Feline foamy virus in Cats (Felis) | Vetlexicon
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Feline foamy virus

ISSN 2398-2950

Synonym(s): FFV, FeSFV, feline syncytium-forming virus




  • Family: Retroviridae.
  • Genus: Spumavirus.


  • In tissue culture, FFV (also known formerly as FeSFV) causes fusion of adjacent cells into large, multinucleated cells or syncytia, giving rise to the name "synctium forming" or "foamy" virus. "Spuma" is Latin for foamy.


  • Worldwide.
  • Ubiquitous.


  • In cats:
    • Generally considered to be apathogenic (Loh 1993).
    • Main significance is as potential contaminant of cell cultures in research and vaccine production.

Active Forms

Active Form 1


  • Enveloped, RNA virus about 100 nm in diameter.
  • Central core (pentagonal) of approximately 50 nm in diameter.
  • Envelope has many short surface spikes.
  • Contains the enzyme reverse transcriptase.
  • Contains genes that encode regulatory proteins Bet, Bel1/Tas and Bel-2.


  • Virus is highly cell-associated and thus free virus is seldom detected. As with all retroviruses, relatively labile in the environment due to lipid envelope.

Resting Forms

Clinical Effects



  • Unknown - possibly by biting. Also transplacental - 25-50% of kittens born to FFV-infected queens reported to be infected at birth, ie some siblings in the same litter will be infected and others uninfected.

Pathological effects

  • As in FIV, infected cats have antibodies to FFV.
  • Antibodies appear from 3 weeks post-infection.
  • FFV has been isolated from healthy cats as well as cats with diverse diseases.
  • Reported association with polyarthritis (Pedersen et al, 1980).
  • Most evidence suggests virus is non-pathogenic.
  • No disease induced following experimental infection (Alke et al, 2000, Schwantes et al, 2002, German et al, 2008).


Useful samples


  • FFV can be isolated in cell culture when samples are tested for other agents associated with disease. Virus isolation can be performed on request by Companion Animal Diagnostics at the University of Glasgow.


  • Whole blood in heparin.


  • Serological response in domestic cats has been described in detail where antibodies against Gag proteins (p52 and p48) may be considered diagnostic (Romeet al, 2006). Antibodies may be detected by using either immunoblot (whole virus) or ELISA Enzyme linked immunosorbent assay (ELISA) (recombinant proteins) (Romeet al, 2006), although neither technique is widely available due to lack of known disease association.

Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • German A C, Harbour D A, Helps C R et al (2008) Is feline foamy virus really apathogenic? Vet Immunol Immunopathol 123 (1-2), 114-118 PubMed.
  • Romen F, Pawlita M, Sehr P et al (2006) Antibodies against Gag are diagnostic markers for feline foamy virus infections while Env and Bet reactivity is undetectable in a substantial fraction of infected cats. Virology 345 (2), 502-508 PubMed.
  • Schwantes A, Ortlepp I, Löchelt M et al (2002) Construction and functional characterization of feline foamy virus-based retroviral vectors. Virology 301 (1), 53-63 PubMed.
  • Alke A, Schwantes A, Zemba M et al (2000) Characterization of the humoral immune response and virus replication in cats experimentally infected with feline foamy virus. Virology 275 (1), 170-176 PubMed.
  • Linial M L (1999) Foamy viruses are unconventional retroviruses. J Virol 73 (3), 1747-1755 PubMed.
  • Wang G, Mulligan M J (1999) Comparative sequence analysis and predictions for the envelope glycoproteins of foamy viruses. J Gen Virol 80 (Pt 1), 245-254 PubMed.
  • Winkler I G, Flügel R M, Löchelt M et al (1998) Detection and molecular characterisation of feline foamy virus serotypes in naturally infected cats. Virology 247 (2), 144-151 PubMed.
  • Pedersen N C, Pool R R, O'Brien T (1980) Feline chronic progressive polyarthritis. Am J Vet Res 41 (4), 522-535 PubMed.

Other sources of information

  • Loh P (1993) Spumaviruses. In: J A Levy (ed) The Retroviridae, vol 2. Plenum Press, New York, NY.


  • Companion Animal Diagnostics, Veterinary Diagnostic Services, Faculty of Veterinary Medicine, University of Glasgow, Bearsden Road, Glasgow, G61 1QH, Scotland. Tel: + 44 141 330 5777; Fax: + 44 141 330 5748; E-mail: companion@vet.gla.ac.uk