Flashcards in Feline Infectious Diease Deck (81)
What group of viruses does FeLV belong to?
Retroviridae Oncovirinae Gammaretrovirus
What are the characteristics of FeLV?
Replicates in many tissues and is non-cytopathic
Labile, enveloped ssRNA virus that uses reverse transcriptase and integrates into host DNA
What are the three fates of a cell infected with FeLV?
Immune system destroys infected cell
Infection of cell with or without virus production
Transformation into a neoplastic cell
What is the structure of FeLV?
RNA and reverse transcriptase inside a p27 icosahedral capsid surrounded by matrix and an envelope with p15E and gp70 envelope proteins
What is p27?
Gag protein which is the basis for most diagnostic tests and is produced in infected cells and can circulate free in plasma or excreted in tears or saliva
What is p15E?
Spike protein that leads to immunosuppression
What is gp70?
Knob and defines viral subgroup (A,B,C) and is important for inducing antiviral neutralising antibodies as they are subgroup specific
Target for vaccine production
What is FeLV subgroup A characteristics?
Present in almost all infected cats and is only transmitted cat to cat
Provides basis for production of other subgroups and is the least pathogenic
What are the characteristics of FeLV subgroup B?
Recombination of A with endogenous FeLV proviral sequences and is oncogenic
What are the characteristics of FeLV subgroup C?
Arises from the mutation of A and causes non-regenerative anaemia
What is the prevalence of FeLV in UK cat population?
1-2% in healthy cats
20% in symptomatic cats
How is FeLV transmitted?
Source of infection is persistently infected cats with virus shed in saliva, nasal secretions, faeces, urine and milk
Short survival time in the environment lasting only hours
Transmitted by intimate prolonged contact e.g. sharing food/water
What are the risk factors for FeLV infection?
Greater risk in males than females
Young cats between 1-6
Multicat households especially outdoor cats
Susceptibility highest in young kittens under 4-5 months of age
What are the four possible results of infection with FeLV?
What happens to persistently viraemic cats infected with FeLV?
Majority of cats developing FeLV associated disease within 3-5 years of infection
Don't develop virus neutralising antibody
Show signs of neoplastic or non-neoplastic disease
What happens to cats with FeLV transient viraemia?
Virus is completely eliminated usually after about 3 months with high titres of neutralising antibody measures
What happens to cats with latent FeLV infection?
Virus persists but doesn't replicate so is undetected and difficult to diagnose requiring bone marrow/PCR and occurs in 30% of infected cats resulting in remaining latent, becoming persistent or eliminating after 30 months
What happens to cats with a localised FeLV infection?
Uncommon with the virus sequestered in certain tissues such as mammary gland, bladder or eyes and may give discordant test results
What are the clinical signs of FeLV infection?
Many cats are asymptomatic with those showing signs varied and non-specific depending on organ system and secondary disease but include inappetance, weight loss, wasting, persistent diarrhoea, poor coat condition, lymphadenopathy, persistent fever, pale MM, ocular disease, gingivitis, stomatitis, skin/bladder/URT infection, seizures, behavioural changes, other neurological disorders, abortion
Why do secondary infections occur with FeLV?
Immunosuppression and depletion or interference with function of lymphocytes and/or neutrophils
Which haematological disorders can be found with FeLV?
Bone marrow suppression due to viral infection of haematopoietic stem cells and stromal cells resulting in non-regenerative anaemia, aplastic anaemia, regenerative anaemia, thrombocytopaenia or granulocytopaenia
Myelodysplasia leading to myelodysplasitc syndrome
Leukaemia of any/all cell lines
How many more times likely is lymphoma in FeLV positive cats?
60 times and is expected to develop in 25% of FeLV positive cats within two years
What kind of lymphoma affects cats with FeLV?
Mediastinal (thymic) and multicentral
What is Feline Oncoronavirus Cell Membrane Antigen (FOCMA)? What can it be used for?
Present on membrane of malignant cells but absent on all other body cells so anti-FOCMA antibodies can be used to complement lyse tumour cells leading to immune surveillance against tumour development
Why does immune-mediated disease occur with FeLV?
Overactive or dysregulated response to virus and includes IMHA, glomerulonephritis, uveitis and polyarthritis
What reproductive diseases can FeLV cause?
Infertility causes foetal death and resorption in middle trimester
Abortion is less common
Transmission of virus transplacentally and via colostrum in both viraemic and latently infected queens can result in Fading Kitten Syndrome
What skeletal abnormalities can occur with FeLV?
Osteochondromatosis = benign proliferative disease of bone resulting in multiple cartilaginous extoses of flat bones
Chronic progressive polyarthritis
What neurological diseases are associated with FeLV infection?
Neuropathies are infrequent and need to be distinguished from CNS lymphoma
Clinical signs of aniscoria, urinary incontinence, vague pain or spinal hyperaesthesia, posterior paresis
Acute demyelinating myelopathies are also seen
How are cats diagnosed with FeLV?
Immunoassay such as ELISA for p27
IFA to detect p27 in leukocytes and platelets (confirmatory)
PCR to detect viral nucleic acid (confirmatory)
Viral culture (gold standard)
Antibody test doesn't diagnose but indicates exposure