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FIV
FIV-protease
FIV-protease
Videnskabelig klassifikation
DomæneVira (Virus)
(urangeret)Gruppe VI (ssRNA-RT)
FamilieRetroviridae (Retrovirus)
SlægtLentivirus
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FIV (felin immundefektvirus) er en lentivirus, der påvirker tamme huskatte over hele verden og er den virus, der forårsager katteaids. Ca. 11%[1] af katte på verdensplan, og omkring 2,5% af alle katte i USA[2] er inficeret med FIV. FIV adskiller sig taxonomisk fra to andre katte-retrovira, felin leukæmi-virus (FeLV) og katteskummende virus (FFV), og er mere tæt forbundet med human immundefektvirus (HIV). FIV har fem undertyper (der er identificeret), som baseret på nukleotidsekvens-forskelle, der koder for den virale envelop (ENV) eller polymerase (POL). FIV er den eneste ikke-primatære lentivirus, der forårsager en AIDS-lignende syndrom, men FIV giver ikke altid en dødsdom til katte; de kan leve forholdsvis sundt som bærere og sendere af sygdommen i mange år. Der findes en vaccine, selv om dens effekt er fortsat usikker, og katte vil blive testet positiv for FIV-antistoffer efter vaccination.

FIV blev først opdaget i 1986 i en koloni af katte, der havde en høj forekomst af opportunistiske infektioner og degenerative betingelser, og er siden blevet identificeret som en endemisk sygdom i huskatte, gældende for hele verden[2].

Smitte

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De primære former for FIV-smitte forekommer ved dybe bide-sår og skrammer, hvor kattens infecerede spyt bliver ført ind i en anden kats blodårer. FIV kan også overføres fra gravide hunkatte til deres fostre i livmoderen[3]. Dette adskiller sig fra FeLV, der kan spredes via mere afslappet ikke-aggressiv kontakt, da virus er også til stede ved slimhindeinfektioner som dem i munden, endetarmen og skeden. Tilfældig kontakt kan derfor ikke udelukkes som en potentiel transmission.

Testning

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Når dyrlæger vil kontrollere en kats historie og stamtræ for at se om sygdommen blev overført arveligt, og eventuelt administrere en blodprøve for FIV-antistoffer. FIV rammer 2-3% af alle katte i USA og derfor er testning let tilgængelig. Det skal bemærkes, at denne test identificerer de katte som er påført FIV-antistof, og detekterer ikke selve virussen. Derfor finder en positiv test nødvendigvis ikke at katten er bærer af FIV.

Falske positiver opstår når katten bærer FIV-antistof (som er uskadeligt), men ikke selve virus. Den hyppigste forekomst af dette er når killingerne er testet efter indtagelse af antistoffer fra modermælken, og test af katte der tidligere er blevet vaccineret for FIV. Af denne grund er hverken killinger under 8 uger eller katte, der tidligere er blevet vaccineret, testes.

Killinger og unge katte der testes positive for FIV-antistof, kan med en test, hvor forekomst af et negativt resultat på et senere tidspunkt på grund af seroreversion, forudsat at de aldrig er blevet smittet med FIV og aldrig er blevet vaccineret med FIV-vaccinen.

Katte der er blevet vaccineret vil testes positiv for FIV-antistof for resten af deres liv på grund af serokonversionen, selv om de ikke er smittet. Derfor er tests af adopterede katte er noget usikre, da det er umuligt at vide hvorvidt de er blevet vaccineret i fortiden. Af disse grunde bør en positiv FIV-antistoftest i sig selv aldrig bruges som kriterier for aktiv dødshjælp.[kilde mangler]

Test kan gennemføres i en dyrlæges rum med resultater på få minutter, der giver mulighed for hurtig konsultation. Tidlig opdagelse hjælper med at bevare kattens sundhed og forhindrer spredning af smitte til andre katte. Med ordentlig pleje kan smittede katte lever langt og sundt liv.

Vaccine

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A vaccine for FIV is available (ATCvet code: Skabelon:ATCvet), and was developed using isolates of two of the five FIV subtypes (or clades): A and D.[4] The vaccine was shown to be moderately protective (82% of cats were protected) against subtype A FIV,[5] but a later study showed it to offer no protection against subtype A.[6] It has shown 100% effectiveness against two different subtype B FIV strains.[7][8] Vaccination will cause cats to have positive results on FIV tests, making diagnosis more difficult. For these reasons the vaccine is considered "non-core", and the decision to vaccinate should be made after discussion with a veterinarian and consideration of the risks vs. the effectiveness.[9]

Godkendt behandling

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In 2006, the United States Department of Agriculture issued a conditional license for a new treatment aid termed Lymphocyte T-Cell Immune Modulator.[10] Lymphocyte T-Cell Immune Modulator is manufactured by T-Cyte Therapeutics, Inc., exclusively licensed by IMULAN BioTherapeutics, LLC and distributed in the United States by ProLabs Animal Health (www.prolabsanimalhealth.com). However, thus far, only one trial has been published in a reputable veterinary journal, and that trial consisted of only about half a dozen cats. At this time, rigorous clinical trials have yet to be conducted and published. The cost of obtaining the treatment aid is very high and its efficacy is often disappointing in individual cases.

Lymphocyte T-Cell Immune Modulator is intended as an aid in the treatment of cats infected with feline leukemia virus (FeLV) and/or feline immunodeficiency virus (FIV), and the associated symptoms of lymphocytopenia, opportunistic infection, anemia, granulocytopenia, or thrombocytopenia. The absence of any observed adverse events in several animal species, suggests that the product has a very low toxicity profile.

Lymphocyte T-Cell Immune Modulator is a potent regulator of CD-4 lymphocyte production and function.[11] It has been shown to increase lymphocyte numbers and Interleukin 2 production in animals.[12]

Lymphocyte T-Cell Immune Modulator is a single chain polypeptide. It is a strongly cationic glycoprotein, and is purified with cation exchange resin. Purification of protein from bovine-derived stromal cell supernatants produces a substantially homogeneous factor, free of extraneous materials. The bovine protein is homologous with other mammalian species and is a homogeneous 50 kDa glycoprotein with an isoelectric point of 6.5. The protein is prepared in a lyophilized 1 microgram dose. Reconstitution in sterile diluent produces a solution for subcutaneous injection.[13]

Effekter

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FIV can attack the immune system of cats, much like the human immunodeficiency virus (HIV) can attack the immune system of human beings. FIV infects many cell types in its host, including CD4+ and CD8+ T lymphocytes, B lymphocytes, and macrophages. FIV can be tolerated well by cats, but can eventually lead to debilitation of the immune system in its feline hosts by the infection and exhaustion of T-helper (CD4+) cells.

FIV and HIV are both lentiviruses; however, neither can infect the other's usual host: humans cannot be infected by FIV nor can cats be infected by HIV. FIV is transmitted primarily through saliva (bites), such as those incurred during territorial battles between males. Cats housed exclusively indoors are much less likely to be infected, provided they do not come in contact with infected cats.

Consensus whether there is a need to euthanize FIV infected cats has not been established. The American Associations of Feline Practitioners, as well as many feral cat organizations, recommend against euthanizing FIV+ cats, or even spending funds to test for the virus, as spaying or neutering cats seems to effectively control transmission - as neutered cats are less likely to engage in territorial fights. A vigilant pet owner who treats secondary infections can assist an infected cat to live a reasonably long life. The chance that an FIV infected cat will pass the disease on to other cats within a household remains, and increases with serious fighting or biting (American Association of Feline Practitioners 2002). There is a quantifiable risk that cats living outside of a home can spread the disease to others and can also spread the disease in a group setting in a shelter. Cats living alone as a single pet, rarely left to roam free, pose a diminished, but not non-existent risk.

The disease occurs in three stages: First is the Acute Stage (1–2 months after transmission) in which fever, depression, and generalized lymphadenopathy are observed (Wise 2005). Second is the Subclinical Stage (4 weeks to X months after transmission), in which symptoms of the disease decrease or disappear; however, all cats remain viremic for life. Third is the Chronic Stage, in which cats eventually succumb to chronic infections due to suppressed immune system function. Cats may incur stomatitis, odontoclasia, periodontitis, gingivitis, rhinitis, conjunctivitis, pneumonitis, enteritis, and dermatitis in the later stages of infection. FIV+ cats are less likely to develop AIDS-like symptoms than HIV+ humans.

FIV infects other feline species, and in fact is endemic in some large wild cats, such as African lions. Unlike domestic cats, these species do not necessarily exhibit symptoms, perhaps because they have developed evolutionary mutations that confer resistance.

Referencer

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  1. ^ Richards, J (2005). "Felin immundefektvirus-vaccine: Implikationer for diagnosticering og sygdomsbehandling". Biologicals. 33: 215. doi:10.1016/j.biologicals.2005.08.004.
  2. ^ a b Zislin, A (2005). "Felin immundefektvirus-vaccine: En rationel paradigme for kliniske beslutningsprocesser". Biologicals. 33: 219. doi:10.1016/j.biologicals.2005.08.012.
  3. ^ Amerikanske Forbindelser mellem Felin-Praktikere (2002). "Felin Immundefektirus". Cornell Felin Helbreds-Center. Cornell-Universitetet, Universitetet for Veterinærmedicin. Hentet 2008-11-12.
  4. ^ Levy, J (2008), "2008 American Association of Feline Practitioners' feline retrovirus management guidelines", Journal of Feline Medicine & Surgery, 10: 300, doi:10.1016/j.jfms.2008.03.002
  5. ^ Huang, C.; Conlee, D.; Loop, J.; Champ, D.; Gill, M.; Chu, H.J. (2004), "Efficacy and safety of a feline immunodeficiency virus vaccine", Animal Health Research Reviews, 5: 295-300, doi:10.1079/AHR200487
  6. ^ Dunham, S.P.; Bruce, J.; Mackay, S.; Golder, M.; Jarrett, O.; Neil, J.C. (2006), "Limited efficacy of an inactivated feline immunodeficiency virus vaccine.", Veterinary Record, 158: 561-562
  7. ^ Kusuhara, H.; Hohdatsu, T.; Okumura, M.; Sato, K.; Suzuki, Y.; Motokawa, K.; Gemma, T.; Watanabe, R.; Huang, C.; Arai, S.; Koyama, H. (2005), "Dual-subtype vaccine (Fel-O-Vax FIV) protects cats against contact challenge with heterologous subtype B FIV infected cats.", Veterinary Microbiology, 108: 155-165, doi:10.1016/j.vetmic.2005.02.014
  8. ^ Pu, R.; Coleman, J.; Coisman, J.; Sato, E.; Tanabe, T.; Arai, M.; Yamamoto, JK. (2005), "Dual-subtype FIV vaccine (Fel-O-Vax FIV) protection against a heterologous subtype B FIV isolate.", Journal of Feline Medicine and Surgery, 7: 65-70, doi:10.1016/j.jfms.2004.08.005
  9. ^ Levy, J (2008), "2008 American Association of Feline Practitioners' feline retrovirus management guidelines", Journal of Feline Medicine & Surgery, 10: 300-316, doi:10.1016/j.jfms.2008.03.002
  10. ^ United States Department of Agriculture. Veterinary Biological Products; Licensees and Permittees, December 2006.
  11. ^ Beardsley, et al. "Induction of T-Cell Maturation by a Cloned Line of Thymic Epithelium (TEPI) Immunology 80: pp. 6005-6009, (Oct. 1983).
  12. ^ Skabelon:Ref patent
  13. ^ Skabelon:Ref patent
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