TORQUE TENO VIRUS
FRANCISCO RUIZ-FONS
Instituto de Investigacion en Recursos Cinegeticos IREC (CSIC-UCLM-JCCM), Ciudad Real, Spain
Torque teno virus (TTV), also named transfusion transmitted virus, or TT virus, is an unenveloped, spherical virus with a single-stranded 2.8-3.9kb circular DNA genome belonging to the floating genus (genus classification not ascribed) Anellovirus.
Torque teno viruses have been classified into five different genogroups with at least 39 genotypes identified. TTV- infecting swine are distinct from human TTV, and currently TTV1 and TTV2 genogroups have been described in domestic pigs and wild boar(45).TTV has a ubiquitous distribution and has been detected in humans, several nonhuman primates, cattle, sheep, camels, water buffalo, swine, dogs, cats, a tree shrew (Tupaia belangeri chinensis) and chickens. Swine TTV has been reported in domestic pigs and also in wild boar (Sus scrofa) from Spain(45).
Epidemiological studies of TTV in animals are scarce. Nonetheless, it seems that age is a risk factor for increasing prevalence in humans, domestic pigs and wild boar(45). TTV has been detected in excretions from humans and animals, and vertical transmission is also possible.
Human TTV seems to replicate in bone marrow, liver and respiratory tract, but shortly after infection nearly all organs harbour TTV No information on the sites of swine TTV replication is available.
Attempts to link TTV infection with clinical disease in humans have been unsuccessful. Experimentally infected gnotobiotic piglets developed post-weaning multisystemic wasting syndrome when infected by porcine circovirus type 2 (PCV2) after TTV1 infection and TTV1 has been also found associated with porcine respiratory and reproductive syndrome virus in triggering porcine dermatitis and nephropathy syndrome in the absence of PCV2. No clinical manifestations have been found to date in wild boar.
PCR is the most useful diagnostic test for TTV in humans and animals, whereas serological methods are only used in humans.
Information on TTV in wildlife is scarce, and the potential role of the virus in possibly triggering clinical disease is unknown. The role of wildlife in the epidemiology of TTV cannot be ruled out with the available information.