Inactivation of foot-and-mouth disease virus in epithelium samples for safe transport and processing in low-containment laboratories

Evaluation of long-term preservation methods for viral RNA in mosquitoes at room temperature

Mosquitoes are important vectors of various pathogenic viruses. Almost all viruses transmitted by mosquitoes are RNA viruses. Therefore, to detect viral genes, mosquito samples must be kept at low temperatures to prevent RNA degradation. However, prolonged transport from the field to laboratory can pose challenges for temperature control. The aim of this study was to evaluate methods for preserving viral RNA in mosquito bodies at room temperature. Virus-infected mosquito samples were immersed in ethanol, propylene glycol, and a commercially available nucleic acid preservation reagent at room temperature, and viral RNA stability was compared. As a result, for the two RNA viruses (San Gabriel mononegavirus and dengue virus 1) subjected to this experiment, no significant decrease in the viral RNA was observed for at least eight weeks after immersion in the reagents, and the amount of RNA remaining was equivalent to that of samples stored at - 80 °C. These results indicate that immersion storage in these reagents used in this study is effective in preserving viral RNA in mosquitoes under room temperature conditions and is expected to be implemented in epidemiologic surveillance that is not limited by the cold chain from the field to the laboratory.

Diagnostic application of formalin fixed archived tissues for detection of foot-and-mouth disease

Early and definitive disease diagnosis is critical for effective disease control. 50% buffered glycerine is commonly used viral transport medium, which is not always available and required cold chain. Tissues samples archived in 10% neutral buffered formalin (NBF) can preserve nucleic acid that can be used in molecular studies and disease diagnosis. The present study's goal was to detect the foot-and-mouth disease (FMD) viral genome in formalin-fixed archived tissue which may avoid cold chain during transportation. This study used FMD suspected samples preserved in 10% neutral buffered formalin from 0 to 730 days post fixation (DPF). All archived tissues were positive for FMD viral genome by multiplex RT-PCR and RT-qPCR up to 30 DPF, whereas archived epithelium tissues and thigh muscle were positive for FMD vial genome up to 120 DPF. FMD viral genome was detected in cardiac muscle up to 60 DPF and 120 DPF, respectively. The findings suggest that 10% neutral buffered formalin could be used for sample preservation and transportation for timely and accurate FMD diagnosis. More samples need to be tested before implementing the use of 10% neutral buffered formalin as a preservative and transportation medium. The technique may add value in ensuring biosafety measures for creation during disease free zone as well.

DNA/RNA Preservation in Glacial Snow and Ice Samples

The preservation of nucleic acids for high-throughput sequencing is an ongoing challenge for field scientists. In particular, samples that are low biomass, or that have to be collected and preserved in logistically challenging environments (such as remote sites or during long sampling campaigns) can pose exceptional difficulties. With this work, we compare and assess the effectiveness of three preservation methods for DNA and RNA extracted from microbial communities of glacial snow and ice samples. Snow and ice samples were melted and filtered upon collection in Iceland, and filters were preserved using: (i) liquid nitrogen flash freezing, (ii) storage in RNAlater, or (iii) storage in Zymo DNA/RNA Shield. Comparative statistics covering nucleic acid recovery, sequencing library preparation, genome assembly, and taxonomic diversity were used to determine best practices for the preservation of DNA and RNA samples from these environments. Our results reveal that microbial community composition based on DNA was comparable at the class level across preservation types. Based on extracted RNA, the taxonomic composition of the active community was primarily driven by the filtered sample volume (i.e., biomass content). In low biomass samples (where <200 ml of sample volume was filtered) the taxonomic and functional signatures trend toward the composition of the control samples, while in samples where a larger volume (more biomass) was filtered our data showed comparable results independent of preservation type. Based on all comparisons our data suggests that flash freezing of filters containing low biomass is the preferred method for preserving DNA and RNA (notwithstanding the difficulties of accessing liquid nitrogen in remote glacial field sites). Generally, RNAlater and Zymo DNA/RNA Shield solutions work comparably well, especially for DNA from high biomass samples, but Zymo DNA/RNA Shield is favored due to its higher yield of preserved RNA. Biomass quantity from snow and ice samples appears to be the most important factor in regards to the collection and preservation of samples from glacial environments.

Chemical inactivation of foot-and-mouth disease virus in bovine tongue epithelium for safe transport and downstream processing

Epithelial tissue or vesicular fluid from an unruptured or recently ruptured vesicle is the sample of choice for confirmatory laboratory diagnosis of foot-and-mouth disease (FMD). However, in 'FMD-free' countries the transport and downstream processing of such samples from potentially infected animals present a biosafety risk, particularly during heightened surveillance, potentially involving decentralised testing in laboratories without adequate biocontainment facilities. In such circumstances, rapid inactivation of virus, if present, prior to transport becomes a necessity, while still maintaining the integrity of diagnostic analytes. Tongue epithelium collected from cattle infected with FMD virus (FMDV) of serotype O (O/ALG/3/2014 - Lineage O/ME-SA/Ind-2001d) or A (A/IRN/22/2015 - Lineage A/ASIA/G-VII) was incubated in the PAXGene Tissue System Fixative (pH 4) and Stabiliser (pH 6.5) components respectively, in McIlvaine's citrate-phosphate buffer (pH 2.6) or in phosphate-buffered saline (PBS, pH 7.4) at room temperature for 2, 6, 24 or 48h. Following incubation, tissues were homogenised and tested by virus isolation and titration using LFBK_αVβ6 cells. The integrity of FMD viral RNA was assessed by RT-qPCR (3D^pol coding region), Sanger sequencing of the VP1 region and transfection of LFBK_αVβ6 cells to recover infectious virus. Viable virus could be recovered from samples incubated in PBS for at least 48hours. The PAXgene Tissue System Stabiliser component yielded variable results dependent on virus serotype, requiring at least 6hours of incubation to inactivate A/IRN/22/2015 in most samples, whereas the Fixative component required up to 2hours in some samples. McIlvaine's citrate-phosphate buffer rapidly inactivated both viruses within 2hours of incubation. There was no demonstrable degradation of FMD viral RNA resulting from incubation in any of the buffers for up to 48hours, as assessed by RT-qPCR, and 24hours by sequencing and transfection to recover infectious virus. McIlvaine's citrate-phosphate buffer (pH 2.6) is easy to prepare, inexpensive and inactivates serotype A and O FMDV in epithelial tissue within 2hours, while maintaining RNA integrity for downstream diagnostic processes and virus characterisation.

Non-discriminatory Exclusion Testing as a Tool for the Early Detection of Foot-and-Mouth Disease Incursions

Endemic circulation of foot-and-mouth disease (FMD) in Africa and Asia poses a continuous risk to countries in Europe, North America, and Oceania which are free from the disease. Introductions of the disease into a free region have dramatic economic impacts, especially if they are not detected at an early stage and controlled rapidly. However, farmers and veterinarians have an obvious disincentive to report clinical signs that are consistent with FMD, due to the severe consequences of raising an official suspicion, such as farm-level quarantine. One way that the risk of late detection can be mitigated is offering non-discriminatory exclusion testing schemes for differential diagnostics, wherein veterinarians can submit samples without the involvement of the competent authority and without sanctions or costs for the farmer. This review considers the benefits and limitations of this approach to improve the early detection of FMD in free countries and gives an overview of the FMD testing schemes currently in use in selected countries in Europe and the Americas as well as in Australia.

Detection of Foot-and-Mouth Disease Virus in Swine Meat Juice

Foot-and-mouth disease virus (FMDV) is a highly contagious agent that impacts livestock industries worldwide, leading to significant financial loss. Its impact can be avoided or minimized if the virus is detected early. FMDV detection relies on vesicular fluid, epithelial tags, swabs, serum, and other sample types from live animals. These samples might not always be available, necessitating the use of alternative sample types. Meat juice (MJ), collected after freeze-thaw cycles of skeletal muscle, is a potential sample type for FMDV detection, especially when meat is illegally imported. We have performed experiments to evaluate the suitability of MJ for FMDV detection. MJ was collected from pigs that were experimentally infected with FMDV. Ribonucleic acid (RNA) was extracted from MJ, sera, oral swabs, and lymph nodes from the same animals and tested for FMDV by real-time reverse transcription polymerase chain reaction (rRT-PCR). MJ was also tested for FMDV antigen by Lateral Flow Immunoassay (LFI). FMDV RNA was detected in MJ by rRT-PCR starting at one day post infection (DPI) and as late as 21 DPI. In contrast, FMDV RNA was detected in sera at 1–7 DPI. Antigen was also detected in MJ at 1–9 DPI by LFI. Live virus was not isolated directly from MJ, but was recovered from the viral genome by transfection into susceptible cells. The data show that MJ is a good sample type for FMDV detection.