Generation and protective efficacy of a cold-adapted attenuated genotype 2b porcine epidemic diarrhea virus

Won, Hokeun; Lee, Dong-Uk; Jang, Guehwan; Noh, Yun-Hee; Lee, Seung-Chul; Choi, Hwan-Won; Yoon, In-Joong; Yoo, Han Sang; Lee, Changhee

Piglet challenge trials was conducted to determine the infectious dose and virulence of a PEDV Aram strain using 3-day-old conventional suckling piglets delivered from commercial crossbred sows (Great Yorkshire × Dutch Landrace). Thirty pigs were divided into six groups (group 1-group 6) of five animals and were fed commercial milk replacer frequently (4 times daily) with ad libitum access to water for the study (7 days). Animals in groups 1-6 were allowed to acclimate for two days and then inoculated orally with 1 mL of 10 −2 , 10 −3 , 10 −4 , 10 −5 , and 10 −6 dilutions of the Aram-P5 virus (10 5.0 TCID 50 /mL) and cell culture medium at 5 days of age, respectively. After inoculation, piglets were observed daily for clinical signs, including diarrhea and mortality. Stool samples from pigs in all groups were collected prior to inoculation and daily with 16-inch cotton-tipped swabs and scored for fecal consistency for 5 days post-inoculation (DPI): 0 = normal; 1 = pasty; 2 = semi-liquid; 3 = liquid or watery. Mean pig diarrhea dose (PDD 50 ) and lethal dose (LD 50 ) were determined as the reciprocal of the virus dilution at which 50% of the pigs developed watery diarrhea (score 3) or died at a given time point using the Reed and Muench method.