EN
The purpose of the study was to compare two models of multiplication patterns of equine influenza virus H7N7 - subtype A1 and H3N8 — subtype A2, after inoculation into embryonated chicken eggs through the allantoic cavity and the yolk sack. The relationship between the presence of haemagglutinin activity in allanto-amniotic fluid and the presence of Ml protein in chorioallantoic membranes, vitteline membranes, and embryos body was determined. The distribution of equine influenza virus multiplication sites in embryonated chicken eggs has revealed different patterns for A1 and A2 viruses. Virus subtype A1 multiplied better after inoculation into the yolk sack than into the allantoic cavity. Virus subtype A2 multiplied equally well after inoculation into the allantoic cavity as well as after inoculation into the yolk sack. There were cases with negative haemagglutination titers of allanto-amniotic fluid of eggs inoculated into the yolk sack with both influenza virus subtypes, though the M1 protein was detected in the vitteline membranes. Thus, the negative haemagglutination titres of allanto-amniotic fluid cannot be treated as the only indicator of virus multiplication after inoculation into the yolk sack.