periodically had a respiratory disease, which was characterized by a chronic course and low fever. A similar pathology in horses is described as such a chronic obstructive pulmonary disease. Sometimes the clinical picture comprised diarrhea and urticaria. In our research, several H3N8 equid influenza viral strains were isolated from the sick horses. Phenetic method of evolutionary relationships revealed their short tree distance to the equid influenza virus “A/eq/China/Ulumuqi/2015 (H3N8)” (nucleotide identity 98.43%) and viruses isolated from horses and camels in 2011-2013 in the southern regions of Kazakhstan and Mongolia (nucleotide identity 98.17%). The results supplement the data obtained by other authors characterizing the evolution and expansion of the H3N8 equid influenza virus in different geographical areas. This may allow improving the tools of diagnosis and prevention of infection.