Swine torque teno virus (TTV) infection and excretion dynamics in conventional pig farms

Abstract

14Torque teno virus (TTV) is a non-enveloped, single stranded DNA (ssDNA) 15 virus infecting human and non-primate species. Two genogroups of TTV (TTV1 and 16 TTV2) have been described in swine so far. In the present study, TTV1 and TTV2 17 prevalences in serum, and nasal as well as rectal swabs of 55 randomly selected piglets 18 from seven Spanish multi-site farms, were monitored from 1 to 15 weeks of age. Also, 19 blood from their dams (n=41) were taken at 1 week post-farrowing. Samples were 20 tested by means of two TTV genogroup specific PCRs. Although prevalence of TTV1 21 and TTV2 in sows was relatively high (54% and 32%, respectively), it was not directly 22 associated to their prevalence in the offspring. Percentage of viremic pigs for both TTV 23 genogroups followed similar dynamics, increasing progressively over time, with the 24 highest rate of detection at 11 weeks of age for TTV1 and at 15 weeks for TTV2. Forty-25 two (76%) and 33 (60%) of the 55 studied pigs were TTV1 and TTV2 PCR positive in 26 serum, respectively, in more than one sampling time. TTV1 and TTV2 viremia lasted in 27 a number of animals up to 15 and 8 weeks, respectively. Co-infection with both TTV 28 genogroups in serum was detected at all sampling points, but at 1 week of age. On the 29 contrary, there were animals PCR negative to both genogroups in serum at all sampling 30 times but at 15 weeks of age. During the study period, TTV1 and TTV2 nasal shedding 31 increased also over time and faecal excretion was intermittent and of low percentage 32 (<20%). In conclusion, the present study describes for the first time the infection 33 dynamics of TTV1 and TTV2 as well as the nasal and faecal excretion throughout the 34 life of in pigs from conventional, multi-site farms. Moreover, results indicate that both 35 swine TTV genogroups are able to establish persistent infections in a number of pigs. 36

Torque teno sus virus (TTSuV) infection at different stages of pig production cycle

“…These results indicate that TTSuV infection has spread to pigs of all production stages. Finisher pigs had significantly higher rates of TTSuV detection than animals from the other stages, in agreement with previous studies that have reported that TTSuV infection increases with the age of the animals (Sibila et al 2009b, Aramouni et al 2010). …”

“…In our study, the overall percentage of TTSuV-positive pigs (66.3%) was higher than that described in a study performed with rectal swabs (Sibila et al 2009b), which reported a low percentage (<20%) of TTSuV detection. Previous studies reported higher rates for TTSuV in fecal samples, suggesting that the fecal-oral route is an important route of TTSuV transmission (Brassard et al 2008, Leme et al 2012).…”

“…These findings are corroborated by the results at the farm level; 5 of the 9 grower-to-finish farms did not present positive results for single infections of TTSuV1. A similar result was obtained in a longitudinal study performed with 1 to 15 week-old animals, which evaluated the presence of TTSuV in different biological samples (Sibila et al 2009b). Specifically, in that study TTSuV1 was detected more frequently than TTSuV2 from the nasal swabs of animals up to 7 weeks of age, but the rate of TTSuV2 detection was higher (p<0.05) than the rate of TTSuV1 in pigs Different letters indicate statistically significant differences (p<0.05).…”

“…Moreover, analysis of the rectal swabs demonstrated that the percentage of TTSuV2-positive pigs increased progressively from 7 weeks of age onwards, whereas the detection of TTSuV1-positive pigs was fairly constant throughout the study (Sibila et al 2009b). Although the data from both studies show similar trends, there is no clear explanation for the inversion in the rates of infection by TTSuV species.…”

“…Studies have demonstrated the presence of TTSuV in the serum and organs of pigs of different ages (Kekarainen & Segalés 2012) and have shown that the prevalence increases with the age of the animals (Sibila et al 2009b, Aramouni et al 2010. In Brazil, TTSuV infection has been identified in suckling piglets (Leme et al 2012) and slaughter-age pigs (Leme et al 2013), and in the reproductive tracts of boars and sows (Ritterbusch et al 2012).…”