Evaluation of porcine epidemic diarrhea virus transmission and the immune response in growing pigs

Abstract

Clinical disease associated with porcine epidemic diarrhea virus (PEDV) infection in naïve pigs is well chronicled; however, information on endemic PEDV infection is limited. To characterize chronic PEDV infection, the duration of infectious virus shedding and development of protective immunity was determined. On Day 0 (D0), a growing pig was challenged with PEDV and 13 contacts were commingled. On D7, 9 contact pigs (principal virus group (PG)), were selected, moved to a separate room and commingled with one sentinel pig (S1). This process was repeated weekly with S2, S3 and S4. The PG was PEDV-positive by PCR from D3-11, with some pigs intermittently positive to D42. Pigs S1 and S2 were PEDV-positive within 24 hours of commingling. Antibodies were detected in all PG by D21 and by 7 days post-contact in S1 and S2. Pigs S3 and S4 were PCR and antibody negative following commingling. To evaluate protective immunity, 5 naïve pigs (N) and the PG were challenged (N/C, PG/C) with homologous virus on D49. All N/C pigs were PEDV PCR-positive by D52 with detection out to D62 in 3/5 N/C pigs. All PG/C pigs were PEDV PCR-negative post-challenge. By D63, all N/C seroconverted. Although PEDV RNA was demonstrated in pigs after primary infection until D42, infectious PEDV capable of horizontal transmission to naïve pigs was only shed 14–16 days after infection to age-matched pigs. Homologous re-challenge 49 days post initial PEDV exposure did not result in re-infection of the pigs. This demonstrates potential for an effective PEDV vaccine.

Experimental Infection of Young Pigs with an Early European Strain of Porcine Epidemic Diarrhoea Virus and a Recent US Strain

“…These infections were demonstrated by a variety of means including the appearance of fairly mild clinical disease, the presence of high levels of PEDV RNA in the intestine (at PID 4) or the prolonged excretion of PEDV RNA and the induction of anti‐PEDV antibodies within 10 days post‐inoculation. The time course of seroconversion is consistent with previous results using the US PEDV (Madson et al., ; Crawford et al., ).…”

“…In the current study, faecal shedding of PEDV RNA was observed through to PID 18 in both infected Groups and faecal shedding of PEDV RNA has been reported to occur until PID 24 and even PID 42 but it is not known whether infectious virus is shed beyond PID 21 (Madson et al., ; Crawford et al., ).…”

“…Sequence analysis of the recent PED viruses circulating in the United States, China and Europe has been reported (Chen et al., ; Vlasova et al., ; Wang et al., ; Hanke et al., ). Some initial animal studies using the recent PEDV strains to determine the characteristics of the infection have been performed (Jung et al., ; Madson et al., ; Crawford et al., ; Jung et al., ; Yamamoto et al., ) and also previously animal experiments with an early European strain have been described (Debouck et al., ). The experiments described here extend these studies and also demonstrate the efficacy of current diagnostic systems to detect and monitor infections by distinct PEDVs viruses.…”

Evaluation of two real-time polymerase chain reaction assays for Porcine epidemic diarrhea virus (PEDV) to assess PEDV transmission in growing pigs

“…Clinically, no signs of diarrhea were shown in pigs on the same days in which they tested negative by gN and gS realtime RT-PCR assay (Cq > 34.99). 8 Therefore, if we take signs of diarrhea as a true positive standard, sensitivity (DSe) and specificity (DSp) can be estimated as DSe 96.82-100.00% (95% confidence interval [CI]) and DSp 71.85-77.47% (95% CI) for the gN assay, and DSe 96.82-100.00% (95% CI) and DSp 72.39-77.98% (95% CI) for the gS assay.…”

“…8 Conventionally raised pigs free of clinical disease were purchased at 3 weeks of age from a herd that was negative for Porcine reproductive and respiratory syndrome virus. The pigs were transported to the NADC and housed according to NADC Institutional Animal Care and Use Guidelines.…”