Objective—To determine whether genogroup 1 porcine torque teno virus (g1-TTV) can potentiate clinical disease associated with porcine circovirus type 2 (PCV2).
Sample population—33 gnotobiotic baby pigs.
Procedures—Pigs were allocated into 7 groups: group A, 5 uninoculated control pigs from 3 litters; group B, 4 pigs oronasally inoculated with PCV2 alone; group C, 4 pigs inoculated IP with first-passage g1-TTV alone; group D, 4 pigs inoculated IP with fourth-passage g1-TTV alone; group E, 6 pigs inoculated IP with first-passage g1-TTV and then oronasally inoculated with PCV2 7 days later; group F, 6 pigs inoculated IP with fourth-passage g1-TTV and then inoculated oronasally with PCV2 7 days later; and group G, 4 pigs inoculated oro-nasally with PCV2 and then inoculated IP with fourth-passage g1-TTV 7 days later.
Results—6 of 12 pigs inoculated with g1-TTV prior to PCV2 developed acute onset of postweaning multisystemic wasting syndrome (PMWS). None of the pigs inoculated with g1-TTV alone or PCV2 alone or that were challenge exposed to g1-TTV after establishment of infection with PCV2 developed clinical illness. Uninoculated control pigs remained healthy.
Conclusions and Clinical Relevance—These data implicated g1-TTV as another viral infection that facilitates PCV2-induced PMWS. This raises the possibility that torque teno viruses in swine may contribute to disease expression currently associated with only a single infectious agent.
Objective—To determine whether porcine dermatitis and nephropathy syndrome (PDNS) could be experimentally induced in gnotobiotic swine.
Sample Population—Plasma samples from 27 sows and 20 conventional weaned piglets were obtained, and 30 gnotobiotic pigs were used in experiments.
Procedures—3 experiments were conducted. Groups of 3-day-old gnotobiotic pigs were inoculated with pooled plasma samples obtained from healthy feeder pigs in a herd that was in the initial phases of an outbreak of respiratory disease; gross and histologic lesions of PDNS were detected in the inoculated pigs. In a second experiment, 2- and 3-day-old gnotobiotic pigs were inoculated with porcine reproductive respiratory syndrome virus (PRRSV) and with PRRSV-negative tissue homogenate containing genogroup 1 torque teno virus (g1-TTV). Lesions of PDNS were detected.
Results—Pigs inoculated with pooled plasma or the combination of tissue-culture–origin PRRSV and g1-TTV tissue homogenate developed systemic hemostatic defects, bilaterally symmetric cutaneous hemorrhages, generalized edema, icterus, bilaterally symmetric renal cortical hemorrhage, dermal vasculitis with hemorrhage, and interstitial pneumonia consistent with a clinical and pathologic diagnosis of PDNS. The PRRSV RNAs and g1-TTV DNAs were detected in plasma; all pigs seroconverted to PRRSV, and all had negative results for porcine circovirus type 2 when tested by use of PCR assays.
Conclusions and Clinical Relevance—These data suggested that PDNS is a manifestation of disseminated intravascular coagulation in swine. For the experimental conditions reported here, combined infection with g1-TTV and PRRSV was implicated in the genesis of these lesions.
Objective—To determine whether commercial Mycoplasma hyopneumoniae bacterins sold for use in swine contain porcine torque teno virus (TTV).
Sample Population—22 commercially available M hyopneumoniae bacterins.
Procedures—Direct and nested PCR assays for genogroup-specific TTV DNAs were performed on serials of M hyopneumoniae bacterins by use of published and custom-designed primer pairs at 3 laboratories in North America and Europe.
Results—Of the 22 bacterins tested by use of direct and nested PCR assays, 7 of 9 from the United States, 2 of 5 from Canada, and 4 of 8 from Europe contained genogroup 1– and genogroup 2–TTV DNAs. In some bacterins, the TTV DNAs were readily detected by use of direct PCR assays.
Conclusions and Clinical Relevance—Analysis of these data indicated that many of the commercially available M hyopneumoniae bacterins were contaminated with TTV DNA. It is possible that some of these bacterins could inadvertently transmit porcine TTV infection to TTV-naïve swine.