Feline leukaemia virus (FeLV)

Question 1

What is FeLV?

Answer 1

Feline Leukaemia Virus

Question 2

What type of retrovirus is FeLV?

Answer 2

Oncornavirus

Question 3

There are 3 subtypes of FeLV. What are they and which type is transmissible?

Answer 3

A, B, C
Only type A transmissible
(B and C need type A for replication)

Question 4

FeLV is the most common infectious cause of death in what age cats?

Answer 4

Young

Question 5

What syndromes does FeLV cause?

Answer 5

Neoplasia
Immunodeficiency
Anaemia
Reproductive failure

Question 6

How is FeLV transmitted?

Answer 6

Close contact via saliva, faeces, urine, milk

Placental transmission

Question 7

What is the pathogenesis of FeLV?

Answer 7

Ingested and replicate in oropharynx and primary lymph nodes
Causes primary viraemia
Replicate in secondary lymphoid tissue to form secondary viraemia

Question 8

Infection of FeLV can lead to what two outcomes? (Depending on immune status, dose of virus and age)

Answer 8

Persistent latent infection and possibly elimination (strong immune response)
Persistent viraemia, clinical disease and death

Question 9

What does pathogenesis depend on? (will it cause persistent latent infection or clinical disease and death)

Answer 9

Dose of virus
Age
Immune status

Question 10

How does FeLV cause oncogenesis?

Answer 10

Insertion of FeLV A activates proto-oncogene

Disrupts tumour suppressor gene

Question 11

FeLV causes 4 main types of lymphoma (neoplasia). What are these 4 types?

Answer 11

Mediastinal lymphoma
Multicentric lymphoma
Alimentary lymphoma
Lymphoid leukaemia

Question 12

Mediastinal lymphoma causes cancer where? In what age cats is it usually found?

Answer 12

Thymus (mainly) blood and LNs

<3 y/o (majority have FeLV)

Question 13

What are the symptoms of mediastinal lymphoma?

Answer 13

Muffled heart sounds
Regurgitation 
Weight loss
Tachypnoea/dyspnoea
Pleural fluid containing neoplasticism lymphocytes
Resistance in thorax palpation

Question 14

Multicentric lymphoma can affect any tissue. What does it cause?

Answer 14

Lymphadenopathy
Can cause paralysis and renal failure depending on location
Mild anaemia

Question 15

How is mediastinal lymphoma Dx?

Answer 15

Ultra sound
Radiography
Biopsy
Cytology

Question 16

How is multi centric lymphoma diagnosed?

Answer 16

Clinical signs

Biopsy

Question 17

Alimentary lymphoma causes what? What clinical signs does this lead to?

Answer 17

Abdominal masses, often with local LNs and kidneys

Anorexia, weight loss, D+, V+, anaemia

Question 18

Lymphoid leukaemia is based where? What does it affect?

Answer 18

Bone marrow

Haematopoiesis

Question 19

What are the symptoms of lymphoid leukaemia?

Answer 19

Raised WBC count (leukocytosis)
Anaemia
Thrombocytopenia
Pyrexia
Weakness 
Anorexia

Question 20

How is lymphoid leukaemia diagnosed?

Answer 20

Haematology

Bone marrow biopsy

Question 21

FeLV can also cause myeloid leukaemia but this is rare. What symptoms does this cause?

Answer 21

Lesions in bone marrow
Secondary lesions in liver, spleen, LNs
Anaemia 
weight loss
Thrombocytopenia
Petechia 
Haemorrhage

Question 22

FeLV is a common cause of reproductive failure. What does it cause?

Answer 22

Foetus reabsorption at 3-5 wks
Vulval discharge
All kittens infected

Question 23

How can FeLV be controlled?

Answer 23

Rehome or PTS infected cats
Vaccinate
Feed cat from own bowl
Test and remove (house all +ves separately, retest regularly)

Question 24

The efficacy of FeLV vaccine is difficult to estimate. What type of vaccine is it? At what age is it given

Answer 24

Killed or recombinant

8 weeks, then 4 weeks later and every 2-3 years

Question 25

What ages does FeLV typically affect? Why?

Answer 25

4-16 weeks MDA protection until 4 weeks Not likely to be affected after 16 weeks Vaccine not effective until 13 weeks

Question 26

What is the Tx for FeLV?

Answer 26

mainly supportive Interferon may lengthen survival Cytotoxic drugs for lymphomas

Question 27

FeLV can lead to 3 other FeLV issues. What are these

Answer 27

FeLV related anaemia FeLV-FAIDS Feline sarcoma virus

Question 28

FeLV related anaemia is the most common cause of anaemia in cats. What are the 2 types of anaemia?

Answer 28

Primary - total RBC/marrow aplasia (non-regenerative) | Secondary - regenerative. Associated with FeLV C - mutation causes decrease haematopoiesis

Question 29

What are the symptoms of FeLV-FAIDS?

Answer 29

Immunosuppression: secondary infections, pour healing abscesses, thin, pyrexia, chronic infections

Question 30

How can FeLV cause feline sarcoma virus? (RARE) | What proportion of these cats are FeLV positive?

Answer 30

FeLV recombines with host cell genome | All FeLV positive

Question 31

What does feline sarcoma virus cause?

Answer 31

Ulcerative lesions Recur May be metastatic

Question 32

How is FeLV diagnosed?

Answer 32

FeLV antigen

Question 33

Why are Ags used to Dx FeLV rather than Abs?

Answer 33

Ab levels fluctuate | Most infected cats are recovered or have a dormant infection

Question 34

In low prevalence populations, what must be done for all positive tests and why?

Answer 34

Repeat by an independent test | Low positive predictive value (PPV)