Prevalence of antibody to Japanese encephalitis virus nonstructural 1 protein among racehorses in Japan: indication of natural infection and need for continuous vaccination.
Abstract: Japanese encephalitis virus (JEV) causes fatal diseases in equines as well as humans. In Japan, racehorses are vaccinated with inactivated JE vaccine every year and no equine JE cases have been reported since 1986. However, the current reduction in JEV activity in nature has raised an argument against the requirement of continuous vaccination. Here, we studied natural infection rates in racehorses to address the issue. To identify naturally-infected individuals from vaccinated populations, we used an immunostaining method for detecting antibodies to JEV nonstructural 1 (NS1) protein. A total of 779 horses in eight nationwide locations showed NS1 antibody prevalences ranging from 15 to 73%. NS1 antibody prevalences among 2-year-old individuals that had spent one epizootic season in a particular location, therefore representing annual infection rates, were 15-67%. Individuals aged >/=3 years showed higher NS1 antibody titers than the 2-year-olds, suggesting that NS1 antibody levels were boosted by repeated exposures to JEV antigen over >/=2 epizootic seasons. These results indicate that horses in Japan are exposed to natural JEV infections, confirming the need for continuous vaccination for protecting horses from JE.
Publication Date: 2004-03-09 PubMed ID: 15003636DOI: 10.1016/j.vaccine.2003.10.001Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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This research paper investigates the prevalence of antibodies to the Japanese encephalitis virus (JEV) in racehorses in Japan and highlights the need for continued vaccination, despite arguments to the contrary, due to the ongoing risk of natural infection.
Introduction and Background
- Japanese encephalitis virus (JEV) is a major health concern in several parts of the world, causing fatal diseases in both humans and horses.
- In Japan, the practice of annual vaccination with an inactivated vaccine for racehorses has resulted in no reported cases of equine Japanese encephalitis since 1986.
- However, a decline in naturally occurring JEV has led to debates about whether continuous vaccination is still necessary.
Methods and Approach
- To understand the rate of natural infection among racehorses and contribute to the ongoing vaccination discussion, the researchers conducted a study that monitored the presence of antibodies to JEV nonstructural 1 (NS1) protein, which indicates exposure to JEV.
- A total of 779 horses from eight locations across the country were tested for these antibodies.
- The researchers specifically looked at horses that were 2 years old and had spent one season in an environment conducive to the spread of the virus—these were thought to represent annual infection rates.
Findings
- The results indicated that between 15% and 73% of the horses studied had antibodies to the NS1 protein, suggesting a considerable level of natural infection.
- Between 15% and 67% of the 2-year-old horses were found to have these antibodies, indicating exposure to JEV.
- Furthermore, horses aged 3 years or above showed higher levels of NS1 antibodies compared to the 2-year-old horses. This suggests that the level of antibodies increases with repeated exposure to the virus over multiple seasons of risk.
Conclusions
- The researchers concluded that despite the perceived reduction in JEV in the natural environment, horses in Japan are still exposed to naturally occurring JEV infection.
- This research underscores the need for continuous vaccination of racehorses to protect them against Japanese encephalitis.
Cite This Article
APA
Konishi E, Shoda M, Kondo T.
(2004).
Prevalence of antibody to Japanese encephalitis virus nonstructural 1 protein among racehorses in Japan: indication of natural infection and need for continuous vaccination.
Vaccine, 22(9-10), 1097-1103.
https://doi.org/10.1016/j.vaccine.2003.10.001 Publication
Researcher Affiliations
- Department of Health Sciences, Kobe University School of Medicine, 7-10-2 Tomokaoka, Suma-ku, Kobe 654-0142, Japan. ekon@ams.kobe-u.ac.jp
MeSH Terms
- Animals
- Animals, Newborn
- Antibodies, Viral / analysis
- Coloring Agents
- Encephalitis Viruses, Japanese / immunology
- Encephalitis, Japanese / immunology
- Encephalitis, Japanese / prevention & control
- Encephalitis, Japanese / veterinary
- Female
- Hemagglutination Inhibition Tests
- Horse Diseases / epidemiology
- Horse Diseases / immunology
- Horse Diseases / prevention & control
- Horses / immunology
- Immunochemistry
- Immunohistochemistry
- Japan / epidemiology
- Japanese Encephalitis Vaccines / immunology
- Male
- Vaccination
- Viral Nonstructural Proteins / immunology
Citations
This article has been cited 8 times.- Wang H, Liang G. Epidemiology of Japanese encephalitis: past, present, and future prospects.. Ther Clin Risk Manag 2015;11:435-48.
- Lobigs M, Diamond MS. Feasibility of cross-protective vaccination against flaviviruses of the Japanese encephalitis serocomplex.. Expert Rev Vaccines 2012 Feb;11(2):177-87.
- Kitai Y, Kondo T, Konishi E. Complement-dependent cytotoxicity assay for differentiating West Nile virus from Japanese encephalitis virus infections in horses.. Clin Vaccine Immunol 2010 May;17(5):875-8.
- Yang DK, Kim BH, Kweon CH, Nah JJ, Kim HJ, Lee KW, Yang YJ, Mun KW. Serosurveillance for Japanese encephalitis, Akabane, and Aino viruses for Thoroughbred horses in Korea.. J Vet Sci 2008 Dec;9(4):381-5.
- Hashimoto S, Kawado M, Murakami Y, Izumida M, Ohta A, Tada Y, Shigematsu M, Yasui Y, Taniguchi K, Nagai M. Epidemics of vector-borne diseases observed in infectious disease surveillance in Japan, 2000-2005.. J Epidemiol 2007 Dec;17 Suppl(Suppl):S48-55.
- Konishi E, Kitai Y, Kondo T. Utilization of complement-dependent cytotoxicity to measure low levels of antibodies: application to nonstructural protein 1 in a model of Japanese encephalitis virus.. Clin Vaccine Immunol 2008 Jan;15(1):88-94.
- Kitai Y, Shoda M, Kondo T, Konishi E. Epitope-blocking enzyme-linked immunosorbent assay to differentiate west nile virus from Japanese encephalitis virus infections in equine sera.. Clin Vaccine Immunol 2007 Aug;14(8):1024-31.
- Konishi E, Shoda M, Ajiro N, Kondo T. Development and evaluation of an enzyme-linked immunosorbent assay for quantifying antibodies to Japanese encephalitis virus nonstructural 1 protein to detect subclinical infections in vaccinated horses.. J Clin Microbiol 2004 Nov;42(11):5087-93.
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