Involvement of porcine astrovirus in an enteric episode in piglets in Italy

Astroviruses are emerging viruses in the Family Astroviridae that infect a wide range of mammalian and avian species. They are nonenveloped viruses with a single-stranded positive sense RNA genome. They can be found in the intestines and several other organs in diseased and healthy animals. Porcine astroviruses (PAstVs) belong to the Mamastrovirus genus and are distributed worldwide. Five lineages are recognised, possibly reflecting different species of origin, interspecies transmission and recombination events, these latter having occurred even with human strains. Here we report a diagnostic case of acute gastroenteritis in piglets in Italy with the involvement of PAstVs.

In November 2015 an acute episode of gastroenteritis was observed in pig farm located in North east Italy, Treviso province. The farm is organized in an open cycle of about 460 sows. Piglets during the first phases of post weaning presented diarrhea, reduction of food intake, high morbidity and low mortality. Fecal samples collected from diseased piglets and one piglet were submitted to the diagnostic veterinary laboratory. Bacteriology tests were performed on intestine, liver and faeces. Faeces were analysed by electron microscopy (EM) and by a pan mamastrovirus RTPCR. Sequence and phylogenetic analysis was performed on the polymerase gene obtained from PCR positive samples.

The necropsy on dead piglet showed a discrete nutrition status with severe catarrhal enteritis with foam and lose of tone of the intestinal tract. Peritonitis, edema of colon and hyperemia of pyloric region of gut were also observed. Presence of Escherichia Coli not belonging to relevant serogroups or serotypes in intestine and faeces was detected. Presence of Salmonella and Clostridium perfringes was excluded. Faeces were positive for astrovirus by EM and RT-PCR. Sequence BLAST analysis of the 288 bp of polymerase gene revealed the highest homology with PAstV 2 from South Korea and with Porcine Mamastrovirus 3 from China. The detected astrovirus clusters with a lower homology with other PAstV 2 from US and, interestingly with a deer astrovirus isolated in Denmark.

The present case report indicates that PAstVs may be involved in enteric disorders in piglets. Genetic data highlight the complexity of PAstVs classification and may suggest a unique ability to cross the species barriers. However still fragmentary data are available on the role of PAstVs in the multifactorial enteric disorders of pigs. Better surveillance and diagnosis in the field of enteric disorders in pigs may clarify the epidemiology and taxonomical classification of PAstVs.

Disclosure of Interest: None Declared.