Feline infectious Disease & Vaccines part 2

FIV & FELV overview

Caused by Retroviruses

• Slow to develop

• Clinical signs occur at varying times

• Found in cats that are seemingly healthy

retrovirus overview

Enveloped viruses

• Sensitive to heat & disinfectants

• Often create oncogenic infections

Feline Leukemia virus

More pathogenic

Major cause of death

Prevalence has decreased

FeLV transmission

Disease of social cats

shed in saliva

Grooming and licking

Transplacently

fomites

What cats are at a great risk for FeLV

Those exposed via prolonged

close contact

Cats living with infected cats or

with cats of unknown status

Cats allowed outdoors

unsupervised

Kittens born to infected mothers

FELV pathogenesis

Oronasal exposure

Replication in regional lymphoid

tissue

Spread to lymphoid tissues &

bone marrow*

Latent bone marrow infection

established

Further spread & shedding

FeLV possible outcomes for regressor cats

Regressor cats

Viral replication stopped by CMI response then

Virus eliminated from body

Cats have high levels of FeLV neutralizing

antibody

Never have (+) antigen test

Possible outcomes for transient viremia cats (virus in blood)

Transient viremia (3-6 weeks)

• Virus spreads within lymph tissue

• Cats are infectious to others

• Have (+) antigen test

• Many will clear viremia/terminate the virus

& develop antibodies

• Those that don’t —>persistently infected

Possible outcomes for persistent viremia FeLV

Persistent viremia

• Bone marrow infected

• Precursor cells produce infected

granulocytes and platelets

• High level viremia

• Have (+) antigen test

Possible outcomes for latent (dormant) bone marrow infection FeLV

Those that don’t eliminate the virus

• Have (-) antigen test

• Can be re-activated (+) test

• Latent cats don’t shed virus until re-

activated

FeLV clinical signs

The incubation period is months to years

Most persistently infected cats die

Related to non-neoplastic disease

FeLV early signs

Lethargy, fever, lymphadenopathy

or no signs at all

Later stages of chronic infection

FeLV diagnosis

ELISA test (IDEXX Snap Test) detects FeLV antigen

Positive cats should be retested in 4-6 months

IFA test used to confirm ELISA

FeLV vaccines do not interfere with results on

ELISA, IFA, or any other available FeLV tests!

FeLV treatment

symptomatic and supportive care

FeLV prevention

Decrease exposure

Keep infected and infection

free separated

Don’t allow sharing of

house items

Test all new cats prior to

entering the home

Vaccination

FeLV vaccination

Start at 8 weeks booster once in 3-4 weeks then 1 year booster

Not a core vaccine

Recommended that all kittens be vaccinated

FeLV immunodeficiency Virus

An acquired immunodeficiency syndrome

Comparable to HIV in humans

Increased risk for opportunistic infections, neurologic diseases, and tumors

Does not cause a severe clinical syndrome

With proper care, infected cats can live many years and die from unrelated causes

FIV transmission

shed through saliva

Saliva and blood most make contact

disease of fighting cats

Bite wounds necessary

Infection rates highest in free-roaming adult male cats

FIV pathogenesis

• Primarily replicates in T lymphocytes

• Infected cats are persistently viremic (peaks @ 8-12 weeks)

• Antibodies formed 2 weeks after infection

• Viremia declines as cat enters asymptomatic carrier phase

• Viremia causes progressive destruction of cell-mediated immunity

• Viremia peaks again as terminal phase begins

FIV clinical signs

• Acute phase

• Fever, lethargy, lymphadenopathy,

neutropenia

• Asymptomatic carrier phase

• Clinically normal

• Terminal phase

• Anemia, recurrent fever, weight loss

• Chronic infections

FIV diagnosis

ELISA test - detects circulating antibodies

• May not produce antibodies for 2 weeks - several months

• Terminally ill may not have detectable antibodies

• Kittens of infected moms may test positive up to 5 months because of colostral antibodies

FIV treatment

If no clinical signs are present

• No treatment is indicated

• Cat should be kept strictly indoors and

should not be vaccinated (may consider

vaccinating with only KILLED vaccines)

• If clinical signs are present

• Always look for underlying disease

• FIV alone is typically not responsible for

clinical signs

• Treat underlying disease as indicated

FIV control

Vaccination not available but is also NOT recommended

What to do with positive FIV animals

Keep indoors to reduce exposure/ spread

spayed/ neutered

Feed a nutrion/ balanced diet

wellness visits every 6 months

IDEXX FeLV & FIV Testing

FeLV- detects the presence of circulating

ANTIGEN

• FIV- detects presence of ANTIBODY

• False Negative FIV test results

• Binding of Ab to Ag in terminal

phase

• Can take 2 weeks to several

months to develop Ab

• Evaluate all test results in conjunction

with clinical signs

What do we do with a positive test FELV

FeLV Positive Test

• If suspicious disease present- likely

true

• If kitten- retest in 1-2 months

• If healthy adult- can wait/retest or

perform additional test

what do we do with a FIV positive test

• If suspicious disease present, likely

true

• If kitten <12 weeks, likely has

maternal antibodies

• If healthy adult- may be true positive

or vaccinated

Feline infectious peritonitis

Caused by certain strains of feline coronavirus

• Large, enveloped RNA viruses

• Susceptible to disinfectants and heat

• Most strains of feline coronavirus are avirulent

• Cats that are infected generally do not show any

symptoms during the initial viral infection

• Small percent of infected cats (5 to 10 %), either by a

mutation of the virus or by an aberration of the immune

response, the infection progresses into clinical FIP

FIP transmission

Shed in feces and oronasal secretions

Litterboxes most common source of infection

FIP pathogenesis

Not all cats infected with FIP virus develop

disease

Roughly 1/9 cats infected with FCoV (corona virus) develop FIP

• Effective cell mediated immunity (CMI)

important to restrict viral replication and

elimination of virus

• Defective CMI leads to formation of non-

protective antibodies

• When these antibodies contact FIP virus,

immune complexes form leading to immune-

mediated vasculitis

FIP clinical signs

Incubation weeks to months

Onset of clinical signs varies from slow to acute

Early signs nonspecific

FIP Clinical signs 2 forms

Effusive (wet) form-more common

Non-effusive (dry) form

FIP diagnosis

Biopsy results are needed for definitive diagnosis, so FIP is seldom confirmed until necropsy

Lab findings

History & clinical signs

FIP treatment

Symptomatic treatment FIP

• Antibiotics

• Corticosteroids

• Fluid therapy

• Abdominocentesis

• Nutritional support

FIP control

ID and removal

Breeding bloodlines free of FIP

Proper cattery management

Vaccine isn’t reliable or recommended