The first isolation and whole genome characterization of Porcine
Deltacoronavirus from pigs in Peru
Abstract
Porcine Deltacoronavirus is a newly emergent enteric pathogen affecting
swine farms worldwide. It has been detected in several countries in
Europe, Asia and North America. Yet, it has not been reported in South
America. In November 2019, an enteric disease outbreak in a pig farm
located in San Martin, Peru was reported along with submission of three
intestinal samples from pigs who succumbed to the disease. Samples were
processed for molecular detection by qRT-PCR, viral isolation and
further sequencing analysis. A taqman-based RT-PCR was performed to
differentiate among the most relevant swine enteric coronaviruses
described to date. All samples were positives to Porcine
Deltacoronavirus with a cycle threshold (Ct) between 9-14, revealing a
high viral load, while tested negatives to Porcine Epidemic diarrhea and
Transmissible Gastroenteritis viruses. Following detection, viral
isolation was performed using PK-15 and Vero cell lines. After 5 days of
inoculation, no cytopathic effect was observed. A second blind passage
allowed the observation of cytopathic effect on PK-15 cells, while it
remained absent in Vero cells. One sample was processed for whole genome
sequencing (NGS). In short, raw reads were imported into CLC genomics
and assembled de novo. Out of 479k reads generated from the sample, 436k
assembled into a 25501 bp contig which was 99.5% identical to a
reference Porcine Deltacoronavirus strain from US within the North
American phylogroup. Yet, there are relevant differences at the
nucleotide and amino acid levels compared to previously described
Porcine Deltacoronavirus strains. Altogether, our findings represent the
first report of Porcine Deltacoronavirus in South America, its genomic
characterization, which provides information of its evolutionary origin.
Thus, this study offers new insights into the molecular epidemiology of
Porcine Deltacoronavirus infections in the swine industry.