High Prevalence of Co-Infection with Multiple Torque Teno Sus Virus Species in Italian Pig Herds

Abstract

Torque teno viruses (TTVs) are a large group of vertebrate-infecting small viruses with circular single-stranded DNA, classified in the Anelloviridae family. In swine, two genetically distinct species, Torque teno sus virus 1a (TTSuV1a) and 1b (TTSuV1b) are currently grouped into the genus Iotatorquevirus. More recently, a novel Torque teno sus virus species, named Torque teno sus virus k2b (TTSuVk2b), has been included with Torque teno sus virus k2a (TTSuVk2a) into the genus Kappatorquevirus. In the present study, TTSuV1 (TTSuV1a and TTSuV1b), TTSuVk2a and TTSuVk2b prevalence was evaluated in 721 serum samples of healthy pigs from Sardinian farms, insular Italy. This is the largest study to date on the presence of TTSuV in healthy pigs in Italy. The global prevalence of infection was 83.2% (600/721), being 62.3% (449/721), 60.6% (437/721), and 11.5% (83/721) the prevalence of TTSuV1, TTSuVk2a and TTSuVk2b, respectively. The rate of co-infection with two and/or three species was also calculated, and data show that co-infections were significantly more frequent than infections with single species, and that TTSuV1+TTSuVk2a double infection was the prevalent combination (35.4%). Quantitative results obtained using species-specific real time-qPCR evidenced the highest mean levels of viremia in the TTSuV1 subgroup, and the lowest in the TTSuVk2b subgroup. Interestingly, multiple infections with distinct TTSuV species seemed to significantly affect the DNA load and specifically, data highlighted that double infection with TTSuVk2a increased the viral titers of TTSuV1, likewise the co-infection with TTSuVk2b increased the titers of TTSuVk2a.

Global impact of Torque teno virus infection in wild and domesticated animals

“…Data related to infection with TTSuVk2b, the most recently identified species, are still limited. A study on 244 pig serum samples from 17 different countries reported an overall 40% prevalence of infection [36], whereas Blois et al reported an 11.5% prevalence of TTSuVk2b in 721 Italian pigs [70]. The high prevalence of TTSuV in the swine population indicates the existence of effective mechanisms of transmission.…”

“…Regarding AVs infecting animals, most studies to date have focused on the role of TTSuV in pig diseases. Although TTSuVs were found at particularly high frequency in healthy animals [70,72], they are currently receiving more attention due to the latest results on disease association. In fact, TTSuVs are considered non-pathogenic by themselves, but there is increasing evidence that points to their influence on the development of some diseases or suggests that these viruses even affect disease outcome [66].…”

High detection rates of Torque teno sus virus in co-infection with important viral pathogens in porcine kidneys on St. Kitts Island, Lesser Antilles

“…TTSuVs possess a single‐stranded, circular DNA genome (Meng, ). Porcine TTSuVs have been classified into two genera, genus Iotatorquevirus (TTSuV1, species TTSuV1a and TTSuV1b) and genus Kappatorquevirus (TTSuVk2a, and the more recently reported novel TTSuV species, TTSuVk2b) (Blois et al., ; Cornelissen‐Keijsers et al., ; Kekarainen & Segalés, ; Rogers et al., ). TTSuV DNA has been found in various porcine tissues including brain, bone marrow, heart, liver, lungs, lymph nodes, kidneys and spleen, indicating a tropism for multiple tissues (Aramouni, Segalés, Cortey, & Kekarainen, ; Kekarainen & Segalés, ; Meng, ; Monini et al., ; Nieto, Kekarainen, Aramouni, & Segalés, ).…”

“…High prevalence rates of TTSuV1 and TTSuVk2a including co‐infection with these viruses species have been reported in both diseased and apparently healthy pigs from different parts of the world (Blois et al., ; Kekarainen & Segalés, ; Meng, ). Although the pathogenicity of TTSuV remains to be clearly elucidated, it is possible that TTSuVs may act as a cofactor, or trigger the development of disease caused by other porcine pathogens (Kekarainen & Segalés, ; Meng, ; Rogers et al., ).…”

“…High prevalence rates of TTSuV1 and TTSuVk2a including coinfection with these viruses species have been reported in both diseased and apparently healthy pigs from different parts of the world (Blois et al, 2014;Meng, 2012).…”