Pathology of the outbreak of subgenotype 2.5 classical swine fever virus in northern Vietnam

Abstract

Classical swine fever (CSF) is an endemic disease in southeastern Asia and is one of the most important swine diseases in Vietnam. This study was conducted to characterize the pathology of natural cases of CSF in northern Vietnam in 2018 and their genetic prevalence. A total of 10 representative pigs were collected from four provinces (Hung Yen, Ha Noi, Quang Ninh and Thai Binh) during five outbreaks and examined pathologically. The gross and histopathological findings showed the disease was expressed as the acute or the subacute to chronic form of CSF, depending on the age of the animals. The most consistently observed lesions associated with infection by the classical swine fever virus (CSFV) included lymphoid depletions in tonsils, lymph node and spleen; histiocytic hyperplasia in spleen; cerebral haemorrhage; perivascular cuffing in the brain; renal erythrodiapedesis; urothelial vacuolation and degeneration and interstitial pneumonia. The immunohistochemical findings showed a ubiquitous CSFV antigen mainly in the monocytes/macrophages and in the epithelial and endothelial cells in various organs. CSFV neurotropism was also found in the small neurons of the cerebrum and the ganglia of the myenteric plexus. Analysis of the full‐length envelope protein (E2) genome sequence showed that all strains were genetically clustered into subgenotype 2.5, sharing a nucleotide identity of 94.0%–100.00%. Based on the results of this study, the strain was categorized as a moderately virulent CSFV.

Abrogation of the RNase activity of Erns in a low virulence classical swine fever virus enhances the humoral immune response and reduces virulence, transmissibility, and persistence in pigs

“…Nowadays, CSFV strains of low and moderate virulence continue to be prevalent in some endemic countries, making the CSF control particularly difficult [ 18 , 34 ]. However, data on the viral factors that determine attenuation and persistence remain scarce.…”

Pathological investigation and viral antigen distribution of emerging African swine fever in Vietnam

“…Even though ASFV mainly targeted the macrophages/mononuclear phagocytic system similar to both HP‐PRRSV and CSFV, the histopathological lesions in the lymph node tissues were found to be different among the viruses. There were marked histiocytic hyperplasia in CSFV infection, which is not seen in ASFV infection (Izzati et al, 2020 ). In contrast, CSFV infection manifested more marked and severe lymphoid depletion (disappearance of lymphoid follicles) compared to HP‐PRRSV infection in relation to the strain causing outbreaks in Vietnam from 2010 to 2018 (personal observation by Izzati; Huong Giang et al., 2016 ).…”

“…phoid follicles) compared to HP-PRRSV infection in relation to the strain causing outbreaks in Vietnam from 2010 to 2018 (personal observation byIzzati;Huong Giang et al, 2016). Bacterial diseases causing similar haemorrhagic lesions, such as in septicaemic salmonellosis and swine erysipelas, were also ruled out based on negative PCR detection (data not shown) and the lack of histopathological characteristics of both bacterial infections.…”

Determination of Intestinal Viral Loads and Distribution of Bovine Viral Diarrhea Virus, Classical Swine Fever Virus, and Peste Des Petits Ruminants Virus: A Pilot Study

“…Thus far, the presence of CSFV was not quantified per intestinal layer, mucosa, submucosa, and muscular layer/serosa in infected pigs. However, the presence of CSFV was detected by immunohistochemistry (IHC) in the superficial and crypt mucosal epithelial cells of the ileum and in macrophages and lymphocytes of the Peyer’s patches [ 16 , 17 ]. Previous studies involving natural casings derived from CSFV-infected pigs have shown the presence of infectious viruses in natural casings (submucosa) after processing; however, in none of these studies, the amount of the virus was quantified [ 18 , 19 , 20 ].…”