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Ho Chi Minh City, Vietnam

Wilna V.,CSIRO | Hong N.T.T.,National Veterinary Company | Geoffrey F.T.,University of Pretoria | Jacqueline M.M.,CSIRO | And 12 more authors.

Early protection with a high potency (>6PD50) foot-and-mouth disease (FMD) O1 Manisa (Middle-East South Asia lineage) vaccine against challenge with O/VIT/2010 (O Mya98 lineage) was tested in pigs. Only two pigs that were vaccinated seven days prior to challenge had any demonstrable antibodies as a result of vaccination at the time of challenge. However, 80% and 60% of pigs that were vaccinated seven and four days prior to coronary band challenge were protected. Vaccination significantly reduced the amount of virus excreted in nasal swabs, saliva and faeces compared to unvaccinated and infected controls. Virus and viral RNA could be detected in some pigs until termination of the experiment 14 days after challenge. Antibodies to the non-structural proteins (NSP) were detected in only one pig that was challenged four days post vaccination (dpv) and transiently in two pigs that were challenged sevendpv at only one time point. For each vaccine and control group, a group of unvaccinated pigs were kept in the same room but with no direct contact with the infected pigs to determine whether vaccination prevented transmission. Despite the presence of live virus and viral RNA in these indirect contact pigs, the groups in contact with the vaccinated and infected pigs did not develop clinical signs nor did they sero-convert. Contact pigs in the same room as unvaccinated challenged controls did show signs of disease and virus infection that resulted in sero-conversion to the NSP. A breach of the wall that separated the two groups at nine days post challenge might have contributed to this finding. This study showed that high potency vaccine can provide protection to pigs soon after vaccination and that aerosol transmission within rooms is a rare event. © 2015 The Authors. Source

Nagendrakumar S.B.,CSIRO | Hong N.T.T.,National Veterinary Company | Geoffrey F.T.,University of Pretoria | Jacqueline M.M.,CSIRO | And 12 more authors.

Pigs play a significant role during outbreaks of foot-and-mouth disease (FMD) due to their ability to amplify the virus. It is therefore essential to determine what role vaccination could play to prevent clinical disease and lower virus excretion into the environment. In this study we investigated the efficacy of the double oil emulsion A Malaysia 97 vaccine (>6PD50/dose) against heterologous challenge with an isolate belonging to the A SEA-97 lineage at 4 and 7 days post vaccination (dpv). In addition, we determined whether physical separation of pigs in the same room could prevent virus transmission. Statistically there was no difference in the level of protection offered by 4 and 7 dpv. However, no clinical disease or viral RNA was detected in the blood of pigs challenged 4 dpv, although three of the pigs had antibodies to the non-structural proteins (NSPs), indicating viral replication. Viral RNA was also detected in nasal and saliva swabs, but on very few occasions. Two of the pigs vaccinated seven days prior to challenge had vesicles distal from the injection site, but on the inoculated foot, and two pigs had viral RNA detected in the blood. One pig sero-converted to the NSPs. In contrast, all unvaccinated and inoculated pigs had evidence of infection. No infection occurred in any of the susceptible pigs in the same room, but separated from the infected pigs, indicating that strict biosecurity measures were sufficient under these experimental conditions to prevent virus transmission. However, viral RNA was detected in the nasal swabs of one group of pigs, but apparently not at sufficient levels to cause clinical disease. Vaccination led to a significant decrease in viral RNA in vaccinated pigs compared to unvaccinated and infected pigs, even with this heterologous challenge, and could therefore be considered as a control option during outbreaks. © 2015 The Authors. Source

Vosloo W.,CSIRO | Morris J.,CSIRO | Davis A.,CSIRO | Giles M.,CSIRO | And 15 more authors.
Transboundary and Emerging Diseases

In high-density farming practices, it is important to constantly monitor for infectious diseases, especially diseases that have the potential to spread rapidly between holdings. Pigs are known to amplify foot-and-mouth disease (FMD) by excreting large amounts of virus, and it is therefore important to detect the virus quickly and accurately to minimize the spread of disease. Ropes were used to collect oral fluid samples from pigs, and each sample was compared to saliva samples collected from individual animals by detecting FMD virus RNA using real-time PCR. Two different experiments are described where groups of pigs were infected with different serotypes of FMD virus, either with or without vaccination, and unvaccinated pigs were kept in aerosol contact. The sensitivity of the rope sampling varied between 0.67 and 0.92, and the statistical agreement between this method and individual sampling ranged from substantial to moderate for the two different serotypes. The ease of collecting oral fluids using ropes together with the high sensitivity of subsequent FMD detection through PCR indicates that this could be a useful method to monitor pig populations for FMD virus infection. With further validation of the sensitivity of detection of FMD virus RNA, this can be a cost-effective, non-invasive diagnostic tool. © 2013 Blackwell Verlag GmbH. Source

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