Feline Leukemia Virus (FeLV)✪FeLV is distributed worldwide. The domestic cat is the predominant host, but the virus can also infect other felidae

Navies 2011

Etiology

FeLV retrovirus in family Oncoviae Subgroups

A. Subgroup A: All infected cats have this type, causes immune suppression

B. Subgroup B: 50% along with subgroup A• Neoplastic Disease (abnormal tisue growth)

C. Subgroup C: Isolated from 1% along with subgroup A

• Can sometimes have all three

History

•The Name "Feline Leukemia Virus" is a misnomer stuck. •FeLV is NOT leukemia, but leukemia was one of the first diseases associated with the virus, and thus, the name was applied. By the time it was discovered that this actually was a virus and not leukemia, the term had already stuck and was in popular use. • Discovered in1964 in a cluster of cats with lymph sarcoma

History

The feline leukemia virus (FeLV) was discovered in 1964 in a cluster of cats with lymphosarcoma. The observed clustering of cases of feline lymphosarcoma suggested that FeLV was an infectious agent for cats. The development of a simple immunofluorescent test for FeLV permitted a seroepidemiological study to be undertaken on the distribution of the virus in cats living in their natural environment. Over 2000 cats were tested, and the results showed conclusively that FeLV is an infectious agent for cats.

http://cancerres.aacrjournals.org/content/36/2_Part_2/582.full.pdf

Signalment

Young kittens Males are 1.7x more likely to be

infected 1-6 years of Age All breeds Studies indicate that it cannot be passed on to other species. Cats only.

Transmission

Incidence is directly related to the population Healthy cats can transmit this virus, they can be a carrier Large quantities are secreted through saliva Tears, urine , & feces (less likely but still possible) Vertically & Horizontally Enveloped Virus is unstable within the environment close contact must occur

for infection to take place Incubation Period: about 8 weeks Some strains of FeLV can be grown in human tissue cultures. This

has led to concerns of possible transmission to humans. Several studies have addressed this concern; none have shown any evidence that any zoonotic risk exists

CLINICAL SIGNS

Regressive form: transient infection Progressive infection (primary viremia):

persistent viremia and no clinical signs. Diagnosed by ELISA

Active form: Clinical signs and secondary viremia. Point of no most cats will be infected for the rest of their lives. Diagnosed by IFA/ ELISA

Clinical Signs

Fever Anorexia Weight loss Anemia “Secondary infections”: non healing

wounds Vomiting & diarrhea Spontaneous abortion Renal disease Tumors of lymphoid origin

LYMPHOMA Neurological signs

★ Anisocoria is occasional within FeLV patients

Pansystemic disease

Clinical Signs• Vary because so many body systems can be affected•Loss of appetite, fever, weight loss, and weakness are the most common.

•Enlarged lymph nodes, blood in stool, diarrhea, jaundice, non healing wounds.

•could appear normal and actually have the disease in its system

Diagnosis

IFA (Immuno Florescence Assay)Tests for the presence of structural antigens in the

cytoplasm of infected cells ELISA Tests for the presence of FeLV p27 Tests for antigens vs. virus itself Accuracy is higher when both tests are run

There are 6 stages of FeLV infection as follows: Stages 1-3 - FeLV is

disseminated through the lymphoid tissue.

Stage 4 – FeLV infects the bone marrow.

Stage 5 - Viral-infected neutrophils and platelets are

released from the bone marrow.

Stage 6 – FeLV appears in epithelial tissues (e.g., salivary

glandular epithelium).

Treatment

HusbandryIsolationKept indoorsVaccinatedElimination of stressMedicalNO CUREImmunomodulator drugs Acemannan Propionibacterium acnes Human recombinant interferon-α

★These drugs are toxic to bone marrow.

Cats should have hemograms reevaluated

frequently during treatment. Limit

treatment to 3-week intervals to avoid

marrow toxicity.

Antiviral DrugsBroad Spectrum AntibioticsAppetite StimulantsChemotherapyBlood transfusionsFluid therapyPain medicationTherapeutic diets

Prognosis

Depends on immune status, exposure to virus, & vaccination history

70% develop immunity & are able to fight of the virus before developing the symptoms

30% that’s don’t develop the immunity are persistently viremic

Stress, or drugs that suppress the immune system, can develop a viremic breakout

IFA positive =will succumb within 6 months of detection Average lifespan is less than 3 years

Pathologic Lesions

★The virus causes both immune cell depletion and dysfunction which result in several FeLV-inducedimmunopathologic diseases and numerous secondary immunosuppressive diseases which together arethe major cause of death of FeLV-infected cats

Persistently veremic cats may manifest single or multiple neoplastic diseases:Lymphoma (Most Common) Thymic lymphoma (usually in young cats <3 years old) Alimentary lymphoma Multicentric lymphoma Unclassified lymphomaLymphocytic LeukemiaErythroid and Myeloid LeukemiasFibro SarcomaMyelodysplastic SyndromeImmunosuppressionEnteropathyInfertility, Fetal Resorption or Abortion

Pathologic Lesions (Examples)

Prevention

o Kittens should be vaccinated at 9 to 10 weeks of age, again 3 to 4 weeks later, and then annually.

o Current commercial vaccines include a killed virus with adjuvant, killed virus without adjuvant, or a recombinant gp70 protein vaccine with an adjuvant.

o The recommended site for FeLV vaccination is on the left rear thigh or tail. o If you have an infected cat in a multi-cat household, keep them separate and be

persistent when it comes to cleaning!o Before vaccinating cats against FeLV, owners should consider the risks of FeLV

exposure versus the potential of vaccine-related complications.

Client Education

Even though a cat may be positive for FeLV the cat does not need to be euthanized

If cat is positive these precautions must be taken:

(Keep animal indoors, Isolate from all other cats, Keep up with vaccines and see a vet if any symptoms develop)

Management of FeLV + cats Confine FeLV-infected cats indoors to reduce their exposure to other

infectious agents carried by animals, and to prevent the spread of infection to other cats in the neighborhood.

Spay or neuter FeLV-infected cats. Feed nutritionally complete and balanced diets. Avoid uncooked food, such as raw meat and eggs, and unpasteurized dairy

products because the risk of food-borne bacterial and parasitic infections is much higher in immunosuppressed cats.

Schedule wellness visits with your veterinarian at least once every six months.

Veterinarian should pay special attention to the health of the gums, eyes, skin, and lymph nodes. A complete blood count, serum biochemical analysis, and a urine analysis should be performed at every examination.

Weight: your cat's weight should be accurately measured and recorded, as weight loss is often the first sign of deterioration.

Closely monitor the health and behavior of your FeLV-infected cat. Alert your veterinarian to any changes in your cat's health immediately.

To “Sum It Up”

Feline Leukemia Overview

References http://www.lbah.com/feline/felv.html http://cancerres.aacrjournals.org/content/36/

2_Part_2/582.full.pdf http://merckvetmanual.com Common Diseases of Companion Animals