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Infection dynamics of foot-and-mouth disease virus in pigs using two novel simulated-natural inoculation methods

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In order to characterize foot-and-mouth disease virus (FMDV) dynamics in pigs, two simulated-natural inoculation systems were developed and evaluated using two different strains of FMDV (O1-Manisa and A24-Cruzeiro) at varying doses. Direct intra-oropharyngeal (IOP) and intra-nasopharyngeal (INP) inoculation both enabled precise control of dose and timing of inoculation while emulating field exposure conditions. There were substantial differences in the outcomes of the two inoculation routes. IOP inoculation resulted in consistent and synchronous infection, for both virus strains investigated, with viral RNA detectable in serum and swabs from 24- 48 hours post infection (hpi) and clinical lesions appearing at 48-72 hpi. INP inoculation of FMDV O1 Manisa at low or medium doses resulted in delayed, or completely absent clinical infection, whereas high dose inoculation with this virus caused fulminant FMD. Dose-dependence was less marked amongst pigs inoculated with FMDV A24 Cruzeiro in that all pigs developed clinical FMD, although with a delayed onset following INP inoculation. All pigs that developed clinical infection (regardless of inoculation route) had detectable levels of FMDV RNA in their oropharynx directly following inoculation. Furthermore, FMDV antigens were localized by immunomicroscopy to the oropharyngeal tonsils suggesting a role in early infection of pigs. The utility of the IOP inoculation system was further demonstrated through comparison to intradermal heel bulb inoculation in a vaccine-challenge experiment. Thus, the novel system of IOP inoculation described herein, offers a valid alternative to traditionally used systems for FMDV inoculation of pigs, applicable for experimental studies of FMDV pathogenesis and vaccinology.
C. Stenfeldt , J. M. Pacheco , L. L. Rodriguez , J. Arzt
USDA Scientist Submission
Research in veterinary science 2014 Apr. v.96 no.2
Elsevier Ltd
Journal Articles, USDA Authors, Peer-Reviewed
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