Torque teno virus (TTV) is a single-stranded DNA virus that has been detected in serum of primate and non-primate species including swine. Little information on swine TTV infection and transmission dynamics is nowadays available. Five papers published during 2009 describe the latest results obtained by the swine TTV group at CReSA.

TTVs are vertebrate infecting, single-stranded circular DNA viruses. Two genetically distinct TTV genogroups (TTV1 and TTV2) infect swine worldwide with high prevalence. Currently, swine TTVs are considered non-pathogenic, although TTV2 has been linked to post-weaning multisystemic wasting syndrome, a porcine circovirus disease .

A schematic representation of the genomic structure of swine TTV (an anellovirus). The size of the genome is given in base pairs.

Research on swine TTV at CReSA has been carried out since 2006. During 2009 the group has published five papers based on the results obtained. Below the main results of these papers are summarized:

• Horizontal route has been considered the main way of TTV transmission. However, no conclusive studies on vertical transmission have been done. This paper reports vertical transmission of swine TTVs, including transplacental and/or intra-uterine routes as well as via lactation.
  In: Evidence of Torque teno virus (TTV) vertical transmission in swine. Martínez-Guinó L, Kekarainen T, Segalés J. (2009) Theriogenology 71:1390-5.

• This review summarizes research on animal TTV, focusing in particular on TTV infection in pig, and considers how a porcine experimental infection model might assist in the study of human TTV infection.
  In: Torque teno virus infection in the pig and its potential role as a model of human infection. Kekarainen T, Segalés J. (2009) Veterinary Journal 180:163-8.

• The infection and transmission of TTV in suckling piglets was shown to occur early in the production system and virus may be transmitted from sow-to-piglet but also from piglet-to-piglet in farrowing facilities.
  In: Torque teno virus (TTV) infection in sows and suckling piglets. Sibila M, Martínez-Guinó L, Huerta E, Mora M, Grau-Roma L, Kekarainen T, Segalés J. (200) Veterinary Microbiology 137: 354-8.

• Pig materials are an important source of components used in porcine vaccine manufacturing, human drugs and commercial enzyme products. Results show that swine TTVs are contaminants not only of swine vaccines but also of human drugs containing porcine components and enzymes for laboratory use.
  In: Swine torque teno virus detection in pig commercial vaccines, enzymes for laboratory use and human drugs containing components of porcine origin. Kekarainen T, Martínez-Guinó L, Segalés J. (2009) Journal of General Virology 90:648-53.

• Data compiled in a retrospective study indicate that both swine TTV genogroups have been circulating at least since 1985 in the Spanish pig population, 14 years before the first description of TTV existence in pigs. Moreover, this is also the earliest evidence of TTV infection in any species.
  In: Retrospective study on swine Torque teno virus genogroups 1 and 2 infection from 1985 to 2005 in Spain. Segalés J, Martínez-Guinó L, Cortey M, Navarro N, Huerta E, Sibila M, Pujols J, Kekarainen T. (2009) Veterinary Microbiol ogy 134:199-207.