Feline Leukaemia Virus (FeLV) 🐱
Feline leukaemia virus (FeLV) is a retrovirus belonging to
the Gammaretrovirus genus. It affects both domestic and wild feline species,
including domestic cats, bobcats, lynxes, and panthers. The virus contains an
enveloped ribonucleic acid (RNA) strand that integrates into the host cell's
genome, forming a provirus. FeLV has three associated genes, namely gag, pol,
and env, which play crucial roles in the virus's oncogenic capacity.
- Definition and Overview of Feline
Leukaemia Virus (FeLV)
- Importance and Distribution of
FeLV
2. Understanding FeLV Epidemiology
- Global Distribution and Prevalence
- Transmission and Risk Factors
3.
Pathogenesis of FeLV Infection
- Initial Contact and Replication
- Immunocompetent vs.
Immunocompromised Cats
4.
Clinical Signs and Manifestations
- Immunodepression and Its Impact
- Cancer and Tumours Linked to FeLV
Infection
5.
Diagnosis of FeLV Infection
- Immunofluorescent Antibody
Test (IFA)
- PCR Techniques for Detection
6. Management and Treatment of FeLV Infection
- Confined Living and Preventive
Measures
- Regular Health Assessments and
Care
- Potential Use of Immunomodulators and
Antiviral Drugs
7. Prevention and Vaccination against FeLV
- Vaccination Schedule and
Recommendations
Introduction
Definition
and Overview of Feline Leukaemia Virus (FeLV)
Feline Leukaemia Virus (FeLV) is
a retrovirus that poses a significant threat to domestic cats and various wild
feline species, including bobcats, lynxes, and panthers. Belonging to the
Gammaretrovirus genus, FeLV contains an enveloped ribonucleic acid (RNA)
strand, and upon contact with a host cell, it integrates into its genome, forming
a provirus. This integration process allows the virus to cause a range of
severe health consequences for infected cats. FeLV infection leads to
immunosuppression, making cats vulnerable to various infections, anemia, and
the development of cancer and other tumors.
Importance
and Distribution of FeLV
FeLV has a global distribution,
with varying prevalence rates in different regions. The presence and impact of
the virus are influenced by factors such as cat population density, awareness
about the virus and its transmission, availability of diagnostic tests, and the
use of effective vaccines. While some regions have managed to decrease FeLV
prevalence to less than 1%, other areas still face higher prevalence rates of
up to 20%.
Structure and
Genes of FeLV
FeLV is a complex retrovirus with
an outer envelope and an inner core. The viral genome contains three major
genes: gag, pol, and env. The gag gene encodes core proteins, pol encodes the
viral enzymes necessary for replication, and env encodes the viral envelope
glycoproteins essential for host cell entry. Understanding the viral structure
and genes is crucial for developing effective diagnostic and therapeutic
strategies.
Understanding
FeLV Epidemiology
Global
Distribution and Prevalence
FeLV's distribution is
widespread, affecting domestic and wild feline populations worldwide. The
prevalence of the virus varies depending on geographical locations and the
level of preventive measures in place. Countries with well-established
vaccination programs and awareness campaigns have succeeded in reducing FeLV
prevalence significantly.
Transmission
and Risk Factors
FeLV transmission primarily
occurs through viraemic cats via various bodily fluids, including saliva, nasal
secretions, faeces, and milk. High population density, young age, and poor
hygiene are considered risk factors for transmission. Pregnant viraemic females
can pass the virus to their offspring, leading to adverse pregnancy outcomes
and the birth of weak kittens.
Vulnerability
in Kittens
Kittens are particularly
vulnerable to FeLV infection, especially when exposed to the virus at a young
age. Their immature immune systems make them more susceptible to the
consequences of the infection, leading to a higher risk of developing severe
health issues and experiencing rapid perinatal death or weakness.
Pathogenesis
of FeLV Infection
Initial
Contact and Replication
Upon initial exposure to FeLV,
the virus replicates in cells of the oropharyngeal cavity. The outcome of this
phase varies based on the cat's immune response.
Immune
Response Variations
FeLV infection can lead to
different immune responses in cats, depending on their immune status.
Immunocompetent cats may mount an effective immune response, preventing
systemic dissemination of the virus, while immunocompromised cats may
experience progressive or persistent viraemia.
Immunocompetent
vs. Immunocompromised Cats
Immunocompetent cats can
effectively control FeLV infection, leading to limited or no systemic
dissemination of the virus. In contrast, immunocompromised cats may experience
viraemia and become persistently infected, leading to severe health
consequences over time.
Clinical Signs
and Manifestations
Immunodepression
and Its Impact
FeLV-induced immunosuppression
leads to a range of clinical signs and makes infected cats susceptible to
various opportunistic infections. Atrophy of the thymus and loss of T
lymphocytes play a crucial role in immunodepression, leading to chronic
infections and concurrent diseases.
Anaemia and Its
Types
FeLV infection can cause
different types of anaemia, including non-regenerative anaemia and regenerative
anaemia associated with haemolysis. Anaemia is a significant consequence of
FeLV infection and can worsen the cat's overall health.
Cancer and Tumours
Linked to FeLV Infection
FeLV has been linked to various
types of cancer, particularly lymphoma and leukaemia. Additionally, FeLV can
contribute to the development of malignant non-hematopoietic tumours, such as
fibrosarcoma. Understanding these associations is crucial for diagnosing and
managing FeLV-infected cats effectively.
Diagnosis of
FeLV Infection
Virus Isolation
Virus isolation is the definitive
test for the presence of FeLV, but it is not commonly used due to its
sensitivity issues and time-consuming nature.
ELISA (p27) Test
The enzyme-linked immunoassay,
known as the ELISA test, detects the presence of FeLV antigen (p27 protein) in
blood, plasma, or serum. It is highly sensitive and specific, making it a
commonly used diagnostic method for FeLV infection.
Immunofluorescent
Antibody Test (IFA)
The IFA test detects viral p27
antigen within infected cells, particularly platelets and neutrophils. It is
highly sensitive and has been used in field conditions to diagnose FeLV
infection.
PCR Techniques
for Detection
Polymerase chain reaction (PCR)
techniques are used to detect FeLV infection by identifying either the provirus
DNA or the viral RNA in various bodily fluids. These tests are highly sensitive
and specific and play a crucial role in diagnosing FeLV infections, especially
in cases where other diagnostic methods produce contradictory results.
Management
and Treatment of FeLV Infection
Confined
Living and Preventive Measures
Once a cat is diagnosed with
FeLV, appropriate management becomes essential to prevent further transmission
and protect the cat's well-being. Infected cats should be confined indoors to
avoid infecting other cats and to protect them from potential infectious
processes.
Regular
Health Assessments and Care
Regular health assessments,
including blood tests, urinalysis, and deworming, are essential for monitoring
the health status of FeLV-infected cats. This helps in detecting and managing
concurrent infections and other health issues promptly.
Potential Use of
Immunomodulators and Antiviral Drugs
Specific antiviral drugs, such as
feline interferon ω and Raltegravir, have shown promise in improving the
clinical status of FeLV-infected animals. Immunomodulators can also be
considered to support the cat's immune response and overall well-being.
Prevention
and Vaccination against FeLV
Significance
of Vaccines
Vaccination plays a crucial role
in preventing FeLV infection and reducing its prevalence in feline populations.
Vaccines are essential in protecting susceptible cats, especially kittens, from
the virus's fatal consequences.
Types of FeLV
Vaccines
Various FeLV vaccines are
available, including inactivated adjuvanted vaccines and recombinant
non-adjuvanted vaccines. These vaccines offer a high degree of protection against
FeLV infection and its associated health issues.
Vaccination
Schedule and Recommendations
Vaccination against FeLV is
recommended, especially for kittens. The first dose is typically administered
at 8 to 9 weeks of age, followed by a second dose at 12 to 13 weeks.
Revaccination is usually done one year later and can be repeated every 2 to 3 years,
depending on the cat's risk of exposure to FeLV.
Feline Leukaemia Virus (FeLV) remains a significant health concern for feline populations worldwide. Understanding its epidemiology, pathogenesis, clinical signs, and appropriate diagnostic and preventive measures is crucial for veterinarians and cat owners. Through effective management, vaccination, and preventive strategies, we can work towards reducing the prevalence of FeLV and ensuring the well-being of our feline companions. Ongoing research and collaboration between veterinary professionals and researchers will further our knowledge and improve outcomes for FeLV-infected cats.
Disclaimer:
The information provided in this article is for educational
purposes only and should not be considered as a substitute for professional
veterinary advice.
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