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. 2022 Jul;23(4):e57.
doi: 10.4142/jvs.22042.

Epidemiological investigation and phylogenetic analysis of Classical Swine Fever virus in Yunnan province from 2015 to 2021

Jun Yao #  1 , Linlin Su #  2 , Qiaoping Wang  2 , Lin Gao  1 , Jiarui Xie  1 , Yuwen He  1 , Xianghua Shu  2 , Chunlian Song  2 , Jun Chai  2 , Yifang Zhang  3 , Shibiao Yang  4
Affiliations

Epidemiological investigation and phylogenetic analysis of Classical Swine Fever virus in Yunnan province from 2015 to 2021

Jun Yao et al. J Vet Sci. 2022 Jul.

Abstract

Background: Classical swine fever virus (CSFV), the causative agent of classical swine fever (CFS), is a highly contagious disease that poses a serious threat to Chinese pig populations.

Objectives: Many provinces of China, such as Shandong, Henan, Hebei, Heilongjiang, and Liaoning provinces, have reported epidemics of CSFV, while the references to the epidemic of CSFV in Yunnan province are rare. This study examined the epidemic characteristics of the CSFV in Yunnan province.

Methods: In this study, 326 tissue samples were collected from different regions in Yunnan province from 2015 to 2021. A reverse transcription-polymerase chain reaction (RT-PCR), sequences analysis, and phylogenetic analysis were performed for the pathogenic detection and analysis of these 326 clinical specimens.

Results: Approximately 3.37% (11/326) of specimens tested positive for the CSFV by RT-PCR, which is lower than that of other regions of China. Sequence analysis of the partial E2 sequences of eleven CSFV strains showed that they shared 89.0-100.0% nucleotide (nt) and 95.0-100.0% amino acid (aa) homology, respectively. Phylogenetic analysis showed that these novel isolates belonged to the subgenotypes 2.1c and 2.1d, with subgenotype 2.1c being predominant.

Conclusions: The CSFV was sporadic in China's Yunnan province from 2015 to 2021. Both 2.1c and 2.1d subgenotypes were found in this region, but 2.1c was dominant.

Keywords: Classical swine fever virus; Yunnan province; sequence analysis; subgenotype 2.1c.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Fig. 1
Fig. 1. Typical clinical and pathological signs were observed in CSFV-infected pigs, such as bleeding points on the skin (A, B), tonsil ulcers (C), welling and hemorrhage of lymph nodes (D), hemorrhagic spots on the kidneys (E), infarction of spleen (F), necrosis of intestine (G, H) and button-shaped ulcers in the ileocecal valves (I).
CSFV, classical swine fever virus.
Fig. 2
Fig. 2. Agarose gel electrophoresis analysis of PCR products of partial NS5B gene sequence of CSFV strains. “+” and “–” were regarded as positive and negative controls during PCR amplification, respectively. 1–4 represents the samples from CSFV-infected pigs.
Fig. 3
Fig. 3. Phylogenetic tree based on the partial E2 gene sequence of the CSFV strains obtained in this study and available in the GenBank database generated by the neighbor-joining method in MEGA 7.0 software. The black and red diamonds represented CSFV strains obtained here and vaccine strains, respectively.
*Represents the strain isolated successfully.
Fig. 4
Fig. 4. Indirect immunofluorescent assay for the detection of the CSFV in ST cells using anti-CSFV E2 primary antibodies. Scale bar = 100 μm.
CSFV, classical swine fever virus.
See this image and copyright information in PMC

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