Feline leukaemia virus (FeLV) PCR

Feline leukaemia virus (FeLV) PCR

Species: Feline

Specimen: 0.5-1 mL of EDTA anticoagulated blood, bone marrow aspirate (up to 0.5 mL collected into an EDTA tube)

Container: EDTA

Collection protocol: Standard venepuncture or bone marrow biopsy

Special handling/shipping requirements:

Blood samples are stable at room temperature and can be sent un-refrigerated. If collecting in warm conditions, it is recommended that samples be stored out of the heat, preferably in an insulated container, until they can be transferred indoors to a controlled environment.

General information about the disease:

Feline leukaemia virus (FeLV) is a retrovirus; a single stranded RNA virus belonging to the same viral family as the more common Feline Immunodeficiency Virus (FIV). It is found worldwide but incidence can be quite varied. Although many cats will overcome infection with FeLV, experiencing a transient viraemia or seroconverting with no detectable viraemia, some become persistently infected. Most persistently viraemic cats will develop a range of conditions including anaemia and/or lymphoma, cancers, intermittent immunosuppression and reproductive problems, and die within 3 years. In particular, cats may become susceptible to secondary infections if immunosuppressed. The cat’s age at the time of infection is a major determinant of clinical outcome. A cat found to be persistently viraemic should be isolated from other cats to reduce the risk of passing on the virus.

FeLV invades and replicates in some cells of the cat’s immune system and blood-forming cells. During viral replication, the nucleic acid of FeLV inserts itself into the genome of the infected cells it has invaded. The result can be death of the cell or the viral insert being carried by the cell and passed on to the next generation during cell division. The change in the cells genetic code can also potentially result in cellular changes that can lead to neoplastic disease (cancer). The development of cancer or other conditions may not occur for months or years after the initial infection.

A cat that has overcome viraemia will remain latently infected. Once a cat becomes latently infected, it remains so for life. FeLV may be reactivated on rare occasions from these cats when immunosuppressed or under chronic stress and such cats should still then be considered potential sources of infection.

FeLV is passed from cat to cat via saliva. Unlike FIV that is transmitted via biting, the transfer of FeLV is usually between friendly cats. This can occur during grooming or by sharing food bowls. Occasionally mothers can pass the infection to their kittens either in the womb or via milk. Kittens are particularly susceptible to contracting persistent infections, whereas most adult cats are able to eliminate the virus. Once a cat becomes persistently infected, it remains so for life. Cats known to be persistently infected should be isolated from other cats to reduce the risk of passing on the virus.

Polymerase chain reaction (PCR) detects the presence of infectious agents by identifying the genomic material of the agent being investigated. Unlike serology, which indicates whether an animal has been infected in the past, PCR determines if the agent is still present thereby informing the clinician that an active infection is in progress. It is often more sensitive and specific than other available tests including culture (especially for viruses) and is usually more rapid to achieve a result.

General information about when this test is indicated:

This test is a quantitative PCR test for the detection of FeLV proviral DNA. The FeLV PCR will detect the majority of strains of the virus.

Comparison with other related tests:

The FeLV PCR will detect the majority of strains of the virus. The PCR is based on the method used by most diagnostic laboratories and is considered to be both reliable and sensitive for the diagnosis of viral infection. Serology (to detect antibody) is also available but is considered less sensitive and specific; positive serology indicates the animal has been exposed to FeLV, whereas positive PCR indicates genuine persistent infection is present.