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Flashcards in Feline leukaemia virus Deck (28)
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Viruses cats vs dogs

MORE complex in cats than dogs


What are the most common retroviruses you will come across?

1. Feline leukaemia virus (FeLV)
2. Feline immunodeficiency virus (FIV)
--------- most common above
3. Feline syncytium-forming virus (FeSFV) (less common) but not associated with clinical disease
4. endogenous viruses


What is virus classification based on?

1. genome (RNA or DNA)
2. Number and sense of RNA/ DNA strands
3. Morphology
4. Genome sequence similarity
5. Ecology
6. Enveloped (less stable in environment)
7. RNA virus - mutates a lot



1. enveloped = not v stable, important for transmission - not transmitted well in environment
2. RNA virus, mutates a lot
3. characteristic genome structure, 3 same main proteins
4. DIPLOID CELL *unique* so had 2 copies of RNA
Once injected, use reverse transcriptase to make DNA of their RNA genome
5. Then move viral DNA into host cell's nucleus, integrate the DNA copy of their genome into host cell genome = PRO virus
6. every time cell undergoes transcription, makes copy of viral DNA
7. Basically with retrovirus go from RNA - DNA - *****Pro virus***** - RNA - translation occurs


What is a pro virus

virus genome that is integrated into the DNA of a host cell


Feline leukarmia virus, diff types

Three subtypes A, B and C
o distinguished by genome analysis and serology
BUT Only type A is transmissible so in general only type A we are likely to deal with
Also can't get type B or C without A as need for replication.
Will only ask about A in exam


Clinical signs of FeLV (Feline leukaemia Virus)

1. Most common infectious cause of death in young cats
2. RAIN - list of importance
Repro failure


What are the routes of infection of FeLV

1. excreted in saliva (predominantly) urine, faeces and milk
2. CLOSE contact. FRIENDLY- nursing, multicat household
3. Vertical transplacental transmission = infected queen FeLV pos kittens


Difference in route of infection FeLV vs FIV

1. FeLV = friendly, FIV = fights
2. FeLV vertical transmission possible, not in FIV


Pathogenesis of FeLV "normal"

1. cats become infected by "friendly" contact
2. Virus replicates locally in oropharynx
3. Primary viraemia
4. In blood
5. replicates in other lymphoid tissues, bone marrow etc
6. secondary viraemia
7. Ineffective immune response
8. Persistently viraemic
9. Clinical disease


What is primary viraemia, what would diff tests show?

1. relatively shortly after infection, before becomes either persistently viraemic or effective immune response
2. tests ran would show positive for pro virus, protein in blood and VIRUS positive (PCR picking up RNA of viral genome)
BUT antibody negative as shortly after infection


Is a cat is persistently viraemic, how would this show up on tests?

1. Provirus positive (hihg)
2. Antigen positive
3. Antibody positive
4. virus positive


What is the difference between primary viraemia and

In secondary Ab POSITIVE but in primary Ab negative


BUT how can some cats live with FeLV?

1. At either the primary or secondary viraemia stage they can develop a strong immune response.


Talk through infection with FeLV and strong immune response

1. cats become infected by "friendly" contact
2. Virus replicates locally in oropharynx
3. At either primary or secondary viraemia can develop STRONG IMMUNE RESPONSE
4. means suppress virus and appear clinically normal
5. think some cats may eliminate this entirely, not sure though


If a cat is has a strong immune response, how would this show up on tests? + why?

o provirus positive but LOW level.
o Antigen NEGATIVE – not sufficient enough virus in blood to make sufficient protein that you detect by measuring antigen
o VIRUS negative – no virus in blood as suppressed to low levels but will have antibody


What do we think affects whether a cat becomes persistently infected or overcomes?

1. Dose of virus - hihg more likely persistent
2. Age - susceptibility to persistent infection decreases with age.
o only 1 in 5 cats >16 weeks old becomes persistently infected – rest die
o Over 16 weeks age 4/5 cats go to persistent latent infection

3. Immune status
Maternally derived antibodies for first 4 weeks


What secondary disease can FeLV cause? adn why?

Due to pro virus


How does FeLV cause tumours?

1. FeLV provirus is sporadically inserted into host cell's DNA
2. If this is close to the cellular oncogene gene (most common) or tumour suppressor then can cause tumours
3. e.g. promote replication of the cellular genome = inc division of cell with pro virus in
4. e.g. disrupt tumour suppressor gene


The most important clinical disease of FeLV and what it is

An abnormal mass of tissue that forms when cells grow and divide more than they should or do not die when they should. Neoplasms may be benign (not cancer) or malignant (cancer)


What are the 4 main types of lymphoma associated with FeLV?
and also where can you get them?
How does this affect diagnosis?

o mediastinal (thymic)
o multicentric
o alimentary
o leukaemic
Can also get tumours in lots of other areas e.g. kidney, nose, eye, skin, CNS.
Affects diagnosis as means can have a cat presenting with almost any conditon. e.g. renal failure - tumour in kidney etc
blind, nose bleed due to tumours etc


Talk about FeLV and anaemia

1. FeLV probs the most common cause of anaemia in cats
2. FeLV causes Primary and secondary anaemia


Primary anaemia

 RBC production switched off
 red cell aplasia (normal WBC, RBC <10%)
 total marrow aplasia (rare; low RBC and WBC)
 non-regenerative; normocytic, normochromic,
• juvenile RBC – bigger and diff colour. RBC production switched off, RBC in peripheral circulation look NORMOCHROMIC (normal colour) and NORMOCYTIC (normal size)


Secondary anaemia

 Regenerative – juvenile RBC = bigger and diff colour RBC
 due to space-occupying myeloid tumours in bone marrow
• not as much functional RBC production
 haemolytic anaemia common in FeLV-infected cats - mild and often missed


Animal presents witha range of infections that are either worse than they should be or don't get better after treatment, what are you thinking

FELV and FIV on differential diagnosis list due to immunosuppression of both diseases


How to control FeLV?

1. test adn remove: rehome or euthanise
2. Vaccination 8-9 weeks and 3 weeks later!!! still can't for HIV and FIV:(
3. one food bowl per cat


How to test for FeLV

1. test twice to differentiate between negative, primary, secondary or persistent
2. Test all cats in colony
3. Retest all cats 12 weeks later
4. retest all cats every 6-12 months and ALL cats entering colony


FeLV treatment:

1. LArgely supporting
2. No specific antivirals
o Often effective in cell culture but toxic in the cat
3. Interferon may prolong survival
4. Might treat some lymphomas (e.g. thymic) with cytotoxic drugs - but if FeLV +ve, other problems will develop