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Open Access Research

A replication analysis of foot-and-mouth disease virus in swine lymphoid tissue might indicate a putative carrier stage in pigs

Teresa Rodríguez-Calvo1, Fayna Díaz-San Segundo12, Marta Sanz-Ramos3 and Noemí Sevilla1*

  • * Corresponding author: Noemí Sevilla sevilla@inia.es

  • † Equal contributors

Author Affiliations

1 Centro de Investigación en Sanidad Animal, (CISA-INIA), Ctra. Algete-El Casar s/n, 28130 Valdeolmos, Madrid, Spain

2 Plum Island Animal Disease Center, North Atlantic Area, Agricultural Research Service, U.S. Department of Agriculture, Greenport, New York, 11944, USA

3 Centro de Biología Molecular Severo Ochoa (CSIC-UAM) Cantoblanco, 28049 Madrid, Spain

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Veterinary Research 2011, 42:22  doi:10.1186/1297-9716-42-22

Published: 7 February 2011

Abstract

Foot-and-mouth disease virus (FMVD), one of the most contagious viruses of cloven-hoofed animals, may cause a prolonged, asymptomatic but persistent infection in ruminants, named the "carrier state". However, it remains an open question whether this carrier state occurs in pigs. Here we present quantitative analyses of the duration of FMDV RNA and infectivity in lymphoid and epithelial tissues in experimentally infected pigs with FMDV C-S8c1. The data indicated that although FMDV RNA remained in blood until day 14 post-infection (pi), viremia was cleared by day 7 pi. However, all tissues tested were positive for FMDV until day 14-17 pi. Interestingly, the specific infectivity of FMDV in these tissues was in some cases even higher than the FMDV C-S8c1. We therefore propose that a "pseudopersistent state" may occur in pigs in which virus replicates in lymphoid tissues for a prolonged period of time, thereby representing a potential source of virus.