Classical Swine Fever in a Cuban Zone Intended for Eradication: Spatiotemporal Clustering and Risk Factors

Porvac® subunit vaccine induces neutralizing antibodies against all three main classical swine fever virus genotypes

Classical swine fever (CSF) is endemic in Cuba and is one of the major health problems of the Cuban swine industry. The current efforts to control the disease in Cuba include vaccination with Porvac®, a subunit marker vaccine. Although the efficacy of Porvac against CSF virus (CSFV) subgenotype 1.4 has been extensively documented, little is known about the ability of the antibodies induced by this vaccine to neutralize other CSFV genotypes. In this study, sera collected from three pigs vaccinated with Porvac were able to efficiently neutralize CSFV strains belonging to genotypes 1, 2, and 3. The findings from this study indicate that additional in vivo studies are warranted to confirm the ability of this vaccine to protect pigs against CSFV genotypes 2 and 3.

Stability of closed and needle-punctured vials of Porvac® subunit vaccine against classical swine fever subjected to thermal stress

BACKGROUND

Classical Swine Fever (CSF) is still one of the most economically important viral diseases of pigs. In endemic countries, the disease is controlled mostly through vaccination; hence, the availability of safe and effective vaccines is of utmost importance. Vaccines intended for application in developing countries must also be thermally stable, since the infrastructure needed to maintain a cold chain in those countries is usually lacking. Porvac® is a second-generation subunit marker vaccine against CSF that has demonstrates to be safe and protective. Previous studies have also shown that the vaccine is stable for 1 week at 37 oC and have a shelf life of at least 36 months at 2-8 oC. The aim of this work was to further explore the accelerated stability of Porvac® by assessing the physicochemical properties of the emulsion, and the safety and immunogenicity of the vaccine subjected to more drastic conditions of thermal stress: (1) 25 oC for 12 months; (2) 30oC and 37 oC for one month and (3) 15 days at 37 °C after the cap of the vials had been needle-punctured.

RESULTS

The vaccine subjected to all these conditions did not show significant changes in the physicochemical properties of the emulsion; did not produce local or systemic adverse reactions in pigs, and the chromatographic profile of the recovered antigen was preserved. All vaccinated swine developed neutralizing antibody titers ≥ 1:1000 at 28 days post vaccination.

CONCLUSIONS

Porvac® is stable in all the experimental conditions tested, even after cap puncture, and retains the capacity to induce high titers of neutralizing antibodies, well above the threshold of protection. These results reinforce the robustness of the vaccine, and support its use as a very attractive alternative to modified live vaccines in developing countries endemic for CSF.

Spatiotemporal analysis of reported classical swine fever outbreaks in China (2005-2018) and the influence of weather

Classical swine fever (CSF) is a viral disease that causes enormous economic losses in the swine industry in endemic countries including China. The aims of the current study were to describe the spatial distribution of annual CSF reports in China from 2005 to 2018, identify spatiotemporal clusters of annual CSF reports during this time period and to investigate the correlations between climate factors (rainfall, wind speed, temperature, vapour pressure and relative humidity) and the occurrence of CSF outbreaks. The strongest (Moran's index > 0.19), significant (p < .05) spatial clustering of reported outbreaks was observed during the first 4 years of the study period. This clustering was apparent in the four southern provinces of Guizhou, Guangxi, Guangdong and Yunnan. Five of the six significant (p ≤ .0001) spatiotemporal clusters occurred during the period 2005-2012. These were widely dispersed, with four clusters persisting for only 1 or 2 years, whereas two clusters (Jiangxi and Yunnan) persisted for 8 and 7 years, respectively. As a result of implementation of a national animal disease control plan and increasing coverage of vaccination, CSF outbreaks in China have generally been controlled and reduced, becoming sporadic in most provinces by 2018. We also confirmed that low relative humidity and high wind speed were significant weather variables associated with the occurrence of CSF. Furthermore, our study has confirmed that CSF is still endemic in some Chinese provinces, and we recommend that the national CSF control protocol be updated and standardized.

Safety and immunogenicity in piglets of two immunization schedules initiated at two or three weeks of age with PorvacÒ, a classical swine fever subunit marker vaccine

Classical swine fever is a highly contagious viral disease with a significant impact on food production worldwide. It currently represents one of the main limitations for the development of the pig industry in Cuba. PorvacÒ is a subunit marker vaccine that confers a very rapid onset of protection. Since there are different production systems in pig breeding, readjustments in the vaccination program are often required. This study compares the safety and efficacy in piglets of two vaccination schedules with PorvacÒ (0-2 weeks and 0-3 weeks), initiated at two or three weeks of age. Clinical monitoring was conducted, and a neutralization peroxidase-linked assay was used to measure the neutralization titers. All immunization regimens were safe and well-tolerated, without local or systemic adverse reactions in the vaccinated animals. Geometric mean neutralizing antibody titers higher than 1/1500 were detected in all groups during the six months of the trial. One month after the second immunization, piglets primed at two weeks of age, and boostered three weeks later, developed significantly higher neutralization titers (1/15644) compared to those vaccinated at a similar age but with a two-week interval between doses (1/5760). However, no significant differences in the titers were found three and six months after vaccination among the four regimens. In summary, all the variants studied are effective, but it is recommended to start vaccination at two weeks old, with the second dose at either two or three weeks later, depending on the production system and the purpose of the farm.

A Critical Review about Different Vaccines against Classical Swine Fever Virus and Their Repercussions in Endemic Regions

Classical swine fever (CSF) is, without any doubt, one of the most devasting viral infectious diseases affecting the members of Suidae family, which causes a severe impact on the global economy. The reemergence of CSF virus (CSFV) in several countries in America, Asia, and sporadic outbreaks in Europe, sheds light about the serious concern that a potential global reemergence of this disease represents. The negative aspects related with the application of mass stamping out policies, including elevated costs and ethical issues, point out vaccination as the main control measure against future outbreaks. Hence, it is imperative for the scientific community to continue with the active investigations for more effective vaccines against CSFV. The current review pursues to gather all the available information about the vaccines in use or under developing stages against CSFV. From the perspective concerning the evolutionary viral process, this review also discusses the current problematic in CSF-endemic countries.