Resurgence of bovine ephemeral fever in mainland Japan in 2015 after a 23-year absence

Abstract

In September and October 2015, suspected cases of bovine ephemeral fever (BEF) were reported in the mainland region of Kagoshima Prefecture and on Tanegashima Island. The genome of the BEF virus (BEFV) was detected in the diseased cows and the cows that had recovered. The serum obtained from the affected cows contained high titers of BEFV-neutralizing antibody. In total, 18 affected cows were demonstrated to be infected with BEFV during the outbreak. Our findings showed evidence that BEF occurred in mainland Japan after a 23-year absence. Phylogenetic analysis based on the surface glycoprotein (G) gene revealed that BEFVs detected in the affected cows were genetically distinct from previous Japanese BEFVs, but were close to BEFVs circulating in Taiwan and mainland China in recent years. Amino acid substitution in the neutralizing epitope domains of the G protein was limited between the detected viruses and the vaccine strain (YHL isolate), and high titers of the neutralizing antibody against the YHL isolate were induced in the infected cattle during the disease occurrences. Therefore, current BEF vaccines probably elicit protective immunity against the BEFVs detected in 2015, although their effectiveness should be assessed. Since the BEFV vaccination rates are estimated to be low, a BEF outbreak should be considered a possibility in mainland Japan.

Endemic and Emerging Arboviruses in Domestic Ruminants in East Asia

“…Although the mortality rate of BEF is known to be <1% (9), a high case-fatality rate due to a novel genogroup of BEFV was observed in several recent outbreaks in mainland China and Taiwan (23,29). This novel genogroup of BEFV was first isolated in mainland China in 2011 and was then detected in Taiwan and Japan 2 and 4 years later, respectively (22,23,30). These reports indicate that the virus rapidly spread in East Asia.…”

“…Since then, the epidemics had been limited to the southwestern islands of Japan, which are close to Taiwan (20,21). However, in 2015 a reoccurrence of BEF was reported in the southern end of Kyushu, which is one of the main islands of Japan (22).…”

“…Extensive surveillance in Australia obtained many arboviruses, and some of them are also endemic or were recently emerged in East Asia (278). However, phylogenetic studies of orthobunyaviruses and BEFV indicated that they evolved independently in separate gene pools with different geographical origins (22,108,279). In contrast, BEFV, BTV, BANV, and JEV strains, which were isolated in Southeast Asia, often have closed genetic relationships with those isolated in East Asia (280)(281)(282)(283).…”

Emerging Threats to Animals in the United Kingdom by Arthropod-Borne Diseases

“…The virus is transmitted by arthropod vectors although an exact association with a particular species has not been established, with BEFV being detected in both Culicoides midges and mosquitoes in Australia (165). Bovine ephemeral fever is either enzootic or occasionally epizootic in Africa, Asia and Australia (168)(169)(170). There have been no cases reported from Europe, with the exception of possible cases in the European region of Turkey, so currently there is a low risk of its emergence in the UK.…”

Bovine Ephemeral Fever in Asia: Recent Status and Research Gaps

“…The 29% mortality (24/83) in beef cattle attracted the attention of farmers and animal health agencies. [18]. This reoccurrence of BEF in Kyushu suggests that cattle on the main islands can become afflicted with BEF when their acquired immunity is insufficient.…”