Optimized protocol for double vaccine immunization against classical swine fever and porcine reproductive and respiratory syndrome.

BACKGROUND: Classical swine fever and porcine reproductive and respiratory syndrome have seriously affected the development of the swine breeding industry in China. Vaccine immunization remains the main way to prevent these infections. The aim of this study was to establish an optimized protocol for vaccine immunization against classical swine fever virus (CSFV) and porcine reproductive and respiratory syndrome virus (PRRSV). METHODS: Blood samples were collected from the anterior vena cava of pigs after immunization, and blood indices, secreted levels of specific antibodies and neutralizing antibodies associated with humoral immunity, the proliferation capacity of T lymphocytes as a measure of cellular immunity, and secreted levels of IFN-γ and TNF-α were determined. RESULTS: The results showed that simultaneous immunization against CSFV and PRRSV infections induced strong and specific humoral and T-cellular immune responses, high levels of cytokine IFN-γ secretion and delayed secretion of cytokine TNF-α. Moreover, significantly higher lymphocyte percentages and red blood cell and leukocyte counts were found in the group simultaneously immunized against CSFV and PRRSV. However, no statistically significant differences were observed in hemoglobin values, neutrophil counts, and median cell percentages among the S + PRRS, PRRS-S, and S-PRRS groups. CONCLUSION: This study demonstrated that simultaneous immunization against CSFV and PRRSV had the advantages of inducing a rapid, enhanced, and long-lasting immune response. These findings provide a theoretical basis for the establishment of a reasonable and optimized vaccine immunization protocol against CSFV and PRRSV in combination with a variety of other vaccine inoculations.

Prevalence of African Swine Fever in China, 2018-2019.

African swine fever (ASF) has spread widely across China since 2018. It represents a significant threat to the pig production industry, as no treatment or vaccine is available for this disease. In this study, the geographical distribution and epidemiological features of ASF from all endemic regions of China were analyzed. We focused on the epidemiological data from 149 ASF cases among domestic pigs and wild boars, confirmed during 2018-2019. We found that, in the 1-year period from August 2018 to July 2019, ASF was reported in most geographical regions of the country, which comprises 31 provinces. The outbreaks were mainly located along the important economic zones and tended to increase southward in general. The southwest region was the most severely affected, with 22% of cases, followed by the Northeast, with 20% of cases. There was no significant difference among other regions. Additionally, the overall mean rate of case-incidence/fatality was 12.5% and 64%, respectively, in this period and varied significantly different months, with a general trend towards a decrease over time. The highest incidence rate (30.4%) occurred in April-May 2019, and the highest fatality rate (81.21%) in October-November 2018, demonstrating the marked seasonality in ASF transmission. Furthermore, anthropogenic effects were a major significant risk factor for the spread of the disease. In summary, this initial epidemiological analysis of ASF provides a global perspective on ASF and facilitates detection of trends and patterns, which will be useful for updating preventive actions at a national level and evaluating their impact on public health.