Background Porcine epidemic diarrhea (PED) is a lethal infectious disease in suckling piglets with symptoms including watery diarrhea caused by PED virus (PEDV). Since the late 1990’s, live vaccines based on genogroup 1 virus have been used in Japan, and a significant amount of the vaccine has been used even after new genogroups invaded in 2013. In this study, we evaluated the effect of a conventional PED live vaccine on a newly prevalent genogroup 2 field strain in experimental and field situations. Methods Two pregnant sows were administered twice the live vaccine before farrowing. A pregnant sow was served as a negative control. All newborn piglets were challenged with the genogroup 2 virus, and clinical signs were monitored for 7 days post challenge. PEDV-specific immune responses in serum and milk of the sows were assayed by virus neutralization assay. The efficacy of PED live vaccine in vaccinated or non-vaccinated farms was evaluated by comparing the mortality rate of suckling piglets after the onset of PED. Results The challenged piglets exhibited watery diarrhea with or without vaccination. However, the clinical score of piglets born from vaccinated sows significantly improved after the 4th day of the challenge. The survival rate of piglets in the vaccinated group at the end of the experimental period was 80%, whereas in the control group was 0%. Neutralizing antibody titers in serum and milk of control sow was negative throughout the experimental period, whereas high titers were observed in the vaccinated sows. The vaccinated farms significantly reduced the mortality rate of suckling piglets after the onset of PED, compared to farms not vaccinated. Conclusions The conventional PED live vaccine induced the lactogenic immunity to vaccinated sows and showed partial protection against the genogroup 2 virus both under the experimental and field conditions. Electronic supplementary material The online version of this article (10.1186/s12985-018-0940-8) contains supplementary material, which is available to authorized users.
【저자키워드】 Vaccine, Porcine epidemic diarrhea virus, Lactogenic immunity, Porcine epidemic diarrhea, 【초록키워드】 Efficacy, immune response, vaccination, Immunity, Symptom, Infectious disease, diarrhea, virus, serum, Newborn, Antibody titer, Virus neutralization, Japan, survival rate, mortality rate, pregnant, epidemic diarrhea, control group, supplementary material, PEDV, Clinical sign, Administered, prevalent, negative control, Result, caused, significantly, evaluated, reduced, exhibited, the vaccine, conditions, watery, lactogenic, 【제목키워드】 Japan, epidemic diarrhea,