What types of feline cancer can be transmitted between cats, specifically through direct contact or other means?

Transmissible Feline Cancers

The only well-documented transmissible cancer in cats is feline leukemia virus (FeLV)-associated lymphoma and leukemia, which spreads between cats through direct contact with infected saliva, blood, urine, and feces. 1, 2

Primary Transmissible Cancer: FeLV-Associated Malignancies

Feline leukemia virus is a contagiously transmitted oncogenic retrovirus that directly causes cancer in cats through horizontal transmission. 1 This represents a true transmissible cancer where the causative viral agent spreads between cats and subsequently induces malignant transformation.

Mechanism of Transmission

• FeLV spreads readily between cats through direct contact, particularly in environments where cats are housed communally for extended periods. 1, 3
• The virus is transmitted via infected saliva, blood, urine, and feces, making grooming, biting, and shared food/water bowls key transmission routes. 2
• Shelters with high cat density demonstrate significantly higher seroprevalence and increased risk of viral transmission and recombination. 3

Cancer Types Caused by FeLV

• FeLV causes a variety of hematopoietic and lymphoid neoplasms, with the most common being alimentary, multicentric, and thymic lymphosarcoma, as well as lymphatic leukemia. 2
• Cats infected with FeLV have 3.9 times higher odds of developing lymphoma and 19.4 times higher odds of developing leukemia compared to uninfected cats. 4
• Cats coinfected with both FeLV and FIV have 19.3 times higher odds of leukemia, demonstrating the oncogenic potency of FeLV. 4

Pathogenic Variability

• Natural FeLV isolates exist as mixtures of closely related virus genotypes, with minor genetic variations imparting major differences in pathogenicity and disease-inducing capacity. 1
• Specific FeLV strains target different cell populations, leading to either malignant transformation or cytopathic deletion of lymphocyte and hematopoietic cells. 1
• The genetic regions responsible for specific disease induction (thymic lymphoma, acute immunosuppression, or aplastic anemia) have been mapped to the virus surface glycoprotein and long terminal repeat regions. 1

FIV: Not a Transmissible Cancer

Feline immunodeficiency virus (FIV), while transmissible between cats, does not directly cause cancer and should not be considered a transmissible cancer agent. 5, 4

• FIV-infected cats show no significant increase in neoplastic diseases compared to uninfected cats, with infection not associated with any specific cancer condition. 4
• FIV primarily causes immunodeficiency that may increase opportunistic infection risk, but most naturally infected cats live many years without severe clinical signs or cancer development. 5

Clinical Implications

• FeLV prevalence varies considerably by geographic location, with some regions showing up to 26.9% infection rates in necropsied cat populations. 4
• Infected cats are significantly younger than uninfected cats, suggesting early transmission and rapid disease progression. 4
• Many cats mount an effective immune response to FeLV and can eliminate the virus, with serum antibody titers of 32 or more indicating cats are unlikely to suffer ill effects. 2
• The outcome of FeLV infection depends on the cat's immunological competence, viral dose received, and the virus's ability to induce immunosuppression. 2

Important Caveat

While FeLV represents a transmissible cancer through viral transmission, this differs from the extremely rare phenomenon of direct cancer cell transmission (as seen in Tasmanian devil facial tumor disease), which has not been documented in domestic cats. The cancer transmission in cats occurs through viral infection that subsequently causes malignant transformation, not through transfer of malignant cells themselves. 1, 2