Investigation into the protective ability of monovalent and bivalent A Malaysia 97 and A22 Iraq 64 vaccine strains against infection with an A/Asia/SEA-97 variant in pigs.

Over the last 15 years, FMDV serotype A viruses in South-East Asia (A/ASIA/SEA-97 lineage) have diverged into several clusters. Variants from Thailand in 2011-2013 have caused vaccine failures and returned poor r1-values (<0.30) to A22 Iraq 64 (A22) and A Malaysia 97 (A May) vaccine strains. We investigated the protective ability of monovalent and bivalent A Malaysia 97 and A22 Iraq 64 vaccine strains against infection with an A/Asia/SEA-97 variant in pigs. Pigs were challenged with a variant of A/Asia/SEA-97 lineage either 21- or 7- days post-vaccination (V21 or V7) using the heal-bulb challenge. Only one in five pigs were protected in the V21 monovalent vaccine groups. Less severe clinical signs were observed in the A22 IRQ group compared to the A MAY 97 group. In the V21 combination group, 4 out of 5 pigs were protected and viraemia was significantly reduced compared to the monovalent V21 groups. V7 vaccine groups were not protected. The neutralising antibody response was below the detection limit in all groups on the challenge day, showing a poor correlation with protection. There was no evidence that the pigs protected from systemic disease had protective antibody responses sooner than other pigs in the study, implying other immune mechanisms might play a role in protecting these animals. FMDV was detected in the nasal and oral swab samples between 1 and 6 dpc. Viral loads were lower in the nasal swab samples from the V21 combination group than the other groups, but there was no difference in the oral swab samples. Since all unvaccinated controls were euthanised by 6-day post-challenge for ethical reasons, the 'area under the curve (AUC)' method was used to compare the viraemia and virus excretion in different groups. We recommend that for the A/Asia/SEA97 variants, a combination vaccine with A Malaysia 97 and A22 Iraq 64 vaccine strains would be ideal compared to monovalent vaccines.

Experimental Infection of Foot and Mouth Disease in Indian Sheep and Goats.

Foot-and-mouth disease (FMD) is an economically important contagious disease of livestock mainly cattle, buffalo, sheep, goats, and pig. There is limited data available on pathogenesis of foot and mouth disease in goats. In the study, the sheep and goats were infected experimentally with a serotype O foot-and-mouth disease virus by different challenge routes. The sheep and goats challenged by coronary band route and coronary band and intra-dermo-lingual route exhibited FMD clinical signs at 2-5 days post challenge. Whereas intra-dermo-lingual challenged sheep and goats did not exhibit FMD clinical signs. Live virus could be isolated from blood of infected sheep and goats at 2-5 days post challenge. Viral RNA could be detected from blood of infected sheep and goats at 1-10 days post challenge. The neutralizing antibody titre was detected at 10 days post challenge and maintained up to 35 days post challenge in all infected sheep and goats. Non structural protein (NSP) antibodies were detected as early as 5-10 days post challenge and remain positive up to 35 days post challenge in the infected sheep and goats. In conclusion, the pathogenesis of sheep and goats with serotype O foot and mouth disease virus by different challenge routes could be demonstrated.

Further development of a reverse-transcription loop-mediated isothermal amplification (RT-LAMP) assay for the detection of foot-and-mouth disease virus and validation in the field with use of an internal positive control.

Foot-and-mouth disease (FMD) is a highly contagious viral disease of cloven-hooved animals. Global outbreaks have highlighted the significant economic, trade, psychosocial and animal welfare impacts that can arise from the detection of disease in previously 'FMD-free' countries. Rapid and early diagnosis provides significant advantages in disease control and minimization of deleterious consequences. We describe the process of further development and validation of a reverse-transcription loop-mediated isothermal amplification foot-and-mouth disease virus (RT-LAMP-FMDV) test, using a published LAMP primer set, for use in the field. An internal positive control (IPC) was designed and introduced for use with the assay to mitigate any intrinsic interference from the unextracted field samples and avoid false negatives. Further modifications were included to improve the speed and operability of the test, for use by non-laboratory trained staff operating under field conditions, with shelf-stable reaction kits which require a minimum of liquid handling skills. Comparison of the assay performance with an established laboratory-based real-time reverse transcriptase PCR (rRT-PCR) test targeting the 3D region of FMD virus (Tetracore Inc) was investigated. LAMP has the potential to complement current laboratory diagnostics, such as rRT-PCR, as a preliminary tool in the investigation of FMD. We describe a strategic approach to validation of the test for use in the field using extracted RNA samples of various serotypes from Thailand and then finally unextracted field samples collected from FMD-suspected animals (primarily oral lesion swabs) from Bhutan and Australia. The statistical approach to validation was performed by Frequentist and Bayesian latent class methods, which both confirmed this new RT-LAMP-FMDV test as fit-for-purpose as a herd diagnostic tool with diagnostic specificity >99% and sensitivity 79% (95% Bayesian credible interval: 65, 90%) on unextracted field samples (oral swabs).