Download Feline Leukemia Virus - Dr. Brahmbhatt`s Class Handouts

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
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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
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Fever
Anorexia
Weight loss
Anemia
“Secondary infections”: non healing
wounds
Vomiting & diarrhea
Spontaneous abortion
Renal disease
Pansystemic
Tumors of lymphoid origin
disease
LYMPHOMA
Neurological signs
★
Anisocoria
is
occasional
within FeLV
patients
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
Husbandry
Isolation
Kept indoors
Vaccinated
Elimination of stress
Medical
NO CURE
Immunomodulator drugs
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Acemannan
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Propionibacterium acnes
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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 Drugs
Broad Spectrum Antibiotics
Appetite Stimulants
Chemotherapy
Blood transfusions
Fluid therapy
Pain medication
Therapeutic diets
Prognosis
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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-induced
immunopathologic diseases and numerous secondary immunosuppressive diseases which together are
the 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)
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Alimentary lymphoma
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Multicentric lymphoma
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Unclassified lymphoma
Lymphocytic Leukemia
Erythroid and Myeloid Leukemias
Fibro Sarcoma
Myelodysplastic Syndrome
Immunosuppression
Enteropathy
Infertility, Fetal Resorption or Abortion
Pathologic Lesions (Examples)
Prevention
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Kittens should be vaccinated at 9 to 10 weeks of age, again 3 to 4 weeks later, and
then annually.
Current commercial vaccines include a killed virus with adjuvant, killed virus
without adjuvant, or a recombinant gp70 protein vaccine with an adjuvant.
The recommended site for FeLV vaccination is on the left rear thigh or tail.
If you have an infected cat in a multi-cat household, keep them separate and be
persistent when it comes to cleaning!
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
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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