FelV - Katzen-Leukose / Feline Leukemia Virus

Katzenleukose ist eine Virusinfektion, die durch das Katzenleukämievirus, abgekürzt FeLV, hervorgerufen wird. Untersuchungen haben klar gezeigt, dass beinahe jeder 6. Todesfall bei Katzen durch Leukose verursacht wird. Die häufigste tödliche Infektionskrankheit. Die Krankheit kommt weltweit vor und betrifft Katzen jeden Alters. Von der Ansteckung bis zur Erkrankung können Jahre vergehen. In dieser Zeit wird aber der Erreger millionenfach mit dem Speichel ausgeschieden. Nicht nur kranke, sondern auch gesund erscheinende Katzen können das Virus übertragen. Übertragungswege sind gegenseitiges Lecken, Beißen und Katzentoiletten. Ansteckungsgefahr auch durch gesund erscheinende, dauerhaft infizierte Katzen. Deshalb sollten FeLV-infizierte Katzen aufgrund der hohen Ansteckungsgefahr unbedingt von gesunden Katzen getrennt werden. Die Katzenleukose kann mit den vielfältigsten Krankheitserscheinungen einhergehen. Beginnend mit Lustlosigkeit, Fieber, plötzlicher Abmagerung, blassen Schleimhäuten (Anämie), Zahnfleischentzündungen bis hin zu bösartigen Tumoren in der Brusthöhle und im Bauch (Leber, Niere, Darm). Katzenleukose besteht jedoch in einer Schwächung der Abwehrkraft durch das Virus. Betroffene Katzen sind den verschiedensten Infektionserregern praktisch schutzlos ausgeliefert. Die Leukose ist somit auch Grundlage für viele andere, oft tödlich verlaufende Infektionskrankheiten. Vielfältige Krankheitserscheinungen. Solche Folgekrankheiten maskieren oft die eigentliche Ursache, wodurch die Diagnosestellung manchmal sehr erschwert wird. Als Faustregel kann aber gelten: Plötzlich auftretende Mattigkeit, unerklärliche Gewichtsabnahme, Durchfall oder Verstopfung, Schweratmigkeit, bei Zuchtkatzen Fruchtbarkeitsstörungen, Zahnfleischentzündungen und vieles mehr können Hinweise auf Katzenleukose sein. Ebenso gilt auch: Jede Gesundheitsstörung bei der Katze, die sich schon über längere Zeit hinzieht, d. h. chronisch ist, bei der eine Behandlung keine oder nur eine vorübergehende Besserung bewirkt, ist leukoseverdächtig. Bei kranken Katzen kann der Tierarzt bereits durch seine Untersuchung einen Leukoseverdacht aussprechen. Der sog. Leukosetest kann diesen Verdacht erhärten. Katzenleukose ist unheilbar! – Impfen schützt. Die sicherste Methode, die Krankheit zu verhindern, ist die Schutzimpfung. Eine Impfung gegen FeLV ist sehr sicher und verleiht eine gute Immunität. Dabei sollte darauf geachtet werden, dass der Impfstoff auch in der Lage ist, nicht nur vor Schwächung des Immunsystems, sondern auch vor Tumorentwicklungen zu schützen. Feline Leukemia Virus (source: Cornell Feline Health Center) What is feline leukemia virus? Feline leukemia virus (FeLV), a retrovirus, so named because of the way it behaves within infected cells. All retroviruses, including feline immunodeficiency virus (FIV) and human immunodeficiency virus (HIV), produce an enzyme, reverse transcriptase, which permits them to insert copies of their own genetic material into that of the cells they have infected. Although related, FeLV and FIV differ in many ways, including their shape: FeLV is more circular while FIV is elongated. The two viruses are also quite different genetically, and their protein consituents are dissimlar in size and composition. Although many of the diseases caused by FeLV and FIV are similar, the specific ways in which they are caused differs. What does FeLV do to a cat? Feline leukemia virus adversely affects the cat's body in many ways. It is the most common cause of cancer in cats, it may cause various blood disorders, and it may lead to a state of immune deficiency that hinders the cat's ability to protect itself against other infections. The same bacteria, viruses, protozoa, and fungi that may be found in the everyday environment—where they usually do not affect healthy animals—can cause severe illness in those with weakened immune systems. These secondary infections are responsible for many of the diseases associated with FeLV. What are the signs of disease caused by FeLV? During the early stages of infection, it is common for cats to exhibit no signs of disease at all. However, over time—weeks, months, or even years—the cat's health may progressively deteriorate or be characterized by recurrent illness interspersed with periods of relative health. Signs can include: Loss of appetite Slow but progressive weight loss, followed by severe wasting late in the disease process Poor coat condition Enlarged lymph nodes Persistent fever Pale gums and other mucus membranes Inflammation of the gums (gingivitis) and mouth (stomatitis) Infections of the skin, urinary bladder, and upper respiratory tract Persistent diarrhea Seizures, behavior changes, and other neurological disorders A variety of eye conditions In unspayed female cats, abortion of kittens or other reproductive failures How is infection diagnosed? Two types of FeLV blood tests are in common use. Both detect a protein component of the virus as it circulates in the bloodstream. ELISA (enzyme-linked immunosorbent assay) and similar tests can be performed in your veterinarian's office. ELISA-type tests detect both primary and secondary stages of viremia. IFA (indirect immunofluorescent antibody assay) tests must be sent out to a diagnostic laboratory. IFA tests detect secondary viremia only, so the majority of positive-testing cats remain infected for life. Each testing method has strengths and weaknesses. Your veterinarian will likely suggest an ELISA-type test first, but in some cases, both tests must be performed—and perhaps repeated—to clarify a cat's true infection status. How long can I expect my FeLV-infected cat to live? It is impossible to accurately predict the life expectancy of a cat infected with FeLV. With appropriate care and under ideal conditions, infected cats can remain in apparent good health for many months, although most succumb to a FeLV-related disease within two or three years after becoming infected. If your cat has already experienced one or more severe illnesses as a result of FeLV infection, or if persistent fever, weight loss, or cancer is present, a much shorter survival time can be expected. Overview Feline leukemia virus (FeLV) infection is responsible for more deaths among cats than any other infectious disease. The virus affects domestic cats and occurs in some wild felines as well. Types of FeLV There are three main types of feline leukemia virus: FeLV-A, FeLV-B, and FeLV-C. FeLV-positive cats can be infected with one, two, or all three types: FeLV-A occurs in all FeLV-infected cats and causes severe immunosuppression (weakened immune system). FeLV-B occurs in about 50%of all FeLV-infected cats and causes more neoplastic disease (i.e., tumors and other abnormal tissue growths) than cats infected only with FeLV-A. FeLV-C occurs in about 1% of FeLV-infected cats and causes severe anemia. After the initial infection, the virus replicates in the tonsils and pharyngeal lymph nodes (the pharynx is the muscular tube in the neck). Then it spreads via the bloodstream to other parts of the body, especially the lymph nodes, bone marrow, and intestinal tissue, where it continues to replicate. Viremia, the presence of virus in the blood, usually shows up 2 to 4 weeks after the initial infection. FeLV doesn't survive long outside a cat's body—probably less than a few hours under normal household conditions. Incidence FeLV is one of the most devastating feline diseases worldwide. In the United States, FeLV infects about 2% to 3% of all cats. Risk Factors Sick cats may be four times more likely than healthy cats to be infected with FeLV. Researchers estimate that about 50% of cats with severe bacterial infections, and 75% of cats with toxoplasmosis—a protozoan disease—also have FeLV infections. Males are 1.7 times more likely to be infected than females, and younger cats are more susceptible to infection than older cats. FeLV is found mostly in cats from 1 to 6 years old; the average age is 3 years. Outdoor cats are more likely to be infected with FeLV. Less than 1% of healthy indoor cats in the United States are infected with FeLV, compared to 1% to 2% of healthy outdoor cats, and as many as 13% of sick stray cats. FeLV is more common in multicat households than in single-cat households, especially when cats go outdoors. Transmission FeLV usually spreads through infected saliva. It can also spread through infected urine, tears, and feces, and through an infected mother to her kittens during gestation and nursing. Twenty percent of FeLV-positive mothers pass the virus to their kittens. Methods of transmission include the following: Bite wounds from infected cats (more common among outdoor and indoor-outdoor cats) Blood transfusions Mouth and nose contact with infected saliva or urine Mutual grooming Nose-to-nose contact Shared food dishes and water bowls Shared litter trays Sneezing Diagnosis Diagnostic tests can detect all three types of feline leukemia virus but can't distinguish between them. There are two FeLV blood tests that detect antigens to FeLV including: enzyme-linked immunosorbent assay (ELISA) immunofluorescence assay (IFA) also called the Hardy, or slide test The main difference between these tests is that ELISA detects antigens in the blood serum, and IFA detects them in the white blood cells. ELISA can detect FeLV antigens early in the course of the infection, while the virus is in the blood and before it invades the bone marrow and white blood cells. Once FeLV reaches the bone marrow, both ELISA and IFA can detect it. ELISA results in more false positive results. ELISA can also be used to test for antigens in a cat's saliva and tears, but the results are not reliable. Saliva and tear tests are used to screen a large number of cats, and to test cats from whom it is difficult to obtain sufficient blood samples. Kittens that test positive by ELISA should be retested when they're older than 16 weeks. Uninfected kittens can test positive, if they are carrying their mother's antigens to FeLV. By 16 weeks of age, the mother's antigens should be out of a kitten's system. A cat may test positive by ELISA, but several weeks later, test negative. This means that the cat has developed immunity, and will likely never show any sign of infection. Cats that test positive by IFA are generally positive for life. Negative results do not necessarily mean that the cat is uninfected. Negative test results can occur in infected cats that have been exposed only recently to the virus and aren't producing antibodies yet. The cat's blood may reveal certain abnormalities indicative of FeLV infection, including: anemia (abnormally low level of circulating red blood cells), lymphopenia (abnormally low level of lymphocytes in the blood), and neutropenia (abnormal decrease in the number of circulating neutrophils, a type of white blood cell). Treatment There is no cure for FeLV. All treatments, including the following, are aimed at relieving pain and discomfort: Antibiotics to treat secondary bacterial infections Blood transfusions Chemotherapy to treat tumors Dietary supplements Immunomodulatory drugs (e.g., drugs that target the immune system), such as interferon, immunoregulin, and acemannan Prognosis The prognosis varies considerably. About 70% of cats that are infected with FeLV develop immunity and are able to fight the virus before developing symptoms. These cats usually live a normal life. Some cats that develop initial immunity suffer a viremic breakout months or years later, usually after being stressed or medicated with drugs that suppress the immune system. Thirty percent of FeLV-infected cats that don't develop immunity to the virus are persistently viremic. These cats may live months or years, depending on how far the disease has progressed when the cat is diagnosed. More than 50% of these cats die within a couple of years. Because FeLV can be spread through litter trays, water and food bowls, and bedding, these should be disinfected with a solution containing 4 ounces of household bleach per 1 gallon of water, or they should be replaced after isolating the FeLV-positive cat. Floors should be cleaned and disinfected with a bleach solution, and rugs should be thoroughly vacuumed.