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Veterinary microbiology2013; 166(1-2); 22-34; doi: 10.1016/j.vetmic.2013.04.027

Duration of equine influenza virus shedding and infectivity in immunised horses after experimental infection with EIV A/eq2/Richmond/1/07.

Abstract: Equine influenza (EI) is a major respiratory disease of horses. Recent outbreaks of EI have demonstrated the ease with which EI virus (EIV) can be transmitted internationally. This study aimed to improve our understanding of EIV shedding after infection of vaccinated horses, which would inform possible changes to current quarantine requirements. Our objectives were to compare commonly used diagnostic tests and to evaluate the relative merits of nasal and nasopharyngeal swabs for detection of EIV in vaccinated and unvaccinated ponies following EIV infection and to use these data to inform optimal quarantine procedures for the safe international movement of horses. Five ponies vaccinated against EI were infected experimentally with A/eq/Richmond/1/07 (Florida clade 2), 11 weeks after V2. Nasal and nasopharyngeal swabs were taken daily for 14 days and every 2 days for another 2 weeks. The 5 vaccinates were introduced sequentially for 48h to 3 groups of 2 naïve sentinel ponies each on days 2, 4 and 6 post-challenge respectively. Clinical signs of disease and EIV shedding were monitored for 14 days after co-mingling. EIV was detected by 3 different methods of detection (EIV nucleoprotein ELISA, EIV nucleoprotein qRT-PCR and isolation/titration in embryonated hens' eggs). Directigen™ EZ Flu A+B tests were also performed on samples from the vaccinated ponies for 6 days after infection. Results show that nasopharyngeal swabs were superior to nasal swabs, with increased frequency and amount of virus detected. The average mean duration of shedding was 6-8 days in naïve animals. All 3 sentinel groups were infected successfully with EIV after commingling with vaccinates, indicating up to 6 days of transmission. EI protection induced by vaccination is a dynamic process, naturally fluctuating and dependent on the time since last immunisation, with periods of high immunity (peak of immunity shortly after boost immunisation) and periods of susceptibility to EIV infection. This result indicates that vaccinated horses may actively transmit EIV if the immunity gap (a usual period of susceptibility between V2 and V3) is not adequately closed by immunisation. In infected sentinels EIV was detectable up to 12 days after commingling. Results also suggest that tests such as qRT-PCR may be a suitable substitute for time spent in pre-export quarantine.
Copyright © 2013 Elsevier B.V. All rights reserved.
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Publication Date: 2013-05-09 PubMed ID: 23769636DOI: 10.1016/j.vetmic.2013.04.027Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research study explores the duration of Equine Influenza Virus (EIV) shedding and infectivity in immunized horses. Findings suggest that nasopharyngeal swabs are more effective than nasal swabs for detecting EIV in horses, with an average shedding duration of 6-8 days in naïve animals. The results could potentially inform changes to quarantine requirements for horses.

Analysis of Diagnostic Tests

  • The study compares common diagnostic tests for EIV in horses, namely EIV nucleoprotein ELISA, EIV nucleoprotein qRT-PCR, isolation/titration in embryonated hens’ eggs, and Directigen™ EZ Flu A+B tests.
  • Results indicate that nasopharyngeal swabs are superior to nasal swabs, catching the virus more frequently and in larger amounts, thus providing a more comprehensive profile of the virus in the horse’s system.

Duration of Virus Shedding

  • The average duration of virus shedding was found to be between 6 to 8 days in unvaccinated animals.
  • In infected “sentinel” animals that were deliberately exposed to the virus, EIV was detectable up to 12 days after mingling with infected horses.

    • Implications on Horse Quarantine Procedures

    • The research findings potentially provide insights into how quarantine procedures could be improved for international horse transport.
    • Tests like qRT-PCR, which was found reliable in detecting EIV, could potentially be considered as an alternative to pre-export quarantine, saving both time and resources.

    Effectiveness of Horse Vaccinations

    • The study also provides some insights into the effectiveness of horse vaccinations and the impact on EIV transmission.
    • Vaccinated horses were observed to actively transmit the virus if the immunity gap, or the period of susceptibility between two vaccinations, was inadequately closed by immunization.
    • This highlights the importance of closely adhering to the horse’s vaccination schedule, thus giving the horse’s immune system the best chance of successfully dealing with exposure to EIV.

Cite This Article

APA
Paillot R, Prowse L, Montesso F, Stewart B, Jordon L, Newton JR, Gilkerson JR. (2013). Duration of equine influenza virus shedding and infectivity in immunised horses after experimental infection with EIV A/eq2/Richmond/1/07. Vet Microbiol, 166(1-2), 22-34. https://doi.org/10.1016/j.vetmic.2013.04.027

Publication

Veterinary microbiology
ISSN: 1873-2542
NlmUniqueID: 7705469
Country: Netherlands
Language: English
Volume: 166
Issue: 1-2
Pages: 22-34

Researcher Affiliations

Paillot, R
  • Animal Health Trust, Centre for Preventive Medicine, Lanwades Park, Newmarket, Suffolk CB8 7UU, UK. romain.paillot@aht.org.uk
Prowse, L
    Montesso, F
      Stewart, B
        Jordon, L
          Newton, J R
            Gilkerson, J R

              MeSH Terms

              • Animals
              • Antibodies, Viral / immunology
              • Australia / epidemiology
              • Disease Outbreaks / veterinary
              • Horse Diseases / epidemiology
              • Horse Diseases / immunology
              • Horse Diseases / prevention & control
              • Horse Diseases / virology
              • Horses
              • Influenza A virus / genetics
              • Influenza A virus / immunology
              • Influenza A virus / physiology
              • Orthomyxoviridae Infections / epidemiology
              • Orthomyxoviridae Infections / immunology
              • Orthomyxoviridae Infections / veterinary
              • Orthomyxoviridae Infections / virology
              • Vaccination / veterinary
              • Virus Shedding

              Citations

              This article has been cited 15 times.
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