Feline Immunodeficiency Virus Infection

Feline immunodeficiency virus (FIV) is an important pathogen infecting feline. It was first isolated from domestic cats in California, USA in 1986. Since then, different branches of FIV have been reported all over the world. BioVenic has been studying the etiology and pathogenesis of FIV and has formed a unique understanding of FIV. Our team is highly skilled in creating innovative diagnostic methods and kits, and comprehensive preventative solutions for our clients.

Etiology

FIV is an RNA virus belonging to the Retroviridae family and the Lentivirus genus and has many similar characteristics to HIV. FIV is round or oval with a capsule and a diameter of about 105-125 nm. FIV genomic RNA is about 9.5 Kbp in length, with long terminal repeats (LTRs) of about 355 bp in length at both ends. FIV has three main open reading frames (ORFs), gag, pol, and env. In addition, FIV also contains several small ORFs, which are related to the expression and replication of viral genes.

Fig. 1 Schematic diagram of the Gag protein of FIV and the structure of the virus.¹

Prevalence of FIV in the United States

The prevalence of FIV in the United States varies across different regions and populations of cats. According to studies and veterinary data, it is estimated that approximately 2-4% of healthy cats in the general population are FIV-positive. However, in high-risk populations, such as outdoor and stray cats, the prevalence can be significantly higher, ranging from 15% to 20%.

Susceptible Animals

FIV naturally infects more than 20 species of cats. While FIV primarily affects domestic cats, some wild felids, such as lions, pumas, and bobcats, are also susceptible to FIV infection. However, the virus strains that infect these species are different from the strains affecting domestic cats. FIV-Ple infected lion, FIV-Fca infected domestic cat, FIV-Pco infected puma.

Transmission

FIV primarily spreads through aggressive encounters, such as fighting and biting, among cats. Key risk factors for FIV transmission encompass an outdoor lifestyle, intact male cats, and involvement in territorial disputes. It's important to note that casual contact, sharing food bowls, and grooming do not pose a significant risk of transmission.

Does FIV Positive Mean Feline AIDS?

FIV infection does not automatically lead to feline-acquired immunodeficiency syndrome (FAIDS), the terminal phase of FIV infection. Not all FIV-positive cats advance to FAIDS, and some may remain asymptomatic for extended periods. The disease progression varies among individuals and generally unfolds through acute, asymptomatic, and FAIDS stages.

• In the acute stage, cats may exhibit mild clinical signs such as fever and lymphadenopathy.
• The subsequent asymptomatic stage is characterized by infected cats showing no apparent signs of illness.
• The FAIDS stage is marked by the development of severe immunodeficiency, leading to a spectrum of opportunistic infections and malignancies.

Pathogenesis

The pathogenesis of FIV is not yet fully understood. Following infection, FIV causes a transient attenuation of CD4 antigen expression and syncytium formation in T4 cell cultures, whereas persistent infection causes a progressive attenuation of major histocompatibility complex type I (MHC I) antigen expression. As a result, the body's immune system is dysfunctional, the body's ability to resist various infectious agents is reduced, and a series of clinical symptoms appear.

Furthermore, FIV infection of the central nervous system (CNS) results in neuropathy, yet the histological examination of the brain typically reveals mild findings. This is characterized by scattered or focal microglial lesions and vascular cuffs.

Fig. 2 Schematic diagram of the inflammatory response and pathogenesis caused by FIV.²

Signs and Symptoms

Clinical signs of FIV infection can include,

However, it is important to note that some infected cats may not exhibit any symptoms initially.

Diagnosis

Due to the similarity of symptoms between FIV infection and various other feline illnesses, its diagnosis can be challenging. Immunodiagnostic techniques play a crucial role in detecting antibodies associated with the disease. Antibody detection is commonly conducted through methods such as ELISA, immunofluorescence assay (IFA), and immunospot. In the event of a positive antibody test, molecular diagnostic techniques like RT-PCR can be employed to further validate the diagnosis. Conversely, if the antibody test yields negative results, a combination of virus isolation and RT-PCR can be utilized for conclusive identification.

Relying solely on the detection of the virus or its antibodies is not sufficient for a conclusive diagnosis. The extended incubation period of the disease often means that cats with positive antibodies may not exhibit symptoms throughout their lifetime. Moreover, the presence of FIV antibodies can also be detected in cases where other viruses, such as poxvirus, are present. It's noteworthy that the antibody levels in the late stages of FIV infection are frequently very low and may escape detection. Consequently, a comprehensive approach is essential for diagnosing this disease. We offer tailored and effective veterinary diagnostic solutions to meet your specific needs.

Treatment

Currently, there is no efficacious drug available for the treatment of this disease. The approach to managing FIV-infected cats exhibiting clinical symptoms focuses on controlling secondary infections and alleviating symptoms.

• Immunomodulators can be used to ameliorate immunosuppressed conditions.
• Antibiotics prevent further infection by secondary and opportunistic microorganisms.
• Surgery can temporarily relieve symptoms such as chronic stomatitis and gingivitis.

Cats infected with FIV, if they get appropriate treatment, can prevent the occurrence of other diseases and ensure a high quality of life, most of them survive for a long time.

Prevention and Control

Prevention of this disease mainly includes the following measures,

• Minimize the number of stray cats and sterilize stray cats infected with FIV.
• Reduce the amount of time your cat spends outside.
• Prevent biting and fighting between cats.
• Keep the cat's feeding environment and eating utensils clean and disinfected frequently.
• Avoid using communal eating utensils.
• Cats with FIV should be isolated from healthy cats to prevent transmission.

Vaccination against FIV is available but has limitations and is not universally recommended. Careful consideration should be given to vaccination based on individual risk factors and geographic prevalence. If customers need it, we provide customized and innovative anti-FIV vaccine development services.

As a leading company in the field of veterinary diagnostics, BioVenic is committed to researching and developing innovative solutions to combat FIV. We aim to advance diagnostics kits, treatment options, and preventive vaccines to improve the management of FIV-positive cats. If you need more information, please feel free to contact us.

References

1. Long, Mathieu, et al. "Review and perspectives on the structure-function relationships of the gag subunits of feline immunodeficiency virus." Pathogens 10.11 (2021): 1502.
2. Meeker, Rick B, et al. "Feline immunodeficiency virus neuropathogenesis: A model for HIV-induced CNS inflammation and neurodegeneration." Veterinary Sciences 4.1 (2017): 14.