13264 Pond Springs Road

Austin, Texas 78729

(512) 258-2024 - Voice 

FELINE RETROVIRUSES

The feline retroviruses have earned a rather dubious reputation for their ability to leave infected cats with an array of  physical ailments.  Feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV), for example, can affect virtually every organ.  Immune-compromised cats are more susceptible to opportunistic infections and subcutaneous neoplasms.

 The oncovirus subfamily, which includes FeLV and feline sarcoma virus (FeSV), is distinguished by its ability to transform cells and produce neoplasia.  The lentivirus subfamily is not oncogenic but produces an array of chronic progressive diseases, including acquired immunodeficiency syndrome in humans.  Both FeLV and FIV are immunosuppressive.  All retroviruses replicate in host animals in the same manner.  The key to their ability to outmaneuver the immune system lies in their capacity to integrate DNA into the genome of infected cells.  When the host cell replicates its own DNA it also repicates the viral DNA.  As the host cell translates its DNA into proteins, the viral DNA is translated to produce precursor viral proteins that are further processed and assembled into virons which are then released fromt eh cell.

 Feline leukemia virus is abundant in the saliva of viremic cats and transmission occurs predominantly by contact with saliva and nasal secretions.  After it is released into the environment, FeLV typically survives less than two hours, unless it is deposited in a moist environment, such as a water or food dish, that allows the virus to survive longer.  In comparison, FIV is transmitted directly from cat to cat, usually as a result of aggressive behavior.  Although FIV has been isolated from saliva, blood, serum, plasma, cerebrospinal fluid, and semen, it is most readily transmitted through bite wounds.  Therefore intact male cats are most commonly infected.

 Categories of FeLV-infection

1.      “Progressive infection” – characterized by persistent viremia and antigenemia and viral shedding.  30% of all exposed cats.  Can become clinically ill within weeks of the onset of viremia.  Younger cats tend to become ill more quickly and often die during this early period.  Category 1 cats become leukopenic and acutely immunosuppressed.  Less immunosuppressive isolates tend to produce only transient immunosuppression before infected cats enter a latency period.  During this time, leukocyte numbers return to normal for months to years before ultimately decreasing again.  After the latency period, cats become immunosuppressed and can develop clinical signs, such as weight loss, gingivitis, stomatitis, persistent diarrhea, and various opportunistic bacterial and viral infections, including cutaneous infections

2.      “Regressive infection” – self-limiting.  60% of exposed cats.  Contain the virus and develop immunity, although approximately 30 – 40% have latent provirus in some cells.  The risk of these cats developing reactivated infection is considered low.

3.   Category 3 experiences transient viremia, usually lasting only days, before they revert to either category 1 or 2 (more common)

4.      “Atypical or sequestered infection” – 5 – 10% of exposed.  Incomplete containment of the virus, leading to low-level or intermittent antigenemia and viral shedding.  Eventually reverts to category 2 or 1.

 Stages of FIV infection

Cats infected with FIV infection remain infected.  There is no containment of the virus

1.      Acute viremia – Can last from weeks to months before progressing.  Symptoms vary from mild to severe

2.      Latency – Can last several years and cats show no obvious clinical signs but can still transmit FIV to other cats

3.      Clinical reappearance – Cats again exhibit clinical signs although often to a greater extent than in phase 1.  This is often when many owners first consult a veterinarian

4.      Terminal illness – Cats often suffer from more frequent and severe infections.  Neoplasms may be discovered and more extensive neurologic signs may develop

Coinfection with both viruses can occur, producing a rather marked synergism that increases the severity of immunosuppression and onset of clinical disease.

For additional information, please e-mail kpercival@cathospitalofaustin.com.

Number of Times this Page has been Viewed