Transmission of foot-and-mouth disease from persistently infected carrier cattle to naive cattle via transfer of oropharyngeal fluid

Authors: Arzt, Jonathan; BELSHAM, GRAHAM - Technical University Of Denmark; LOHSE, LOUISE - Technical University Of Denmark; BOTNER, ANETTE - Technical University Of Denmark; STENFELDT, CAROLINA - University Of Minnesota

Submitted to: mSphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/15/2018
Publication Date: 9/12/2018
Citation: Arzt, J., Belsham, G.J., Lohse, L., Botner, A., Stenfeldt, C. 2018. Transmission of foot-and-mouth disease from persistently infected carrier cattle to naive cattle via transfer of oropharyngeal fluid. mSphere. 3(5):e00365-18. https://doi.org/10.1128/mSphere.00365-18.
DOI: https://doi.org/10.1128/mSphere.00365-18

Interpretive Summary: Foot-and-mouth disease (FMD) is a highly contagious viral disease which affects livestock including pigs and cattle. FMD is difficult to control as some infected animals may carry infectious virus in their respiratory tracts, without showing any disease symptoms. This phenomenon is known as the FMD virus (FMDV) carrier state. However, it is not known if these carrier animals can transmit FMDV to other animals and thereby start a disease outbreak. In the current investigation, one group of cattle were infected with FMDV and monitored for four weeks. At the end of the study period, samples of fluid from the upper respiratory tract (oropharyngeal fluid; OPF) were collected from animals that were carriers of FMDV. This fluid was then deposited within the upper respiratory tract of a group of naïve cattle, which developed characteristic signs of FMD within one week. Interestingly, pigs that were inoculated using the same oropharyngeal fluid, or that were fed tissues obtained from the infected FMDV carriers, did not become sick. The findings from this study demonstrate that biological materials obtained from FMDV carriers under certain conditions transmit disease to susceptible animals. This knowledge is an important contribution to development of FMD control strategies to protect US livestock from disease.

Technical Abstract: Control and eradication of foot-and-mouth disease (FMD) is impeded by the existence of a persistent, subclinical, phase of infection in ruminants; animals with this status are referred to as carriers. However, the epidemiological significance of these FMD virus (FMDV) carriers is uncertain. In the current investigation, the contagion associated with FMDV carrier cattle was investigated by exposure of susceptible cattle and pigs to oropharyngeal fluid (OPF) or tissues harvested from persistently infected cattle. Naïve cattle were inoculated through intra-nasopharyngeal deposition of unprocessed OPF that had been collected from FMDV carriers at 30 days post infection. These inoculated cattle developed clinical FMD of similar severity as animals that had been infected with a high-titer inoculum. In contrast, pigs exposed via intra-oropharyngeal inoculation of the same OPF, or by ingestion of nasopharyngeal tissues harvested from the same cohort of persistently infected cattle, did not develop FMD. These findings indicate that there is demonstrable contagion associated with FMDV carrier cattle despite the lack of evidence for transmission by direct contact. The findings presented herein provide novel information that should be considered for FMD risk mitigation strategies.