Recurrent viremia in pigs naturally exposed to PCV2 infection and the shedding mainly through the fecal route are the two most important epidemiologic phenomena that allows both horizontal and vertical PCV2 transmission. One way to test the ability of a strategy to reduce PCV2 circulation is to measure its influence on viremia and on shedding through natural routes (nasal, fecal, vaginal). In this paper we present quantitative data on the effect of PCV2 vaccination in 2 trials run in the same conditions and aimed to assess PCV2 viremia and shedding in conventional gilts from a farm with high serological and viral prevalence of PCV2. Animals were purchased from a PCV2 infected farm in which no PCV2 vaccination was performed. Thirty pure Large White gilts were randomly divided in 3 groups and stabled in three different rooms as follows: vaccinated-infected (VI) group (n=6 trial 1 and n=6 trial 2), first vaccination at 16 weeks of age, the second one month later (CIRCOVAC®, MERIAL, France- 2 mL, IM), non-vaccinated infected (NVI) group (n=6 trial 1 and n=6 trial 2), and control (C) group (not-vaccinated not-infected) (n=3 trial 1 and n=3 trial 2). Hormonal estrus synchronization was followed by artificial insemination with a single (trial 1) or double (trial 2) semen dose (PCV2 negative by PCR) spiked with 0.2 ml of a suspension containing 103.9 TCID50/25 μl of PCV2 (VI and NVI groups), and one or two doses (trial 1 or 2, respectively) with no viral particles (C group). After ultrasonography at 29 days post-insemination (DPI), empty animals were euthanized at 30 DPI whilst pregnant ones between 52 and 56 DPI. Vaginal, nasal and rectal swabs, and blood samples were weekly collected from -2 DPI till the end of the experimental period and tested by real time-PCR for PCV2. During necropsy tissues from each fetus as well as placentas were collected and submitted to PCV2 real time-PCR (qPCR). Results of trials 1 and 2 were pooled since both the experimental conditions and the readouts were equivalent. In each of the VI and NVI groups respectively 7 and 6 out of the 12 gilts were pregnant at 29 DPI, while 4 out of 6 in the C group. VI group showed a significantly lower proportion of qPCR positive in vivo collected samples: 88/224 (VI) vs 174/306 (NVI) and 80/165 (C) (Chi Square =45.2.; P<0.0001). Results of these two trials show a significantly lower proportion of viremia and shedding in the VI group compared to the NVI and C groups, but not between these latter two groups. The percentage of fetal tissues positive to PCV2 by PCR was significantly higher in NVI group compared to the other two but not between VI and C and the same observation was apparent also for placenta. The vaccine has clearly demonstrated an active role in reducing viremia and shedding even after an experimental infection. A probable consequence of the reduced viremia is the lowest percentage of placentas and fetal tissues PCV2 positive by qPCR. The synthesis of data strongly highlights a conclusive role of vaccination to reduce as well as the horizontal also the vertical transmission of PCV2. The choice to use in these trials conventional gilts from a PCV2 infected farm was aimed to produce data on the vaccination effect as close as possible to field condition and by using a category of animals, the gilt, in which, due to the highly variable level of antibodies after natural exposure, the possibility of PCV2 infection is higher.

Anti-PCV2 vaccination significantly reduces viremia and shedding after experimental infection of conventional gilts / F. Ostanello; S. Panarese; C. Bianco; G. Galeati; M.L. Bacci; M. Dottori; P. Bonilauri; G. Leotti; T. Vila; F. Joisel; G. Sarli. - STAMPA. - II:(2014), pp. 344-344. (Intervento presentato al convegno 23rd International Pig Veterinary Society (IPVS) Congress tenutosi a Cancun, Quintana Roo, Mexico nel June 8 – 11, 2014).

Anti-PCV2 vaccination significantly reduces viremia and shedding after experimental infection of conventional gilts

OSTANELLO, FABIO;PANARESE, SERENA;BIANCO, CARLO;GALEATI, GIOVANNA;BACCI, MARIA LAURA;SARLI, GIUSEPPE
2014

Abstract

Recurrent viremia in pigs naturally exposed to PCV2 infection and the shedding mainly through the fecal route are the two most important epidemiologic phenomena that allows both horizontal and vertical PCV2 transmission. One way to test the ability of a strategy to reduce PCV2 circulation is to measure its influence on viremia and on shedding through natural routes (nasal, fecal, vaginal). In this paper we present quantitative data on the effect of PCV2 vaccination in 2 trials run in the same conditions and aimed to assess PCV2 viremia and shedding in conventional gilts from a farm with high serological and viral prevalence of PCV2. Animals were purchased from a PCV2 infected farm in which no PCV2 vaccination was performed. Thirty pure Large White gilts were randomly divided in 3 groups and stabled in three different rooms as follows: vaccinated-infected (VI) group (n=6 trial 1 and n=6 trial 2), first vaccination at 16 weeks of age, the second one month later (CIRCOVAC®, MERIAL, France- 2 mL, IM), non-vaccinated infected (NVI) group (n=6 trial 1 and n=6 trial 2), and control (C) group (not-vaccinated not-infected) (n=3 trial 1 and n=3 trial 2). Hormonal estrus synchronization was followed by artificial insemination with a single (trial 1) or double (trial 2) semen dose (PCV2 negative by PCR) spiked with 0.2 ml of a suspension containing 103.9 TCID50/25 μl of PCV2 (VI and NVI groups), and one or two doses (trial 1 or 2, respectively) with no viral particles (C group). After ultrasonography at 29 days post-insemination (DPI), empty animals were euthanized at 30 DPI whilst pregnant ones between 52 and 56 DPI. Vaginal, nasal and rectal swabs, and blood samples were weekly collected from -2 DPI till the end of the experimental period and tested by real time-PCR for PCV2. During necropsy tissues from each fetus as well as placentas were collected and submitted to PCV2 real time-PCR (qPCR). Results of trials 1 and 2 were pooled since both the experimental conditions and the readouts were equivalent. In each of the VI and NVI groups respectively 7 and 6 out of the 12 gilts were pregnant at 29 DPI, while 4 out of 6 in the C group. VI group showed a significantly lower proportion of qPCR positive in vivo collected samples: 88/224 (VI) vs 174/306 (NVI) and 80/165 (C) (Chi Square =45.2.; P<0.0001). Results of these two trials show a significantly lower proportion of viremia and shedding in the VI group compared to the NVI and C groups, but not between these latter two groups. The percentage of fetal tissues positive to PCV2 by PCR was significantly higher in NVI group compared to the other two but not between VI and C and the same observation was apparent also for placenta. The vaccine has clearly demonstrated an active role in reducing viremia and shedding even after an experimental infection. A probable consequence of the reduced viremia is the lowest percentage of placentas and fetal tissues PCV2 positive by qPCR. The synthesis of data strongly highlights a conclusive role of vaccination to reduce as well as the horizontal also the vertical transmission of PCV2. The choice to use in these trials conventional gilts from a PCV2 infected farm was aimed to produce data on the vaccination effect as close as possible to field condition and by using a category of animals, the gilt, in which, due to the highly variable level of antibodies after natural exposure, the possibility of PCV2 infection is higher.
2014
Proceedings of the 23rd International Pig Veterinary Society (IPVS) Congress
344
344
Anti-PCV2 vaccination significantly reduces viremia and shedding after experimental infection of conventional gilts / F. Ostanello; S. Panarese; C. Bianco; G. Galeati; M.L. Bacci; M. Dottori; P. Bonilauri; G. Leotti; T. Vila; F. Joisel; G. Sarli. - STAMPA. - II:(2014), pp. 344-344. (Intervento presentato al convegno 23rd International Pig Veterinary Society (IPVS) Congress tenutosi a Cancun, Quintana Roo, Mexico nel June 8 – 11, 2014).
F. Ostanello; S. Panarese; C. Bianco; G. Galeati; M.L. Bacci; M. Dottori; P. Bonilauri; G. Leotti; T. Vila; F. Joisel; G. Sarli
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/341917
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