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BMC veterinary research2019; 15(1); 280; doi: 10.1186/s12917-019-2036-0

Epizootiological investigation of equine herpesvirus type 1 infection among Japanese racehorses before and after the replacement of an inactivated vaccine with a modified live vaccine.

Abstract: Equine herpesvirus type 1 (EHV-1) infection is a major cause of pyrexias in winter among Japanese racehorses. In 2014-2015, the Japan Racing Association (JRA) changed the EHV-1 vaccine from an inactivated vaccine to a live vaccine (both produced by Nisseiken). To evaluate the effect of changing the vaccines, the capacities of these vaccines to induce virus-neutralizing (VN) antibodies were compared, and an epizootiological investigation of EHV-1 was performed at the JRA Ritto Training Center during epizootic periods from 2010-2011 to 2016-2017. Results: Three-year-old horses that received the first dose of live vaccine showed higher geometric mean (GM) VN titers (205 and 220) than those that received inactivated vaccine (83, P < 0.05). The response rates after vaccination with the live vaccine (76 and 90%) were higher than that after vaccination with inactivated vaccine (42%, P < 0.05). Four-year-old horses from 2015 to 2017 that had received the live vaccine in the previous epizootic periods had higher GM titers (205 to 246) than those from 2011 to 2014, which had received the inactivated vaccine (139 to 164, P < 0.05). The estimated numbers of horses infected with EHV-1 or EHV-4, or both, in 2011-2012 (29 [95%CI: 21-37]) and 2013-2014 (37 [95%CI: 27-47]) were higher than those in the other periods (7 [95%CI: 2-12] to 16 [95%CI: 9-23]). Likewise, the seroconversion rates to EHV-1 in horses that stayed at the training center in 2011-2012 (66.0%) and 2013-2014 (52.0%) were higher than those in the other periods (12.0 to 28.6%). Conclusions: The live EHV-1 vaccine is highly immunogenic and provides greater VN antibody responses than the inactivated vaccine. Unlike the period when the policy was to use inactivated vaccine, there was no detectable epizootic EHV-1 infection at the training center during three consecutive periods after the introduction of the live vaccine. These results suggest that the replacement of inactivated vaccine with live vaccine, together with the achievement of high vaccination coverage, reinforced the herd effect, and contributed to better control of EHV-1 epizootics in the training center.
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Publication Date: 2019-08-06 PubMed ID: 31387602PubMed Central: PMC6683523DOI: 10.1186/s12917-019-2036-0Google 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.

This study explored the effectiveness of a modified live vaccine compared to an inactivated one in curbing the infection of equine herpesvirus type 1 (EHV-1) among Japanese racehorses, noting that the live vaccine showed stronger results in inducing virus-neutralizing antibodies and controlling EHV-1 outbreaks at the training center.

Vaccine Comparison

  • The researchers investigated the potency of two vaccines, a previously used inactivated vaccine and a currently utilized live vaccine, both produced by xNisseiken, targeting EHV-1 among Japanese racehorses.
  • They set out to compare the ability of these vaccines to stimulate the production of virus-neutralizing (VN) antibodies, that is, antibodies that can block the effects of viruses, thereby preventing them from causing an infection.

Virus-neutralizing Antibodies

  • The study found that three-year-old horses that had received the first dose of the live vaccine exhibited higher geometric mean (GM) VN titers or concentration of antibodies (205 and 220) in comparison to those vaccinated with the inactivated vaccine (83).
  • Additionally, the response rates after vaccination using the live vaccine (76 and 90%) were significantly higher than that with the inactivated vaccine (42%).
  • Similarly, four-year-old horses from 2015-2017 who had received the live vaccine in previous epizootic periods displayed higher GM titers (205 to 246) than those from 2011-2014, which had received the inactivated vaccine (139 to 164).

EHV-1 Infection Rates

  • The study also made an estimated count of horses infected with either EHV-1, EHV-4, or both, during the years 2011-2012 and 2013-2014, which was higher than during other periods.
  • Consequently, the seroconversion rates to EHV-1, or the development of detectable specific antibodies to the virus in the blood serum as a result of infection or immunization, were higher during these two periods (66.0% and 52.0%) compared to other periods (12.0 to 28.6%).

Conclusions

  • The results showed that the live EHV-1 vaccine was more immunogenic than the inactivated vaccine, leading to better VN antibody responses.
  • Furthermore, unlike the period during which the policy was to utilize the inactivated vaccine, there were no detectable EHV-1 outbreaks at the training center during three consecutive periods following the implementation of the live vaccine.
  • These findings suggest that the switch from inactivated to live vaccines, along with high vaccination coverage, amplified the herd effect (resistance to the spread of a contagious disease within a population if a sufficiently high proportion of individuals are immune), thereby contributing to better control of EHV-1 outbreaks in the training center.

Cite This Article

APA
Bannai H, Tsujimura K, Nemoto M, Ohta M, Yamanaka T, Kokado H, Matsumura T. (2019). Epizootiological investigation of equine herpesvirus type 1 infection among Japanese racehorses before and after the replacement of an inactivated vaccine with a modified live vaccine. BMC Vet Res, 15(1), 280. https://doi.org/10.1186/s12917-019-2036-0

Publication

BMC veterinary research
ISSN: 1746-6148
NlmUniqueID: 101249759
Country: England
Language: English
Volume: 15
Issue: 1
Pages: 280
PII: 280

Researcher Affiliations

Bannai, Hiroshi
  • Equine Research Institute, Japan Racing Association, 1400-4 Shiba, Shimotsuke, Tochigi, 329-0412, Japan. bannai@equinst.go.jp.
Tsujimura, Koji
  • Equine Research Institute, Japan Racing Association, 1400-4 Shiba, Shimotsuke, Tochigi, 329-0412, Japan.
Nemoto, Manabu
  • Equine Research Institute, Japan Racing Association, 1400-4 Shiba, Shimotsuke, Tochigi, 329-0412, Japan.
Ohta, Minoru
  • Equine Research Institute, Japan Racing Association, 1400-4 Shiba, Shimotsuke, Tochigi, 329-0412, Japan.
Yamanaka, Takashi
  • Equine Research Institute, Japan Racing Association, 1400-4 Shiba, Shimotsuke, Tochigi, 329-0412, Japan.
Kokado, Hiroshi
  • Equine Research Institute, Japan Racing Association, 1400-4 Shiba, Shimotsuke, Tochigi, 329-0412, Japan.
Matsumura, Tomio
  • Equine Research Institute, Japan Racing Association, 1400-4 Shiba, Shimotsuke, Tochigi, 329-0412, Japan.

MeSH Terms

  • Animals
  • Antibodies, Viral / blood
  • Herpesvirus 1, Equid
  • Herpesvirus 4, Equid
  • Horse Diseases / epidemiology
  • Horse Diseases / prevention & control
  • Horse Diseases / virology
  • Horses
  • Japan / epidemiology
  • Seasons
  • Serologic Tests
  • Vaccines, Inactivated
  • Viral Vaccines / immunology

Conflict of Interest Statement

The authors declare that they have no competing interests.

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Citations

This article has been cited 4 times.
  1. El Brini Z, Fassi Fihri O, Paillot R, Lotfi C, Amraoui F, El Ouadi H, Dehhaoui M, Colitti B, Alyakine H, Piro M. Seroprevalence of Equine Herpesvirus 1 (EHV-1) and Equine Herpesvirus 4 (EHV-4) in the Northern Moroccan Horse Populations. Animals (Basel) 2021 Sep 29;11(10).
    doi: 10.3390/ani11102851pubmed: 34679874google scholar: lookup
  2. Bannai H, Kambayashi Y, Tsujimura K, Nagashima T, Takebe N, Tominari M, Nemoto M, Ohta M. Persistence of virus-neutralizing antibodies in horses inoculated with two doses of a live equine herpesvirus type 1 vaccine with different vaccination intervals. J Equine Sci 2021;32(3):99-102.
    doi: 10.1294/jes.32.99pubmed: 34539211google scholar: lookup
  3. Bannai H, Kambayashi Y, Kume K, Takebe N, Endo Y, Kawanishi N, Nemoto M, Tsujimura K. Reduction in endemic equine herpesvirus type-1 and type-4 infection among Thoroughbred yearlings through an updated vaccination program. J Equine Sci 2025 Jun;36(2):67-74.
    doi: 10.1294/jes.36.67pubmed: 40831999google scholar: lookup
  4. Osterrieder K, Dorman DC, Burgess BA, Goehring LS, Gross P, Neinast C, Pusterla N, Hussey GS, Lunn DP. Vaccination for the prevention of equine herpesvirus-1 disease in domesticated horses: A systematic review and meta-analysis. J Vet Intern Med 2024 May-Jun;38(3):1858-1871.
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