title: Transmission of Porcine reproductive and respiratory syndrome virus 1 to and from vaccinated pigs in a one-to-one model.
abstract: The present study examined transmission by contact of Porcine reproductive and respiratory syndrome virus (PRRSV) 1 in a one-to-one model to vaccinated and unvaccinated pigs and from vaccinated infected pigs to other vaccinated pigs. The experiment started by randomly assigning weaned pigs to groups V (n=24) and U (n=26). V pigs were vaccinated with a commercial live attenuated PRRSV vaccine and the U animals were kept as unvaccinated controls. Twenty-eight days later, 6U pigs were separated and allocated in individual boxes. The remaining 20U pigs were intranasally inoculated with PRRSV isolate 3267 (from now on designated as seeder (S) pigs) and 48h later were distributed in boxes where they were commingled with either V or U pigs in 1:1 groups (first contact phase), resulting in 6S:U and 14S:V pairs. As soon as a V pig was detected to be viremic because of contact with a S, the infected V (from now on designated as Vinf) was transferred (<24h after detection) to a new pen where it was comingled with a new V pig (designated as V2) in a second contact phase. For the first contact phase, pigs were maintained 21days at maximum and for the second contact phase the maximum exposure period was 14days. Two V pigs tested positive for the vaccine virus (>99.5% similarity) when they were relocated with the corresponding V2pigs and they were removed; thus, only 12Vinfwere finally considered. All V pigs (12/12) exposed to S animals became infected although the first detection of viremia occurred at 13.6±3.6days, one week later than in U (p<0.05). Also, duration of viremia was shorter for Vinfcompared to U, (5.5±4.3days versus 12.5±2.7days). The Vinfgroup showed remarkable individual variability: eight animals had a viremic period of 5 or less days (3.0±1.4) while the remaining four had a longer viremic period of more than one week (10.8±2.9). This situation was not observed in U. In the second contact phase, transmission from Vinfto V2pigs occurred in 7/8 cases (87.5%). The mean duration of viremia for V2was 4.8±3.4 and two different patterns were again observed: two animals had viremias of 9-10days and the rest averaged 3.0±1.4days (range: 2-5days). Vaccinated groups Vinfand V2had a significantly lower PRRSV shedding in oral fluids for at least the first 9days after the onset of the viremia compared to U, and shedding for V2 was even significantly lower (p<0.05) than shedding for Vinf. Our experimental design reproduced the worst-case scenario for evaluating the effect of vaccination and, under such conditions; it was still efficacious in slowering PRRSV transmission and decreasing the global viral load and particularly oral shedding.
authors.affiliation: UAB, Centre de Recerca en Sanitat Animal (CReSA, IRTA-UAB), Campus de la Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain; Departament de Sanitat i Anatomia Animals, Facultat de Veterinària, UAB, 08193 Bellaterra, Barcelona, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Pileri
authors.affiliation: Departament de Sanitat i Anatomia Animals, Facultat de Veterinària, UAB, 08193 Bellaterra, Barcelona, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Gibert
authors.affiliation: Departament de Sanitat i Anatomia Animals, Facultat de Veterinària, UAB, 08193 Bellaterra, Barcelona, Spain.
authors.forename: G E
authors.initials: GE
authors.lastname: Martín-Valls
authors.affiliation: Departament de Sanitat i Anatomia Animals, Facultat de Veterinària, UAB, 08193 Bellaterra, Barcelona, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Nofrarias
authors.affiliation: Departament de Sanitat i Anatomia Animals, Facultat de Veterinària, UAB, 08193 Bellaterra, Barcelona, Spain.
authors.forename: S
authors.initials: S
authors.lastname: López-Soria
authors.affiliation: UAB, Centre de Recerca en Sanitat Animal (CReSA, IRTA-UAB), Campus de la Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain; Departament de Sanitat i Anatomia Animals, Facultat de Veterinària, UAB, 08193 Bellaterra, Barcelona, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Martín
authors.affiliation: Departament de Sanitat i Anatomia Animals, Facultat de Veterinària, UAB, 08193 Bellaterra, Barcelona, Spain.
authors.forename: I
authors.initials: I
authors.lastname: Díaz
authors.affiliation: UAB, Centre de Recerca en Sanitat Animal (CReSA, IRTA-UAB), Campus de la Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain; Departament de Sanitat i Anatomia Animals, Facultat de Veterinària, UAB, 08193 Bellaterra, Barcelona, Spain.
authors.forename: L
authors.initials: L
authors.lastname: Darwich
authors.affiliation: UAB, Centre de Recerca en Sanitat Animal (CReSA, IRTA-UAB), Campus de la Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain; Departament de Sanitat i Anatomia Animals, Facultat de Veterinària, UAB, 08193 Bellaterra, Barcelona, Spain. Electronic address: enric.mateu@uab.cat.
authors.forename: E
authors.initials: E
authors.lastname: Mateu
mesh_terms: D000281:Administration, Intranasal / Q000662:veterinary; D000818:Animals; D019318:Porcine Reproductive and Respiratory Syndrome / Q000517:prevention & control / Q000635:transmission* / Q000821:virology; D019316:Porcine respiratory and reproductive syndrome virus / Q000276:immunology*; D013552:Swine; D013553:Swine Diseases / Q000517:prevention & control / Q000635:transmission* / Q000821:virology; D014611:Vaccination / Q000662:veterinary*; D014613:Vaccines, Attenuated / Q000276:immunology; D019562:Viral Load / Q000662:veterinary; D014765:Viral Vaccines / Q000276:immunology*; D014766:Viremia / Q000662:veterinary; D017201:Virus Shedding
chemical_list: D014613:Vaccines, Attenuated; D014765:Viral Vaccines
keywords: Porcine reproductive and respiratory syndrome virus; Transmission; Vaccination