FeLV was first described in cats in 1964.[25] The disease was originally associated with leukemia; however, it was later realized that the initial signs are generally anemia and immunosuppression.[25] The first diagnostic test became available in 1973, which led to a "test and elimination" regime, dramatically reducing the number of infected cats in the general population.[26] The first vaccine became available in 1986.[26]
Progression
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The disease has a wide range of effects. The cat can fight off the infection and become totally immune, can become a healthy carrier that never gets sick itself but can infect other cats, or a mid-level case in which the cat has a compromised immune system.[citation needed] Nevertheless, the development of lymphomas is considered the final stage of the disease. Although it is thought that virus protein has to be present to induce lymphomas in cats, newer evidence shows that a high percentage of FeLV-Antigen negative lymphomas contain FeLV-DNA, indicating a "hit-and-run" mechanism of virus-induced tumor development.[5]
Once the virus has entered the cat, there are six stages to a FeLV infection[citation needed]:
- Stage One: The virus enters the cat, usually through the pharynx where it infects the epithelial cells and infects the tonsilar B-lymphocytes and macrophages. These white blood cells then filter down to the lymph nodes and begin to replicate.
- Stage Two: The virus enters the blood stream and begins to distribute throughout the body.
- Stage Three: The lymphoid system (which produces antibodies to attack infected and cancerous cells) becomes infected, with further distribution throughout the body.
- Stage Four: The main point in the infection- where the virus can take over the body's immune system and cause viremia. During this stage the hemolymphatic system and intestines become infected.
If the cat's immune system does not fight off the virus, then it progresses to:
- Stage Five: The bone marrow becomes infected. At this point, the virus will stay with the cat for the rest of its life. In this phase, the virus replicates and is released four to seven days later in infected neutrophils, and sometimes lymphocytes, monocytes, and eosinophils (all white blood cells formed in the bone marrow).
- Stage Six: The cat's body is overwhelmed by infection and mucosal and glandular epithelial cells (tissue that forms a thin protective layer on exposed bodily surfaces and forms the lining of internal cavities, ducts, and organs) become infected. The virus replicates in epithelial tissues including salivary glands, oropharynx, stomach, esophagus, intestines, trachea, nasopharynx, renal tubules, bladder, pancreas, alveolar ducts, and sebaceous ducts from the muzzle.
Comparison with feline immunodeficiency virus
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FeLV and feline immunodeficiency virus (FIV) are sometimes mistaken for one another, though the viruses differ in many ways. Although they are both in the same retroviral subfamily (Orthoretrovirinae), they are classified in different genera (FeLV is a gamma-retrovirus and FIV is a lentivirus like HIV-1). Their shapes are quite different: FeLV is more circular while FIV is elongated. The two viruses are also quite different genetically, and their protein coats differ in size and composition. Although many of the diseases caused by FeLV and FIV are similar, the specific ways in which they are caused also differ. Also, while the feline leukemia virus may cause symptomatic illness in an infected cat, an FIV infected cat can remain completely asymptomatic its entire lifetime.[citation needed]
See also[edit]
https://en.wikipedia.org/wiki/Feline_leukemia_virus
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