FELINE IMMUNODEFICIENCY VIRUS

VetSuite Veterinarians
Infectious Diseases

Feline immunodeficiency virus (FIV) is a viral infection that affects the immune system of cats. FIV is a lentivirus, part of the retrovirus family of viruses. This virus was first isolated in 1986 but has probably been around much longer. FIV destroys T-lymphocytes, resulting in immunodeficiency. Syndromes associated with FIV can include infections, anemia, leukopenia, infections of the gums and mouth, cancer and neurologic disease. This disease is chronic and ultimately fatal. Infection is thought to be in anywhere from 1 to 14 percent of the cat population

DIAGNOSIS OF FELINE IMMUNODEFICIENCY VIRUS

ETIOLOGY AND RISK FACTORS

• Causes - FIV is an infectious disease that is spread from cat to cat, primarily by biting. FIV can be transmitted by the queen to her kittens through her milk. Transmission in household cats with normal contact is thought to be unlikely.
• Risk factors
• Age - Cats over 5 years of age are more at risk but cats of any age are susceptible.
• Breed/genetics - No known risk
• Sex - Male cats are predisposed, probably because of territorial fighting.
• Geographic/environmental - Prevalence is higher in areas with free roaming cats. Cats exposed to the outdoors or indoor healthy cats exposed to indoor/outdoor cats are at an increased risk for exposure.
• Other medical disorders - Co-infection with feline leukemia virus can occur.

• Prevention - Preventing infection is aimed at reducing risk. Cats should be kept indoors and fighting avoided between cats. Cats should be neutered to reduce fighting, and new cats should be isolated and tested. Recently, a vaccine has been developed to help reduce the risk of contracting FIV.

HISTORY AND CLINICAL SIGNS

• Species affected - Cats
• Presenting signs and historical problems - FIV has three stages of infection: The acute phase, which begins 4 to 6 weeks after exposure, is associated with infections, fever, and lymph node enlargement. The subclinical phase lasts from months to years at which time many cats appear healthy. The final phase, which also lasts from months to years, is associated with chronic infections and deterioration of the immune function.

PHYSICAL EXAMINATION FINDINGS

• General
• Attitude - Mental status can vary, depending on the stage of infection. Many cats have a normal attitude, but some may be depressed or even comatose.
• Body condition - Body condition can vary, depending on the stage of infection. In later stages, most cats have a poor body condition.
• Vital signs - Usually normal but fever may accompany infections. Tachycardia and increased respiratory rate may accompany anemia.
• Mucous membranes - Often normal but gum color may be pale if anemia is present.
• Hydration status - In later stages, dehydration may be present.
• Head and neck - In the acute and late phases, facial dermatitis, otitis and mandibular lymph node enlargement may be seen. In the late phase, purulent nasal discharge, associated with chronic rhinitis, may be seen.
• Eyes - Some cats may develop conjunctivitis. Uveitis, glaucoma and retinal hemorrhages may develop.
• Oral cavity - Stomatitis, gingivitis and periodontitis may be present in the acute and terminal phases.
• Thorax (cardio-pulmonary) - Heart sounds are usually normal but breath sounds may be abnormal. Pneumonia may develop, resulting in harsh breath sounds.
• Abdomen (gastrointestinal/urinary) - Diarrhea is common and may result in thickened bowel loops. Abdominal masses may be palpable since neoplasia may develop.
• Reproductive system - Infertility may occur. Intact females have an increased risk of developing pyometra.
• Lymph nodes - Generalized lymphadenopathy is common in the acute phase and in the late phase.
• Integumentary system - Dermatitis and abscesses may occur.
• Neurologic examination - Various behavioral changes can occur as the disease progresses. Dementia, persistent wandering, vocalization, twitching and seizures may occur.
• Musculoskeletal examination - In later stages of infection, muscle wasting and emaciation are common.

DIAGNOSTIC STUDIES

• Special examination techniques
• Thoracocentesis or paracentesis may be necessary for pleural effusion or ascites, respectively. Aspirated fluid should be submitted for cytology.
• Bone marrow biopsy may be indicated in cases of anemia.
• Cerebral spinal fluid (CSF) tap may be indicated with active neurologic disease. Evaluation of the CSF may demonstrate antibodies positive to FIV and increased protein levels and cell counts.
• Clinical laboratory tests
• CBC - A complete blood count is recommended to detect anemia, leukocytosis, leukopenia or thrombocytopenia.
• Serum biochemical tests - The biochemical profile is especially important if there are secondary or concurrent conditions. This test is usually normal with FIV.
• Urinalysis - Urinalysis is usually normal unless urinary tract infection is present.
• Serology/immunologic tests - There are several ways to diagnose FIV. The ELISA, IFA and Western Blot are the most common methods. The ELISA is used as a screening test and is up to 99 percent accurate. The IFA and Western Blot are performed in various laboratories. The IFA is about 99 percent accurate and the Western Blot is considered the gold standard and should be used to confirm positive ELISA or IFA tests.
  
  In addition to FIV tests, serology may be necessary to determine concurrent infection with toxoplasmosis, feline leukemia virus, feline infectious peritonitis and ehrlichiosis.
• Parasitology - Fecal examination should be performed to detect concurrent gastrointestinal parasite infection.
• Microbiology - Abscesses and suspected sites of infection should be cultured.
• Diagnostic imaging
• Radiographs (thoracic/abdominal) - Thoracic radiographs may be indicated if dyspnea is present. If abdominal palpation is abnormal, abdominal radiographs are indicated.
• Contrast radiography - Contrast radiographs are indicated in cases of gastrointestinal abnormalities, such as gastrointestinal ulcers or masses.
• Ultrasound (abdominal) - Abdominal ultrasound may be necessary for suspected concurrent abdominal abnormalities.
• Pathology
• Cytology (fluid or tissue) - Cytology of any aspirated fluid (thoracocentesis, paracentesis) should be performed.
• Biopsy/histopathology - Biopsy or fine needle aspirate cytology should be performed on any solid masses.

DIAGNOSIS AND PROGNOSIS

• Differential diagnosis - Other medical problems can lead to symptoms similar to those encountered in feline immunodeficiency virus. It is important to exclude these conditions before establishing a definite diagnosis.
• Anemia from other causes
• Feline ehrlichiosis
• Feline leukemia virus (FeLV)
• Feline infectious peritonitis (FIP)
• Infectious diseases such as those caused by fungal, bacterial, viral and parasitic organisms
• Hemobartonella felis
• Leukemia
• Lymphoma
• Myeloma
• Myeloproliferative disease
• Non-viral neoplastic disease
• Rocky mountain spotted fever
• Sepsis
• Systemic lupus erythematosus
• Thrombocytopenia
• Toxoplasmosis
• Recommended tests - ELISA and/or Western Blot, CBC and biochemical profile.
• Summary of diagnostic criteria - ELISA and/or Western Blot confirm the diagnosis of FIV. CBC and biochemical profile may reveal anemia, neutropenia, lymphopenia and dehydration.
• Prognosis - FIV is eventually a fatal disease, although most cats live for several years with the infection. Providing adequate nutrition and excellent health care can prolong the cat's life significantly.

TREATMENT OF FELINE IMMUNODEFICIENCY VIRUS

TREATMENT PRINCIPLES

Treatment of feline immunodeficiency virus must be individualized based on the severity of the condition and other factors. There has been no proven effective treatment for FIV infection.

INITIAL/HOSPITAL THERAPY

• Symptomatic therapy
• Antibiotics for bacterial infections
• Nutritional support
• Fluid therapy when required
• Parasite control
• Biopsy and removal of tumors
• Specific therapy
  A number of drugs used to treat humans with immunosuppressive diseases have been used empirically in cats. Drugs used may include:
• Alpha interferon (Roferon) may be effective for some cats as it may aid in reduction of viral replication. Some research suggests that it is associated with increased activity, increased appetite, improvement of hematologic abnormalities, clearance of virus and prolonged survival times.
• Immunomodulators could be beneficial in FIV-infected cats by restoring immune function. Examples include Propionbacterium acnes (Immunoregulin) and Acemannan (Carrisyn).
• Azothiouridine (AZT) is an antiviral drug that has been shown to abort experimental infection.
• Both AZT and 9-(2-phosphonylmethoxylethyl) adenine (PMEA) have been reported to reduce the severity of chronic mouth infections in affected cats.
• Bone marrow transplantation has been performed and is successful in resolving low neutrophil cell counts in some cases; however, the cats remain infected with the virus.

LONG-TERM/HOME THERAPY

All FIV infected cats should remain indoors to decrease exposure to other cats. Medications are often continued for the life of the cat.

FOLLOW-UP CARE

A test and remove program is a method to eliminate cats with positive infections in a cattery or a multi-cat household. The principles include:

• Do not bring any new cats into the household.
• Remove all FIV positive sick cats from the household. Quarantine all FIV positive cats to one area. They should have no contact with FIV negative cats. There should be entirely separate bedding, food dishes, food and water.
• Test all remaining cats for FIV.
• Disinfect all bedding, food and water dishes, and litter pans.
• Quarantine all FIV negative cats to one area. Retest these cats in 3 months. If the cats are negative, they are considered free of FIV.
• Quarantine all new cats; test, isolate for 3 months, and re-test at the end of the 3 months. Cats are considered free of infection with two negative tests 3 months apart.
• Retest the positive cats.
• Cats that test negative for FIV after testing positive on the first test should continue to be isolated. Re-testing is recommended in an additional 3 months.