Origin, Evolution, and Virulence of Porcine Deltacoronaviruses in the United States

Abstract

A novel porcine deltacoronavirus (PdCV) was first discovered in Ohio and Indiana in February 2014, rapidly spread to other states in the United States and Canada, and caused significant economic loss in the swine industry. The origin and virulence of this novel porcine coronavirus are not known. Here, we characterized U.S. PdCV isolates and determined their virulence in gnotobiotic and conventional piglets. Genome analyses revealed that U.S. PdCV isolates possess unique genetic characteristics and share a close relationship with Hong Kong and South Korean PdCV strains and coronaviruses (CoVs) of Asian leopard cats and Chinese ferret-badgers. The PdCV-positive intestinal content (Ohio CVM1) and the cell culture-adapted PdCV Michigan (MI) strain were orally inoculated into gnotobiotic and/or conventional piglets. Within 1 to 3 days postinfection, profuse watery diarrhea, vomiting, and dehydration were observed. Clinical signs were associated with epithelial necrosis in the gastric pits and small intestine, the latter resulting in severe villous atrophy. Mild interstitial pneumonia was identified in the lungs of PdCV-infected piglets. High levels of viral RNA (8 to 11 log RNA copies/g) were detected in intestinal tissues/luminal contents and feces of infected piglets, whereas moderate RNA levels (2 to 5 log RNA copies/g) were detected in blood, lung, liver, and kidney, indicating multisystemic dissemination of the virus. Polyclonal immune serum against PdCV but not immune serum against porcine epidemic diarrhea virus (PEDV) reacted with PdCV-infected small-intestinal epithelial cells, indicating that PdCV is antigenically distinct from PEDV. Collectively, we demonstrate for the first time that PdCV caused severe gastrointestinal diseases in swine.

Development of a multiplex RT‐PCR for the detection of major diarrhoeal viruses in pig herds in China

“…A recent example showed the existence of PDCoV in pig herds for many years in mainland China and Hong Kong; however, the virus had no observable clinical symptoms (Pan et al, ; Woo et al, ). Unfortunately, this virus caused severe outbreaks in some states of the United States since 2014 (Ma et al, ; L. Wang, Byrum, & Zhang, ). This virulence change was most likely caused by previous exposure to PEDV or other coinfected swine enteric viruses.…”

Herd-level prevalence and incidence of porcine epidemic diarrhoea virus (PEDV) and porcine deltacoronavirus (PDCoV) in swine herds in Ontario, Canada

“…PEDV emerged in North America in May 2013, while PDCoV was first confirmed in February 2014, both in the United States (Chen et al., ; Ma et al., ). These novel viruses rapidly disseminated throughout the US swine population, resulting in the mortality of an estimated seven million animals by May 2014 (Jung & Saif, ).…”

The detection and phylogenetic analysis of porcine deltacoronavirus from Guangdong Province in Southern China

“…It was identified later in several states of USA (Li et al., ; Marthaler, Jiang, Collins, & Rossow, ; Wang, Byrum, & Zhang, ) and has now spread to South Korea, mainland China, Thailand and Laos (Lee & Lee, ; Lee et al., ; Lorsirigool et al., ; Madapong et al., ; Song et al., ). The emergence of PDCoV was most often associated with clinical infection symptoms including diarrhoea, vomiting and dehydration in pigs, especially in sucking and nursing piglets (Janetanakit et al., ; Ma et al., ; Marthaler, Raymond et al ; Song et al., ). These worldwide outbreaks of PDCoV have caused economic losses to the global commercial swine industry (Chen, Gauger et al., ; Chen, Zhu et al., ; Homwong et al., ; Song et al., ; Wang et al., ).…”