Feline Retroviral Diseases Flashcards
What are the 2 major Retroviruses that affect cats?
- feline leukemia virus (gamma)
- feline immunodeficiency virus
What are the FeLV proteins that are found on its core and envelope?
CORE = p27 - produced by infected cells and detected by FeLV antigen tests
ENVELOPE = gp70 - responsible for attachment to infect cells, neutralizing Ab produced against it
What signalment is most commonly affected by FeLV? What are the 2 modes of transmission?
young, outdoor kittens in large populations
- high amounts in plasma - close contact, bite, mutual grooming
- vertical - in utero, nursing
(short survival in the environment)
What are the 5 steps to the pathogenesis of FeLV?
- oronasal exposure
- viral replication in local lymphoid tissue
- lymphocytes infected, circulate, and cause low-level viremia
- systemic infection of lymphoid tissue = LNs, spleen
- bone marrow infection = persistent high-level viremia affecting granulocytes and platelets
What are the 3 possible outcomes of FeLV infection?
- progressive infection = permanent, systemic infection and viremia, high risk of clinical disease, FeLV test positive
- abortive infection (regressor) = virus never spreads beyond local lymphoid tissue, no viremia
- regressive infection (transient, latent) = no persistent viremia, viral DNA incorporated into genome of infected cells
FeLV:
What is prognosis of FeLV like?
- 80% die within 3 years, will most likely develop disease
- survival time can possibly be extended with supportive care
What is the most common disease related to FeLV? What does it make these cates predisposed to?
potent immunosuppression
- recurrent infections
- FIP, FIV
- hemotropic mycoplasma
- chronic stomatitis and rhinitis
What is the most common hematologic disorder seen with FeLV? What is this a result of?
nonregenerative anemia - red cell aplasia due to a lack of early erythroid precursors = MACROCYTOSIS
infection of bone marrow elements
What 6 other hematologic disorders can be seen with FerLV?
- aplastic anemia - pancytopenia due to a lack of production of all cell lines
- hemolytic anemia
- anemia of chronic disease
- myelophthisis - normal marrow space is infiltrated and replaced by nonhematopoietic or abnormal cells
- thrombocytopenia
- neutropenia
What 2 things is hemolytic anemia due to FeLV associated with?
- immune-mediated
- Mycoplasma haemofelis infection due to immunosuppression
How can patients with FeLV develop neoplasia? What neoplasias are associated?
recombination of FeLV-A with a cellular oncogene forms and recombinant virus
- FeLV-B or feline sarcoma virus
- lymphoma
- fibrosarcoma
- leukemia
What are the 2 most common neoplasias associated with FeLV? Why does it make diagnosis difficult?
lymphoma and leukemia
cats with lymphoma will likely test negative on FeLV antigen tests
- high prevalence of viremia in mediastinal lymphoma
- low prevalence of viremia in alimentary lymphoma
What immune-mediated, reproductive, and neurologic diseases are associated with FeLV infection?
IMMUNE - glomerulonephritis, polyarthritis, uveitis
REPRO - infertility, fetal absorption
NEURO - spastic pupil syndrome, urinary incontinence, paresis
What 4 miscellaneous syndromes are associated with FeLV infection?
- enteritis
- hepatopathy
- Fading Kitten Syndrome - newborn kittens fail to thrive and are likely to expire prematurely, usually prior to weaning
- osteochondromatosis
How is FeLV diagnosed? How does it compare to other methods?
SNAP ELISA detects p27 soluble antigen not seen in cells
very sensitive and specific —> more sensitive than IFA
When can FeLV-positive patients begin to test positive on SNAP tests? How is it confirmed?
within 4 weeks of infection
repeat test or perform an IFA
What are 3 possible causes of a positive FeLV ELISA?
- viremia present
- progressive or regressive infection
- (rare) false positive
What are 4 possible causes of a negative FeLV ELISA?
- no exposure
- recently exposed, but not viremic
- abortive or regressive infection
- false negative
How does an FeLV IFA test work? When is it positive?
detects p27 antigen in cells (WBCs, platelets) on a blood smear or bone marrow biopsy/aspirate
progressive infection
- early transient viremia does NOT result in a positive IFA, since the virus is not in the cells
- false positive likely
What are the 2 possibilities of negative FeLV IFA tests?
- not exposed
- transient viremia or cytopenias = false negative
What can a positive ELISA and negative IFA in a possible FeLV patient mean?
- transient viremia
- low level cell-associated viremia (cytopenia)
- false positive ELISA (rare)
What can a negative ELISA and positive IFA in a possible FeLV patient mean?
most likely a false positive IFA
What 6 types of cats should be tested for FeLV?
- newly acquired - at adoption AND 28 days later
- known exposure to infected cells
- ill cats
- cats with high risk lifestyles
- prior to FeLV vaccination
- blood donors
What is considered a high-risk lifestyle for becoming infected with FeLV?
- outdoor cats
- those housed with infected cats
How is FeLV treated?
SUPPORTIVE, treat associated diseases
- anemia: transfusion, EPO
- neutropenia: antibiotics, G-CSF
- myelodysplasia: G-CSF, cytosar
- gingivitis: dental cleaning, extractions, antimicrobials
- infections: antimicrobials
- neoplasia: chemotherapy
- immune-mediated: glucocorticoids
How is FeLV infection prevented?
- keep cats indoors
- test prior to introduction of new cats
- vaccination
What is the FeLV vaccine like? What should be done before it is given?
- not a core vaccine - recommended for catteries, outdoor cats, FeLV+ household, and kittens regardless of lifestyle
- efficacy not as high as others, preventable fraction 85-90%
ELISA test —> no need to vaccinate infected cats
How does a prior FeLV vaccination affect SNAP ELISA tests?
- DOES NOT cause a positive FeLV test
- DOES cause a positive FIV test
What vaccines are associated with sarcomas? How do they develop? How has this changed how vaccines are given to cats?
rabies and FeLV —> risks outweigh rabies and FeLV infection!!
chronic granuloma formation is response to vaccine or adjuvant
commonly administered SQ in distal hind limbs, keep cat to monitor vaccination site —> consider excision if a nodule persists for >3 months
How do vaccine-associated sarcomas act?
invasive and high metastatic potential —> excise with large margins and perform radiation
What are the 5 steps to the pathogenesis of FIV?
- infection of local lymphatic tissue
- viremia with dissemination to other tissue
- depletion of CD4+ cells
- decreased function of all lymphocytes
- immunosuppression
What are the 2 major risk factors associated with FIV? What are the modes of transmission?
- males
- outdoor cats
bite wounds and vertical through placenta or nursing
What are the 3 most common clinical findings seen with FIV?
- transient and mild signs in the initial stage
- chronic = immunosuppression —> recurrent infections, stomatitis
- no signs
What is most commonly seen on CBC and chemistry in patients with FIV?
CBC = neutropenia, lymphopenia, anemia
CHEM = hyperglobulinemia
What are the 2 ways of diagnosing PIV?
- FIV antibodies seen with ELISA or Western blot
- PCR - false negatives and positives possible
What are the 4 possibilities of a positive FIV antibody test?
- infected
- vaccination
- false positive
- maternal antibodies if less than 6 m/o
What are the 2 possibilities of a negative FIV antibody test
- not infected
- infected, but not seroconverted - takes 8 weeks to 6 months
What treatment is available for FIV? What does it do? What side effect is commonly seen?
Azidothymidine (AZT) - nucleoside antiviral
cat remains infected, but it improves clinical condition, QoL, immune status, and survival
anemia in the first month
How does the prognosis of FIV compare to FeLV?
cats with FIV did not have a significant difference in survival compared to cats without FIV
FIV does NOT affect longevity, unlike FeLV
