Extent of reduction of foot-and-mouth disease virus RNA load in oesophageal-pharyngeal fluid after peak levels may be a critical determinant of virus persistence in infected cattle.
To investigate whether foot-and-mouth disease virus (FMDV) RNA loads in oesophageal-pharyngeal fluid (OP-fluid) in the early course of infection is related to the outcome of virus persistence, viral RNA in OP-fluid samples from cattle experimentally infected with FMDV type O was quantitatively analysed by using a quantitative real-time RT-PCR. Viral RNA was detected within 24 h post-infection (p.i.) in all infected animals. Rapid virus replication led to peak levels of viral RNA load by 30-53 h p.i., and then the load declined at various rates. In some animals (n=12, so-called non-carriers) viral RNA became undetectable between 7 and 18 days p.i. In contrast, in persistently infected animals (n=12, so-called carriers) viral RNA persisted in OP-fluid samples at detectable levels beyond 28 days p.i. Analysis of early viral decay/clearance and virus clearance half-life in OP-fluid samples showed that the extent of reduction of viral RNA in OP-fluid samples immediately following peak levels is a critical determinant of the outcome of FMDV persistence.
Zhang
Zhidong
Z
Institute for Animal Health, Ash Road, Pirbright, Woking, Surrey GU24 0NF, UK.
Murphy
Ciara
C
Institute for Animal Health, Ash Road, Pirbright, Woking, Surrey GU24 0NF, UK.
Quan
Melvyn
M
Institute for Animal Health, Ash Road, Pirbright, Woking, Surrey GU24 0NF, UK.
Knight
Jeanette
J
Institute for Animal Health, Ash Road, Pirbright, Woking, Surrey GU24 0NF, UK.
Alexandersen
Soren
S
Institute for Animal Health, Ash Road, Pirbright, Woking, Surrey GU24 0NF, UK.
D000818:Animals; D001826:Body Fluids / Q000821:virology; D002353:Carrier State / Q000175:diagnosis / Q000662:veterinary*; D002417:Cattle; D004947:Esophagus / Q000821:virology*; D005536:Foot-and-Mouth Disease / Q000175:diagnosis*; D029544:Foot-and-Mouth Disease Virus / Q000235:genetics / Q000302:isolation & purification; D010614:Pharynx / Q000821:virology*; D012367:RNA, Viral / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000662:veterinary; D007507:Therapeutic Irrigation / Q000662:veterinary; D019562:Viral Load
D012367:RNA, Viral