Full-Length Genomic RNA of Foot-and-Mouth Disease Virus Is Infectious for Cattle by Injection

Abstract

Safe sample transport is of great importance for infectious diseases diagnostics. Various treatments and buffers are used to inactivate pathogens in diagnostic samples. At the same time, adequate sample preservation, particularly of nucleic acids, is essential to allow an accurate laboratory diagnosis. For viruses with single-stranded RNA genomes of positive polarity, such as foot-and-mouth disease virus (FMDV), however, naked full-length viral RNA can itself be infectious. In order to assess the risk of infection from inactivated FMDV samples, two animal experiments were performed. In the first trial, six cattle were injected with FMDV RNA (isolate A22/IRQ/24/64) into the tongue epithelium. All animals developed clinical disease within two days and FMDV was reisolated from serum and saliva samples. In the second trial, another group of six cattle was exposed to FMDV RNA by instilling it on the tongue and spraying it into the nose. The animals were observed for 10 days after exposure. All animals remained clinically unremarkable and virus isolation as well as FMDV genome detection in serum and saliva were negative. No transfection reagent was used for any of the animal inoculations. In conclusion, cattle can be infected by injection with naked FMDV RNA, but not by non-invasive exposure to the RNA. Inactivated FMDV samples that contain full-length viral RNA carry only a negligible risk of infecting animals.

Field Evaluation of a Safe, Easy, and Low-Cost Protocol for Shipment of Samples from Suspected Cases of Foot-and-Mouth Disease to Diagnostic Laboratories

“…Finally, different kinds of alternative procedures have been previously described to preserve and inactivate suspected FMDV samples to simplify their submission to RL, such as the use of FTA cards [35,[54][55][56] or treatment of tissue samples with commercial buffers such as RNAlater [46], RNA Shield [44] or citrate-phosphate buffer [47]. LFDs have the advantage of allowing first-line diagnostic testing in the field, which can provide a first idea about a clinical FMD suspicion in less than 30 min.…”

“…In conclusion, the field inactivation protocol described in this study is a safe, fast, and inexpensive way to submit suspected samples of FMDV to RL. Recommendations for the application of this protocol were published in a joint opinion of the EuFMD Standing Technical Committee and the EuFMD Special Committee for Biorisk Management [54]. This will encourage the submission of loaded LFDs and thus promote an active surveillance of circulating FMDV strains for the rapid implementation of control measures.…”