Differential responses of Equus caballus and Equus asinus to infection with two pathogenic strains of equine infectious anemia virus

• Published in: Veterinary microbiology 2001-03, Vol.79 (2), p.93-109
• Main Authors: Cook, S.J., Cook, R.F., Montelaro, R.C., Issel, C.J.
• Format: Article
• Language: English
• Subjects: Animal viral diseases; Animals; Biological and medical sciences; Cells, Cultured; Donkeys; EIAV; Enzyme-Linked Immunosorbent Assay - veterinary; Epidemiology; Equidae; Equine Infectious Anemia - virology; Equine infectious anemia virus; Equus asinus; Equus caballus; Fundamental and applied biological sciences. Psychology; Horses; Infectious Anemia Virus, Equine - classification; Infectious Anemia Virus, Equine - pathogenicity; Infectious diseases; Medical sciences; Microbiology; Pathogenesis; Platelet Count - veterinary; Reverse Transcriptase Polymerase Chain Reaction - veterinary; RNA-Directed DNA Polymerase - metabolism; Viral diseases; Virology
• ISSN: 0378-1135; 1873-2542
• DOI: 10.1016/S0378-1135(00)00348-5

Most in vivo studies with equine infectious anemia virus (EIAV) have been performed in horses and ponies ( Equus caballus) with little published information available detailing the clinical responses of donkeys ( Equus asinus) to infection with this virus. Consequently, donkeys were inoculated with two strains of EIAV (EIAV PV and EIAV WY) which have been documented to produce disease in E. caballus. Four ponies, 561, 562, 564 and 567 and two donkeys, 3 and 5 were infected with EIAV PV and one horse (94-10) and one donkey (4) were infected with EIAV WY. Although the horse and ponies all experienced clinical signs of disease, which in some cases were severe, the donkeys remained asymptomatic throughout a 365-day observation period, except for mild transient reductions in platelet counts. The results from serological assays, virus isolation from plasma and detection of plasma-associated viral RNA by RT-PCR, indicated that initial replication of EIAV PV and EIAV WY was lower in donkeys than in horses and ponies. This conclusion was confirmed using competitive RT-PCR, in which viral RNA levels in the plasma of EIAV PV-infected ponies was up to 100,000-fold higher than in infected donkeys during the first 20 days post-infection (dpi). Similar results were obtained in the EIAV WY-infected animals, in which viral RNA burdens in the donkey at 20 dpi were 1000-fold less than in the horse. However, infection of donkey and horse monocyte-derived macrophage cultures with EIAV PV demonstrated that these cells in vitro were equally susceptible to virus-induced cytopathic effects and yielded similar levels of progeny virus. This result suggests that factors other than host cell permissiveness mediate the clinical differences observed between horses and donkeys infected with EIAV PV or EIAV WY.