Dynamics of vanishing of maternally derived antibodies of Ungulate protoparvovirus 1 suggests an optimal age for gilts vaccination

Duration of maternally derived antibodies of porcine parvovirus in growing pigs and presence of antibodies in gilts and sows vaccinated with three different parvovirus vaccines

While gilts and sows are regularly vaccinated against the porcine parvovirus (PPV), little is known on the presence of antibodies in vaccinated sows nor the decline of maternally derived antibodies (MDA) in their offspring. On twelve farms serum samples were taken from 180 gilts and sows vaccinated at least twice with one of three different commercial PPV vaccines. On nine farms, additional 270 serum samples were collected from growing pigs of three different age categories. All 450 samples were examined for PPV antibodies (Abs) by ELISA and haemagglutination inhibition (HI) assay. In total, 65% of all gilts vaccinated twice with either vaccine 1 or vaccine 3 were seronegative by HI assay. In each farm, there were at least three animals with high Ab titres (≥ 1:1280) indicating the presence of PPV in all twelve study farms. However, PPV DNA could not be detected in collected faecal samples. While low to moderately high Ab titres (1:10-1:640) were measured in 98% of twelve-weeks-old pigs, ELISA was only positive in 30% of the same pigs. Though, the statement on the duration of MDA may depend on the applied test, we could confirm an exponential decay of MDA. In addition, we could demonstrate that applied serological tools are insufficient for the confirmation of successful vaccination.

Prevalence of porcine parvovirus 1 through 7 (PPV1-PPV7) and co-factor association with PCV2 and PRRSV in Korea

Background

Classical porcine parvovirus (PPV1) and novel porcine parvoviruses designated porcine parvovirus 2 through 7 (PPV2-PPV7) are widespread in pig populations. The objective of this study was to investigate the prevalence rates of PPV1-PPV7 in Korea by detecting PPVs in serum, lung and fecal samples and to elucidate the association of PPVs with porcine circovirus type 2 (PCV2) and porcine reproductive and respiratory virus (PRRSV), major pathogens involved in porcine respiratory disease complex (PRDC). A total of 286 serum, 481 lung, and 281 fecal samples collected from 2018 to 2020 were analyzed.

Results

The results showed that PPVs are widespread in Korea; the highest detection rates were found in lung samples and ranged from 7.9% (PPV1) to 32.6% (PPV2). Regarding age groups, fattening pigs had the highest detection rates of PPVs, ranging from 6.4% (PPV1) to 36.5% (PPV6); this finding suggests the chronic nature of PPV infections and the continual circulation of these viruses. When compared with PCV2- and PRRSV-negative lung samples, PCV2-positive samples with or without PRRSV positivity had significantly higher detection levels of PPV1 and PPV6. In contrast, the prevalence of PPV2 and PPV7 was significantly higher in PRRSV-infected lung samples regardless of PCV2 detection. PPV5 was detected significantly more frequently in samples  with both PCV2 and PRRSV positivity.

Conclusions

This study could offer a better understanding of the role of PPVs in PCV2 and/or PRRSV infection though further studies are needed to experimentally assess the impact of PPVs in coinfections.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-022-03236-1.

Impact of maternally derived immunity on immune responses elicited by piglet early vaccination against the most common pathogens involved in porcine respiratory disease complex

Background

Newborn piglets can trigger an elementary immune response, but the acquirement of specific antibodies and/or cellular immunity against pathogens before they get infected post-natally is paramount to preserve their health. This is especially important for the pathogens involved in porcine respiratory disease complex (PRDC) as they are widespread, fairly resistant at environment, and genetically variable; moreover, some of them can cause intrauterine/early life infections.

Main body

Piglet protection can be achieved by either passive transfer of maternal derived immunity (MDI) and/or actively through vaccination. However, vaccinating piglets in the presence of remaining MDI might interfere with vaccine efficacy. Hence, the purpose of this work is to critically review the putative interference that MDI may exert on vaccine efficacy against PRDC pathogens. This knowledge is crucial to design a proper vaccination schedule.

Conclusion

MDI transferred from sows to offspring could potentially interfere with the development of an active humoral immune response. However, no conclusive interference has been shown regarding performance parameters based on the existing published literature.

A novel subunit vaccine based on the viral protein 2 of porcine parvovirus: safety profile in bred pigs at different stages of the reproduction cycle and in offspring

Porcine parvovirus 1 (PPV1) viral protein (VP) 2 is the primary antigen responsible for inducing specific protective immunity, so it is a desirable target for development of recombinant subunit vaccines to prevent PPV1 disease. The objective of this study was to evaluate repeated doses of a novel VP2-based PPV1 subunit vaccine, namely ReproCyc® ParvoFLEX, for safety in bred pigs and in offspring under experimental settings. Therefore, the investigation of safety at all breeding stages was evaluated in four independent studies involving: pre-breeding gilts (study A), breeding-age gilts and boars (study B), early and late gestating sows and offspring (study C) and lactating sows and offspring (study D). In all four studies, animals were free from PPV1 based on serology and PCR prior to inclusion. All studies comprised one or two vaccinated groups that received the PPV1 subunit vaccine and a negative control group. Thus, safety was established due to the lack of significant differences between the vaccinated groups and the corresponding unvaccinated (negative control) groups. Gilts, sows and boars were evaluated for local and systemic reactions after vaccination as well as for reproductive performance. The survival rate and average daily weight gain (ADWG) from birth to weaning in offspring was evaluated in studies C and D. Additionally, serology was determined in studies A, C and D. The vaccine was shown to be safe with no relevant significant differences between vaccinated and unvaccinated groups in any experiment. Therefore, repeated doses of ReproCyc® ParvoFLEX were safe in target animals at different stages of the reproductive cycle and in offspring, placing this vaccine as a suitable candidate for mass vaccination programs in breeding herds.

Effect of Porcine circovirus 2 (PCV-2) maternally derived antibodies on performance and PCV-2 viremia in vaccinated piglets under field conditions

Background

Nowadays, the most common presentation of PCV-2 is the subclinical infection in piglets after weaning. The success of PCV-2 vaccination is associated with the control of the clinical disease as well as the improvement of production parameters. In consequence, the objective of the present study was to analyse the effect of PCV-2 maternally derived antibody (MDA) levels on vaccine efficacy in piglets vaccinated at three weeks of age with a commercial PCV-2 subunit vaccine. The study was performed analysing a database with 6112 wean-to-slaughter piglets from 4 different European regions.

Results

Results showed that the use of the vaccine was able to decrease the PCV-2 viremia calculated as area under the curve (AUC = 60.29 ± 3.73), increase average daily weight gain (ADWG = 0.65 ± 0.01 kg/day) and reduce mortality (7%) in vaccinated piglets compared to non-vaccinated ones (AUC of 198.27 ± 6.14, 0.62 ± 0.01 kg/day and 11% respectively). The overall difference of ADWG between both groups was close to 30 g per day (p < 0.05), also when they were split for low and high levels of MDA titres. Moreover, the animals with the highest ADWG were observed in the group of piglets vaccinated with high or extremely high antibody titres (0.66 and 0.65 kg/day respectively). Considering only animals with extremely high antibody titres, both study groups performed similar, however there was a numerical difference of 10 g/day in favour of vaccinated piglets. Likewise, lack of correlation between ADWG and MDA was observed suggesting that no maternal antibody interference was present with the tested vaccine because the vaccinated animals grew faster compared to unvaccinated control animals, regardless of the level of maternal antibodies present at the time of vaccination.

Conclusions

The results of the present study demonstrated that the MDA against PCV-2 transferred through the colostrum intake has a protective effect against this viral infection. The vaccine used in the present study (Ingelvac CircoFLEX®) was effective when applied at three weeks of age and was not affected by the level of MDA at the time of vaccination.

Increasing diversity of swine parvoviruses and their epidemiology in African pigs

Detection of infectious viral agents has been on the increase globally with the advent and usage of more sensitive and selective novel molecular techniques in the epidemiological study of viral diseases of economic importance to the swine industry. The observation is not different for the pig-infecting member of the subfamily Parvovirinae in the family Parvoviridae as the application of novel molecular methods like metagenomics has brought about the detection of many other novel members of the group. Surprisingly, the list keeps increasing day by day with some of them possessing zoonotic potentials. In the last one decade, not less than ten novel swine-infecting viruses have been added to the subfamily, and ceaseless efforts have been in top gear to determine the occurrence and prevalence of the old and new swine parvoviruses in herds of pig-producing countries worldwide. The story, however, is on the contrary on the African continent as there is presently a dearth of information on surveillance initiatives of the viruses among swine herds of pig-producing countries in the region. Timely detection and characterization of the viral pathogens is highly imperative for the implementation of effective control and prevention of its spread. This review therefore presents a concise overview on the epidemiology of novel porcine parvoviruses globally and also provides up-to-date highlights on the reported cases of the viral agents in the African sub-region.

Detection Patterns of Porcine Parvovirus (PPV) and Novel Porcine Parvoviruses 2 through 6 (PPV2-PPV6) in Polish Swine Farms

Porcine parvovirus (PPV) is a major causative agent in reproductive failure, but in the last two decades many novel porcine parvoviruses were described and designated as porcine parvovirus 2 through 6 (PPV2–PPV6). However, their role for pig health is largely unknown. The aim of this study was to better understand the on-farm prevalence of PPVs in different age groups of pigs, and to assess the diagnostic applicability of testing different diagnostic materials. In total, 271 oral fluids, 1244 serum samples, and 1238 fecal samples were collected from 3–21-week-old pigs from 19 farms, and after pooling by 4–6, tested by real-time PCR. The results showed that PPVs are widely spread in Poland and that the highest detection rates were obtained for oral fluids (ranging from 10.7% (PPV1) to 48.7% (PPV2)). Fattening pigs were the age group with the most frequent detection of PPVs (ranging from 8.6% (PPV1) to 49.1% (PPV2)). Porcine parvoviruses were detected mostly in growing-finishing pigs and the infection persisted until the late fattening period, which may suggest the chronic character of the infection (especially for PPV2, which was found to commonly infect animals of all ages). Particularly low Ct values detected for PPV2, PPV3, PPV5, and PPV6 in serum pools from some farms suggested that these viruses may cause high levels of viremia in one or more individuals included in these pools. Further studies are needed to quantify the levels of PPVs viremia and to assess the impact in co-infections with other, often endemic pig viruses, such as porcine circovirus type 2 (PCV2) and porcine reproductive and respiratory syndrome virus (PRRSV).

Biology of Porcine Parvovirus (Ungulate parvovirus 1)

Porcine parvovirus (PPV) is among the most important infectious agents causing infertility in pigs. Until recently, it was thought that the virus had low genetic variance, and that prevention of its harmful effect on pig fertility could be well-controlled by vaccination. However, at the beginning of the third millennium, field observations raised concerns about the effectiveness of the available vaccines against newly emerging strains. Subsequent investigations radically changed our view on the evolution and immunology of PPV, revealing that the virus is much more diverse than it was earlier anticipated, and that some of the “new” highly virulent isolates cannot be neutralized effectively by antisera raised against “old” PPV vaccine strains. These findings revitalized PPV research that led to significant advancements in the understanding of early and late viral processes during PPV infection. Our review summarizes the recent results of PPV research and aims to give a comprehensive update on the present understanding of PPV biology.