Risk of transmission of foot-and-mouth disease by wild animals: infection dynamics in Japanese wild boar following direct inoculation or contact exposure.

Understanding of disease dynamics and viral shedding in wild boar and of the potential for disease spreading within wild boar and domestic pig populations is critical for developing effective control and eradication measures for foot-and-mouth disease (FMD). Accordingly, we infected experimentally wild boar and domestic pigs with FMD virus (FMDV) strains O/TAI/315/2016 and A/MOG/2013, and studied their susceptibility and viral transmissibility in both populations. Similar to FMDV-infected pigs, wild boar inoculated with both viruses exhibited vesicular lesions on their feet, snout, tongue and lip, although they did not show lameness. Further, inoculated wild boar were equally capable of transmitting the virus to all of their contact animals. While all contact pigs developed vesicular lesions after contact with inoculated animals, in contrast, no wild boar when exposed to the same infected animals showed obvious clinical signs. These results will be useful for further understanding of the critical roles in occurring and sustaining an FMD outbreak, and will be useful for establishing epidemiological surveillance programs and effective countermeasures for wild boar.

Seroepidemiology of Foot and Mouth Disease using passive surveillance techniques in selected provinces of Lao PDR.

Foot and Mouth Disease (FMD) is a high-impact, contagious transboundary animal disease that is endemic in Southeast Asia. Abattoir samples were routinely collected in six selected provinces between March and December 2019. A total of 1280 samples of abattoir animals were tested for FMD Non-Structural Protein (NSP) antibodies to indicate natural infections. Overall, 22.8% were seropositive for FMD NSP antibodies while seroprevalence of cattle (n = 469), buffalo (n = 214), and pigs (n = 597) were 44.6%, 35.0%, and 1.3%, respectively. The highest seroprevalence destination province was Xiengkhouang (35.3% of 272 samples), followed by Savannakhet (27.0% of 244 samples). Risk factors for evidence of natural infection identified by a multivariate logistic regression model included age groups (p-value = 0.02) and origin provinces (p-value = 2.8 × 10-5) of the animals. There were significant differences of FMD NSP seroprevalence between age groups and origin provinces of the animals. The odds ratio of a seropositive result in the less than 1 year old group was 2.5 (95% CI; 1.4, 4.4) when compared to the 3-4 years old group, while the odds ratios for animals that originated from Khammouane and Xiengkhouang provinces were 4.5 (95% CI; 1.1, 18.7) and 2.4 (95% CI; 1.4, 4.1), respectively, when compared to Champasak province. Serotype-specific antibody ELISA for 44 NSP antibody-positive samples revealed evidence of FMD serotypes O and A virus circulation in some provinces. Despite the passive abattoir survey providing useful information on FMD virus previous exposure and geographic locations of the animals, timely information on FMD virus circulation and distribution is also crucial to an effective control program. Alternative approaches to increase the cost-effectiveness of the surveillance network are also discussed.

Evaluation and comparison of performances of six commercial NSP ELISA assays for foot and mouth disease virus in Thailand.

ELISA kits that detect antibodies to the non-structural protein (NSP) of the foot-and-mouth disease virus (FMDV), commonly referred to as NSP-ELISA, can distinguish between vaccinated and naturally infected animals. They can play an essential role in demonstrating 'proof-of-freedom' during the control of FMD. Although various NSP-ELISA kits are available in Thailand, information regarding their performance is lacking. To select the most appropriate NSP-ELISA kit for our specific purpose, we must compare their performance using carefully characterized sera. This will ensure that we maximize the benefits of our testing. In this study, six NSP-ELISA kits sold in Thailand-Biovet, ID Screen, VDPro, IDEXX, PrioCHECK, and KUcheck-F-were evaluated and compared. A total of 800 serum samples were examined, including samples from 357 cattle and 29 buffaloes in outbreak areas, as well as 14 swine serum samples from the Vaccine Quality Control Unit of the Bureau of Veterinary Biologics, Ministry of Agriculture and Cooperation, Thailand. Four hundred samples were confirmed to originate from animals infected with FMDV through ELISA typing (n = 11, tested as representative samples in each farm) and/or RT-PCR (n = 400, all samples), serving as positive control sera. Additionally, 400 negative control sera were obtained from Japan (97 cattle and 300 pigs) and Australia (3 goats), certified by the World Organisation for Animal Health as 'free of FMD'. The sensitivity and specificity of the six tests were determined based on the results obtained from two-by-two tables. Cohen's kappa statistics were calculated for the six tests to assess their concordance, and the diagnostic accuracy of the assays was also determined. For all six NSP-ELISA kits, the sensitivity ranged from 97.75 to 99.50%, and the specificity ranged from 97.25 to 100%. Cohen's kappa statistics ranged from 0.96 to 1.00, and diagnostic accuracy ranged from 98.13 to 99.75%. The study results indicated that the test kits have statistically similar sensitivity, specificity, concordance, and diagnostic accuracy, suggesting they can be used interchangeably. However, ID Screen demonstrated the highest sensitivity and specificity among all kits tested. Therefore, if a single kit were to be selected from the six evaluated, ID Screen would be the most appropriate choice. These findings can aid in selecting the most suitable test kit. Therefore, it is recommended to consider purchasing a diverse range of effective test kits. Furthermore, these findings can provide guidance for expanding the use of test kits, particularly with the growing availability of NSP-ELISA kits in the market.

Near-Complete Genome Sequences of Three Foot-and-Mouth Disease Virus O/ME-SA/Ind-2001e Isolates Obtained from Cattle and Pigs in Thailand in 2016.

Here, we report near-complete genome sequences of three foot-and-mouth disease viruses isolated in 2016 from bovine and porcine epithelial tissue samples collected in Nonthaburi, Songkhla, and Ratchaburi provinces, Thailand. These viruses were classified as serotype O, topotype ME-SA, and sublineage Ind-2001e.

Development of a real-time RT-PCR system applicable for rapid and pen-side diagnosis of foot-and-mouth disease using a portable device, PicoGene® PCR1100.

Foot-and-mouth disease (FMD) is a highly contagious viral vesicular disease, causing devastating losses to the livestock industry. A diagnostic method that enables quick decisions is required to control the disease, especially in FMD-free countries. Although conventional real-time reverse transcription polymerase chain reaction (RT-PCR) is a highly sensitive method widely used for the diagnosis of FMD, a time lag caused by the transport of samples to a laboratory may allow the spread of FMD. Here, we evaluated a real-time RT-PCR system using a portable PicoGene PCR1100 device for FMD diagnosis. This system could detect the synthetic FMD viral RNA within 20 min with high sensitivity compared to a conventional real-time RT-PCR. Furthermore, the Lysis Buffer S for crude nucleic extraction improved the viral RNA detection of this system in a homogenate of vesicular epithelium samples collected from FMD virus-infected animals. Furthermore, this system could detect the viral RNA in crude extracts prepared using the Lysis Buffer S from the vesicular epithelium samples homogenized using a Finger Masher tube, which allows easy homogenization without any equipment, with a high correlation compared to the standard method. Thus, the PicoGene device system can be utilized for the rapid and pen-side diagnosis of FMD.

Evolution of antigenic and genetic characteristics of foot-and-mouth disease virus serotype A circulating in Thailand, 2007-2019.

Foot-and-mouth disease (FMD) is a persistent, major economic concern for livestock productivity, which is highly exacerbated by outbreaks in Thailand. FMD virus (FMDV) serotype A is more highly antigenic and genetically diverse than other serotypes, which has important implications for vaccine development as well as selection. Therefore, it is essential to continuously monitor antigenic and genetic changes of field isolates of FMDV serotype A. Here we used antisera against three vaccine strains (A/118/87, A/Sakolnakorn/97, and A/Lopburi/2012) to analyze the antigenicity of 133 field isolates of FMDV serotypes A in Thailand from 2007 to 2019. The majority of the isolates from 2007 to 2008 reacted only with the antiserum against strain A/118/87. In contrast, antigenic analysis revealed broad cross-reactivity and antigenic variations of the isolates from 2009 through 2019 against strains A/Sakolnakorn/97 and A/Lopburi/2012. These results indicate periodic changes in the antigenicity of field isolates of FMDV serotype A. Phylogenetic analysis of the VP1 region revealed that all isolates were of the Sea-97 lineage within the ASIA topotype. Analysis of the L-fragment genome sequences of 30 FMDV isolates collected throughout Thailand revealed highly variable amino acid sequences of VP1 and 3A, with the lowest average identity (94.56 %) and invariant (78.43 %) rates, respectively. The present findings indicate the importance of an active routine surveillance system incorporating antigenic and genetic analysis designated to continually update information about field isolates of FMDV serotype A. Such a system is essential for establishing and improving measures to control FMDV infections in Thailand and in neighboring Asian countries.

Reconstructing the evolutionary history of pandemic foot-and-mouth disease viruses: the impact of recombination within the emerging O/ME-SA/Ind-2001 lineage.

Foot-and-mouth disease (FMD) is a highly contagious disease of livestock affecting animal production and trade throughout Asia and Africa. Understanding FMD virus (FMDV) global movements and evolution can help to reconstruct the disease spread between endemic regions and predict the risks of incursion into FMD-free countries. Global expansion of a single FMDV lineage is rare but can result in severe economic consequences. Using extensive sequence data we have reconstructed the global space-time transmission history of the O/ME-SA/Ind-2001 lineage (which normally circulates in the Indian sub-continent) providing evidence of at least 15 independent escapes during 2013-2017 that have led to outbreaks in North Africa, the Middle East, Southeast Asia, the Far East and the FMD-free islands of Mauritius. We demonstrated that sequence heterogeneity of this emerging FMDV lineage is accommodated within two co-evolving divergent sublineages and that recombination by exchange of capsid-coding sequences can impact upon the reconstructed evolutionary histories. Thus, we recommend that only sequences encoding the outer capsid proteins should be used for broad-scale phylogeographical reconstruction. These data emphasise the importance of the Indian subcontinent as a source of FMDV that can spread across large distances and illustrates the impact of FMDV genome recombination on FMDV molecular epidemiology.