Feline Immunodeficiency Virus

Feline immunodeficiency virus is a lentivirus belonging to the family Retroviridae that causes a chronic, progressive immunodeficiency syndrome in domestic cats and certain wild felid species. First isolated in 1986 from a colony of cats in Petaluma, California, that exhibited clinical signs resembling human acquired immunodeficiency syndrome, FIV has since been identified in cat populations on every continent and is recognized as one of the most significant infectious diseases of domestic cats worldwide. Seroprevalence estimates vary considerably by geographic region, population type, and risk category, but surveys generally report infection rates of approximately two to four percent in healthy pet cat populations, rising to fifteen to thirty percent or higher among free-roaming, feral, and shelter populations with high rates of inter-cat aggression.

FIV shares fundamental biological characteristics with human immunodeficiency virus, including its lentiviral classification, tropism for CD4-positive T lymphocytes, progressive immune depletion, and ultimate progression to an AIDS-like terminal syndrome. Both viruses employ the enzyme reverse transcriptase to convert their single-stranded RNA genomes into double-stranded proviral DNA that integrates permanently into the host cell's chromosomal DNA, establishing a lifelong infection that cannot be eliminated by the host immune response or by currently available therapeutic interventions. Despite these profound parallels, FIV is strictly species-specific and poses no zoonotic risk to humans, dogs, or other non-felid species. The virus cannot survive outside the feline host for extended periods and is readily inactivated by common disinfectants, desiccation, and ultraviolet light.

The clinical trajectory of FIV infection follows a staged progression analogous to the course of untreated HIV infection in humans. Following initial exposure and acute viremia, the virus establishes a persistent latent infection during which the cat may appear clinically healthy for months, years, or even a decade or more. During this prolonged asymptomatic phase, the virus continues to replicate at low levels and progressively depletes the CD4-positive T lymphocyte population, gradually eroding the immune system's capacity to mount effective responses against opportunistic pathogens. Eventually, immune function deteriorates to the point where the cat becomes susceptible to a constellation of secondary infections, neoplasms, and organ dysfunctions that collectively define the acquired immunodeficiency syndrome, or feline AIDS, stage of the disease.

The significance of FIV infection extends beyond the individual cat to encompass important implications for shelter medicine, multi-cat household management, feral cat colony programs, and the broader understanding of lentiviral biology and immunodeficiency syndromes. FIV-positive cats were historically euthanized at shelters based on the assumption that their diagnosis precluded adoption and quality of life, but evolving understanding of the disease's typically prolonged asymptomatic course has led many shelters and rescue organizations to adopt policies supporting the placement of FIV-positive cats in appropriate homes. The management of FIV in multi-cat environments requires careful consideration of transmission risks balanced against the welfare benefits of social housing. Research on FIV continues to inform comparative virology and immunology, contributing insights relevant to the development of vaccines and therapies for both feline and human lentiviral diseases.

The primary route of FIV transmission is through deep bite wounds inflicted during aggressive encounters between cats, a mode of spread that directly accounts for the strong epidemiological association between infection status and male sex, intact reproductive status, outdoor access, and territorial aggression. The virus is present at high concentrations in the saliva of infected cats, and the deep puncture wounds characteristic of cat bites provide an efficient mechanism for depositing virus-laden saliva directly into subcutaneous tissues and the bloodstream of the recipient cat. This bite-wound transmission pathway explains why intact male cats, which are far more likely to engage in territorial fighting than neutered males or females of either reproductive status, are disproportionately represented among FIV-positive cats, with male-to-female infection ratios typically ranging from two-to-one to four-to-one in most surveyed populations.

Transmission through casual non-aggressive contact between cats is considered inefficient and epidemiologically insignificant under most circumstances. Studies of stable multi-cat households in which FIV-positive and FIV-negative cats cohabitate without aggression have demonstrated very low rates of seroconversion among the initially negative cats over observation periods of several years, supporting the conclusion that grooming, shared food and water bowls, shared litter boxes, and close physical proximity without bite-wound exchange pose minimal transmission risk. This finding has important practical implications for the management of FIV-positive cats in households and shelters, as it indicates that FIV-positive cats can safely coexist with FIV-negative housemates provided the social dynamics are stable and non-aggressive. The caveat is that any change in social structure that introduces fighting or redirected aggression could create opportunities for bite-wound transmission.

Vertical transmission from an infected queen to her kittens can occur through transplacental infection during gestation, exposure to virus in the birth canal during parturition, or ingestion of virus-containing milk during nursing. The frequency of vertical transmission varies considerably depending on the stage of the queen's infection and her viral load at the time of pregnancy and birth, with reported rates ranging from approximately zero to seventy percent across different study populations. Acute infection during pregnancy, when viral loads are highest, carries the greatest risk of vertical transmission. Kittens born to FIV-positive queens present a diagnostic challenge because they acquire maternal antibodies through colostrum that may persist in their circulation for up to six months after birth, causing them to test antibody-positive on standard screening assays even if they are not truly infected. Confirmatory testing at six months of age or older, or PCR testing for proviral DNA, is necessary to determine the true infection status of kittens born to FIV-positive queens.

Other potential transmission routes exist but contribute minimally to the overall epidemiology of FIV infection. Sexual transmission has been demonstrated experimentally through artificial insemination with virus-containing semen, and the virus has been detected in seminal fluid of naturally infected toms, but the practical significance of venereal transmission under natural mating conditions remains uncertain. Blood transfusion from an infected donor to a naive recipient represents a highly efficient iatrogenic transmission route, underscoring the importance of FIV screening for all feline blood donors. Shared needles or contaminated surgical instruments could theoretically transmit the virus, though standard aseptic practices effectively prevent this route. Flea transmission has been hypothesized but has not been convincingly demonstrated as a significant natural transmission mechanism.

The epidemiological profile of FIV infection reflects the primacy of bite-wound transmission and identifies the populations and individual risk factors associated with the highest infection prevalence. Free-roaming intact male cats in urban and periurban environments, where population density and competition for territory and mates drive frequent aggressive encounters, represent the highest-risk demographic. Feral cat colonies experience variable prevalence depending on colony density, sex ratios, neutering rates, and the frequency of immigration by new males that trigger territorial disputes. Indoor-only cats in stable single or multi-cat households with no history of aggressive interactions face negligible risk. The geographic distribution of FIV infection is worldwide but non-uniform, with higher prevalence reported in areas with large populations of free-roaming unneutered cats and lower prevalence in regions with high rates of pet cat neutering and indoor confinement.

The clinical course of FIV infection is divided into distinct stages that mirror the staged classification system used for HIV infection in humans, progressing from acute infection through a prolonged asymptomatic carrier state to a terminal immunodeficiency phase. The acute phase begins one to three weeks after exposure and is characterized by a transient viremia during which the virus replicates rapidly in lymphoid tissues throughout the body. During this initial burst of viral replication, circulating viral loads reach their peak and the virus disseminates to lymph nodes, spleen, thymus, bone marrow, and other lymphoid organs where it establishes persistent reservoirs of infection. Clinical signs during the acute phase are typically mild and self-limiting, including transient fever, lethargy, mild generalized lymphadenopathy, and occasionally mild upper respiratory signs or diarrhea. Many cats pass through the acute phase without their owners noticing any abnormality.

The asymptomatic carrier phase follows resolution of the acute viremia and represents the longest stage of FIV infection, commonly persisting for years and sometimes extending beyond a decade. During this period, the cat appears clinically healthy and maintains normal activity, appetite, and body condition despite harboring the virus in its lymphoid tissues and peripheral blood mononuclear cells. Viral replication continues at lower levels than during the acute phase but remains sufficient to sustain a gradually progressive decline in CD4-positive T lymphocyte counts. The balance between ongoing viral replication and the host's immune control mechanisms determines the rate of CD4 cell depletion and consequently the duration of the asymptomatic phase. Factors that influence the pace of immunological decline include the viral subtype and strain virulence, the host's genetic background and immune competence, concurrent infections that activate the immune system and stimulate viral replication, and the cat's general health and nutritional status.

The progressive generalized lymphadenopathy stage, considered by some classification systems as a distinct phase and by others as a late feature of the asymptomatic carrier state, is characterized by persistent, non-painful enlargement of multiple peripheral lymph nodes. This lymphadenopathy reflects the ongoing struggle between viral replication and immune containment within the lymphoid architecture and may persist for months before either resolving or progressing to more advanced disease. The enlarged lymph nodes contain hyperplastic follicles with active germinal centers as the remaining functional B and T lymphocytes mount increasingly strained responses against the virus and the expanding array of secondary pathogens to which the cat becomes progressively vulnerable. Cytological examination of aspirates from enlarged lymph nodes typically reveals reactive lymphoid hyperplasia without evidence of neoplastic transformation at this stage, though lymphoma development is a recognized late complication of FIV infection.

The AIDS-related complex phase marks the transition from clinically silent infection to overt immunodeficiency-associated disease and is characterized by the emergence of chronic, recurrent, or treatment-resistant infections alongside progressive systemic decline. Cats in this phase develop persistent or intermittent fever, progressive weight loss, decreased appetite, chronic respiratory infections, recurrent oral disease, and skin infections that respond poorly or incompletely to standard therapy. Laboratory findings during this phase commonly include progressive lymphopenia with declining CD4-positive T cell counts, neutropenia, anemia, and hyperglobulinemia reflecting polyclonal B cell activation. The duration of the AIDS-related complex phase is variable and may evolve gradually into the terminal phase or may be punctuated by acute crises precipitated by severe opportunistic infections.

The terminal AIDS phase represents the end stage of FIV infection, in which profound immunodeficiency leaves the cat unable to mount effective immune responses against even normally harmless environmental organisms. Cats in this phase suffer from severe, refractory opportunistic infections involving multiple organ systems, wasting syndrome with progressive cachexia, neurological disease from direct viral effects on the central nervous system or secondary opportunistic infections, and increased incidence of certain neoplasms particularly lymphoma and squamous cell carcinoma. Quality of life deteriorates markedly, and humane euthanasia is frequently elected when supportive care can no longer maintain acceptable comfort and function. The overall progression from initial infection to the terminal phase spans a median of approximately five to eight years in most study populations, though individual variation is substantial, with some cats succumbing within two to three years and others surviving more than twelve years with good quality of life.

The clinical manifestations of FIV infection are overwhelmingly a consequence of the progressive immunodeficiency rather than direct pathological effects of the virus itself, meaning that the spectrum of disease observed in FIV-positive cats largely reflects the array of opportunistic and secondary infections to which the compromised immune system can no longer respond effectively. Chronic gingivostomatitis is one of the most common and debilitating conditions associated with FIV infection, affecting an estimated fifty to eighty percent of symptomatic FIV-positive cats. This severe inflammatory condition of the oral cavity extends beyond the gingiva to involve the buccal mucosa, fauces, and pharynx, causing intense pain that manifests as reluctance to eat, dropping food while chewing, pawing at the mouth, drooling, weight loss, and unkempt coat from reduced grooming. The pathogenesis involves a dysregulated immune response to oral commensal bacteria and calicivirus in the setting of impaired T cell function, and treatment frequently requires aggressive dental extraction combined with anti-inflammatory and antimicrobial therapy.

Respiratory infections occur with increased frequency and severity in FIV-positive cats, reflecting the impaired mucosal immune defenses that normally protect the upper and lower respiratory tracts. Chronic rhinosinusitis with persistent nasal discharge, sneezing, and congestion is common and may be caused by feline herpesvirus, calicivirus, Chlamydophila felis, Mycoplasma species, or secondary bacterial invaders including Bordetella bronchiseptica and Pasteurella multocida. Lower respiratory infections including bacterial pneumonia and pulmonary mycoses develop with greater frequency in severely immunocompromised cats. These respiratory conditions tend to respond more slowly and less completely to standard antimicrobial therapy than in immunocompetent cats, often requiring prolonged treatment courses and experiencing more frequent relapses.

Dermatological manifestations of FIV-associated immunodeficiency encompass a range of skin infections and inflammatory conditions that reflect the impaired cutaneous immune surveillance. Chronic or recurrent bacterial skin infections, dermatophytosis that is unusually severe or widespread, Demodex gatoi or Demodex cati infestations that are resistant to standard treatment, and chronic non-healing wounds occur with increased prevalence. Ear infections caused by bacteria or yeasts may become chronic and recalcitrant to therapy. Cutaneous manifestations of systemic mycoses including cryptococcosis, which has a particular predilection for the nasal cavity, subcutaneous tissues, and central nervous system in immunosuppressed cats, may present with facial swelling, nasal granulomas, or disseminated nodular skin lesions. The skin may also be the site of FIV-associated neoplasia, with squamous cell carcinomas and cutaneous lymphoma occurring at elevated rates.

Gastrointestinal disease in FIV-positive cats may result from opportunistic enteric infections, immune-mediated inflammatory processes, or direct viral effects on the gastrointestinal lymphoid tissue. Chronic diarrhea, sometimes alternating with constipation, affects a significant proportion of symptomatic FIV-positive cats and may be caused by Cryptosporidium, Giardia, Salmonella, Campylobacter, or other enteric pathogens that an immunocompetent cat would normally suppress. Chronic enteritis with lymphoplasmacytic or eosinophilic infiltration can develop, producing malabsorption, weight loss, and nutritional deficiency. Hepatic disease including cholangitis and hepatic lymphoma has been reported at increased frequency. The combination of poor appetite from oral pain, malabsorption from enteric disease, and the catabolic effects of chronic infection and inflammation drives the progressive wasting syndrome that characterizes advanced FIV infection.

Neurological manifestations occur in a subset of FIV-positive cats and may result from direct viral invasion of the central nervous system or from opportunistic infections of neural tissue. FIV demonstrates neurotropism and can be isolated from the cerebrospinal fluid and brain tissue of infected cats. Direct viral effects on neurons, astrocytes, and microglia can produce behavioral changes including aggression, dementia-like cognitive dysfunction, compulsive behaviors, disrupted sleep-wake cycles, and psychomotor slowing. Peripheral neuropathies causing facial nerve paralysis, anisocoria, or limb weakness have been reported. Opportunistic central nervous system infections including toxoplasmosis, cryptococcal meningitis, and viral encephalitis can produce seizures, ataxia, vestibular dysfunction, and progressive neurological deterioration. The prognosis for cats with significant neurological involvement is generally poor.

Diagnostic testing for FIV employs a two-tier strategy consisting of initial screening with a highly sensitive assay followed by confirmatory testing with a highly specific assay to eliminate false-positive results, an approach that parallels the diagnostic algorithm used for HIV screening in human medicine. The initial screening test for FIV in clinical practice is typically a point-of-care enzyme-linked immunosorbent assay or rapid immunochromatographic assay that detects antibodies against FIV-specific antigens in whole blood, serum, or plasma. These screening tests offer high sensitivity, meaning they detect the vast majority of truly infected cats, but their specificity is somewhat lower, meaning that a proportion of cats testing positive on the screening assay are not actually infected. The positive predictive value of any screening test is influenced by the prevalence of infection in the tested population, so positive results in low-prevalence populations such as indoor-only pet cats carry a higher probability of being false positives and require confirmation.

Confirmatory testing for cats that test positive on initial screening is performed using either Western blot analysis or polymerase chain reaction for proviral DNA, each of which offers distinct advantages and limitations. Western blot detects antibodies against specific FIV proteins separated by molecular weight on an electrophoretic gel, providing a pattern of reactivity that can differentiate true infection-generated antibodies from cross-reactive antibodies responsible for false-positive screening results. PCR testing detects viral genetic material integrated into the host cell DNA and offers the advantage of direct viral detection independent of the antibody response, making it particularly valuable for confirming infection in cats with discordant serological results, testing kittens under six months of age in whom maternal antibodies may confound serological interpretation, and detecting early infection before seroconversion has occurred. However, PCR sensitivity varies with the primer sequences used and the viral subtype present, and false-negative results can occur, particularly with subtypes not well represented in the primer design.

The timing and context of FIV testing significantly influence result interpretation and require careful consideration by the veterinary clinician. Seroconversion following natural infection typically occurs within two to four weeks of exposure but may be delayed for up to eight weeks or occasionally longer, creating a window period during which a recently infected cat will test antibody-negative despite harboring the virus. Cats with known or suspected exposure to FIV through bite wounds or other routes should therefore be tested at the time of exposure to establish a baseline result and retested sixty days later to allow for seroconversion. Kittens born to FIV-positive queens acquire maternal antibodies through colostral transfer that persist in their circulation for variable periods up to approximately six months of age, producing positive antibody test results that do not indicate true infection. These kittens should be retested after six months of age, with a negative result at that point confirming that the initial positive was due to passive maternal antibody transfer rather than genuine infection.

Routine FIV testing is recommended in several clinical scenarios to ensure that infected cats are identified and appropriately managed. All cats should be tested at the time of adoption or acquisition regardless of their known or presumed history. Cats that have had potential exposure to FIV through bite wounds, fighting, or introduction to environments with cats of unknown FIV status should be tested following the baseline-and-retest protocol described above. All cats being considered as blood donors must test negative for FIV before donation. Cats presenting with clinical signs consistent with immunodeficiency-associated disease, including chronic recurrent infections, gingivostomatitis, unexplained weight loss, persistent lymphadenopathy, or unusual neoplasms, should be tested if their FIV status is unknown. Annual or periodic retesting of previously negative cats with ongoing risk of exposure through outdoor access or introduction of new housemates of unknown status may be considered.

Additional diagnostic evaluation beyond FIV testing itself is warranted in cats confirmed to be FIV-positive to assess their current immunological status, identify concurrent infections or conditions, and establish baseline values for long-term monitoring. A complete blood count provides information about lymphocyte counts, neutrophil numbers, and red blood cell parameters that reflect the degree of immunocompromise and identify cytopenias requiring monitoring or intervention. Serum biochemistry evaluates organ function and detects metabolic abnormalities. Urinalysis screens for proteinuria and urinary tract infection. Concurrent testing for feline leukemia virus is essential, as co-infection with both retroviruses carries a significantly worse prognosis than either infection alone. Baseline thoracic radiography and abdominal ultrasonography provide organ assessment and screening for lymphoma or other neoplasia.

There is no curative treatment for FIV infection, and the primary therapeutic objectives center on maintaining immune function for as long as possible, preventing and promptly treating secondary infections, managing specific clinical manifestations as they arise, and optimizing the overall quality of life for the infected cat. Antiviral therapy has been explored extensively in both experimental and clinical settings, but no antiviral agent has demonstrated sufficient efficacy, safety, and practical applicability to earn consensus recommendation for routine clinical use in FIV-positive cats. Zidovudine, a nucleoside reverse transcriptase inhibitor used in human HIV therapy, has shown some antiviral activity against FIV in experimental studies and has been used clinically in cats with stomatitis and neurological disease, with variable reported results. The practicalities of long-term antiviral therapy in cats, including the need for frequent dosing, potential for bone marrow suppression, and lack of robust clinical trial evidence, limit its widespread adoption.

Management of secondary infections represents the most impactful aspect of clinical care for FIV-positive cats, as opportunistic infections are the primary cause of morbidity and mortality throughout the course of the disease. Aggressive, early, and prolonged antimicrobial therapy is warranted when bacterial infections are identified, with antibiotic selection guided by culture and sensitivity testing whenever possible rather than relying on empirical choices that may be inadequate for the resistant organisms more commonly encountered in immunocompromised hosts. Treatment courses should typically extend beyond the standard duration used for immunocompetent cats, as the impaired immune response requires more time and more complete antimicrobial suppression to achieve clinical resolution. Fungal infections, particularly cryptococcosis, require prolonged systemic antifungal therapy with agents such as fluconazole or itraconazole, with treatment continuing for weeks to months beyond the resolution of clinical signs and confirmed by serial antigen titer monitoring.

Chronic gingivostomatitis, one of the most debilitating consequences of FIV infection, frequently requires aggressive multimodal management combining dental intervention with medical therapy. Full-mouth or near-full-mouth extraction of the premolar and molar teeth, while seemingly radical, provides the best long-term outcomes for cats with chronic faucitis and caudal stomatitis, achieving significant clinical improvement or complete resolution in approximately sixty to eighty percent of cases by removing the tooth-associated bacterial plaque that drives the dysregulated immune response. Medical management for cats that do not respond adequately to dental extraction or as bridging therapy may include corticosteroids for anti-inflammatory effect, cyclosporine for immunomodulation, and pain management with buprenorphine or other appropriate analgesics. The challenge of managing oral disease in FIV-positive cats lies in the tension between the need for immunosuppressive therapy to control oral inflammation and the risk of further compromising an already deficient immune system.

Nutritional support and general wellness optimization form the foundation of long-term care for FIV-positive cats. A high-quality, nutritionally complete diet providing adequate protein from animal sources supports immune function and helps maintain lean body mass. Raw or undercooked meat-based diets should be strictly avoided because the risk of exposure to bacterial and parasitic pathogens in unprocessed animal products is unacceptable in immunocompromised individuals. Weight monitoring at regular intervals detects early trends toward the wasting syndrome that characterizes progressive disease. Environmental stress reduction through provision of secure resting areas, predictable routines, vertical territory, and avoidance of crowded or competitive housing conditions helps minimize the chronic stress that can accelerate immune decline. Indoor confinement protects the FIV-positive cat from exposure to environmental pathogens while simultaneously preventing transmission to other cats.

Vaccination of FIV-positive cats requires careful risk-benefit assessment because the immunocompromised state raises questions about both the efficacy of vaccination and the safety of certain vaccine types. Core vaccines including those against feline panleukopenia, feline herpesvirus, and feline calicivirus are generally recommended for FIV-positive cats using killed or recombinant formulations rather than modified-live vaccines, as modified-live vaccines carry a theoretical risk of causing vaccine-associated disease in immunocompromised individuals. Rabies vaccination should be administered as required by law. The immune response to vaccination may be diminished in cats with advanced immunodeficiency, potentially resulting in shorter duration of immunity, but the consensus is that the benefits of maintaining whatever protective immunity can be generated outweigh the risks of leaving the cat unvaccinated against common feline pathogens.

The prognosis for cats diagnosed with FIV infection has evolved substantially over the past three decades as veterinary understanding of the disease's natural history has deepened and as attitudes toward FIV-positive cats have shifted from reflexive euthanasia toward proactive long-term management. Multiple longitudinal studies have demonstrated that FIV-positive cats maintained in appropriate indoor environments with attentive veterinary care can live for many years after diagnosis, with median survival times from the point of diagnosis ranging from approximately five to eight years in most reports and many individual cats surviving well beyond ten years. These survival data reflect cats diagnosed at varying stages of infection and encompass the full spectrum of outcomes from rapid progression to prolonged asymptomatic carriage, emphasizing that an FIV-positive diagnosis is not an immediate death sentence but rather the beginning of a chronic condition requiring ongoing management.

Quality of life for FIV-positive cats during the asymptomatic carrier phase is indistinguishable from that of uninfected cats, and owners should be reassured that their cat can enjoy a full, comfortable, and active life during this period. Asymptomatic FIV-positive cats eat, play, groom, socialize, and behave entirely normally, and many complete their entire lifespan without ever developing clinical signs attributable to their infection. The key to maintaining this quality of life lies in consistent preventive health care, prompt attention to any emerging health concerns, and avoidance of unnecessary immune stressors. Regular veterinary examinations at intervals of six months rather than the standard annual schedule are recommended for FIV-positive cats to enable early detection of secondary infections, weight changes, dental disease, or laboratory abnormalities that might signal progression of immune decline.

Housing and management decisions for FIV-positive cats should balance infection control considerations against the cat's behavioral and social needs. Indoor confinement is strongly recommended for all FIV-positive cats, serving the dual purpose of preventing transmission to other cats through bite wounds and protecting the immunocompromised cat from exposure to environmental pathogens. The question of whether FIV-positive cats can safely cohabitate with FIV-negative cats in the same household is answered affirmatively by the accumulated evidence, provided that the social dynamics are stable and non-aggressive. In households where FIV-positive and FIV-negative cats live together without fighting, the risk of transmission through casual contact, shared food bowls, shared litter boxes, and mutual grooming is negligible. However, any introduction of new cats or disruption of social hierarchies that could precipitate fighting would create transmission opportunities and should be managed carefully.

The emotional and practical experience of caring for an FIV-positive cat is manageable for most dedicated owners and does not require extraordinary measures beyond the general principles of good preventive health care and vigilant observation. The financial implications of FIV-positive cat ownership include the cost of more frequent veterinary examinations, periodic laboratory monitoring, and potentially more frequent and more intensive treatment episodes for secondary infections as the disease progresses over years. Owners benefit from education at the time of diagnosis about the expected disease course, the signs that should prompt veterinary contact, the management strategies that optimize long-term outcomes, and the realistic expectations for their cat's lifespan and quality of life. Support from veterinary teams who approach FIV management with expertise and optimism helps owners navigate the challenges of caring for a chronically infected cat while appreciating the years of good-quality companionship that FIV-positive cats can provide.

Prevention of FIV infection is achievable through practical management strategies that target the primary transmission route of bite-wound inoculation during aggressive encounters between cats. Neutering of male cats substantially reduces roaming behavior and inter-male territorial aggression, directly decreasing the frequency of bite-wound exchanges that transmit the virus. Population-level neutering programs that achieve high sterilization rates in free-roaming and feral cat colonies reduce the overall prevalence of aggressive encounters and consequently lower the transmission pressure within the colony. Indoor confinement eliminates exposure to potentially infected outdoor cats and removes the primary risk scenario for FIV acquisition. For cats that must have outdoor access, supervised outdoor time in enclosed spaces such as catios, screened porches, or leash walks provides environmental enrichment without exposure to aggressive encounters with unfamiliar cats.

A killed adjuvanted FIV vaccine was commercially available in the United States from 2002 until its manufacturer discontinued production, and no FIV vaccine is currently on the market in North America. The vaccine generated significant controversy during its availability because vaccinated cats developed antibodies that were indistinguishable from infection-induced antibodies on standard screening tests, creating diagnostic confusion in which vaccinated cats could not be reliably differentiated from infected cats using routine testing. This interference with diagnostic testing was considered a significant drawback that complicated shelter medicine, where rapid FIV screening is a standard component of intake processing. Research into novel vaccine platforms that might provide protective immunity without generating diagnostic interference continues, but no replacement product has reached the market.

Testing and segregation of FIV-positive cats from naive populations in shelter, cattery, and multi-cat environments represents an important institutional prevention strategy. Routine FIV screening at shelter intake identifies infected cats and allows placement decisions that protect both the infected individual and the uninfected population. In catteries and breeding facilities, exclusion of FIV-positive cats from breeding programs prevents vertical transmission and maintains the FIV-negative status of the colony. Trap-neuter-return programs for feral colonies should include FIV testing to monitor colony prevalence, with the understanding that removal of infected cats from managed colonies is not universally recommended and must be weighed against the welfare implications and practical limitations of such interventions.

Veterinary consultation should be sought promptly whenever an FIV-positive cat develops new clinical signs or when a previously stable cat shows any deterioration in health, appetite, weight, activity level, or behavior. Specific signs warranting urgent evaluation include the development of oral pain manifesting as drooling, difficulty eating, or reluctance to groom; persistent or worsening upper respiratory signs including nasal discharge, sneezing, or labored breathing; skin lesions that fail to heal or that spread despite treatment; unexplained weight loss exceeding five percent of body weight; persistent fever; chronic or bloody diarrhea; any neurological abnormalities including seizures, behavioral changes, balance problems, or vision changes; and the discovery of any new lumps, masses, or lymph node enlargement that could represent neoplastic disease.

Cats of unknown FIV status should be tested following bite-wound incidents, prior to introduction into multi-cat households, at the time of adoption from shelters or rescue organizations, and as part of any diagnostic workup for chronic, recurrent, or unusually severe infections. Owners of FIV-negative cats with outdoor access or potential for contact with cats of unknown status should discuss periodic retesting schedules with their veterinarian to ensure that any new infection is detected as early as possible. All cat owners should understand that FIV is not transmissible to humans or to non-feline species, that FIV-positive cats can live fulfilling lives of normal or near-normal duration with appropriate care, and that a positive FIV diagnosis is a manageable chronic condition rather than a reason for despair or euthanasia.