Getah Virus Infection among Racehorses, Japan, 2014

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Manabu Nemoto

, Hiroshi Bannai, Koji Tsujimura, Minoru Kobayashi, Takuya Kikuchi, Takashi Yamanaka, and Takashi Kondo

Author affiliations: Japan Racing Association, Shimotsuke, Japan (M. Nemoto, H. Bannai, K. Tsujimura, T. Yamanaka, T. Kondo); Japan Racing Association, Miho, Japan (M. Kobayashi, T. Kikuchi)

Abstract

An outbreak of Getah virus infection occurred among racehorses in Japan during September and October 2014. Of 49 febrile horses tested by reverse transcription PCR, 25 were positive for Getah virus. Viruses detected in 2014 were phylogenetically different from the virus isolated in Japan in 1978.

Getah virus (genus Alphavirus, family Togaviridae) is a mosquito-borne virus that was first isolated in Malaysia in 1955 from Culex spp. mosquitoes (1). Serologic evidence suggests that Getah virus is widespread from Eurasia to Australasia (1,2). In horses, the virus causes fever, rash on the body, and edema in the legs (2); the virus is also pathogenic to pig fetuses and newborn piglets (3,4) and can cause fever in humans (5). Outbreaks of Getah virus infection have occurred among horses in 1978, 1979, and 1983 in Japan (2) and in 1990 in India (6).

An inactivated whole-virus vaccine (Nisseiken Co., Ltd, Tokyo, Japan) is available to prevent Getah virus infection and is mainly administered to thoroughbred racehorses registered by the Japan Racing Association. It is recommended that this vaccine be administered twice in the first year of registration (mainly 2-year-old horses) and then annually as a booster before each mosquito season. This vaccine contains the MI-110 strain isolated from a febrile horse during the outbreak in 1978.

In mid-September 2014, the number of febrile horses began to increase at the Miho Training Center of the Japan Racing Association in Ibaraki Prefecture; we identified Getah virus infection among these horses. The outbreak of Getah virus infection in 1978 occurred at this facility. We summarize the epidemiologic features and molecular characterization of the epidemic virus.

Dr. Nemoto is a researcher at the Equine Research Institute of the Japan Racing Association. His research focuses on the diagnosis and epidemiology of equine viral diseases.

Acknowledgments

We are grateful to all the equine practitioners of the Japan Racing Association for collecting the clinical samples and to Akira Kokubun, Akiko Suganuma, Kazue Arakawa, and Kaoru Makabe for their invaluable technical assistance. In addition, we thank Tomio Matsumura for critical reading of the manuscript.

This study was supported financially by the Japan Racing Association.

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Figure

Figure. Phylogenetic analyses of the nucleotide sequences of the (A) nonstructural protein 1 (NSP1) gene (nt 218–598) and (B) capsid gene (nt 7645–8196) of Getah virus isolated in Japan, 2014. The...

Table

Table. Number of newly febrile horses and results of RT-PCR and a virus neutralization test, Japan, 2014

Suggested citation for this article: Nemoto M, Bannai H, Tsujimura K, Kobayashi M, Kikuchi T, Yamanaka T, et al. Getah virus infection among racehorses, Japan, 2014. Emerg Infect Dis. 2015 May [date cited]. http://dx.doi.org/10.3201/eid2105.141975

DOI: 10.3201/eid2105.141975