The New Porcine Epidemic Diarrhea Virus Outbreak May Mean That Existing Commercial Vaccines Are Not Enough to Fully Protect Against the Epidemic Strains

Abstract

Background: On October 30, 2020, piglets and sows in the farrowing house of a pig farm in Jiangxi showed clinical symptoms such as anorexia, watery diarrhea, and vomiting. Epidemiological test, clinical necropsy, and RT-PCR test were carried out on the pig farm for diagnosis. After comprehensive considerations, the disease was judged as porcine epidemic diarrhea virus infection.Results: Thereafter, a series of comprehensive prevention and control measures such as emergency vaccination with autogenous vaccines were adopted. Half a month after inoculation with autogenous vaccines for the farm, the mortality rate of newborn piglets in the farrowing house began to decline, and production gradually returned to being stable. The second-generation sequencing analysis and phylogenetic analysis showed that the porcine epidemic diarrhea virus (PEDV) sequence obtained from the stool and small intestine samples of the diseased pigs on the farm was 97.8% homologous to the vaccine strain. At the same time, antibody testing found that the vaccinated pigs on the pig farm had satisfactory immune response.Conclusion: This case indicated that the PEDV outbreak on the pig farm might aggravate owing to the strain being mutated and could escape the immune protection of the existing vaccine. This case has accumulated technical data for the clinical prevention and control of porcine epidemic diarrhea.

Novel Neutralizing Epitope of PEDV S1 Protein Identified by IgM Monoclonal Antibody

“…Current PEDV vaccines (in use or developing) are either the traditional, first-generation vaccines consisting of live attenuated or inactivated whole PEDV [38,39], second-generation vaccines composed of either the recombinant virus protein [40] or virus-like particles (VLP) [41] combined with immunological adjuvant, or third-generation vaccines comprising DNA plasmid carried by a vector capable of expressing the PEDV protein antigen in the host [42,43]. However, vaccine efficacy is unsatisfactory and recurrent PEDV outbreaks occur [44,45]. Moreover, immunization with some PEDV vaccines has resulted in enhancement of disease symptoms and virus replication in vaccinated pigs exposed to PEDV challenge [46].…”

Oral Administration of Coronavirus Spike Protein Provides Protection to Newborn Pigs When Challenged with PEDV

“…1 Milk was collected on day 6 post-challenge. 2 Piglets were challenged with PEDV virus between days 3-5 of lactation. 3 Piglets were observed for signs of diarrhea, dehydration, and overall health for 11 d post-challenge.…”

“…Porcine epidemic diarrhea virus (PEDV) is a positive strand enveloped RNA virus of family Coronaviridae with a genome of 28 kb. The virus infects swine, resulting in major losses to the industry in the U.S. and worldwide [1,2]. Newborn piglets are especially susceptible, with a high mortality rate reaching up to 100% within 7 d after birth [3].…”

“…PED virus replicates in the mature intestinal enterocytes leading to villus atrophy and enteritis, causing malabsorptive diarrhea and vomiting [3,4]. The disease was first identified in Europe in the early 1970s, in Asia in 2010 and in the United States in 2013, and it continues to be a major problem in the swine industry worldwide [2,5]. The conditionally approved vaccines in North America from Harrisvaccines (Ames, IA, USA) and Zoetis (Parsippany, NJ, USA) are based on RNA or inactivated virus but are only marginally effective [6,7].…”

“…Injected and oral vaccines were administered to sows during gestation: INJ (injection of PEDV vaccine), LOV (low-dose oral PEDV vaccine), HOV (high-dose oral PEDV vaccine), CON (non-vaccinated controls) 1. Milk was collected on day 6 post-challenge 2. Piglets were challenged with PEDV virus between days 3-5 of lactation 3.…”