Disinfection to control African swine fever virus: a UK perspective

A review of African swine fever (ASF) was conducted, including manifestations of disease, its transmission and environmental persistence of ASF virus. Findings on infectious doses of contemporary highly-pathogenic strains isolated from outbreaks in Eastern Europe were included. Published data on disinfectant susceptibility of ASF virus were then compared with similar findings for selected other infectious agents, principally those used in the UK disinfectant approvals tests relating to relevant Disease Orders for the control of notifiable and zoonotic diseases of livestock. These are: swine vesicular disease virus, foot and mouth disease virus, Newcastle disease virus and Salmonella enterica serovar Enteritidis. The comparative data thus obtained, presented in a series of charts, facilitated estimates of efficacy against ASF virus for some UK approved disinfectants when applied at their respective General Orders concentrations. Substantial data gaps were encountered for several disinfectant agents or classes, including peracetic acid, quaternary ammonium compounds and products based on phenols and cresols.

Biological properties of swine vesicular disease virus strain 2348 Italy/2008

Swine vesicular disease (SVD) is a viral infectious disease, which, if acute, is manifested by the clinical pattern similar to a number of vesicular diseases including foot-and-mouth disease. In case of subclinical disease, there are no evident clinical signs, therefore the diagnosis is problematic, and there can be the risk of the disease introduction into the Russian Federation with the infected pigs. The key measure for the prevention of SVD introduction involves control diagnostic testing of all animals imported in the country that makes it necessary to keep updated the currently used methods and tools for the disease laboratory diagnosis. The paper demonstrates data on experimental infection of pigs with SVDV strain 2348 Italy/2008 that belongs to the most recent one of the four known phylogenetic groups. The virus was kindly provided by the World Reference Laboratory for Foot-and-Mouth Disease (Pirbright, Great Britain), and it was adapted to the monolayer continuous cell cultures of porcine origin (IB-RS-2 and PGSK-30). The pigs were intradermally infected with concentrated cultured virus at a dose of 109 TCID50. The infected animals demonstrated clinical signs typical for the acute disease. There was evidence that the virus was not transmitted to the intact animal in case husbandry conditions were met that allowed to avoid the infection transmission by the fecal-oral and contact mechanisms. As a result of the experiment, reference sera were collected at different time intervals post infection and their activity was determined using virus microneutralization test in cell culture and ELISA. Aphthae collected from the infected animals were deposited into the Strain collection of the Reference Laboratory for Foot-and-Mouth Disease, FGBI “ARRIAH”.

Diagnostic Performances of Different Genome Amplification Assays for the Detection of Swine Vesicular Disease Virus in Relation to Genomic Lineages That Circulated in Italy

During the last 25 years, swine vesicular disease (SVD) has occurred in Italy mostly sub-clinically. Therefore, regular testing of fecal samples from suspected holdings and high turnover premises was fundamental to identifying virus circulation and to achieve SVD eradication. In this study, we evaluated diagnostic performances of six genomic amplification methods, using positive fecal samples from 78 different outbreaks (1997–2014), which included different lineages. Comparison of three RT-PCRs, designed to amplify the same 154 nt portion of the gene 3D, demonstrated that a conventional and a real-time based on SYBR Green detection assay showed the highest diagnostic sensitivity, detecting all samples, while a real-time TaqMan-based test missed three cases, owing to two mismatches in the probe target sequence. Diagnostic and analytical specificities were optimal, as 300 negative field samples and other enteroviruses reacted negative. Three further evaluated tests, previously described, were a 3D-targeted reverse transcriptase loop-mediated isothermal amplification (RT-LAMP) and two real-time RT-PCRs targeted on the 5′UTR region. Here, the presence of multiple mismatches in probe and primers reduced the diagnostic performances, and two of the assays were unable to detect viruses from one sub-lineage. These results highlight that the choice of tests using less nucleotide targets significantly contributed to the success of the SVD eradication plan.

Development of a new RT-PCR with multiple primers for detecting Southern African Territories foot-and-mouth disease viruses

Introduction: The extremely high genetic variation and the continuously emerging variants of foot-and-mouth disease virus (FMDV) of Southern African Territory (SAT) serotypes including SAT1, SAT2, and SAT3 make it necessary to develop a new RT-PCR for general use for monitoring viruses based on the updated genome information. Material and Methods: A FMDV SAT-D8 one-step RT-PCR was established based on the 1D2A2B genes of the SAT serotype viruses with a multiplex primer set. FMDV A, O, C, and Asia 1 serotypes, other vesicular disease viruses, inactivated SAT viruses, and 125 bovine, ovine, caprine and porcine tissue samples collected from the Chinese mainland were included for evaluating the assay. Results: The new RT-PCR was proven to be specific without cross-reactions with Eurasian FMDV, swine vesicular disease virus (SVDV), Seneca valley virus (SVV), or other common viral pathogens of cattle, sheep, goat, and pig. An around 257 bp-sized amplicon clearly appeared when the inactivated SAT viruses were detected. However, all 125 samples collected from FMDV-susceptible animals from the Chinese mainland which has not known SAT epidemics showed negative results. Conclusions: A FMDV SAT-D8 one-step RT-PCR is a promising method for primary screening for FMDV SAT serotypes.