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.

A five-month-old Japanese Black calf fed at a farm in Kagoshima Prefecture died as a result of severe diarrhea and dehydration. During necropsy, hyperemia and hemorrhages were found on the mucosa of the jejunum, ileum and rectum. Some Trichuris discolor worms were also obser ved in the mucosa of the rectum. Histopathological examination of the rectum with hemor rhagic enteritis revealed coccidian parasites of various developmental stages in the epithelial cells. Using DNA purified from sections of the rectum, species-specific PCR was conducted and consequently Eimeria (E.) bovis and E. zuernii specific genes were amplified. Through fecal examination of other calves on the farm, oocysts morphologically similar to those of E. bovis and E. zuernii, and eggs of T. discolor were detected. Consequently, we successfully identified E. bovis and E. zuernii from formalin-fixed paraf fin embedded sections and identified a lethal case with these Eimeria species.