Figure legend
Figure 1. Gross lesions in ASFV-infected pigs in Vietnam, 2019
(1a-f). Marble-like haemorrhage in the superficial inguinal lymph
nodes, case 18 (a). Diffuse haemorrhage in the mesenteric lymph nodes,
case 74 (b). Petechial haemorrhage on the renal capsule, renal cortex
and diffuse haemorrhage in the renal pelvis, case 18 (c). Hyperemic
splenomegaly in relation to the size of the stomach. Gastrohepatic lymph
nodes showed diffuse haemorrhage, case 59 (d). Ecchymoses of the
epicardium with serosanguinous pericardial fluid, case 58 (e).
Ecchymoses of the myocardium, case 58 (f).
Figure 2. African swine fever virus isolates phylogenetic tree
based on partial length of B646L gene encodes for the major capsid p72
protein (399 nucleotides). The black circle denotes the eight ASF cases
in the August–September 2019 outbreaks in Vietnam. The phylogenetic
tree was built using the neighbor-joining method with 1000 replicates
bootstrap tests.
Figure 3. Splenic tissue of an ASF-infected pig, HE staining
(1a-c). Mild splenic haemorrhage in case 18. The cells of red pulp are
discernible, and a few lymphoid follicles are present (a). Moderate
splenic haemorrhage in case 19. There are moderate increases of
erythrocytes in the red pulp and fewer discernible lymphoid follicles
(b). Severe splenic haemorrhage in case 57. The red pulp parenchyma is
largely replaced by erythrocytes; there are noticeable necrotic tissues
and less discernable lymphoid follicles (c). Hepatic tissue of
ASF-infected pig, HE staining (1d-f). Mild hepatic haemorrhage of case
58. There is a focus of haemorrhage (arrowhead) in zone 2 (d). Moderate
haemorrhage in case 18. There are multifocal haemorrhages in several
hepatic lobules (e). Severe haemorrhage in pig 20. There are
generalized, diffuse, necrotizing haemorrhage in the hepatic parenchyma
(f).
Figure 4. Tonsillar tissue of ASF-infected pig, HE staining
(2a-c). The tonsil of case 20 under low magnification does not show
remarkable changes (a). In higher magnification, connective fibrous
tissue shows enhanced appearance (b). Apoptotic cells in the diffuse
lymphoid area are easily appreciated in this magnification (asterisk).
The lymphoid follicle (F) contains very few apoptotic bodies (c).
Figure 5. HE staining of tissues from ASF-infected pigs (3a-i).There is sinus haemorrhage in the lymph node tissue of case 58 (a).
Interstitial pneumonia and an increased number of pulmonary
intravascular macrophages are present in the lung tissue of case 58 (b).
Three to four layers of mononuclear cell infiltrations in the meninges
and perivascular cuffing are present in the cerebral tissue of case 20.
The inset shows swollen endothelial cells and apoptotic bodies in the
perivascular cuffing lesion (c). Epicardial and myocardial haemorrhage
with infiltration of mononuclear cells is present in the heart tissue of
case 18 (d). Multifocal haemorrhages are seen in the superficial and
deep lamina propria in the gastric epithelial tissue of case 58 (e).
Multifocal haemorrhages are present in the outer longitudinal muscularis
layer in the small intestinal tissue of case 18 (f). The large
intestinal tissue of case 58 shows multifocal haemorrhages in the deep
lamina propria and dilated capillaries filled with erythrocytes in the
submucosa layer with extensive oedema beneath (g). There is extensive
haemorrhage in the pelvis region of the renal tissue in case 20 (h).
Multifocal haemorrhages are found in the cortical region, sometimes
extended into the capsular layer of the renal tissue in case 19 (i).
Figure 6. Immunohistochemical staining detection of ASFV antigen
in the pig tissues (a-l). Most of the ASFV-positive cells are detected
in necrotizing macrophages in the splenic tissue of case 57 (a). Many
Kupffer cells and/or circulating macrophages are positive in the hepatic
sinusoids of the liver tissue in case 20 (b). Arrowheads show
hepatocytes with positive staining in the liver tissue of case 20 (c).
M-cells in the epithelial crypt of tonsil and mononuclear cells in the
diffuse lymphoid area are positive in the tonsillar tissue of case 20
(d). Positive cells are present in the sinus of the lymph node tissue of
case 58. Many of the positive cells are erythrocyte-laden macrophages
(e). Two pulmonary intravascular macrophages are positive in the lung
tissue of case 58 (f). A few mononuclear cells in the cerebral meninges
are positive in the cerebral tissue of case 20 (g). Positive cells are
present in the perivascular cuffing in the cerebral tissue of case 20
(h). Many spindle-shaped cells are positive in the epicardial
haemorrhage in the cardiac tissue of case 18 (i). Within the hemorrhagic
region of the renal pelvis, macrophage/mononuclear cells and many
spindle-shaped cells are positive in the renal tissue of case 20 (j).
Positive macrophage/mononuclear cells are present in the capillary of a
glomerulus in the renal tissue of case 18 (k). Renal tubular epithelium
shows positive staining in the renal tissue of case 57 (l).