Comparison of Torque Teno Sus Virus (TTSuV) viral load in Porcine Circovirus Type 2 vaccinated and non-vaccinated pig herds

Molecular detection of porcine circovirus (PCV2 and PCV3), torque teno swine virus 1 and 2 (TTSuV1 and TTSuVk2), and histopathological findings in swine organs submitted to regular slaughter in Southeast, Brazil

Porcine circovirus 2 and 3 (PCV2 and PCV3) and torque teno sus virus 1 and 2 (TTSuV1 and TTSuVk2) are important pathogens in pig associated with post-weaning mortality, different clinical syndromes in adults (PCVAD), and a decrease of average daily weight gain (PCV2-SI) but little is known about the infection on asymptomatic pigs. The aim of this study was to evaluate the presence of PCV2, PCV3, TTSuV1, and TTSuVk2 in swine organ samples from asymptomatic pigs slaughtered in Espírito Santo State, South-eastern Brazil, through molecular detection and histopathological analysis. Nested PCR showed the presence of PCV2 DNA in 10% (14/140), PCV3 in 13.6% (19/140), TTSuV1 in 12.9% (18/140), and TTSuVk2 in 30% (42/140) of the tissue samples. All four viruses were detected in the lung, kidney, lymph node, and liver. TTSuVk2 was detecded in 30% (42/140), PCV3 in 13.6% (19/140), TTSuV1 in 12.9% (18/140), and PCV2 in 10% (14/140) of the samples. Single infections were observed in 30.7% (43/140), while co-detections in the same tissue occurred in 15.7% (22/140). The most frequent combinations were TTSuV1/TTSuVk2 in 31.8% (7/22), PCV2/TTSuVk2 in 18.1% (4/22), and PCV2/PCV3/TTSuVk2 in 13.6% (3/22). Lymphocyte depletion was associated with TTSuVk2 infection (p = 0.0041) suggesting that TTSuVK2 plays an induction of PMWS-like lymphoid lesions in pigs. The data obtained in this study show that PCV2, PCV3, TTSuV1, and TTSuVk2 are related to infection in asymptomatic animals with different tissue lesions, and the molecular diagnosis for these pathogens should be considered in the sanitary monitoring of herds.

Postweaning mortality in commercial swine production II: review of infectious contributing factors

Postweaning mortality is extremely complex with a multitude of noninfectious and infectious contributing factors. In the current review, our objective is to describe the current state of knowledge regarding infectious causes of postweaning mortality, focusing on estimates of frequency and magnitude of effect where available. While infectious mortality is often categorized by physiologic body system affected, we believe the complex multifactorial nature is better understood by an alternative stratification dependent on intervention type. This category method subjectively combines disease pathogenesis knowledge, epidemiology, and economic consequences. These intervention categories included depopulation of affected cohorts of animals, elimination protocols using knowledge of immunity and epidemiology, or less aggressive interventions. The most aggressive approach to control infectious etiologies is through herd depopulation and repopulation. Historically, these protocols were successful for Actinobacillus pleuropneumoniae and swine dysentery among others. Additionally, this aggressive measure likely would be used to minimize disease spread if either a foreign animal disease was introduced or pseudorabies virus was reintroduced into domestic swine populations. Elimination practices have been successful for Mycoplasma hyopneumoniae, porcine reproductive and respiratory syndrome virus, coronaviruses, including transmissible gastroenteritis virus, porcine epidemic diarrhea virus, and porcine deltacoronavirus, swine influenza virus, nondysentery Brachyspira spp., and others. Porcine circovirus type 2 can have a significant impact on morbidity and mortality; however, it is often adequately controlled through immunization. Many other infectious etiologies present in swine production have not elicited these aggressive control measures. This may be because less aggressive control measures, such as vaccination, management, and therapeutics, are effective, their impact on mortality or productivity is not great enough to warrant, or there is inadequate understanding to employ control procedures efficaciously and efficiently. Since there are many infectious agents and noninfectious contributors, emphasis should continue to be placed on those infectious agents with the greatest impact to minimize postweaning mortality.

Retrospective study of the relationship of Torque teno sus virus 1a and Torque teno sus virus 1b with porcine circovirus associated disease

Genus Iotatorquevirus consists of 2 species, Torque teno sus virus 1a and Torque teno sus virus 1b, which are ubiquitous in swine populations, and are widely reported in association with porcine circovirus associated disease (PCVAD). To evaluate the relationship with PCVAD, 100 formalin-fixed paraffin-embedded tissue samples were used to detect both Iotatorquevirus species by nested PCR and sequencing. Sixty-eight PCVAD cases were selected as well as 32 porcine circovirus type 2 (PCV2) non-affected cases. Overall, 33 of the 100 cases were positive for Torque teno sus virus 1a and 8 of 100 were positive for Torque teno sus virus 1b. Only 24 of 68 (35%) PCVAD cases were positive for Torque teno sus virus 1a; 39% (9/23) of post-weaning multisystemic wasting syndrome, and 33% (15/45) of PCV2-associated reproductive failure cases. Among PCV2 non-affected cases, 28% were positive for Torque teno sus virus 1a and 6% were positive for Torque teno sus virus 1b. Torque teno sus virus 1b was not detected in PCV2-associated reproductive failure cases. Regardless of the PCV2-status, a lower frequency of both Iotatorquevirus species was found than depicted in other reports and there was no statistical relationship with PCVAD (χ ² < 0.01). Given the worldwide genomic variability of Iotatorquevirus species, it is feasible that species prevalent in Mexico share a lower nucleotide sequence identity, leading to different pathogenic potential.

Molecular detection and genomic characterization of Torque teno canis virus in domestic dogs in Guangxi Province, China

The Torque teno canis virus (TTCaV) is a small virus with circular single-stranded DNA that has been reported to cause infections in dogs. The present study aimed to identify the presence of TTCaV in blood samples obtained from domestic dogs, and examine its diversity and evolution of the genomes. Five strains of TTCaV were detected, and the overall prevalence was found to be 7% (28/400). Phylogenetic analysis showed that the five genomes were closely clustered with the previously known Cf-TTV10 and LDL strains and formed a Thetatorque virus. Homology analysis of the whole genome showed a sequence identity of 94.6%-96.8% among the five genomes. The percent sequence similarity among the five complete genomes ranged from 95.3% to 97.4% and from 95.1% to 97% compared to the Cf-TTV10 and LDL strains respectively. The ORF1-encoded amino acid sequences showed 94.4%-97.2% identity among the five isolates. Our findings suggest that the TTCaV has a large genetic diversity and showed that TTCaV and canine parvovirus (CPV) co-infection exists in China. Further studies on the pathogenicity of TTCaV are required.

Analysis of TTSuV1b antibody in porcine serum and its correlation with four antibodies against common viral infectious diseases

Background

The purpose of the present study was to evaluate the correlation between Torque teno sus virus 1b (TTSuV1b) infection and other viral infections or vaccine immunization in conventional pigs.

Methods

With overexpressed and purified viral protein TTSuV1b as antigen, an indirect enzyme-linked immunosorbent assay (ELISA) method for detecting TTSuV1b antibody was established, which demonstrated great specificity and reproducibility. Porcine serum samples (n = 212) were tested using ELISA. Meanwhile, the antibodies against Classical Swine Fever Virus (CSFV), Pseudorabies Virus (PRV), Porcine Reproductive and Respiratory Syndrome Virus (PRRSV), and Porcine Circovirus 2 (PCV2) were also examined using the commercial kits.

Results

Statistical analysis indicated that the level of anti-TTSuV1b antibody was positively correlated with the level of anti-PCV2 antibody in a lesser extent; the level of antibodies against TTSuV1b or PCV2 were significantly lower in porcine serum with low level of TTSuV1b virus, implicating the potential consistency and synchronization in the mechanism of TTSuV1b and PCV2 infection. Whereas, antibodies against PRRSV or CSFV showed no statistical significance on comparison with anti-TTSuV1b antibody, implicating that in conventional pigs, the antibody level for PRRSV and CSFV were not significantly influenced by TTSuV1b infection.

Conclusion

In conclusion, examination of anti-TTSuV1b antibody in porcine serum with the presently established ELISA method would serve as a supplementary approach for etiological investigation, and the combined statistical analysis of the antibodies against four other viruses might help to further understand the TTSuV1b infection as well as its pathogenicity.

Whole genome sequencing and phylogenetic analysis of feline anelloviruses

Torque teno felis virus (FcTTV) was detected in the cat population in the Czech Republic. A total of 110 serum samples were tested by a nested PCR technique using specific primers, situated in the highly conserved untranslated region of the virus genome. The frequency of feline TT virus in the Czech Republic was found to be 33.63%. Sequencing of PCR product from several virus strains showed that all of them are closely related and belong to the same virus species. Whole genome sequencing of three strains was performed to compare overall genetic heterogeneity of feline TT viruses. One of these three strains showed more that 10% difference at the nucleotide level. Furthermore we didn't find any correlation between FcTTV infection and sex or health status of examined animals.

Increased viral load and prevalence of Torque teno sus virus 2 (TTSuV2) in pigs experimentally infected with classical swine fever virus (CSFV)

Torque teno sus viruses (TTSuVs) are considered non-pathogenic viruses, although lately they have been linked to porcine circovirus diseases, mainly with post weaning multisystemic wasting syndrome (PMWS). These associations point out a possible pathogenic role of TTSuVs or, alternatively, that TTSuV replication is up-regulated under disease conditions. In order to further explore the association of TTSuVs with disease occurrence, TTSuVs prevalence and viral load were assessed before and after an experimental infection with a highly pathogenic classical swine fever (CSF) virus (CSFV) isolate. Serum samples from 56 animals were analyzed by means of a real time quantitative PCR (qPCR) for TTSuV1 and TTSuV2 before and after (between 6 and 13 days post-inoculation) the CSFV challenge. Based on the post-infection clinical evolution and immune response against CSFV, the animals were divided into two groups: group I, with protecting immunity against CSFV and no clinical signs at the day of necropsy, and group II, with no detectable immune response against CSFV and moderate to severe clinical signs. TTSuVs qPCR results indicated that TTSuV2 and not TTSuV1 load in serum increased significantly after challenge with CSFV in the group of pigs with clinical signs, specifically in those with a moderate course of the disease. Therefore, this study emphasizes the different behaviour of both TTSuVs, as already found in the PMWS background, and further supports the association of TTSuV2 with disease occurrence.