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

ISSN 2398-2950

Contributor(s) :

Synonym(s): Feline sarcoma virus, FeSV




  • Family: Retrovirus.
  • Type: Gammaretrovirus.


  • Retro because the viral RNA is reverse transcribed into DNA (proviral DNA).


  • Worldwide.
  • Rare.


  • Feline sarcoma viruses (FeSVs) are recombinant viruses that arise in cats persistently infected with FeLV.
  • Recombinant viruses arise through FeLV recombining with host cellular genes.
  • If reconstruction leads to the incorporation of a cellular oncogene, tumors or leukemias may develop.
  • FeLV recombinant viruses incorporating cellular oncogenes are incapable of replication without the help of wild-type FeLV.
  • There is no evidence of transmission between cats although experimental transmission has been demonstrated.

Active Forms

Active Form 1


  • FeSV is formed by the incorporation of a cat cellular oncogene into a defective FeLV genome. Thus, replication requires a helper virus, namely wild type exogenous FeLV.


  • Fragile - can only survive in vivo.


Reproduction Longevity
  • Should be regareded as for FeLV.

Resting Forms

Clinical Effects



  • The resulting tumors contain both FeLV and FeSV which may be transmitted experimentally.
  • FeSV is not transmitted between cats in nature; the virus arises de novo in cats persistently infected with FeLV.
  • FeLV is transmissable between cats by direct contact.

Pathological effects

  • FeSV will not arise in cats immune to FeLV, thus protection against FeLV protects against FeSV.
  • FeSVs induce multiple, usually subcutaneous, fibrosarcomas of young cats <5 years of age (the more common solitary fibrosarcoma of the older cat (mean age 10 years) is not caused by FeSV).


Control via chemotherapies

  • Unlikely to work, however, a protocol is given by Keller and Helfand (1994) for those desperate to try.

Control via environment

  • As for FeLV.


  • Since FeSV cannot occur without FeLV, FeLV vaccination will also protect cats from FeSV.

Other countermeasures

  • Tumors usually recur after surgery.
  • Since the prognosis for FeSV fibrosarcomas is grave, euthanasia may well be the best option.


Useful samples

  • Tumor biopsy in 10% formol saline.
  • Whole blood, plasma or serum for FeLV testing and virus isolation.

Specimen storage

  • Biopsy will store in 10% formol saline indefinitely at room temperature.
  • If delay in sending blood to laboratory for diagnosis, blood should be separated and plasma or serum frozen at -20°C until sending.

Transport of samples

  • Send by first class post to specialist laboratory.

Field diagnosis

  • Since FeSV can only occur in accompanying FeLV infections, in-practice FeLV tests FeLV test should give positive results.
  • Occurrence of multiple tumors in a young cat should alert clinician to possibility of FeSV.

Laboratory diagnosis

  • See FeLV Feline leukemia virus disease section for the diagnosis of persistent FeLV infection. 
  • Biopsy or histopathology to identify fibrosarcomas Fibrosarcoma.
  • Complete confirmation requires genetic analysis of FeSV involved in the tumor or leukemia.

Further Reading


Refereed papers

Other sources of information

  • Keller E T, Helfand S C (1994) Clinical management of soft-tissue sarcomas. In: Consultations in feline internal medicine 2.  Ed John R. August. W B Saunders Co., Harcourt Brace Jovanovich, Inc. The Curtis Center, Independence Square West, Philadelphia, PA 19106. pp 3-12.
  • Hardy W D Jr. (1987) Oncogenic viruses of cats: the feline leukemia and sarcoma viruses. In: Diseases of the Cat: Medicine and Surgery Ed Holzworth, J. W B Saunders Co., Harcourt Brace Jovanovich, Inc. The Curtis Center, Independence Square West, Philadelphia, PA 19106. pp 256-258.


  • 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 .