PMC7360720_01
Gross pathology of ASFV infected pigs in Vietnam, 2019. (A) Hemorrhagic splenomegaly (arrow) can be observed at the abdominal cavity inspection. (B) Multiple areas of lung consolidation in cranial lobes (arrows) and multifocal hemorrhages. (C) Hemorrhagic lymphadenitis in the gastrohepatic lymph node (arrow). (D) Haemorrhagic lymphadenitis in the mesenteric lymph nodes (arrows). (E) Multiple severe petechial hemorrhages in the renal cortex. (F) Multifocal hemorrhages on the skin (arrows) of the head and neck.
fvets-07-00392-g0001.jpg
PMC7360720_01_fvets-07-00392-g0001.jpg
F1
At post-mortem examination of case 2, hyperemic or hemorrhagic splenomegaly was consistently found in affected animals, characterized by an enlarged spleen with intense dark color (Figure 1A). Lung showed areas of consolidation in different lobes, mostly in the cranial and medial lobes and multifocal hemorrhages (Figure 1B). Lymph nodes also showed hemorrhagic lymphadenitis, mostly affecting the renal, gastrohepatic (Figure 1C) and mesenteric (Figure 1D) lymph nodes. Multiple hemorrhages were found in different organs, including the kidneys (Figure 1E), gastrointestinal, and respiratory tracts or externally on the skin (Figure 1F).
Histopathological changes in ASFV infected pigs in Vietnam, 2019. (A) Lymph node: Severe hemorrhages within the lymph node medulla and lymphoid depletion in the follicles (*). H&E stain, 10X. (B) Lymph node: Severe hemorrhages within the lymph node medulla and lymphoid depletion in the follicles and parafollicular lymphoid tissue (*). H&E stain, 20X. (C) Spleen: Marked lymphoid depletion with the presence of pyknosis, karyorrhexis, and nuclear chromatin condensation within the splenic follicles (*) of the white pulp. H&E stain, 40X. (D) Tonsil: Lymphoid depletion, hyperaemia, and hemorrhages in the tonsil. (E) Kidney: Marked diffuse hemorrhaging within the renal cortex characterized by numerous extravasated red blood cells among renal tubuli. H&E stain, 40X. (F) Spleen: Immunohistochemical detection of ASFV p72 in abundant macrophages within the splenic red pulp (arrowheads). IHC stain (ABC technique), 40X.
fvets-07-00392-g0002.jpg
PMC7360720_01_fvets-07-00392-g0002.jpg
F2
Hemorrhages and lymphoid depletion was a common finding in different lymphoid organs as spleen, lymph nodes (Figures 2A,B), and tonsils from affected animals. Lymphoid depletion was particularly prominent in the splenic follicle within the white pulp (Figure 2C) or lymphoid follicles present in renal, gastrohepatic and mesenteric lymph nodes (Figure 2B) or tonsils (Figure 2D). The kidney showed extravasated red blood cells (hemorrhaging) in between the renal tubules within the cortex and mild to moderate lymphoplasmacytic inflammatory infiltrates (Figure 2E). The main positive cell population was the monocyte-macrophage, with intense presence of positive immunoreaction in the cell debris associated to infection (Figure 2F).
Phylogenetic analysis of major structural proteins p54 (A) and p72 (B) of African swine fever virus isolated from case studies #1 and #2 (VNAU/HY-ASF1/Vietnam/2019; VNAU/HY-ASF2/Vietnam/2019; VNAU/TB-ASF1/Vietnam/2019) and reference isolates including recent ones from China/2018 (Delta).
fvets-07-00392-g0003.jpg
PMC7360720_01_fvets-07-00392-g0003.jpg
F3
Phylogenetic trees revealed that the isolated strains from these two clinical cases belonged to the p72 and p54 genotype II (Figure 3) and were identical to ASFV strains isolates from China in 2018 and other genotype II isolates from Europe (Georgia/2007/1).