| African swine fever(ASF)is an acute and highly contagious disease caused by African swine fever virus(ASFV).Since the first report of ASF epidemic in China in August 2018,the disease broke out all over the country,causing serious economic losses to China’s pig industry.At present,there is no safe and effective vaccine for the prevention and control of ASF.Therefore,revealing the pathogenesis of ASF will contribute to the development of ASF vaccine.This study was the first to study the pathological changes systematically induced by our country’s Pig/HLJ/2018 strain infected with Specific pathogen free(SPF)Landrace pigs and local Landrace pigs.What’s more,the changes were compared with the pathological changes of SPF Landrace pigs infecting with Hu Bei/628/2020 strain to reveal the pathogenesis of ASFV.At the same time,it can provide reference for the clinical diagnosis of ASF.The results showed that the pig infected with ASFV(Pig/HLJ/2018 strain)showed acute clinical symptoms and hemorrhagic lesions in multiple organs,especially the spleen,stomach and liver lymph nodes,which were congested and swollen.At the same time,the immune organs were seriously damaged,mainly manifested as lymphopenia and inflammatory cell infiltration.Ultramicroscopic pathological changes showed cell necrosis and apoptosis.The results of immunohistochemistry showed that ASFV mainly infected monocytes and macrophages of immune organs,Kupffer cells and hepatocytes of liver,macrophages of lung,macrophages around renal arterioles,monocytes of renal interstitium,monocytes of glomerulus,endothelial cells of glomerulus.Importantly,ASFV was found in the heart,adrenal gland and gastrointestinal tract for the first time.The results of serum cytokine detection showed that the expression levels of IL-1Ra,IL-18,IL-1β,IL-2,IL-4 and IL-10 were upregulated in the late stage.The expression levels of IFN-γ and IL-8 were decreased.These results suggest that both pro-inflammatory and anti-inflammatory cytokines are presented in the late pathogenetic progress of ASF.Compared with SPF pigs,local pigs infected ASFV(Pig/HLJ/2018 strain)had longer progress of disease and more severe lesions,especially in gastrointestinal tract;More virus protein positive cells were found in tonsil,thymus,mesenteric lymph node,gastrointestinal tract and adrenal gland of local pigs.Necropsy revealed atrophy of thymus.Histopathology results showed the proliferation of macrophages of thymus and the proliferation of parenchymal blood vessels;the hyperplasia of endothelial venules in the lymph nodes is beneficial to the recirculation of lymphocytes and promotes immune response.SPF pigs infected ASFV(Hu Bei/628/2020 strain)showed acute clinical symptoms in short and with mild lesions.Autopsy showed that the degree of gallbladder atrophy was more obvious than SPF pig infected with ASFV(Pig/HLJ/2018 strain).Compared with the former two groups,SPF pigs infected with the mutant strain had shorter pathegenatic progress,mild lesion,acute clinical symptoms,and cholecystitis on autopsy.In addition,immunohistochemical results showed that the virus existed more in inguinal lymph nodes than in heart.Histopathology manifested diffuse proliferation of lymphocytes in inguinal lymph nodes,mesenteric lymph nodes and submandibular lymphocytes.In conclusion,ASFV can causes blood circulation disorders,systemic hemorrhagic lesions,decreased lymphocyte number,lymphocyte necrosis and inflammatory cell infiltration;Viruses particles mainly exist in the monocyte-macrophages that infect immune organs;inflammation causes damage to tissues and cells,so which destroys the normal structure of the body.Ischemia or hypoxia causes tissue necrosis,further aggravates the inflammatory response,and causes the failure of multiple organs,eventually causes the death of the pig.In this study,the pathological changes caused by ASFV infection in pigs were systematically studied at the macroscopic and microscopic level,and these results have deepened our understanding of the pathogenesis of ASFV. |
PDF Full Text Request