"FRIENDLY CAT DISEASE"

FELINE LEUKEMIA

Mae Marcattilio-McCracken

What is Feline Leukemia Virus?

Feline leukemia virus (FeLV) is a retrovirus that infects cats. This means the genetic information is carried by RNA instead of DNA

FeLV is a virus, NOT a cancer!(however, this is the main cause of cancer in cats and secondary infections due to weakened immune system)

Causes immunosuppression in domestic cats, some evidence indicates the existence of this virus in larger wild cat populations Cheetah, Lynx, Lion

Species Affected & Risk Factors

FeLV is species-specific, and doesn’t infect any other animals but felines

Sick cats are 4x more likely than healthy cats to be infected Males are 1.7x more likely to be infected than females, and

younger cats are more susceptible to infection than older cats

FeLV is most commonly found in cats from 1-6yrs, avg. 3 years old

Outdoor cats and multi-cat households are more predisposed to the virus

Organism Causing Disease- Viral structure: an RNA retrovirus comprised of 5’

and 3’ and 3 genes: Gag (structural), Pol (enzymes), and Env (envelope and transmembrane); total genome approx. 9,600 base pairs!!!

Classification Group: Group VI (ssRNA-RT) Family: Retroviridae Genus: Gammaretrovirus Species: Feline leukemia virus

Two Stages of FeLV Primary viremia (early stage): Cats are unable to

mount an effective immune response, eliminate the virus from the bloodstream, and halt progression to the secondary viremia stage

Secondary viremia (later stage): Characterized by persistent infection of the bone marrow and other tissue.

POINT OF NO RETURN cat will be infected with FeLV for remainder of life once this stage is reached

Parts of the Body Affected Immune system Lymphoid system Hemolymphatic system Bone Marrow Mucosal and glandular epithelial cells Salivary glands, oropharynx, stomach, esophagus,

intestines, trachea, nasopharynx, renal tubules, bladder, pancreas, alveolar ducts, and sebaceous ducts from the muzzle

Clinical Signs Loss of appetite Slow but progressive weight loss, followed by severe wasting late in

the disease process Poor coat condition Enlarged lymph nodes Persistent fever Pale gums and other mucus membranes Inflammation of gums and mouth Infections of the skin, urinary bladder, and upper respiratory tract Persistent diarrhea Seizers, behavior changes, and other neurological disorders A variety of eye conditions In unspayed female cats, abortion of kittens or other reproductive

failures

How FeLV is Diagnosed… ELISA: this and similar tests can be

performed in the clinic. ELISA-type tests detect both primary and secondary stages of viremia.

IFA: (blood or bone marrow smears) tests must be sent out- IFA tests detect only the secondary viremia, this is why the majority of positive-testing cats remain infected for life

--IFA test may be performed to confirm diagnosis

Progression Once the virus enters the cat, there are six phases to

a FeLV infection: P1- virus enters the cat, usually through the pharynx where it infects the

epithelial cells and infects tonsillar B-lymphocytes and macrophages. These WBC then filter down the lymph nodes and begin to replicate.

P2-virus enters the blood stream and begins to distribute throughout the body.

P3- starts then the lymphoid system becomes infects, with further distribution throughout the body.

P4- MAIN PT in the infection-virus takes over immune system and causes viremia. During P4 the hemeolymphatic system and intestines become infected.

IF THE CAT’S IMMUNE SYSTEM DOES NOT FIGHT OFF THE VIRUS, THEN IT PROGRESSES INTO P5 (HENCE, IT IS POSSIBLE FOR CATS TO CLEAR THE INFECTION AFTER INITIAL EXPOSURE)

Progression P5-bone marrow becomes infected. At this pt, virus will stay with cat

for remainder of its life. Virus replicates and is released 4-7 days later in infected neutrophils and sometimes lymphocytes, monocytes, and eosiniphils

P6- cat’s body is overwhelmed by infection and mucosal and glandular epithelial cells become infected. Virus then replicates in epithelial tissues including salivary glands, oropharynx, stomach, esophagus, intestines, trachea, nasopharynx, renaltubules, bladder, pancreas, alveolar ducts, and sebaceous ducts from the muzzle.

○ - Four subgroups of FeLV exist: A; B;C; and T, but only subgroup A is transmissible between cats.

How FeLV is Transmitted… Saliva and close contact, biting another cat (blood), through

a litter box or food dish used by an infected cat, in utero, or an infected cat nursing her kittens

*FeLV won’t survive outside a cat longer than a few hrs in most environments. As a precaution thoroughly disinfect or replace food and water dishes, bedding, litter pans, and toys.

**This disease IS NOT zoonotic, regardless immunosupressed people (ppl receiving chemo, ppl with AIDS, elderyly,infants, unborn children, and pregnant women) should avoid contact with an FeLV infected cat**

How FeLV is Treated… Fluid therapy/blood transfusions Use of antivirals Steroids for cancer Interferon Alpha: chemical that makes the WBC’s

produce toxins to kill the virus ImmunoRegulin Acemannan Staph Protein A Lymphocyte T-cell Immune Modulator Chemo to treat tumors Dietary supplements Antibiotics to treat secondary infection

The Vaccine: Purevax Merial produces a recombinate vaccine consistinfg of

carypox carrying FeLV gag and env genes Vaccine is a MLV- originates from a bird host that does not

replicate in mammals

~ALWAYS given SQ left rear, as distal as possible Given once then boostered 3-4 wks later Annual vaccine Recommended only for “at risk” felines: young, outdoor cats,

exposure to FeLV infected cats Thought to be safer than old vaccine because no adjutants

are needed for it to be effective (sarcomas more likely to develop with old vaccine)

~Not a core vaccine~

Side Effects!

Include:

Tumors at the injection site Fever Weight loss

Prognosis =( FeLV is an incurable, fatal disease Varies considerably, 70% of cats are infected with

FeLV develop immunity and are able to fight the virus before developing symptoms

Some cats that develop initial immunity suffer a viremic breakout or years later, usually after being stresses or medicated with drugs that suppress the immune system

30% of infected cats that don’t develop immunity to the virus may live months to years, depending on how far the disease has progressed when the cat is diagnosed

More than 50% of these cats die within a couple yrs

Sources

en.wikipedia.org/wiki/Feline_leukemia_

virus

www.animalhealthchannel.com

www.vet.cornell.edu