Lack of effect of piglet vaccination against Porcine circovirus type 2 (PCV2) on serum viral loads of Torque teno sus virus 2 (TTSuV2)

Anelloviruses are small, non-enveloped viruses with circular single stranded DNA, which infect a number of animal species as well as humans. In pigs, two distinct Torque teno sus virus (TTSuV) species have been described so far, being one of them linked to disease occurrence. Specifically, TTSuV2 loads in serum have been found increased in pigs suffering from postweaning multisystemic wasting syndrome (PMWS). Since this pathological condition is able to be controlled by means of porcine circovirus type 2 (PCV2) vaccination, it was hypothesized the possibility that such vaccination would have an impact on TTSuV2 prevalence and loads. A total of 150 pigs were divided in two study groups. Half of them received a PCV2 commercial vaccine, while the other half remained as non-vaccinated controls. PCV2 infection was monitored at 3-4, 8, 12, 16 and 21 weeks of age by means of an standard PCR, while TTSuV2 loads were determined at 8, 16 and 21 weeks of age by a quantitative PCR. No obvious PMWS clinical signs were observed among studied animals, although PCV2 infection was confirmed in both groups of pigs. Almost all pigs got TTSuV2 infection throughout the study period, independently of the PCV2 vaccination status of animals. Moreover, TTSuV2 load did not show significant differences between different pig groups at each sampling time, but mean viral load increased with age. Taking into account that previous results suggest that TTSuV2 load in serum is increased in the background of PMWS, the present study suggests that this is not the case in a PCV2 subclinical infection scenario. Therefore, vaccination of PCV2 subclinically infected pigs did not modify the outcome of TTSuV2 infection.