Asociación Mexicana de Médicos Veterinarios Especialistas en Pequeñas Especies

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1 Asociación Mexicana de Médicos Veterinarios Especialistas en Pequeñas Especies XXXI CONGRESO NACIONAL DE LA ASOCIACIÓN MEXICANA DE MÉDICOS VETERINARIOS ESPECIALISTAS EN PEQUEÑAS ESPECIES, A.C. DRA. IRENE JOYCE BLANK Mayo 23 al 25 de 2013 IMMUNOSUPPRESSIVE DISEASES Dr. John R. August Texas A&M University Introduction The incidence of new cases of feline leukemia virus (FeLV) infection in pet cats has decreased significantly over the past 25 years, through improved public education, test and removal or isolation, and vaccination. The incidence of new cases of feline immunodeficiency virus (FIV) infection has not changed significantly during that time, perhaps due to the somewhat isolated population of cats that are at most risk of exposure. It is estimated that 10% or less of all cats in the United States have been tested for retrovirus infection, leaving a large population of cats whose status is unknown.

2 Longevity Public attitudes toward the euthanasia or long-term care of retrovirus-infected cats are changing, and many affected cats now live out their natural lives in loving homes. This poses special challenges for attending veterinarians when the affected cat shares a home with many other cats and when isolation may be difficult. In a study from Germany, Gleich and colleagues determined that the median survival time of FIV- positive cats was not significantly different from a cohort of non-infected cats of similar age. However, the median survival time of FeLV-positive cats was significantly shorter than uninfected cats, as would be expected. Husbandry and Hygiene Isolation Isolation serves two purposes; first to protect in-contact cats from infection, and second to minimize opportunistic infections in the retrovirus-positive patient. Although not often possible, or palatable to the owners, it is recommended that infected cats be isolated in a separate building from healthy cats, rather than in a room in a house occupied by uninfected cats (Gunn-Moore). In shelters, other rescue facilities, and veterinary clinics, retrovirus-positive ideally should not be housed in the isolation room where other cats with infectious diseases are located so that they are not exposed to opportunistic pathogens. Handling Priorities In multiple-cat facilities, care must be taken to prevent iatrogenic transmission of infectious agents to the most susceptible members of the group. In cattery situations, this means the kittens. Using the cattery model, the most susceptible cats are handled first which are the early-weaned kittens. After this group, the caretakers handle the queens with kittens, then the adult breeding cats, incoming cats in quarantine, and finally the sick and infectious cats in the isolation room (August). Strict hand-washing and changes of protective clothing must occur in the transition between each group. On the other hand, retrovirus-positive cats in multiple-cat households should be handled last to protect healthy cats from iatrogenic transmission (especially of FeLV), but only after scrupulous barrier control measures have been fulfilled as described above. Although neither virus survives long outside the host, repeated exposure to damp contaminated fomites (hands, instruments) might place highly susceptible kittens at risk for FeLV infection. Preventing Opportunistic Infections Every effort should be made to minimize exposure of retrovirus-infected cats to pathogens, especially new strains of opportunistic organisms that the cats have not encountered before. Although many FIV-positive cats seem outwardly healthy for months or years, their immunocompetence is declining during that time. Opportunistic infections may accelerate the progression of that immunological dysfunction, shortening lifespan. Affected cats should not be allowed to roam. Intact cats healthy enough to undergo general anesthesia should be spayed or neutered to decrease the urge of roam and to minimize the resulting stress associated with estrus and fighting. Bactericidal antimicrobials should be administered post-operatively to prevent opportunistic infection. Gunn-Moore recommends that owners should impose a night-time curfew on these cats a time when most fights occur. No raw products should be fed to prevent bacterial or parasitic gastrointestinal infections. Maintaining Wellness Identifying and addressing signs of illness as early as possible is an essential strategy for

3 improving longevity of infected cats. Thorough physical examinations should be performed no less often than every 6 months, paying special attention to body weight, eyes (including fundic examination), mouth, skin, and lymph nodes. Complete blood counts are indicated every 6 months for FeLV-positive cats and annually for FIV-positive patients. More frequent assessments may be needed based on history of hematological abnormalities. Fecal examinations should be performed at each visit to identify new parasitic infections. An effective, year-round, flea control program should be instituted to prevent arthropod-borne diseases that may be life-threatening; for example, Mycoplasma haemofelis infection. Vaccination Strategies Retrovirus-infected cats should be vaccinated selectively based on their assessed risk of exposure to infectious diseases. Only outwardly healthy cats should be vaccinated with killed vaccines exclusively, and vaccination against FeLV or FIV has no positive effect on the longevity of cats already infected with the respective viruses. On the other hand, it has been proposed that vaccination of healthy FIV-positive cats may accelerate their immunological decline through immune stimulation and activation of FIV replication. Minimizing the number of killed vaccines administered, in conjunction with strict isolation, may ameliorate this concern. Gunn-Moore recommends that any in- contact cats who are retrovirus-negative should be vaccinated with killed vaccines, rather than modified-live virus products, to prevent exposure of immunocompromised cats to live viruses shed following vaccination. Retrovirus-positive cats may not respond optimally to vaccination, especially later in the disease course, again increasing the need for robust isolation procedures. Reducing Stress Chronic stress may accelerate the decline in immunocompetence of infected cats, especially those patients who are FIV-positive. Every effort should be made to create an enriched environment that minimizes stressful triggers. This is especially important for the infected cat who has been isolated from other cats in the household, and for whom frequent opportunities for social interaction and companionship are essential. Providing resting areas of different levels, a view out of a window, a hiding place (or refuge), a daily routine of feeding and social interaction, and ambient soft music can ameliorate stress for the cat in isolation. Caretakers should be aware of the subtle signs of stress in the cats in isolation, including inappetence, hiding, failure to groom, decreased play, and social withdrawal (Griffin), and should institute enrichment measures when indicated. Promotion of Immunocompetence In general, immunomodulatory drugs provide inconsistent or poor benefits for retroviruspositive cats, and should not be used as the foundation for protection against opportunistic infections or progression of retrovirus infection. The efficacy of immunomodulatory drugs may be enhanced when they are used concurrently with antiviral medications, and retroviruspositive cats should receive at least 3 to 4 weeks of treatment before decisions about efficacy are made (Gunn-Moore). Recombinant feline interferon omega, not available in the United States, may extend survival times, but there is no evidence that the drug has any specific antiviral effects (Lutz). Human recombinant interferon alpha (Roferon A) has been used with some success as an immunestimulator at a dose of 30 IU PO q24h on alternate weeks. The drug is not licensed for use in cats. The antiviral drug zidovudine (AZT) may decrease plasma viral load in FeLV-positive cats and may improve immunological function, clinical status, quality of life, and longevity in some cats

4 (Lutz). A dose of 5 mg/kg PO or SQ q12h is used for FeLV and FIV infections. Non-regenerative anemia is a common complication, especially if higher doses are used, and weekly complete blood counts should be performed initially and then monthly to monitor for this adverse reaction (Hosie). AZT may be more effective for those retrovirus-positive cats with neurological or oral complications. Testing for Retrovirus Infections Once a FeLV-positive or FIV-positive cat has been confirmed to be persistently viremic, there is little point in monitoring the patient s viral status on a regular basis. On the other hand, all in-contact cats should be screened at least every 6 months using an ELISA or other immunochromatographic test on serum or plasma. In-contact healthy cats who are bitten by a retrovirus-positive cat should be tested 60 to 90 days after the bite wound incident, and again at their next scheduled wellness examination if the first test is negative. A recent study by Goldkamp and colleagues illustrates the poor follow- up that occurs in these situations. Only 54.5% of veterinary practices contacted owners 60 days after their cats were treated for bite wounds to schedule an FIV test. Even worse, only 13.4% of clients returned their cats for the recommended testing. Treatment of Infected Cats Corticosteroids should be used very conservatively in retrovirus-positive cats and only in those patients in whom there is a very strong indication; for example, cats with painful stomatitis. Bactericidal antmicrobials should be used whenever possible for infections and the course of treatment should be longer than that administered to an immunocompetent cat. Griseofulvin should not be used for opportunistic dermatophyte infections in FIV-positive cats because the drug may cause life-threatening, idiosyncratic, bone-marrow dyscrasias. References 1. August JR: Husbandry practices for cats infected with FeLV or FIV. JAVMA 199:1474, Gleich SE, Krieger S, Hartmann K: Prevalence of feline immunodeficiency virus and feline leukemia virus among client-owned cats and risk factors for infection in Germany. J Feline Med Surg 11:985, Goldkamp CE, Levy JK, Edinboro CH, et al: Seroprevalences of feline leukemia virus and feline immunodeficiency virus in cats with abscesses or bite wounds and rate of veterinarian compliance with current guidelines for retrovirus testing. JAVMA 232:1152, Griffin B, Hume KR: Recognition and management of stress in housed cats. In August JR (ed): Consultations in Feline Internal Medicine, vol 5, St. Louis, 2006, Elsevier Saunders, p Gunn-Moore D: Management of retrovirus-infected cats. Proceedings of the 1 st Congress in Feline Medicine, GEMFE, Granada, Spain, January Hosie MJ, Addie D, Belák S, et al: Feline immunodeficiency. ABCD guidelines on prevention and management. J Feline Med Surg 11:575, Levy J, Hartmann K, Hofmann-Lehmann R, et al: 2008 American Association of Feline Practitioners feline retrovirus management guidelines. J Feline Med Surg 10:300, Lutz H, Addie D, Belák S, et al: Feline leukemia. ABCD guidelines on prevention and management. J Feline Med Surg 11:565, 2009.

5 Take-Home Messages Infected cats should be housed in a separate building, whenever possible. Opportunistic infections often accelerate immunological decline of FIVpositive cats. A thorough physical examination should be performed at least every 6 months, paying special attention to body weight, mouth, eyes, skin, and lymph nodes. Vaccination strategies should be tailored to each infected cat s unique needs to prevent excessive immunization. Only outwardly healthy cats should be vaccinated, using only killed products. Chronic stress may affect immunocompetence and shorten the life-spans of infected cats. Currently available immunomodulatory drugs do not appear to improve longevity significantly. Immunomodulatory drugs work best when combined with antiviral agents. Serological testing should be performed 60 to 90 days after a healthy, in- contact cat has had a significant exposure to a retrovirus-infected cat. Corticosteroids and other potentially immunosuppressive agents should be used very judiciously in retrovirus-positive cats.