Epidemiology and evolutionary analysis of Torque teno sus virus

A panoramic view of the molecular epidemiology, evolution, and cross-species transmission of rosaviruses

Rosavirus is a newly discovered member of the family Picornaviridae that was initially detected in wild rodents and subsequently in children with diarrhoea. Nevertheless, there is a significant gap in our understanding of the geographical distribution, phylogenetic relationships, evolutionary patterns, and transmission of rosaviruses. To address these issues, we analysed 434 rodents and shrews from five different species that were collected in southern China. Using PCR screening of faecal samples, we detected rosaviruses in Norway rats (Rattus norvegicus) and identified two previously undocumented host species: tanezumi rats (Rattus tanezumi) and Asian house shrews (Suncus murinus). Rosaviruses were particularly common in these animals, with an overall prevalence rate of 32.49% (141/434). For genetic and evolutionary analyses, we selected six representative positive samples to amplify the complete genomes of rosaviruses. Bayesian phylogenetic analysis suggested that our sequences clustered within the genus Rosavirus, where genotype B sequences are the closest relatives. The elevated nonsynonymous-to-synonymous ratios observed in rosavirus B may be attributed to relaxed selection pressures driven by virus spillover events. On the basis of the available data, it is hypothesized that the genus Rosavirus may have originated from Norway rats around the year 1339. In summary, these findings provide valuable insights into the complex evolutionary history of rosaviruses and underscore the urgent need for ongoing surveillance of this virus.

Development and application of a quadruplex real-time PCR method for Torque teno sus virus 1, Porcine circovirus type 2, pseudorabies virus, and porcine parvovirus

Introduction

In clinical diagnosis of porcine diseases, co-infection with multiple viruses often leads to similar clinical symptoms. Postweaning multisystemic wasting syndrome (PMWS) can be caused by infections with TTSuV or PCV2, while PCV2, PRV, and PPV can cause respiratory and reproductive disorders in pigs. The overlapping clinical and pathological features of these infections necessitate the development of a rapid and specific method for differentiating and detecting these four DNA viruses.

Methods

In this study, four pairs of primers and TaqMan probes were designed targeting the conserved sequence of TTSuV, the Rep gene of PCV2, the gE gene of PRV, and the VP2 gene of PPV. After optimizing reaction conditions, including annealing temperature, primer concentration, and probe concentration, a quadruplex real-time PCR method was developed.

Results

This method can specifically detect TTSuV1, PCV2, PRV, and PPV simultaneously, with no cross-reactivity with ASFV, CSFV, PRRSV, PEDV, PSV, and TGEV. The minimum detection limit for each virus was 10 copies/μl, and the inter-assay and intra-assay coefficients of variation ranged from 0.33% to 1.43%. Subsequently, 150 clinical samples were tested to evaluate the practical applicability of this method. The positive rates for TTSuV1, PCV2, PRV, and PPV were 8.6% (13/150), 10.67% (16/150), 14% (21/150), and 11.33% (17/150), respectively.

Discussion

The results indicate that the established quadruplex real-time PCR method can assist in the accurate and rapid diagnosis of TTSuV1, PCV2, PRV, and PPV in clinical settings, providing robust support for the prevention and control of these infections.

The Synergic Role of Emerging and Endemic Swine Virus in the Porcine Respiratory Disease Complex: Pathological and Biomolecular Analysis

Porcine respiratory disease complex (PRDC) represents a significant threat to the swine industry, causing economic losses in pigs worldwide. Recently, beyond the endemic viruses PRRSV and PCV2, emerging viruses such as TTSuV, PCV3, and PPV2, have been associated with PRDC, but their role remains unclear. This study investigates the presence of PCV2 and PRRSV and emerging viruses (PCV3, TTSuV, and PPV2) in the lungs of swine belonging to different age groups by histopathology and real-time PCR. The prevalent lung lesion was interstitial pneumonia with increased severity in post-weaning pigs. PRRSV was detected in 33% of piglets' lungs and in 20% of adults and post-weaning pigs with high Ct, while PCV2 was found in 100% of adult pigs, 33% of post-weaning pigs, and 22% of piglets, with low Ct in post-weaning pigs. PCV3 was present in all categories and coexisted with other viruses. TTSuV was detected in all swine in combination with other viruses, possibly influencing the disease dynamics, while PPV2 was detected in 100% of adults' and 90% of piglets' lungs. The detection of TTSuV, PCV3, and PPV2 in affected pigs prioritizes the need for comprehensive approaches in implementing appropriate control measures and minimizing economic losses associated with PRDC.

Torque Teno Sus Virus (TTSuV) Prevalence in Wild Fauna of Northern Italy

Torque teno sus virus (TTSuV) is a non-enveloped circular ssDNA virus which frequently infects swine and has been associated with hepatic, respiratory, and autoimmune disorders. TTSuV’s pathogenic role is still uncertain, and clear data in the literature on virus reservoirs are lacking. The aims of this study were to investigate the presence of potentially zoonotic TTSuV in wild animals in Northern Italy and to evaluate their role as reservoirs. Liver samples were collected between 2016 and 2020 during four hunting seasons from wild boars (Sus scrofa), red deer (Cervus elaphus), roe deer (Capreolus capreolus), and chamois (Rupicapra rupicapra). Samples originated from areas in Northern Italy characterized by different traits, i.e., mountains and flatland with, respectively low and high farm density and anthropization. Viral identification was carried out by end-point PCR with specific primers for TTSuV1a and TTSuVk2a species. TTSuV prevalence in wild boars was higher in the mountains than in the flatland (prevalence of 6.2% and 2.3%, respectively). In wild ruminants only TTSuVk2a was detected (with a prevalence of 9.4%). Our findings shed light on the occurrence and distribution of TTSuV in some wild animal species, investigating their possible role as reservoirs.