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Molecular characterization and phylogenetic study of African swine fever virus isolates from recent outbreaks in Uganda (2010–2013)

201350 citationsOpen accessMakerere University

In plain language

African swine fever is a highly lethal and economically significant disease affecting domestic pigs in Eastern Africa, with frequent outbreaks reported in Uganda. To clarify the epidemiological patterns over a four-year period, outbreaks occurring between 2010 and 2013 across 15 districts in Uganda were evaluated. Tissue samples from infected domestic pigs were confirmed using an established diagnostic polymerase chain reaction assay targeting the p72 gene. Of 21 confirmed outbreaks, 17 isolates were successfully sequenced and aligned. Genetic analysis of the p72 and P54 genes showed that all isolates belonged to genotype IX, clustering with earlier viruses from Uganda and Kenya. Further examination of tetrameric amino acid repeats within the hypervariable CVR of the B602L gene resolved these isolates into three subgroups, revealing two new subgroups that had not been documented in earlier studies.

Key takeaways

  • Twenty-one African swine fever outbreaks across 15 Ugandan districts were confirmed using a diagnostic polymerase chain reaction assay.
  • All 17 successfully sequenced isolates clustered within genotype IX alongside earlier virus strains from Uganda and Kenya.
  • Analysis of the hypervariable CVR of the B602L gene identified three distinct subgroups based on tetrameric amino acid repeats.
  • Two of the identified CVR subgroups represent novel variants not recorded in previous studies.

Why it matters

African swine fever causes heavy mortality and economic damage in domestic pig farming across Eastern Africa. Tracking the genetic variations of the virus during repeated outbreaks helps veterinary authorities understand how strains are related and how they move between regions, providing essential baseline data for monitoring and controlling the disease in domestic livestock.

Commercialisation angle

The abstract does not describe a commercial product or direct application pathway. The high-resolution genotyping approach combining p72, P54, and CVR markers could potentially assist veterinary diagnostic laboratories and public animal-health agencies in outbreak tracing. However, the findings represent early-stage molecular epidemiology and viral surveillance rather than a deployable commercial technology.

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Abstract

BACKGROUND: African swine fever (ASF) is a highly lethal and economically significant disease of domestic pigs in Eastern Africa particularly in Uganda where outbreaks regularly occur. Sequence analysis of variable genome regions have been extensively used for molecular epidemiological studies of African swine fever virus (ASFV) isolates. By combining p72, P54 and pB602L (CVR), a high level resolution approach is achieved for viral discrimination. The major aim of this study therefore, was to investigate the genetic relatedness of ASF outbreaks that occurred between 2010 and 2013 in Uganda to contribute to the clarification of the epidemiological situation over a four year period. METHODS: Tissue samples from infected domestic pigs associated with an ASF outbreak from 15 districts in Uganda were confirmed as being infected with ASFV using a p72 gene-based polymerase chain reaction amplification (PCR) assay recommended by OIE. The analysis was conducted by genotyping based on sequence data from three single copy ASFV genes. The E183L gene encoding the structural protein P54 and part of the gene encoding the p72 protein was used to delineate genotypes. Intra-genotypic resolution of viral relationships was achieved by analysis of tetramer amino acid repeats within the hypervariable CVR of the B602L gene. RESULTS: Twenty one (21) ASF outbreaks were confirmed by the p72 ASF diagnostic PCR, however; only 17 isolates were successfully aligned after sequencing. Our entire isolates cluster with previous ASF viruses in genotype IX isolated in Uganda and Kenya using p72 and P54 genes. Analysis of the CVR gene generated three sub-groups one with 23 tetrameric amino acid repeats (TRS) with an additional CAST sequence, the second with 22 TRS while one isolate Ug13. Kampala1 had 13 TRS. CONCLUSION: We identified two new CVR subgroups different from previous studies. This study constitutes the first detailed assessment of the molecular epidemiology of ASFV in domestic pigs in the different regions of Uganda.

Research topics

  • Animal Disease Management and Epidemiology
  • Viral Infections and Immunology Research
  • Animal Virus Infections Studies

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DOI: 10.1186/1743-422x-10-247

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