The role of the ancestral sylvatic cycle of the African swine fever virus (ASFV) is not well understood in the endemic areas of eastern Africa. We therefore analysed the ASF infection status on samples collected from 51 free-ranging warthogs () and 1576 ticks from 26 independent warthog burrows at a single ranch in Kenya. Abattoir samples from 83 domestic pigs without clinical symptoms, originating from specific locations with no recent reported ASF outbreaks were included in this study. All samples were derived from areas of central Kenya, where ASF outbreaks have been reported in the past. Infection with ASFV was confirmed in 22 % of pools, 3.22 % of adult warthog serum samples and 49 % of domestic pig serum samples by using -based PCR. All of the warthog sera were positive for anti-ASFV antibodies, investigated by using ELISA, but none of the domestic pig sera were positive. Twenty -, 12 domestic pig- and three warthog-derived viruses were genotyped at four polymorphic loci. The ASFV isolates from ticks and domestic pigs clustered within p72 genotype X. By contrast, ASF viruses genotyped directly from warthog sera, at same locality as the tick isolates, were within p72 genotype IX and genetically similar to viruses causing recent ASF outbreaks in Kenya and Uganda. This represents the first report of the co-existence of different ASFV genotypes in warthog burrow-associated ticks and adult wild warthogs. The data from this and earlier studies suggest transfer of viruses of at least two different p72 genotypes, from wild to domestic pigs in East Africa.


Article metrics loading...

Loading full text...

Full text loading...



  1. Aguero, M., Fernandez, J., Romero, L., Sanchez Mascaraque, C., Arias, M. & Sanchez-Vizcaino, J. M.(2003). Highly sensitive PCR assay for routine diagnosis of African swine fever virus in clinical samples. J Clin Microbiol 41, 4431–4434.[CrossRef] [Google Scholar]
  2. Basto, A. P., Nix, R. J., Boinas, F., Mendes, S., Silva, M. J., Cartaxeiro, C., Portugal, R. S., Leitao, A., Dixon, L. K. & other authors(2006). Kinetics of African swine fever virus infection in Ornithodoros erraticus ticks. J Gen Virol 87, 1863–1871.[CrossRef] [Google Scholar]
  3. Bastos, A. D., Penrith, M. L., Cruciere, C., Edrich, J. L., Hutchings, G., Roger, F., Couacy-Hymann, E. & Thomson, G. R.(2003). Genotyping field strains of African swine fever virus by partial p72 gene characterisation. Arch Virol 148, 693–706.[CrossRef] [Google Scholar]
  4. Bastos, A. D., Penrith, M. L., Macome, F., Pinto, F. & Thomson, G. R.(2004). Co-circulation of two genetically distinct viruses in an outbreak of African swine fever in Mozambique: no evidence for individual co-infection. Vet Microbiol 103, 169–182.[CrossRef] [Google Scholar]
  5. Bastos, A. D., Arnot, L. F., Jacquier, M. D. & Maree, S.(2009). A host species-informative internal control for molecular assessment of African swine fever virus infection rates in the African sylvatic cycle Ornithodoros vector. Med Vet Entomol 23, 399–409.[CrossRef] [Google Scholar]
  6. Boshoff, C. I., Bastos, A. D., Gerber, L. J. & Vosloo, W.(2007). Genetic characterisation of African swine fever viruses from outbreaks in southern Africa (1973–1999). Vet Microbiol 121, 45–55.[CrossRef] [Google Scholar]
  7. Chapman, D. A., Tcherepanov, V., Upton, C. & Dixon, L. K.(2008). Comparison of the genome sequences of non-pathogenic and pathogenic African swine fever virus isolates. J Gen Virol 89, 397–408.[CrossRef] [Google Scholar]
  8. Costard, S., Wieland, B., de Glanville, W., Jori, F., Rowlands, R., Vosloo, W., Roger, F., Pfeiffer, D. U. & Dixon, L. K.(2009). African swine fever: how can global spread be prevented? Philos Trans R Soc Lond B Biol Sci 364, 2683–2696.[CrossRef] [Google Scholar]
  9. De Kock, G., Robinson, E. M. & Keppel, J. J. G.(1940). Swine fever in South Africa. Onderstepoort J Vet Res 14, 31–93. [Google Scholar]
  10. de Villiers, E. P., Gallardo, C., Arias, M., da Silva, M., Upton, C., Martin, R. & Bishop, R. P.(2010). Phylogenomic analysis of 11 complete African swine fever virus genome sequences. Virology 400, 128–136.[CrossRef] [Google Scholar]
  11. Detray, D. E.(1957). African swine fever in warthogs (Phacochoerus aethiopicus). J Am Vet Med Assoc 130, 537–540. [Google Scholar]
  12. Dixon, L. K., Costa, J. V., Escribano, J. M., Rock, D. L., Vinuela, E. & Wilkinson, P. J.(2000). Family Asfarviridae. In Virus Taxonomy, 7th Report of the ICTV, pp. 159–165. Edited by Van Regenmortel, M. H. V., Fauquel, C. M. & Bishop, D. H. L.. San Diego. : Academic Press. [Google Scholar]
  13. Dixon, L. K., Escribano, J. M., Martins, C., Rock, D. L., Salas, M. L. & Wilkinson, P. J.(2005).Asfarviridae. In Virus Taxonomy, VIIIth Report of the ICTV, pp. 135–143. Edited by Fauquet, C. M., Mayo, M. A., Maniloff, J., Desselberger, U. & Ball, L. A.. London. : Elsevier/Academic Press. [Google Scholar]
  14. Gallardo, C., Mwaengo, D. M., Macharia, J. M., Arias, M., Taracha, E. A., Soler, A., Okoth, E., Martin, E., Kasiti, J. & other authors(2009a). Enhanced discrimination of African swine fever virus isolates through nucleotide sequencing of the p54, p72, and pB602L (CVR) genes. Virus Genes 38, 85–95.[CrossRef] [Google Scholar]
  15. Gallardo, C., Reis, A. L., Kalema-Zikusoka, G., Malta, J., Soler, A., Blanco, E., Parkhouse, R. M. & Leitao, A.(2009b). Recombinant antigen targets for serodiagnosis of African swine fever. Clin Vaccine Immunol 16, 1012–1020.[CrossRef] [Google Scholar]
  16. Haresnape, J. M. & Mamu, F. D.(1986). The distribution of ticks of the Ornithodoros moubata complex (Ixodoidea: Argasidae) in Malawi, and its relation to African swine fever epizootiology. J Hyg (Lond) 96, 535–544.[CrossRef] [Google Scholar]
  17. Haresnape, J. M., Lungu, S. A. & Mamu, F. D.(1985). A four-year survey of African swine fever in Malawi. J Hyg (Lond) 95, 309–323.[CrossRef] [Google Scholar]
  18. Haresnape, J. M., Wilkinson, P. J. & Mellor, P. S.(1988). Isolation of African swine fever virus from ticks of the Ornithodoros moubata complex (Ixodoidea: Argasidae) collected within the African swine fever enzootic area of Malawi. Epidemiol Infect 101, 173–185.[CrossRef] [Google Scholar]
  19. Heuschele, W. P. & Coggins, L.(1969). Epizootiology of African swine fever virus in warthogs. Bull Epizoot Dis Afr 17, 179–183. [Google Scholar]
  20. Irusta, P. M., Borca, M. V., Kutish, G. F., Lu, Z., Caler, E., Carrillo, C. & Rock, D. L.,(1996). Amino acid tandem repeats within a late viral gene define the central variable region of African swine fever virus. Virology 220, 20–27.[CrossRef] [Google Scholar]
  21. Jori, F. & Bastos, A. D.(2009). Role of wild suids in the epidemiology of African swine fever. EcoHealth 6, 296–310.[CrossRef] [Google Scholar]
  22. Kleiboeker, S. B. & Scoles, G. A.(2001). Pathogenesis of African swine fever virus in Ornithodoros ticks. Anim Health Res Rev 2, 121–128. [Google Scholar]
  23. Lubisi, B. A., Bastos, A. D., Dwarka, R. M. & Vosloo, W.(2005). Molecular epidemiology of African swine fever in East Africa. Arch Virol 150, 2439–2452.[CrossRef] [Google Scholar]
  24. Lubisi, B. A., Bastos, A. D., Dwarka, R. M. & Vosloo, W.(2007). Intra-genotypic resolution of African swine fever viruses from an East African domestic pig cycle: a combined p72-CVR approach. Virus Genes 35, 729–735.[CrossRef] [Google Scholar]
  25. Malmquist, W. A. & Hay, D.(1960). Hemadsorption and cytopathic effect produced by African Swine Fever virus in swine bone marrow and buffy coat cultures. Am J Vet Res 21, 104–108. [Google Scholar]
  26. Montgomery, R. E.(1921). A form of swine fever occurring in British East Africa (Kenya Colony). J Comp Pathol 34, 159–191.[CrossRef] [Google Scholar]
  27. Nix, R. J., Gallardo, C., Hutchings, G., Blanco, E. & Dixon, L. K.(2006). Molecular epidemiology of African swine fever virus studied by analysis of four variable genome regions. Arch Virol 151, 2475–2494.[CrossRef] [Google Scholar]
  28. OIE(2008). Chapter 2.8.1. African swine fever. In Manual of diagnostic tests and vaccines for terrestrial animals 2008. Office International des Epizooties, Paris, France. http://www.oie.int/eng/normes/mmanual/2008/pdf/2.08.01_ASF.pdf.
  29. Oura, C. A., Powell, P. P., Anderson, E. & Parkhouse, R. M.(1998). The pathogenesis of African swine fever in the resistant bushpig. J Gen Virol 79, 1439–1443. [Google Scholar]
  30. Owolodun, O. A., Bastos, A. D., Antiabong, J. F., Ogedengbe, M. E., Ekong, P. S. & Yakubu, B.(2010). Molecular characterisation of African swine fever viruses from Nigeria (2003–2006) recovers multiple virus variants and reaffirms CVR epidemiological utility. Virus Genes 41, 361–368.[CrossRef] [Google Scholar]
  31. Penrith, M. L.(2009). African swine fever. Onderstepoort J Vet Res 76, 91–95. [Google Scholar]
  32. Penrith, M. L., Thomson, G. R. & Bastos, A. D. S.(2004a). African swine fever. In Infectious Diseases of Livestock with Special Reference to Southern Africa, pp. 1088–1119. Edited by Coetzer, J. A. W. & Tustin, R. C.. Cape Town, South Africa. : Oxford University Press. [Google Scholar]
  33. Penrith, M. L., Thomson, G. R., Bastos, A. D., Phiri, O. C., Lubisi, B. A., Du Plessis, E. C., Macome, F., Pinto, F., Botha, B. & other authors(2004b). An investigation into natural resistance to African swine fever in domestic pigs from an endemic area in southern Africa. Rev Sci Tech 23, 965–977. [Google Scholar]
  34. Perez-Filgueira, D. M., Gonzalez-Camacho, F., Gallardo, C., Resino-Talavan, P., Blanco, E., Gomez-Casado, E., Alonso, C. & Escribano, J. M.(2006). Optimization and validation of recombinant serological tests for African Swine Fever diagnosis based on detection of the p30 protein produced in Trichoplusia ni larvae. J Clin Microbiol 44, 3114–3121.[CrossRef] [Google Scholar]
  35. Phologane, S. B., Bastos, A. D. & Penrith, M. L.(2005). Intra- and inter-genotypic size variation in the central variable region of the 9RL open reading frame of diverse African swine fever viruses. Virus Genes 31, 357–360.[CrossRef] [Google Scholar]
  36. Plowright, W., Parker, J. & Peirce, M. A.(1969). African swine fever virus in ticks (Ornithodoros moubata, murray) collected from animal burrows in Tanzania. Nature 221, 1071–1073.[CrossRef] [Google Scholar]
  37. Reed, L. J. & Muench, H.(1938). A simple method of estimating fifty percent endpoints. Am J Hyg 27, 493–497. [Google Scholar]
  38. Rowlands, R. J., Michaud, V., Heath, L., Hutchings, G., Oura, C., Vosloo, W., Dwarka, R., Onashvili, T., Albina, E. & other authors(2008). African swine fever virus isolate, Georgia, 2007. Emerg Infect Dis 14, 1870–1874.[CrossRef] [Google Scholar]
  39. Tamura, K., Dudley, J., Nei, M. & Kumar, S.(2007).mega4: Molecular Evolutionary Genetics Analysis (mega) software version 4.0. Mol Biol Evol 24, 1596–1599.[CrossRef] [Google Scholar]
  40. Thomson, G. R.(1985). The epidemiology of African swine fever: the role of free-living hosts in Africa. Onderstepoort J Vet Res 52, 201–209. [Google Scholar]
  41. Wilkinson, P. J., Pegram, R. G., Perry, B. D., Lemche, J. & Schels, H. F.(1988). The distribution of African swine fever virus isolated from Ornithodoros moubata in Zambia. Epidemiol Infect 101, 547–564.[CrossRef] [Google Scholar]
  42. Zsak, L., Borca, M. V., Risatti, G. R., Zsak, A., French, R. A., Lu, Z., Kutish, G. F., Neilan, J. G., Callahan, J. D. & other authors(2005). Preclinical diagnosis of African swine fever in contact-exposed swine by a real-time PCR assay. J Clin Microbiol 43, 112–119.[CrossRef] [Google Scholar]

Data & Media loading...

Most cited this month Most Cited RSS feed

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error