FeLV - Feline Leukemia Virus

For PCR testing, samples of blood are taken or swabs of oropharyngeal or conjunctivae mucosae are taken by cotton swabs (is provided by laboratory). Laboratory provides two swabs for one animal – each swab can be used for sampling of different mucosae. Swabs will be analysed together like a mixed sample. If you like test the swabs separately, we will charge you two analysis – it is necesary to ask for separately testing!

FeLV transmission

FeLV spread

Course of FeLV-infection

Therapy

Prevention

Prognosis

FeLV is a retrovirus, which develops multiple clinical symptoms from immune system disorder to oncogenous lymphoproliferatice alterations.
All retroviruses (incl. FeLV, FIV and HIV) produce an enzyme, reverse transcriptase, which permits them to insert copies of their own DNA into that of cells they have infected. Although very similar, FeLV and FIV differ in many ways, for example the shape of FeLV is more circular while FIV is elongated. FeLV and FIV are also different genetically, and their protein constituents are dissimilar in size and composition. Although many FIV and FeLV symptoms are similar, the specific ways in which they are caused differs.

FeLV transmission
For transmission of infection a direct contact between cats is necessary. FeLV can be transferred by saliva, blood, and even virus transfer by mating. There is a frequent transmission from an infected mother cat to her nursed kittens, because of the presence of virus in the milk and the colostrum.
Cats infected with FeLV serve as clear source of infection. Virus is shed in very high quantity in saliva and nasal secretions, but also in urine, feces and milk. Cat-to-cat transfer of virus occurs most often from a bite wound, rarely during mutual grooming (e.g. through the shared litter boxes and feeding dishes).

FeLV spread
Cats infected with FeLV are found all over the world, but the prevalence of infection varies greatly depending on their age, health, environment, and lifestyle. In the United States, approximately 2 to 3% of all cats are infected with FeLV. FeLV-infection in the West European countries is about 6% (can reach up to 50% in cats bred in higher concentrations). In cats bred in very good conditions, kept indoors or placed in a secure enclosure, the infection rate is approx. 1 %. In the Czech Republic, the presence of FeLV-antigen in the blood of examined cats makes approx. 10 %.

Course of FeLV-infection
After being infected with the virus, the cat may not exhibit any clinical signs, but becomes a source of infection for other cats. The disease may lead to a state of immune deficiency (cat becomes perceptive to any infection) or less often to production of lymphoma (tumours) that may occur in hypodermis, lymphnodes, intestines, etc.
Feline leukemia virus affects the cat´s body in many ways. It is the most common cause of cancer in cats. The secondary symptoms are blood disorders leading to a state of immune deficiency that hinders the cat´s ability to protect itself against other infections. Infections that do not usually affect healthy animals can be fatal in cats infected with FeLV.
During the early stages of infection, it is common for cats to exhibit no signs of disease at all. The cat can stay without signs several weeks or months. However, over time, the cat´s health progressively deteriorates or is characterized by recurrent illness interspersed with the periods of relative health. The signs may include loss of appetite, weight loss, poor coat condition, enlarged lymph nodes, persistent fever, gum inflammation, infection of the skin, urinary bladder and upper respiratory tract, persistent diarrhoea, seizures, behaviour changes and other neurological disorders, various eye diseases, abortion of kittens or spontaneous abortion in pregnant cats .
FeLV is present in the blood during two different stages of infection:
• Primary infection stage - during this stage some cats are able to develop an effective immune response, eliminate the virus from the bloodstream, and halt progression to the secondary stage.
• Secondary stage - is characterized by persistent infection of the bone marrow and other tissue. Progressive deterioration of health condition and death.

Therapy
Non-specific therapy is focused on limitation of opportunistic infections and support of the overall health condition, in particular by means of infusion therapy, administration of wide-spectrum antibiotics and antiparasitics. The success depends to a large extent on the stage of immune system deterioration and can be expected particularly in the early stage of the disease. It can be applied preparations with immune-stimulating and antitumor activity. The feeding ration is to be completed with vitamins, antioxidants, and omega fatty acids. The cat should not be fed with raw meat, eggs, and non-pasteurized products because of the risk of bacterial and parasitic infections. The therapy requires close cooperation of the owner with the veterinarian and regular examination of the patient´s health condition including repeated laboratory tests.

Prevention
The prevention consists in complex utilization of breeding possibilities. Stress is to be laid on keeping the positive cat separated from the others to avoid spreading of the infection in the cat population. Thanks to optimization of treatment/care and breeding conditions, FeLV-infected cats can survive for several years without obvious health complications. Among such measures belong stress limitation, nutritionally complete and balanced diet and regular administration of antiparasitic agents. All health complications have to be consulted and immediately treated by the veterinarian. If surgical treatment is indicated, the veterinary personnel are to be informed about the FeLV infection in the patient so that optimum postoperative care and separation of the patient in the hospital can be ensured. Separation in the household enables timely identification of health condition deterioration. In patient with suppressed immune response, this measure reduced the hazard of other infections. In no case, FeLV-infected cats should get vaccines that contain live virus.

Prognosis
In patients with chronic health complications and positive test on FeLV-presence the long-time prognosis is unfavourable. If the disease is diagnosed in early stage, the infected cat can live for several years. The life prognosis for kittens with combined FIV/FeLV, FIV/FIP or FIV/FPV infections is very poor.
The cats should be tested for FeLV and FIV every time they are ill, irrelevant of their age, negative results of previous tests and vaccination status.

References:
Monitoring infekčních onemocnění koček v České republice (1993 - 2003), Z. KNOTEK, Klinika chorob ptáků, plazů a drobných savců, Fakulta veterinárního lékařství Veterinární a farmaceutické univerzity Brno, Veterinářství 2004;54:4-8
Nemoci psa a kočky II. Díl, Prof. MVDr. Miroslav SVOBODA, CSc. Prof. David F. SENIOR, D.V.M., BVSc, dipl. ACVIM, dipl. ECVIM-CA Doc. MVDr. Jaroslav DOUBEK, CSc. MVDr. Jiří KLIMEŠ, Csc.; Česká asociace veterinárních lékařů malých zvířat (ČAVLMZ); Noviko, a. s. Brno 2001
Feline leukemia virus. Immunization and prevention.; Loar AS.;Vet Clin North Am Small Anim Pract. 1993 Jan;23(1):193-211
Immunomodulation therapy for feline leukemia virus infection.; McCaw DL, Boon GD, Jergens AE, Kern MR, Bowles MH, Johnson JC.; Department of Veterinary Medicine, College of Veterinary Medicine, University of Missouri, Columbia 65211, USA; J Am Anim Hosp Assoc. 2001 Jul-Aug;37(4):356-63.