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หัวข้อ : TTV in pig
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TTV in pig 7 เดือน, 1 สัปดาห์ ก่อน
Torque teno virus (TTV) is a non-enveloped, circular, single-stranded DNA (ssDNA) virus that infects human, non-primate and domestic species, including swine (Kekarainen and Segal?s, 2009). In humans, TTV infection is ubiquitous and several genogroups have been identified (Bendinelli et al., 2001). However, up to now, a definitive proof linking infection in humans and a specific disease is missing ([Jelcic et al., 2004], [Peng et al., 2002] and [Maggi et al., 2003]). Frequency of human TTV detection in serum is very variable between countries and increases with age ([Komatsu et al., 2004] and [Saback et al., 1999]). Detection of the virus in serum of mother-to-child pairs, cord blood and breast milk has led to think that it can be transmitted vertically (Komatsu et al., 2004). Moreover, its detection in saliva, nasal secretions and faeces has suggested that it also spreads horizontally (Bendinelli et al., 2001).

In swine, two species-specific TTV genogroups (TTV1 and TTV2) have been so far described (Niel et al., 2005). Swine TTVs are ubiquitous and considered non-pathogenic. Nevertheless, a relation between TTV infection and post-weaning multisystemic wasting syndrome (PMWS) development has been suggested. On one hand, Kekarainen et al. (2006) found a higher TTV2 prevalence in PMWS-affected pigs than in healthy ones. On the other hand, Ellis et al. (2008) reported that a TTV1 inoculation prior to porcine circovirus type 2 (PCV2) infection in gnotobiotic pigs facilitated PMWS development. Furthermore, co-infection of TTV1 with porcine reproductive and respiratory syndrome virus (PRRSV) has been linked with the development of a porcine dermatitis and nephropathy syndrome-like condition in gnotobiotic pigs (Krakowka et al., 2008).

To date, TTV1 has been detected by PCR in sera from pigs from different countries including Canada, China, France, Italy, Spain, Thailand and USA, with prevalences ranging from 24% to 100% ([Bigarr? et al., 2005], [Kekarainen et al., 2006], Martelli et al., 2006 F. Martelli, A. Caprioli, I. Di Bartolo, V. Cibin, G. Pezzotti, F.M. Ruggeri and F. Ostanello, Detection of swine Torque Teno virus in Italian pig herds, J. Vet. Med. B 53 (2006), pp. 234?238. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (13)[Martelli et al., 2006] and [McKeown et al., 2004]). On the contrary, presence of TTV2 DNA in sera has only been described in two countries, Brazil (Niel et al., 2005) and Spain (Kekarainen et al., 2006). Apart from serum, swine TTVs have been also detected by PCR in plasma, semen, faeces and colostrum ([Brassard et al., 2008], [Kekarainen et al., 2007] and [Mart?nez-Guin? et al., 2009]).


Little information on epidemiology of TTV infection in pig herds is nowadays available. In Italy, number of TTV1 infected pigs in farms was very variable, ranging from 0% to 53% but was not related to herd size, sanitary status or biosecurity procedures (Martelli et al., 2006). TTV infections occur early in the production system and may be transmitted from sow-to-piglet or from piglet-to-piglet in the farrowing crates (Sibila et al., 2009). Besides, both swine TTVs have been detected in colostrum samples and in stillborns indicating vertical route of transmission (Mart?nez-Guin? et al., 2009). However, dynamics of infection and excretion of swine TTVs throughout the productive life of pigs are still unknown. Therefore, the purpose of this work was to study the infection and excretion evolution of TTV1 and TTV2 in healthy, naturally infected animals under field conditions between 1 and 15 weeks of age.
 
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