Abstract
This study investigates suspected African swine fever (ASF) outbreaks in two villages of Kannur district in Kerala, India, with the aim of identifying the causative agent and its genotype, the source of infection, and estimating the economic losses due to the outbreaks. Clinically, the disease was acute with high mortality, while gross pathology was characterized by widespread haemorrhages in various organs, especially the spleen, which was dark, enlarged and had friable cut surfaces with diffuse haemorrhages. Notably, histopathological examination revealed multifocal, diffuse haemorrhages in the splenic parenchyma and lymphoid depletion accompanied by lymphoid cell necrosis. The clinico-pathological observations were suggestive of ASF, which was confirmed by PCR. The source of outbreak was identified as swill and it was a likely point source infection as revealed by epidemic curve analysis. The phylogenetic analysis of p72 gene identified the ASFV in the current outbreak as genotype-II and IGR II variant consistent with ASFVs detected in India thus far. However, the sequence analysis of the Central Variable Region (CVR) of the B602L gene showed that the ASFVs circulating in Kerala (South India) formed a separate clade along with those found in Mizoram (North East India), while ASFVs circulating in Arunachal Pradesh and Assam states of India grouped in to different clade. This study represents the first investigation of ASF outbreak in South India, establishing the genetic relatedness of the ASFV circulating in this region with that in other parts of the country. The study also underscores the utility of the CVR of the B602L gene in genetically characterizing highly similar Genotype II ASFVs to understand the spread of ASF within the country.
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Data availability
The sequences are deposited in the NCBI Nucleotide database under accession numbers OR502005-OR502009 (Intergenic region between I73R and I329L), OR490939-OR490943 (B602L) and OR472614-OR472617 (B646L). Any other data if required will be made available on request.
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Acknowledgements
The authors would like to thank Dr. G. Govindaraj, Principal Scientist, ICAR-NIVEDI for providing inputs to improve the presentation of the data on economic loss due to ASF outbreak. We are highly thankful to officials of State Animal Husbandry Department and the District Animal Husbandry Office, Kannur, Kerala for their kind cooperation in carrying out the epidemiological investigation of ASF. We thank Indian Council of Agricultural Research, New Delhi for funding the project No. ANSCNIVEDISIL202300800148.
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Conceptualization: Jagadish Hiremath; Methodology: Jagadish Hiremath, Divakar Hemadri, Shivasharanappa Nayakvadi, Chethan Kumar , C. S. Sathish Gowda; Formal Analysis: Jagadish Hiremath, Divakar Hemadri, Shivasharanappa Nayakvadi, Chethan Kumar , C. S. Sathish Gowda; Investigation: Jagadish Hiremath, Shivasharanappa Nayakvadi, Chethan Kumar , C. S. Sathish Gowda, Ranjini A.R, Jayamohanan T. V, Swapna Susan Abraham; Writing- original draft preparation: Jagadish Hiremath; Writing- review and editing: Divakar Hemadri, Shivasharanappa Nayakvadi, Chethan Kumar , C. S. Sathish Gowda, Damini Sharma, Ramamoorthy. R., Mamatha S S, Sharanagouda Patil, Ranjini A.R, Jayamohanan T. V, Swapna Susan Abraham, Baldev Raj Gulati: Funding Acquisition: Baldev Raj Gulati; Resources: Baldev Raj Gulati.
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Hiremath, J., Hemadri, D., Nayakvadi, S. et al. Epidemiological investigation of ASF outbreaks in Kerala (India): detection, source tracing and economic implications. Vet Res Commun 48, 827–837 (2024). https://doi.org/10.1007/s11259-023-10254-3
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DOI: https://doi.org/10.1007/s11259-023-10254-3