Discussion
The rapid dissemination of PEDV across the US in
months demonstrated the vulnerability of a concen-
trated, interwoven swine production system to a highly
transmissible novel enteric pathogen. This unprece-
dented spread was dependent on many factors including
the duration and magnitude of virus shedding from in-
fected to naïve pigs. The goal of this study was to better
understand the role of pig-to-pig transmission in the US
PEDV epidemic by developing a model to characterize
the host response to infection with PEDV.
In 4-week-old contact pigs, mild-to-moderate diarrhea
was observed for approximately one week post exposure
to a PEDV experimentally-infected seeder pig. No other
clinical disease was observed in the contact pigs. Within
24 hours-post-inoculation or post-exposure, all rectal
swabs were PCR positive demonstrating the rapidity of
transmission and the potential for pigs to shed infectious
virus. In the pigs “naturally” infected by contact, 13/13 pigs
were PCR positive for 9 days and most pigs were positive
for 2-weeks-post exposure during which time one or more
of the pigs shed an infectious dose of virus to pigs S1 and
S2. Like the 13 naturally exposed pigs, S1 and S2 became
PCR positive within 24 hours of contact, and serocon-
verted within 2 weeks post-exposure. The speed by which
all pigs became PEDV RNA positive and the potential for
pigs to shed infectious virus up to 2-weeks-post infec-
tion to age-matched pigs, suggests the basic reproduction
number or R0 should be high for this virus.
As would be expected for a virus with a high R0 value,
the transmissibility of the virus would be enhanced by