It is estimated that about 2 to 10% of all cats are infected. The statistics say that around 80% of all leukemia infected and affected cats die within 3 years. Noteworthy is the addition “and diseased cats,” since not every cat infected with feline leukosis virus also has leukosis. Some cats are viremic for years (that is, the virus is detectable in the blood) without leukosis immediately or at a later date. For others, the disease breaks out the same. And some cats can infect themselves but can also eliminate the virus themselves. These cats have a short infection (up to 3 weeks).
Infection with feline leukemia virus
The Feline Leukemia Virus is distributed worldwide. Infection takes place via the mucous membranes of the mouth and nose or, in special cases, with existing wounds. It must be taken directly infectious material (mostly saliva or blood, feces, and urine are also possible). The infection usually occurs in sociable contact such as the mutual cleansing or turf wars in release cats. Outside the diseased animal, for example in wells or drinking fountains, the virus is only able to survive for a few minutes at room temperature. Due to this fact, it is also relatively unlikely that the cats will become infected by carrying the virus on to shoes or clothing. However, this issue is still discussed controversially among professionals.
Leukemia can manifest itself in the body in many ways, and it often occurs with other illnesses. The following symptoms may indicate an infection:
- Increased sleep
- Matt fur
- A lot of drinking
- Badly healing wounds and abscesses
- Blood in the feces
- Cat flu
- Inflammation of the pharynx
- lung infection
- Difficulty in breathing
- Increased or decreased white blood cells (leukocytes)
- Lymphosarcomas (tumors of the lymphatic organs)
- Tumors of the internal organs
- Kidney disease
- Liver disease
All the symptoms described can also occur in many other diseases; they are not a clear sign of feline leukemia. The diagnosis of leukemia is not always easy or clear; a veterinary veterinarian is of a significant advantage here.
Forms of FeLV infection
As the variety of possible symptoms already show, the clinical picture of feline leukemia is very versatile. A distinction is made in the first step according to whether tumors form or not (neoplastic and non-neoplastic form). The next step is then a finer differentiation based on the main symptoms.
The neoplastic forms form so-called lymphosarcomas. These are malignant tumors that form in the lymphatic organs. The lymphatic organs form lymphocytes, which are white blood cells and are very important for the immune system. In non-neoplastic forms, on the other hand, it is more likely to suppress the immune system and/or alter the blood cells.
Precisely differentiation of all FeLV forms
In laboratory diagnostics, the causative virus types are classified into sub-types of these leukemia forms. The most important are FeLV A, FeLV B, and FeLV C. The latter two are mutations of FeLV A, which can arise in the reproduction of the virus in the body. The sub-type FeLV B usually causes the neoplastic form; here it comes more frequently to tumor formation. In FeLV C, non-neoplastic forms are increasingly common.
Since many other diseases such as FIV, FIP or hemobartonellosis can cause the same symptoms, they must be excluded in any case. A leukosis can not only be diagnosed by the existing symptoms, but laboratory diagnosis is also necessary. The following possibilities are currently offered by the diagnostics:
FeLV antigen rapid test: Many veterinarians have this test in stock in their practice. However, these tests are not always clear. There may be false-positive or false-negative results as the test can only detect antibodies to the FeLV. Both with infections that are currently being fought by the body as well as in the first three weeks after the infection, the rapid test can deliver a negative result. False-positive results may occur in uninfected cats. For this reason, the rapid test should be repeated as a precaution after a few weeks.
Serological tests in the laboratory (ELISA): Due to the different phases of the virus, this test can also lead to false-positive or false-negative results. Repeating the test after a few weeks makes sense.
PCR test: This test is safer than the other two because it detects the virus DNA in the host cell. Further information on the polymerase chain reaction can be found here: PCR test.
There are quite a few cats that can fight the infection with the FeL virus itself and do not fall ill. Many leukemia infected cats do not see the infection. This is due to the different stages of the viral disease or on a different course.
- The cat has become infected with FeLV, and the virus initially proliferates in the lymphoid tissue near the mouth (in case of oral infection). If the cat is otherwise healthy and has a good condition, it can fight and eliminate the virus at this stage with a well-functioning immune system. This usually applies to 50% of all cats in a first infection with FeLV. Mostly, we humans do not notice this infection at all.
- If the cat was unable to fight the virus successfully in the first phase, it would enter the blood (viremia) and possibly also the bone marrow. All secretions of the cat are now contagious. When the cat’s immune system succeeds in successfully combating this viremia, the infection transforms into a transient viremia.
- A transient viremia is when the virus concentration in the blood is only moderately high. In this phase, the virus infection – regardless of a bone marrow involvement – still be terminated by the immune system of the cat. If this happens before the involvement of the bone marrow, the virus can be eliminated. If it does not happen until after involvement of the bone marrow, it is called a latent infection.
- A latent infection is a dormant infection. The virus has retreated into the bone marrow and does not multiply any further. In this phase, the cat does not excrete the virus. However, the disease can break out in these cats at any time. This can be caused by stress, vaccinations, pregnancy, other illnesses or cortisone therapy.
- If a cat can not cope alone with a FeLV outbreak after a latent infection, it is called a persistent viremia. These cats usually die within 3 to 5 years from leukosis and/or the accompanying diseases. As with most diseases of cats especially young, sick and old cats are particularly at risk of persistent viremia.
There is no cure for leukemia. Currently, only the individual comorbidities or disease forms can be treated. Depending on the level of severity, some lifetime can be granted in this way. At an early stage of leucosis, support of the immune system can help.
As with any vaccine, it’s important to weigh all the pros and cons carefully. When leukosis vaccination should always be carried out before a leukosis test. For cats whose immune system has already undergone a FeLV infection, the leukosis vaccine is useless.
The general recommendation is to vaccinate freedmen against leukosis. Pure cats, on the other hand, do not need the vaccine unless they live with a FeLV-positive cat. The vaccine does not provide 100% vaccination coverage for FeLV-negative cats living with positive cats, as the healthy animals are confronted daily with a large amount of virus. Most cat shows, and cat pensions in addition to other vaccinations also prescribe a leucosis vaccine.