DISEASE INFORMATION FACT SHEET Feline Immunodeficiency Virus
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Journal of Feline Medicine and Surgery (2013) 15 , Supplementary File FACT SHEET DISEASE INFORMATION FACT SHEET Feline immunodeficiency virus This Disease Information Fact Sheet accompanies the 2013 AAFP Feline Vaccination Advisory Panel Report published in the Journal of Feline Medicine and Surgery (2013), Volume 15, pp 785 –808. AAFP FELINE VACCINATION ADVISORY PANEL Margie A Scherk Disease facts DVM Dip ABVP The 2013 Report of the Feline Vaccination (Feline Practice) Advisory Panel of the American Association of Advisory Panel Chair* Feline immunodeficiency virus (FIV) is found Feline Practitioners (AAFP) provides practical Richard B Ford recommendations to help clinicians select DVM MS Dip ACVIM worldwide in domestic cats, with variable DACVPM (Hon) seroprevalence depending on geography and appropriate vaccination schedules for their risk factors. Unlike feline leukemia virus feline patients based on risk assessment. Rosalind M Gaskell BVSc PhD MRCVS (FeLV), kittens do not appear to be more sus - The recommendations rely on published data ceptible to infection than adults. Large sero - as much as possible, as well as consensus of a Katrin Hartmann surveys have found a prevalence of 2.5% in multidisciplinary panel of experts in immunology, Dr Med Vet Dr Med Vet Habil 1 Dip ECVIM-CA the United States in 2006 and 4.3% in Canada infectious disease, internal medicine and 2 clinical practice. The Report is endorsed by the Kate F Hurley in 2009, with marked regional variation. DVM MPVM The immuno deficiency viruses of domestic International Society of Feline Medicine (ISFM). cats are classified into several genetically dis - Michael R Lappin DVM PhD Dip ACVIM tinct subtypes or clades, designated A to E, Julie K Levy based on the sequence of the envelope glyco - DVM PhD Dip ACVIM protein, gp120. Prevalence of the various clades 5,6 Susan E Little varies geographically. Within a clade, varia - encing high levels of viremia. Experi men - DVM Dip ABVP (Feline Practice) tions in genotype as well as disease phenotype tally, queens can be infected via semen, but Shila K Nordone may occur, including emergence of more path - it is unknown how important this mode of MS PhD 7 ogenic subtypes. FIV has a high mutation rate transmission is in nature. Andrew H Sparkes due to an error-prone reverse transcriptase Most infected cats will mount an immune BVetMed PhD DipECVIM enzyme, leading to the circulation of many het - response to the virus, which leads to MRCVS erologous strains, even within a single host. decreased virus replication and viral load in *Corresponding author: Some of these mutations may lead to changes infected cats, but not elimination of infec - Email: [email protected] 3 in virulence or antigenicity. This tremendous tion. The ability of the virus to persist variation has an impact on diagnostics, thera - integrated into the cellular genome makes peutics and vaccine development. treatment as well as prevention through The virus is present in the saliva of infected vaccination challenging. One of the main cats, and FIV infection is most likely to occur target cells of FIV is the CD4+ T helper in male cats and free-roaming cats, reflecting lymphocyte, which is essential for both efficient transmission by bite wounds. cell-mediated and humoral immunity. Transmission via sustained contact among Dysfunction and destruction of these cells is infected and uninfected cats, as with FeLV, critical to the pathogenesis of disease. 4 may also occur. In addition, in utero and After infection, cats enter an asympto - lactogenic transmission to kittens from queens matic phase that may last for many years. may occur, especially if the queen is experi - Virus replication continues, but at very low © ISFM and AAFP 2013 Reprints and permission: sagepub.co.uk/journalsPermissions.nav FACT SHEET / Feline immunodeficiency virus levels. Initially, levels of both CD4+ and CD8+ transient lethargy or fever, and vomiting, 11 lymphocytes decline. As the cat mounts an diarrhea or anorexia. immune response, a rebound of CD8+ lym - Other vaccine considerations phocytes above pre-infection levels occurs. This causes an inversion of the CD4+:CD8+ lymphocyte ratio that is persistent. Over time, Vaccinated cats produce antibodies that the level of both CD4+ and CD8+ lympho - cannot be distinguished, by any current com - cytes may gradually decline, ultimately lead - mercially available antibody test, from anti - 19 ing to immunodeficiency in the infected cat. bodies induced by natural infection. These The clinical signs and illnesses associated antibodies are detectable within a few weeks with FIV are varied and non-specific, and are of vaccination. Vaccine-induced antibodies usually not a direct effect of the virus, but are have been shown to persist for more than 19,20 due to secondary infections that may be treat - 4 years in some cats. able. Other common associated diseases include Clients should be informed that vaccinated inflammatory ocular and oral disease, neopla - cats will have positive FIV antibody test 8 sia, neurologic disease and renal disease. results, and the decision to vaccinate should FIV is very labile outside of the host and be reached only after careful consideration. remains infectious for mere minutes in the Vaccinated cats should be permanently identi - environment; in moist secretions it may sur - fied, such as with a microchip, and FIV vacci - vive until dried. It is readily inactivated by nation history should be included in the soap, disinfectants, heat and drying. FIV is not microchip database. zoonotic. In one study of 204 veterinarians Testing of cats prior to vaccination is essen - and other occupationally exposed individu - tial to ensure negative status. Inadvertent use als, no serologic or molecular evidence of of FIV vaccine in a cat infected with FIV is not 9 zoonosis with FIV was detected. harmful, but it is also of no benefit. However, Vaccine types vaccination of a cat that is unknown to be retrovirus infected gives false expectations to the owner and could result in questions about A vaccine for FIV is commercially available, vaccine efficacy and failure to recommend and contains inactivated whole virus isolates testing when the cat tests positive for FIV. from clades A and D, with infected cells and an When a cat is vaccinated against FIV for the adjuvant. It has been found to induce antibod - first time, owners should be instructed to con - 10 ies as well as cell-mediated responses. fine the cat until at least 3 weeks after the final Studies of the currently available vaccine con - vaccination to ensure that an adequate ducted by the inventor or manufacturer have immune response has developed before risk demonstrated efficacy when vaccinated cats of exposure. 11 –14 were challenged with subtypes A and B. One independent study showed that the vac - cine was not able to protect cats when they Advisory Panel Recommendations were challenged by a subtype A field strain 15 from the United Kingdom. While it offers Vaccination against FIV is considered non-core but could be recommended some protection to some cats at high risk, its for cats at high risk of exposure, such as outdoor cats or cats living with FIV- 16,18,21 use remains controversial and it is listed as infected cats. One expert panel recommends against use of the vaccine non-core or not recommended by the major until further evaluation of vaccine efficacy against field strains is performed 16 –18 22 vaccine advisory groups. Another very and test interference is resolved. When FIV vaccination is appropriate, a important concern is that current screening/ three-dose primary series is administered, with the first dose given as early as testing methods cannot reliably distinguish 8 weeks of age. Annual revaccination is recommended subsequent to the initial naturally infected from vaccinated cats. series if the risk of infection continues. Onset and duration of immunity References Onset of immunity occurs by 3 weeks after 14 primary vaccination. According to the manufacturer, FIV vaccine-induced immunity 1 Levy JK, Scott HM, Lachtara JL and Crawford persists for at least 12 months following vacci - PC. Seroprevalence of feline leukemia virus nation, although the actual duration of immu - and feline immunodeficiency virus infection nity is unknown. among cats in North America and risk factors Vaccine safety for seropositivity. J Am Vet Med Assoc 2006; 228: 371 –376. 2 Little S, Sears W, Lachtara J and Bienzle D. Adverse events associated with vaccination Seroprevalence of feline leukemia virus and against FIV include local swelling or pain, feline immunodeficiency virus infection Journal of Feline Medicine and Surgery (2013) 15 , Supplementary File FACT SHEET / Feline immunodeficiency virus among cats in Canada. Can Vet J 2009; 50: subtype B FIV isolate. J Feline Med Surg 2005; 7: 644 –648. 65 –70. 3 de Rozieres S, Mathiason CK, Rolston MR, 15 Dunham SP, Bruce J, MacKay S, Golder M, Chatterji U, Hoover EA and Elder JH. Jarrett O and Neil JC. Limited efficacy of an Characterization of a highly pathogenic molec - inactivated feline immunodeficiency virus ular clone of feline immunodeficiency virus vaccine. Vet Rec 2006; 158: 561 –562. clade C. J Virol 2004; 78: 8971 –8982. 16 Day MJ, Horzinek MC and Schultz RD. WSAVA 4 Addie DD, Dennis JM, Toth S, Callanan JJ, Reid S guidelines for the vaccination of dogs and cats. and Jarrett O. Long-term impact on a closed J Small Anim Pract 2010; 51: 338 –356. household of pet cats of natural infection with 17 Hosie MJ, Addie D, Belak S, Boucraut-Baralon C, feline coronavirus, feline leukaemia virus and Egberink H, Frymus T, et al. Feline immunode - feline immunodeficiency virus. Vet Rec 2000; ficiency. ABCD guidelines on prevention and 146: 419 –424. management. J Feline Med Surg 2009; 11: 5 Allison RW and Hoover EA. Feline immuno - 575 –584. deficiency virus is concentrated in milk early 18 Richards JR, Elston TH, Ford RB, Gaskell RM, in lactation.