Please cite this article as: Segalés, J., Martínez-Guinó, L., Cortey, M., Navarro, N., Huerta, E., Sibila, M., Pujols, J., Kekarainen, T., Retrospective study on swine Torque teno virus genogroups 1 and 2 infection from 1985 to 2005 in Spain, Veterinary Microbiology (2007Microbiology ( ), doi:10.1016Microbiology ( /j.vetmic.2008 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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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