Porcine Epidemic Diarrhoea Virus in Italy: Disease spread and the role of transportation

Abstract

Porcine Epidemic Diarrhoea Virus (PEDV) causes watery diarrhoea, dehydration, and a high mortality rate among suckling pigs. Recently, PEDV had a large negative economic impact on the swine industries in Asia and North America. In 2014, PEDV re-emerged in many European countries, but most countries only reported a few sporadic cases. Here, we report the epidemic wave that occurred in Italy from 2015 to 2017. During this time, PEDV was detected by real-time PCR in 438 farms located mainly in the high-density pig production area in Northern Italy. Most of the outbreaks were in farrow-to-finish, farrow-to-wean and finisher farms. Clinical signs were observed mainly in suckling and fattening animals, while mortality rates were higher in piglets, reaching 50%. A sequence analysis showed that a PEDV strain, similar to the OH851 S-INDEL strain isolated in the USA in January 2014, was responsible for the outbreaks in Italy in 2015 and 2016. However, from January 2017, a recombinant variant strain, containing a portion of the Swine Enteric Coronavirus in the S1 gene, spread and almost completely outcompeted the previous nonrecombinant strain. In total, 14.1% of the environmental swabs collected from trucks at slaughterhouses after animals were unloaded tested positive for PEDV before the trucks were cleaned and disinfected, and 46% remained positive after cleaning and disinfection processes were performed. Moreover, environmental swabs indicated that 17.3% of the empty trucks arriving at the farms to load animals were PEDV-positive. This study indicates that trucks can have an important role in the spread of PEDV in Italy.

Keywords: Italy; PEDV; S-INDEL; enteritis; swine; transport.

Figure 1

Geographical distribution of the Porcine Epidemic Diarrhoea outbreaks. Farms that tested positive were located mainly in the Po Valley, with only a few in the rest of Italy. Finisher, red diamond; wean‐to‐finish, blue circle; farrow‐to‐wean, grey cross; farrow‐to‐finish, orange square; family holding, green circle; and unknown, black triangle

Figure 2

Number of outbreaks per month separated into the causal genetic variant strains of Porcine Epidemic Diarrhoea Virus (PEDV). From January 2015 to June 2017, three PED epidemic peaks occurred during the winter months. From the beginning of 2017, a recombinant variant (PEDV/SeCoV) appeared and became prevalent. The S‐INDEL PEDV strains, recombinant PEDV/SeCoV strains and unavailable sequences are shown with black, grey, and white, respectively. SeCoV, Swine Enteric Coronavirus

Figure 3

Percentages of diarrhoeic pigs per age category in 105 herds. Clinical evaluations were performed on 148 breeders, 39 suckling, 46 weaned, and 141 finishers. Diarrhoea was observed in animals of all ages, but greater percentages were observed in the fattening and piglet groups. Breeders, bars with lines; suckling, bars with dots; weaned, black bars; and finishers, grey bars. Percentage ranges of diarrhoeic animals are fixed on the x‐axis

Figure 4

The Porcine Epidemic Diarrhoea Virus (PEDV)‐associated mortality rate per age category in 105 herds. The mortality rate was higher in piglets than in the other categories. Percentage ranges of mortality rates are fixed on the x‐axis