First detection of porcine circovirus 4 (PCV-4) in Europe.

Porcine circovirus 4 (PCV-4) is a novel virus recently discovered (2019) in domestic pigs from China, although several studies have proven its circulation since 2008. Later, PCV-4 was also detected in wild boar populations from China and domestic pigs from South Korea and Thailand. Currently, Asia is so far the only continent where this novel virus has been reported; few studies carried out in South America and Europe failed in the attempt to detect it. The objective of this Comment is to communicate the first detection of PCV-4 in Europe, specifically in wild boar and domestic pigs from Mid-South-Western Spain. A retrospective study was carried out on wild boar and domestic pigs, both extensively (Iberian breed) and intensively raised, from Spain and Italy, sampled between 1998 and 2022. PCV-4 genome detection was attempted using different conventional or quantitative real time PCR (qPCR) protocols and some positive results were confirmed through Sanger sequencing. A total of 57 out of 166 (34.3%) Spanish wild boar and 9 out of 223 (4%) Iberian pigs (both geographically located in the Mid-South-Western Spain) were qPCR positive, while the rest of tested animals from North-Eastern Spain and Italy were negative. Partial sequences of Rep or Cap genes of selected samples confirmed the presence of PCV-4. The relatively high prevalence in wild boar and the low one in Iberian pigs from the same areas suggests intra- and interspecific transmission, being the wild boar a potential viral reservoir. The epidemiological and clinical importance of these findings are currently unknown, but guarantees further research on this novel virus.

Occurrence of Rotavirus A Genotypes and Other Enteric Pathogens in Diarrheic Suckling Piglets from Spanish Swine Farms.

Species A rotavirus (RVA) is a major viral pathogen causing diarrhea in suckling piglets. Studies on its genetic heterogeneity have implications for vaccine efficacy in the field. In this study, fecal samples (n = 866) from diarrheic piglets younger than 28 days were analyzed over a two-year period (2018-2019). Samples were submitted from 426 farms located in 36 provinces throughout Spain and were tested using real-time PCR (qPCR) and reverse transcription real-time PCR (RT-qPCR) for five enteric pathogens. The individual prevalence was 89.4%, 64.4%, 44.9%, 33.7% and 4.4% for Clostridiumperfringens, Clostridioides (formerly Clostridium) difficile, species A rotavirus, species C rotavirus and porcine epidemic diarrhea virus, respectively. Most specimens (96.9%) were positive for at least one of the target pathogens, and more than 80% of samples harbored mixed infections. Nucleotide sequencing of 70 specimens positive for RVA revealed the presence of the VP7 genotypes G4, G9, G3, G5, G11 and the VP4 genotypes P7, P23, P6 and P13, with the combinations G4P7 and G9P23 being the most prevalent, and especially in the areas with the highest pig population. The study shows the extensive genetic diversity of RVA strains as well as discrepancies with the genotypes contained in the vaccine available in Spain, and multiple amino acid differences in antigenic epitopes of different G- and P- genotypes with the vaccine strains. Further investigations are needed to determine the efficacy of the vaccine to confer clinical protection against heterologous strains.