Sibila et al. Porcine Health Management (2022) 8:41 https://doi.org/10.1186/s40813-022-00284-9 RESEARCH Open Access Descriptive analyses of maternally‑derived antibody levels against porcine circovirus 2 (PCV‑2) in 3‑ and 21‑day‑old piglets from farms of four European countries using different vaccination protocols in sows M. Sibila1,2,3*, A. Llorens1,2,3, E. Huerta1,2,3, C. Fablet4, M. Faderl5, L. Ferrari6, N. Rose4, A. Palzer5, P. Martelli6, M. C. Venegas‑Vargas7, D. Fredrickson7, L. Taylor7, M. Balasch8, M. Bandrick7 and J. Segalés1,3,9 Abstract Background: Up to now, information on the levels of maternally-derived antibodies (MDA) against PCV-2 in suckling piglets born to sows vaccinated with different strategies is scarce in the literature. In the present observational study, the PCV-2-specific MDA titres from piglets from 109 farms (thirty 3-day-old and thirty 21-day-old piglets per farm) across four different European countries (France n = 30, Germany n = 27, Italy n = 22 and Spain n = 30) using different sow vaccination strategies (during gestation, as a gilt, as a piglet or never) were assessed. Results: In all four countries, mean log PCV-2 MDA titres were higher in 3-day-old piglets than in the 3-week-old ones, being significant in most of all the comparisons performed. Within each country, the highest PCV-2-specific MDA titres were observed in the 3-day-old piglets born to sows vaccinated during gestation. Indeed, in the four coun‑ tries, more than 60% of this subpopulation (3-day-old piglets from sows vaccinated during pregnancy) had the high‑ est log PCV-2 titres detectable with the ELISA technique used in this study. The lowest MDA titres were more variable. Whereas in France and Germany the lowest titres corresponded to 21-day-old piglets born from sows vaccinated as a piglet, in Italy, they corresponded to 21-day-old piglets derived from sows vaccinated as a gilt and in Spain to 21-day- old piglets born from non-vaccinated sows. In this study, PCV-2-specific MDA titres at 3 and 21 days of age were not affected by sow parity. Conclusions: Data obtained could be considered as a European global overview of PCV-2-specific MDA titres present in the pre-vaccinated piglet populations in different European countries, with titres tending to be higher in younger piglets, but with values variable among countries and sow vaccination strategies. Keywords: Porcine circovirus 2, Maternally-derived antibodies, Sow vaccination Background Porcine circovirus 2 (PCV-2) is the causal agent of several *Correspondence: marina.sibila@irta.cat clinical conditions known as porcine circovirus diseases 1 Unitat Mixta d’Investigació IRTA‑UAB en Sanitat Animal, Centre de Recerca (PCVDs), which include systemic disease (PCV-2-SD), en Sanitat Animal (CReSA), Campus de la Universitat Autònoma de Barcelona reproductive disease (PCV-2-RD), porcine dermati- (UAB), 08193 Bellaterra, Catalonia, Spain tis and nephropathy syndrome (PDNS), and subclinical Full list of author information is available at the end of the article © The Author(s) 2022. 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The Creative Commons Public Domain Dedication waiver (http://​creat​iveco​ mmons.​org/​publi​cdoma​in/​zero/1.​0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Sibila et al. Porcine Health Management (2022) 8:41 Page 2 of 8 infection (PCV-2-SI) [1]. Vaccination is the most com- n = 30) were selected based on the following sow PCV-2 mon and effective tool to control the clinical outcomes of vaccination strategies: (1) during pregnancy (as a sow): these diseases [2]. sows were vaccinated at least one time during the gesta- PCV-2 vaccination can be applied to sows/gilts, sows tion of their current litter; they may also have been vacci- and piglets, or piglets. From all these combinations, the nated as piglets and gilts; (2) during gilt development (as most widely used at the field level is the immunization a gilt): animals were vaccinated during gilt development of piglets around weaning, but its application in sows is prior to entering the sow herd and prior to breeding; gilts increasing worldwide [3]. Vaccination of sows against were not further vaccinated as sows but may have been PCV-2 may seek two objectives. First, sow vaccination vaccinated as piglets; (3) as piglet only (as a piglet): sows/ may protect gestating animals against PCV-2-RD; in this gilts were vaccinated against PCV-2 as a piglet around scenario, the vaccine should be applied during acclimati- the time of weaning or earlier and no sow/gilt vaccina- zation, prior to mating, during lactation, or at weaning. tion was further performed; and (4) never: sows/gilts had Sow vaccination can also be applied to transfer humoral never been vaccinated for PCV-2 during their lifetime. and cellular immunity to the offspring; in this situation, The PCV-2 vaccines used in the tested farms included all the vaccination takes place during late gestation [2]. those available in Europe at the time of sampling (years A double vaccination program (sow/gilt and piglet) is 2018 and 2019). increasingly practiced under field conditions. In these lat- Within each herd, a cross-sectional study was designed, ter cases, the level of PCV-2-specific maternally-derived with 30 piglets at 3 ± 3 days of age and 30 at 21 ± 3 days antibodies (MDA) at the time of piglet vaccination is par- of age sampled during a one-day visit to the farm (n = 60 amount as it may potentially influence efficacy (mainly in piglets per farm). Within each sampling age, and when terms of seroconversion) of piglet vaccination [4–12]. The possible, the sampled piglets belonged to two litters of risk of potential MDA interference on vaccine efficacy in primiparous (n = 6 piglets per sampling age/farm) and terms of average daily weight gain (ADWG) is considered to eight litters of multiparous sows (parity 2 or higher, negligible based on published literature [3, 12]. However, n = 24 piglets per sampling age/farm). Individual piglets it is very likely that non-successful experimental or field were sampled in a manner to limit bias: small, medium, trials have not been published in peer-reviewed journals. and large pigs were sampled per litter. No data on cross- The level of MDA the piglets can have at the time of fostering was recorded in any of the studied farms. immunization depends mainly on two factors: (1) the sow During the visit to the farm, information on manage- immunological status, which in turn depends on the sow ment (type of production system, source of breeding vaccination status and/or infection pressure at the farm, gilts, number of sows on site and type of sow housing), and (2) the amount of colostrum intake, hardly meas- sanitary status (history of PCV-2-SD or other disease urable and controllable on an individual basis [13]. The outbreaks in the past two years and clinical signs associ- level of MDA gradually wanes (in the absence of natural ated to these scenarios), and PCV-2 vaccination schedule infection or vaccination); waning has been reported to be (PCV-2 vaccine used, number of doses and schedule of between 4 and 12 weeks of age for PCV-2 but depends on doses) were recorded (when possible). the level of MDA ingested via colostrum [8–11, 14]. The This study protocol (BH25R-XG-16-658) was reviewed estimated half-life of PCV-2-specific MDA varies from and approved (July 2019) by the Zoetis Ethical Review 16 to 45 days depending on the serological test used and Board. In addition, owner consent from each farm was the method selected for its calculation [4, 10, 14, 15]. Up received before sample taking. to now, there is a lack of information on the levels and decay rate of PCV-2-specific MDA antibodies in piglets Samples born to sows of various PCV-2 vaccination strategies. Blood samples were collected and transported refriger- The present study aimed to evaluate the PCV-2 MDA ated to each country designated laboratory (Anses Plou- titres in 3- and 21-day-old piglets born to sows/gilts from fragan-Plouzané-Niort laboratory, [France], Veterinary farms located in four European countries, using differ- Practice Scheidegg [Germany] and Department of Veteri- ent vaccination strategies. Moreover, the decay of these nary Science, Parma, [Italy]) where were allowed to clot PCV-2 MDA titers (as reduction of PCV-2 MDA titres and centrifuged. Individual serum samples obtained were from 3 to 21 days in piglets per farm) was estimated. stored at – 20 °C until submission to IRTA-CReSA labo- ratory (Barcelona, Spain). Materials and methods Study design PCV‑2 ELISA different ELISA plates) using the SERELISA® PCV-2 A total of 109 herds from four European countries Individual serum samples were tested in duplicate (in (France n = 30, Germany n = 27, Italy n = 22 and Spain Sibila et al. Porcine Health Management (2022) 8:41 Page 3 of 8 Ab Mono Blocking diagnostic kit (Synbiotics). In each treatment comparisons were made after testing for a sig- plate, in addition to the positive and negative controls nificant (P ≤ 0.05) 3-way interaction, 2-way interactions, included in the kit, one positive and one negative inter- and main effects. Since the highest order interaction that nal reference sample was tested. Serum samples were was significant was the country by treatment, the differ- processed in duplicate following the quantitative method ence between log least square mean of PCV-2 antibody (using a single dilution 1:1000) according to the manu- titres in piglets of 3 and 21 days of age (piglet ages at sam- facturer’s instructions. The sample-to negative corrected pling) within each farm, sow vaccination strategy, and ratio (SNc) was calculated for each well. PCV-2 antibody country was calculated. The difference (decay) in PCV-2 titres were inferred introducing the duplicates SNc mean antibody titres at piglet age of blood collection were com- into the formula provided by the kit. When the mean pared within each country with estimate statements. The ­SNc(1:1000) was < 0.051, the titre was considered + 2484 95% confidence intervals of the least squares mean Log (saturation titre). When mean S ­Nc(1:1000) was > 0.7437 PCV-2 antibody titre within each country, vaccination the titre was considered ≤ 150. Results were expressed as strategy and sampling age were calculated. back-transformed PCV-2 mean titres ± standard devia- tion (SD). Results Farm characteristics Statistical analyses The number and type of farms per treatment type and Data summaries and descriptive analyses were performed country included in the study are detailed in Table 1. with SAS Program (SAS Institute, Cary, NC). For statis- Specific information on management practices, sanitary tical purposes, PCV-2 titres classified as “ + 2484” and status and PCV-2 vaccination schedules of the farms is “ ≤ 150” were considered as “2484” and “75” and parity included in Additional files 1, 2, 3, 4, 5: Tables S1–S5. data were re-classified in two categories: 1 and > 1. Prior to analyses, PCV-2 titres were transformed to log. Since Distribution of PCV‑2 MDA titres among the tested the farm was considered the experimental unit, means population were calculated for each farm within each country, parity Distribution of log least square mean PCV-2 spe- class (1, > 1), and treatment. cific titres of 3- and 21-day-old piglets per treatment and The mean Log PCV-2 antibody titres were analysed country are represented in Fig. 1. In the four countries, using a general linear mixed model with fixed effects: more than 60% of the 3-day-old piglets born to sows vac- country, parity (1, > 1), treatment, all 2-way, and the cinated during pregnancy had the highest log PCV-2 3-way interaction and random effect: residual. Pair-wise titres detectable with the ELISA technique used in the Table 1 Number of samples per country, vaccination strategy, parity, and age groups Country Vaccination treatment 3 days of age 21 days of age P1 P>1 Total P1 P>1 Total France As a sow (n = 9) 54 216 270 54 216 270 As a gilt (n = 9) 54 216 270 54 216 270 As a piglet (n = 9) 54 216 270 54 216 270 Never (n = 3) 18 72 90 18 72 90 Germany As a sow (n = 8) 36 204 240 48 192 240 As a gilt (n = 8) 33 207 240 36 204 240 As a piglet (n = 9) 57 213 270 39 231 270 Never (n = 2) 15 45 60 18 42 60 Italy As a sow (n = 3) 18 72 90 18 72 90 As a gilt (n = 8) 42 168 210 42 168 210 As a piglet (n = 8) 57 213 270 54 216 270 Never (n = 3) 18 69 87 18 68 86 Spain As a sow (n = 9) 54 216 270 54 216 270 As a gilt (n = 9) 54 216 270 54 216 270 As a piglet (n = 9) 54 216 270 54 216 270 Never (n = 3) 18 72 90 18 72 90 P parity. Sibila et al. Porcine Health Management (2022) 8:41 Page 4 of 8 France France France France France France France France Sow Sow Gilt Gilt Piglet Piglet Never Never 3 21 3 21 3 21 3 21 100 80 60 40 20 0 Germany Germany Germany Germany Germany Germany Germany Germany Sow Sow Gilt Gilt Piglet Piglet Never Never 3 21 3 21 3 21 3 21 100 80 60 40 Percent 20 0 Italy Italy Italy Italy Italy Italy Italy Italy Sow Sow Gilt Gilt Piglet Piglet Never Never 3 21 3 21 3 21 3 21 100 80 60 40 20 0 Spain Spain Spain Spain Spain Spain Spain Spain Sow Sow Gilt Gilt Piglet Piglet Never Never 3 21 3 21 3 21 3 21 100 80 60 40 20 0 2 3 4 5 6 7 8 9 10 2 3 4 5 6 7 8 9 10 2 3 4 5 6 7 8 9 10 2 3 4 5 6 7 8 9 10 2 3 4 5 6 7 8 9 10 2 3 4 5 6 7 8 9 10 2 3 4 5 6 7 8 9 10 2 3 4 5 6 7 8 9 10 mean country France Germany Italy Spain Fig. 1 Distribution (in percentages) of log least-square mean of PCV-2 titres in 3- and 21-day-old piglets per vaccination strategy and country present study (8 log). Such predominance (but much Within 3-day-old piglets (Fig. 2A), piglets born to sows less pronounced) was also observed in France and Ger- vaccinated during gestation showed higher PCV-2 spe- many in 21-day-old piglets born from sows vaccinated cific MDA titers when compared to the other vaccination during gestation and in Spain and France in 3-day-old strategies but with the following exceptions: in Germany piglets born from sows vaccinated as Gilts. On the con- when compared to piglets born from sows never vacci- trary, in Italy, the predominance of piglets with very high nated and in Spain when compared to piglets born from PCV-2 titres was not detected in any other treatment and sows vaccinated as a gilts. At this age, the numerically age-group. lower PCV-2 MDA titers were observed in piglets born from sows vaccinated as a piglet (in France, Germany, and Spain) or as a gilt (Italy). Mean PCV‑2 MDA titres per age, vaccination strategy, In 3-week-old piglets, the situation was like the one and country depicted above but reached lower PCV-2 titers (Fig. 2B). In all four countries, mean log PCV-2 specific MDA titres The numerically higher PCV-2 MDA titers were also were higher in 3-day-old piglets than in the 3-week-old observed in piglets born from sows vaccinated during ones, being statistically significant in all the comparisons pregnancy in all countries and the numerically lower performed but in Germany in those sows vaccinated as ones in piglets derived from sows vaccinated as a Piglet a Gilt and in Italy in those vaccinated as a Gilt or Never (France and Germany), as a Gilt (in Italy) and in sows vaccinated (Additional file 6: Fig. S1). never vaccinated or vaccinated as a Piglet (Spain). Sibila et al. Porcine Health Management (2022) 8:41 Page 5 of 8 Fig. 2 Log least square mean [± SD] of PCV-2 titres at 3 (A)- and 21 (B)-day-old piglets per vaccination regimen of the sow and country. Different letters mean p < 0.05 between treatments within a country observed in piglets derived from sows vaccinated as a gilt. PCV‑2 MDA titres versus parity and sow vaccination strategy (per country) No statistically significant differences in PCV-2-specific MDA levels between 3-day-of-age piglets from sows of different parity (= 1 and > 1) across each vaccination regi- men or country were found. Discussion Fig. 3 MDA decay (as difference of Log least square mean [± SD] The present observational study provided descriptive PCV-2 titres from 3 to 21 days of age) per vaccination regime of the sow within each country. Different letters mean p < 0.05 among data on PCV-2 specific MDA titres from 109 farms from different vaccination regimen in a country four different countries using different sow vaccination strategies. The number of farms tested in each coun- try ranged from 22 to 30. Thirty animals of 3 and 30 of PCV‑2 MDA decay from 3 to 21 days of age per farm 21 days of age born from sows of different parity numbers In France, the reduction of PCV-2 MDA titres between were tested from each farm. Overall, the data obtained piglets of 3 and 21 days-of-age was significantly lower could be considered as an overview of PCV-2-specific in piglets coming from sows vaccinated during preg- MDA titres present in the pre-vaccinated piglet popula- nancy compared to the other sow vaccination regimes tions in different European countries. (Fig. 3). In Germany, the reduction in MDA showed a Up to now, the prevalence of PCV-2 infection in young similar profile, but the significant differences were only piglets (< 3 weeks of age) has been assessed in differ- observed between piglets from sows vaccinated during ent studies with the goal of describing pre-vaccination pregnancy and from those born to sows vaccinated only infection rates [16, 17]. However, information on PCV- as a piglet. Although in Italy and Spain no statistically 2-specific MDA titres during the lactation period is significant differences in PCV-2 MDA decay between very limited [7]. This information might be of interest vaccination regimes were detected, a different pattern to assess the level of MDA transferred to the offspring was observed. Whereas in Italy the highest reduction through colostrum intake under different PCV-2 sow was observed in piglets derived from sows vaccinated vaccination strategies. Indeed, most of the studies avail- during pregnancy, in Spain the highest reduction was able in the literature reporting PCV-2 MDA levels in vaccinated populations were focused on comparing the Sibila et al. Porcine Health Management (2022) 8:41 Page 6 of 8 levels of antibodies present at the time of piglet vaccine commercial conditions it would not be expectable having administration, mostly around weaning [5–9, 12, 18]. a high proportion of animals harbouring extremely high The main objective behind such studies was to assess the titres. In line, the results reported in the present study effect exerted by certain PCV-2 MDA levels on the effi- suggest the number of animals with very high PCV-2 cacy of the administered vaccine (reviewed by Poulsen- titers elevated enough to interfere with vaccine efficacy in Nautrup et al. [3]). As far as the authors’ knowledge, this terms of AWDG would not be negligible when the sows is the first description of PCV-2-specific MDA titres in are vaccinated. Obviously, this situation will depend on 3-day-old and 3-week-old piglets derived from sows vac- the gestational time of vaccination, since it would not cinated using different strategies. The fact that PCV-2 be the same to vaccinate early during gestation or dur- titres were measured at 3 and 21 days of age in different ing late gestation [20] and, probably, on the vaccine used. animals (cross-sectional study) is a limitation of this work In the present study, information on the exact moment since the individual half-life and MDA decay rate could of gestational time of vaccination was not available as not be calculated. Nevertheless, the information pro- sow PCV-2 vaccination was mostly done in a blanket vided on the PCV-2 MDA reduction from 3 to 21 days of fashion in Italy and Spain; in the case of France sow vac- age at the farm level might be useful when planning a sow cination was mainly applied before farrowing (range of and/or piglet vaccination strategy. 2–12 weeks pre farrowing) while in Germany the time As expected, vaccinating sows during gestation resulted of sow vaccination was variable depending on the farm. in a high proportion (> 60%) of 3-day-old piglets having Therefore, we cannot reach any conclusion on the effect very high antibody titres. Indeed, in these farms, the level of gestational vaccination timing regarding piglet anti- of MDA observed in 21-day-of-old piglets was still high body levels. Further studies comparing the level of MDA (means from 6.65 to 7.82 Log PCV-2 titres, which would in piglets coming from sows vaccinated at early or late be equivalent to 10.32 to > 14.32 ­Log2 immunoperoxidase gestation would be required. Nevertheless, in a blanket monolayer assay (IPMA) titres based on the comparison fashion vaccination, all possibilities may be represented performed by Pileri et al. [19]). PCV-2-specific MDA [20]; in any case, sow vaccination close to the farrowing levels in 21-day-old piglets from sows vaccinated during time would result in the highest MDA titres in piglets. gestation were higher than those observed in 3-day-old Although one might expect that the lowest PCV-2 piglets coming from sows vaccinated as a gilt (in three MDA titres would be found in the 21-day-old piglets out of four countries). Indeed, PCV-2-specific MDA from non-vaccinated farms, this only happened in Spain. titres of piglets from vaccinated sows had the lowest In France and Germany, the lowest values were detected titre reduction from 3 to 21 days of age (in all countries in 21-day-old piglets from sows vaccinated as piglets, and but Italy). These results could be explained by two main in Italy they were observed in the 21-day-old piglets born reasons: (1) a slower waning of MDA when the titres are from vaccinated gilts. These results probably reflect the high; but this rationale should be confirmed by analys- variation in terms of sow PCV-2 natural infection that ing the MDA decay in the same animals (in the present may have occurred in just a proportion of these farms. study, the sampled piglets at 3 and 21 days of age were Therefore, no sound predictions can be made regarding different), and (2) these animals had the highest titre cal- the piglet PCV-2 specific antibody values at the individ- culated by the ELISA technique used (2484, equivalent ual farm level based on the sow vaccination strategy. to 7.8 Log PCV-2 titres) and, probably, the specific level This study provides information on the PCV-2 MDA of antibodies in animals with titres > 2484 could not be titres in farms where the sows had never been vaccinated. determined unless dilutions would have been applied. This information might be very valuable as there are very In general terms, high titres of MDA (equivalent few farms not vaccinating against PCV-2 nowadays [2]. to ≥ 8.32 ­Log2 IPMA titres) at the time of vaccination This scenario is reflected by the low number of farms have been usually associated to a reduction in vaccine included in this category (France n = 3; Germany n = 2, seroconversion [4–6, 8, 9, 12]. Interference with vaccine Italy n = 3 and Spain n = 3), since they were extremely efficacy, however, was not observed in most of the stud- difficult to be found. High MDA levels (especially in ies using the ADWG as the primary outcome [5, 7, 12, 3-day-old piglets) detected in the herds in which the sows 18]. Noteworthy, ADWG was affected by MDA when the had never been vaccinated may indicate a high viral cir- vaccinated animals had high antibody titres at 1 week culation [21, 22]. of age (> 10.6 – 12.2 ­Log2 ELISA) [7] or when antibody Although in previous studies sow parity has been linked titres were, at 3 weeks of age, extremely high (> 17.32 to different general immunoglobulin concentrations [23], ­Log2 IPMA titres) [12]. In this latter study, such very high PCV-2 MDA titres in the present study were not differ- titres were mainly achieved by vaccinating the sows at ent between piglets from primiparous or multiparous 3- and 6-weeks pre-farrowing; however, under common sows. It cannot be ruled out that these results have been Sibila et al. Porcine Health Management (2022) 8:41 Page 7 of 8 influenced by the different sample size between multipa- Availability of data and materials The datasets used and analysed during the trial are available from the cor‑ rous (2633 and 2631 observations at 3 and 21 days of age, responding author on request. respectively) and primiparous (636 and 633 observations at 3 and 21 days of age, respectively) or by the different Declarations vaccines used in farms. More studies would be needed to ascertain if PCV-2-specific MDA titres are influenced Competing interests M.C. Venegas, D. Fredrickson, M. Bandrick, L. Taylor, M. Balasch are employees by the parity, but it is probably more dependent on the of Zoetis. particular degree of PCV-2 circulation in the farm rather than sow parity. Ethical approval and consent to participate Study protocol BH25R-XG-16-658 was reviewed by the Zoetis Kalamazoo Ethi‑ In summary, the levels of PCV-2-specific MDA in 3- cal Review Board, which included the scope of animal procedures and sample and 21-day-old piglets varied depending on the sow vac- collections and approved on July 12, 2019. The study description and animal cination strategy applied, although certain differences care described are consistent with Zoetis Corporate Animal Care and Welfare Policy. In addition, owner consent was received before sampling. between sow vaccination regimes were observed among the studied countries. Vaccination of sows during gesta- Consent for publication tion implied a high proportion of piglets with high MDA All authors agree with the content of the manuscript. titres both at 3 and 21 days of age. The impact of these Competing interest high titres to piglet vaccination efficacy should be further None. assessed. Author details 1 Unitat Mixta d’Investigació IRTA‑UAB en Sanitat Animal, Centre de Recerca en Sanitat Animal (CReSA), Campus de la Universitat Autònoma de Barcelona Abbreviations (UAB), 08193 Bellaterra, Catalonia, Spain. 2 IRTA, Programa de Sanitat Animal, MDA: Maternally-derived antibodies; SNc: Sample to negative corrected ratio. Centre de Recerca en Sanitat Animal (CReSA), Campus de la Universitat Autònoma de Barcelona (UAB), 08193 Bellaterra, Catalonia, Spain. 3 OIE Col‑ Supplementary Information laborating Centre for the Research and Control of Emerging and Re-Emerging Swine Diseases in Europe (IRTA-CReSA), Bellaterra, Barcelona, Spain. 4 ANSES, The online version contains supplementary material available at https://​doi.​ Laboratoire de Ploufragan-Plouzané-Niort, BP 53, 22440 Ploufragan, France. org/​10.​1186/​s40813-​022-​00284-9. 5 Veterinary Pig Practice Scheidegg, Bahnhofstrasse 30, 88175 Scheidegg, Germany. 6 Department of Veterinary Science, University of Parma, Strada Additional file 1. Table S1. Characteristics of the 30 French Farms del Taglio 10, 43126 Parma, Italy. 7 Zoetis Inc., 333 Portage St, Kalamazoo, MI included in this study. 49007, USA. 8 Zoetis Manufacturing and Research Spain S.L. Ctra, Camprodon Additional file 2. Table S2. Characteristics of the 27 German Farms s/n, Finca La Riba, 17813 Vall de Bianya, Girona, Spain. 9 Departament de included in this study. Sanitat I Anatomia Animals, Facultat de Veterinària, Campus de la Universitat Autònoma de Barcelona (UAB), 08193 Bellaterra, Catalonia, Spain. Additional file 3. Table S3. Characteristics of the 22 Italian Farms included in this study. Received: 11 July 2022 Accepted: 9 September 2022 Additional file 4. Table S4. Characteristics of the 30 Spanish Farms included in this study. Additional file 5. Table S5. Number of farms receiving each particular vaccine and doses (in parenthesis) in each category. References Additional file 6. Figure S1. Log least square mean of PCV-2 titres in 3- 1. Segales J. Porcine circovirus type 2 (PCV2) infections: clinical signs, and 21-day-old (d) piglets per vaccination regimen and country. * means pathology and laboratory diagnosis. Virus Res. 2012;164(1–2):10–9. p ≤ 0.05 between animals of 3 and 21 days of age within each vaccination https://​doi.​org/​10.​1016/j.​virus​res.​2011.​10.​007. regime. 2. Segales J. Best practice and future challenges for vaccination against porcine circovirus type 2. Expert Rev Vaccines. 2015;14(3):473–87. https://​ doi.​org/​10.​1586/​14760​584.​2015.​983084. Acknowledgements 3. Poulsen Nautrup B, Van Vlaenderen I, Mah C, Angulo J. Do high levels of The authors would like to acknowledge the farmers and practitioners for maternally derived antibodies interfere with the vaccination of piglets their willingness to participate in this study. Moreover, we are very grateful against porcine circovirus type 2? A literature review and data analysis. to F. Eono and E. Eveno from France, P. Borghetti, E. De Angelis and A. Caleffi Vaccines (Basel). 2021. https://​doi.​org/​10.​3390/​vacci​nes90​80923. from Italy and P. Pleguezuelos and R. Cuadrado from Spain for participating in 4. Fort M, Sibila M, Perez-Martin E, Nofrarias M, Mateu E, Segales J. One the farm selection and/or sample taking procedures. We are also grateful to dose of a porcine circovirus 2 (PCV2) sub-unit vaccine administered to CERCA Programme/Generalitat de Catalunya. 3-week-old conventional piglets elicits cell-mediated immunity and significantly reduces PCV2 viremia in an experimental model. Vaccine. Author contributions 2009;27(30):4031–7. https://​doi.​org/​10.​1016/j.​vacci​ne.​2009.​04.​028. MBan, DF, LT, MCV, and MBal conceived and designed the study. JS, NR, AP, 5. Fraile L, Sibila M, Nofrarias M, Lopez-Jimenez R, Huerta E, Llorens A, et al. PM coordinated the study in each country. MS, JS, CF MF, LF visited the farms, Effect of sow and piglet porcine circovirus type 2 (PCV2) vaccination on registered the information, and took the samples. MS coordinated the sample piglet mortality, viraemia, antibody titre and production parameters. Vet processing. AL and EH processed all the collected samples. MCV and LT Microbiol. 2012;161(1–2):229–34. https://​doi.​org/​10.​1016/j.​vetmic.​2012.​ performed the statistical analyses. MS and JS drafted the manuscript. All the 07.​021. authors read and approved the final manuscript. 6. Fraile L, Grau-Roma L, Sarasola P, Sinovas N, Nofrarias M, Lopez-Jimenez R, et al. Inactivated PCV2 one shot vaccine applied in 3-week-old piglets: improvement of production parameters and interaction with maternally Sibila et al. Porcine Health Management (2022) 8:41 Page 8 of 8 derived immunity. Vaccine. 2012;30(11):1986–92. https://​doi.​org/​10.​ Publisher’s Note 1016/j.​vacci​ne.​2012.​01.​008. Springer Nature remains neutral with regard to jurisdictional claims in pub‑ 7. Haake M, Palzer A, Rist B, Weissenbacher-Lang C, Fachinger V, Eggen lished maps and institutional affiliations. A, et al. Influence of age on the effectiveness of PCV2 vaccination in piglets with high levels of maternally derived antibodies. 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Maternally derived antibody levels influence on vaccine protection against PCV2d challenge. Animals (Basel). 2021;11(8):15. https://​doi.​org/​10.​3390/​ani11​ 082231. 15. Polo J, Campbell JM, Crenshaw J, Rodriguez C, Pujol N, Navarro N, et al. Half-life of porcine antibodies absorbed from a colostrum supple‑ ment containing porcine immunoglobulins. J Anim Sci. 2012;90(Suppl 4):308–10. https://​doi.​org/​10.​2527/​jas.​53716. 16. Shen H, Wang C, Madson DM, Opriessnig T. High prevalence of porcine circovirus viremia in newborn piglets in five clinically normal swine breeding herds in North America. Prev Vet Med. 2010;97(3–4):228–36. https://​doi.​org/​10.​1016/j.​preve​tmed.​2010.​09.​020. 17. Eddicks M, Koeppen M, Willi S, Fux R, Reese S, Sutter G, et al. Low prevalence of porcine circovirus type 2 infections in farrowing sows and corresponding pre-suckling piglets in southern German pig farms. Vet Microbiol. 2016;187:70–4. https://​doi.​org/​10.​1016/j.​vetmic.​2016.​03.​010. 18. Figueras-Gourgues S, Fraile L, Segales J, Hernandez-Caravaca I, Lopez- Ubeda R, Garcia-Vazquez FA, et al. Effect of Porcine circovirus 2 (PCV-2) maternally derived antibodies on performance and PCV-2 viremia in vac‑ cinated piglets under field conditions. Porcine Health Manag. 2019;5:21. https://​doi.​org/​10.​1186/​s40813-​019-​0128-7. 19. Pileri E, Cortey M, Rodriguez F, Sibila M, Fraile L, Segales J. Comparison of the immunoperoxidase monolayer assay and three commercial ELISAs for detection of antibodies against porcine circovirus type 2. Vet J. 2014;201(3):429–32. https://​doi.​org/​10.​1016/j.​tvjl.​2014.​05.​025. Ready to submit your research ? Choose BMC and benefit from: 20. Pleguezuelos P, Sibila M, Cuadrado R, Lopez-Jimenez R, Perez D, Huerta E, et al. Exploratory field study on the effects of porcine circovirus 2 (PCV-2) • fast, convenient online submission sow vaccination at different physiological stages mimicking blanket vaccination. Porcine Health Manag. 2021;7(1):35. https://​doi.​org/​10.​1186/​ • thorough peer review by experienced researchers in your field s40813-​021-​00213-2. • rapid publication on acceptance 21. Carasova P, Celer V, Takacova K, Trundova M, Molinkova D, Lobova D, • support for research data, including large and complex data types Smola J. The levels of PCV2 specific antibodies and viremia in pigs. Res Vet Sci. 2007;83(2):274–8. • gold Open Access which fosters wider collaboration and increased citations 22. López-Soria S, Maldonado J, Riera P, Nofrarías M, Espinal A, Valero O, et al. • maximum visibility for your research: over 100M website views per year Selected Swine viral pathogens in indoor pigs in Spain. Seroprevalence and farm-level characteristics. Transbound Emerg Dis. 2010;57(3):171–9. At BMC, research is always in progress. 23. Piñeiro C, Manso A, Manzanilla EG, Morales J. Influence of sows’ parity on performance and humoral immune response of the offspring. Porcine Learn more biomedcentral.com/submissions Health Manag. 2019;5:1. https://​doi.​org/​10.​1186/​s40813-​018-​0111-8.