Emergence of African Swine Fever in Sri Lanka, 2024

Figures

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  Figure 1. Gross lesions observed in dead domestic (A–G) and wild pigs (H,I): (A) dead pig with bleeding from the nose; (B) enlarged spleen; (C) hemorrhagic and enlarged mesenteric lymph nodes. (D) Petechial hemorrhages on the kidney surface; (E) hemorrhages on the cardiac muscle; (F) petechial hemorrhages on the serosal surface of the small intestine; (G) enlarged and hemorrhagic gastro hepatic lymph nodes; (H) a dead wild boar found in Western Province; (I) enlarged spleen in a dead wild boar (Western Province).

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  Figure 2. Location of the samples collected. Sri Lanka shapefile was downloaded from https://data.humdata.org/dataset/cod-ab-lka accessed on 23 December 2025 and loaded into R studio. The tmap package was used to generate the map of Sri Lanka, and the GPS coordinates of sample collection sites were used. Red = domestic pigs; blue = wild boar.

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  Figure 3. Phylogenetic analysis of full-length genes encoding ASFV p72, p54, and CD2V. Phylogenetic analysis of ASFV genes p72 (A), p54 (B), and CD2v (C). Nucleotide sequences were aligned in Geneious Prime with MAFFT. IQ-Tree v2.3.5 and FigTree v1.4.4 were used to produce the final midpoint-rooted tree. Other sequences were obtained from NCBI. Sequences generated in this study are indicated with red dots.

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  Figure 4. Histopathology (A,C,E) and immunohistochemistry (B,D,F–H) findings ((A,B) lymph node; (C,D) liver; (E,F) small intestine; (G) stomach; (H) lung): (A) Widespread apoptosis of lymphocytes (arrows). Insets shows higher magnification of dashed boxes. (B) Viral antigen is distributed widely throughout the lymph node (brown staining) and especially in areas with numerous infected macrophages (arrows). Inset (dashed box area): Viral antigen is frequently observed in large cells consistent with macrophages/dendritic cells (arrowheads). (C) Areas of periportal inflammation (arrow) and scattered necrotic shrunken hyper-eosinophilic hepatocytes (arrowheads). (D) Viral antigen in Kupffer cells (arrows) and scattered hepatocytes (arrowheads). (E) Lymphoplasmacytic inflammation in lamina propria (arrows) with scattered necrotic cells. (F) Abundant viral antigen in association with the areas of inflammation and necrosis (brown staining). (G) Pathologic changes observed in the stomach were not significant; however, viral antigen was detected within the superficial lamina propria. (H) Lung tissue was not well preserved; thus, histopathology could not be interpreted; however, viral antigen was…

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  Figure 5. Phylogeographic analysis of whole-genome sequences. (A) Rooted maximum-likelihood phylogenetic tree derived from whole-genome sequences of ASFV genotype II. The tree is colored according to collection country, as displayed on the map (panel (B)). (B) Spatial transmissions of ASFV between host countries, inferred from the maximum-likelihood phylogeny in panel (A). The origin countries of all whole-genome sequences used in this study are shaded on the map. Arcs represent inferred viral transmissions between host countries, colored according to the source country. Only transmissions with a bootstrap support > 60% are displayed. (C) Partial genome alignment of ASFV genotype II, highlighting shared indels between isolates from China, Hong Kong, and Sri Lanka. Gray and black regions represent sequence identity and mismatches, respectively, relative to the full alignment consensus sequence. The full alignment consensus sequence was generated from the alignment used to construct the phylogenetic tree in panel (A) (61 samples, 75% threshold).