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Title: Foot-and-mouth disease virus during the incubation period in pigs

Author
item STENFELDT, CAROLINE - Oak Ridge Institute For Science And Education (ORISE)
item PACHECO, JUAN - Oak Ridge Institute For Science And Education (ORISE)
item BRITO, BARBARA - Oak Ridge Institute For Science And Education (ORISE)
item MORENO-TORRES, KARLA - Oak Ridge Institute For Science And Education (ORISE)
item BRANAN, MATT - Animal And Plant Health Inspection Service (APHIS)
item DELGADO, AMY - Animal And Plant Health Inspection Service (APHIS)
item Rodriguez, Luis
item Arzt, Jonathan

Submitted to: Frontiers in Veterinary Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/7/2016
Publication Date: 11/21/2016
Citation: Stenfeldt, C., Pacheco, J., Brito, B.P., Moreno-Torres, K.I., Branan, M.A., Delgado, A., Rodriguez, L.L., Arzt, J. 2016. Foot-and-mouth disease virus during the incubation period in pigs. Frontiers in Veterinary Science. 3:105. doi: 10.3389/fvets.2016.00105.

Interpretive Summary: In order to control a viral disease, it is important to understand if the virus can transmit between animals before the animals have developed any visible signs of clinical disease (the incubation phase). This study investigated the potential for foot-and-mouth disease virus (FMDV) to transmit between groups of pigs during the incubation phase of infection. Experiments were performed in which several groups of pigs were exposed to “virus donor pigs” during different stages of infection. The earliest transmission of FMDV from donor to contact pigs occurred approximately 24 hours before the donors had developed any signs of foot-and-mouth disease (FMD).The results from this study confirm that pigs can transmit FMDV during the incubation period of infection. These findings are important for designing FMD control strategies to protect US livestock industries.

Technical Abstract: Understanding the quantitative characteristics of a pathogen’s capability to transmit during distinct phases of infection is important to enable accurate predictions of the spread and impact of a disease outbreak. In the current investigation, the potential for transmission of foot-and-mouth disease virus (FMDV) during the incubation (preclinical) phase of infection was investigated in seven groups of pigs that were sequentially exposed to a group of donor pigs that were infected by simulated-natural inoculation. Contact-exposed pigs were co-mingled with infected donors through successive eight-hour time slots spanning from 8 to 64 hours post inoculation (hpi) of the donor pigs. The transition from latent to infectious periods in the donor pigs was clearly defined by successful transmission of foot-and-mouth disease (FMD) to all contact pigs that were exposed to the donors from 24 hpi and later. This onset of infectiousness occurred concurrent with detection of viremia, but approximately 24 hours prior to the first appearance of clinical signs of FMD in the donors. Thus, the latent period of infection ended approximately 24 hours earlier than the end of the incubation period. There were significant differences between contact-exposed groups in the time elapsed from virus exposure to the first detection of FMDV shedding, viremia and clinical lesions. Specifically, the onset and progression of clinical FMD was more rapid in pigs that had been exposed to the donor pigs during more advanced phases of disease, suggesting that these animals had received a higher effective challenge dose. The results from this study confirm the potential of transmission and dissemination of FMD within groups of pigs during the incubation period of infection. These findings may greatly impact modeling of the propagation of FMD outbreaks that initiate in pig holdings, and should be considered when designing FMD control strategies.