Pathogenesis of and recovery from respiratory syncytial and influenza infections in ferrets

Summary

Manifestations of disease produced in ferrets by infection with respiratory syncytial (RS) and strains of influenza A, A₁, A₂ and B at high and low virus dose levels are compared. Inocula of 10⁵ FID₅₀ for influenza and 10^2.8 FID₅₀ for RS viruses were employed as high dosage levels. Virus replication in turbinates and subsequent antibody rise was detected following all infections. Increased nasal resistance to air flow is produced only by influenza A. Interferon in turbinates, increase in neutrophil/ lymphocyte ratios of blood WBC, and fever is detected in response to infection with influenza A, A₂ and B only. Increased erythrocyte sedimentation rate and nasal extrusion of systemically injected riboflavin is limited to influenza infections. Leukocytes in nasal wash increase with all infections, but change is minimal for RS. Infections with lower dose levels of influenza (10¹–10² FID₅₀) result in less virus production as well as delayed and reduced shifts from normal in the manifestations of disease which have been measured. The number and extent of measurable alterations observed generally diminish progressively from A to A₂ to B to A₁ to RS infection. Also, this study demonstrates that the measured manifestations of disease differ quantitatively not only with the strain of virus but the inoculum concentration used.