Feline Calicivirus Infection

Feline calicivirus (FCV) is a highly transmissible viral infection with a primary impact on cats. In recent times, a more potent strain known as virulent systemic feline calicivirus (VS-FCV) has emerged, giving rise to cat virulent systemic disease (VSD). This syndrome extends its deleterious influence across multiple organs and tissues, resulting in heightened fatality rates. With rich experience in the field, BioVenic has been actively involved in the research of FCV, working towards developing effective diagnostic solutions and vaccines.

Etiology

FCV belongs to the Caliciviridae family and is classified under the genus Vesivirus. It is an RNA virus with a high mutation rate, resulting in genetic diversity among FCV strains. This genetic variability plays a significant role in the virulence and clinical manifestations observed in infected cats. FCV has a global distribution, affecting domestic and wild felids across different regions.

Fig.1 Schematic diagram of the open reading frames and genome structure of FCV.^1,2

Susceptible Animals

The primary host of FCV is domestic cats, especially young cats with low immunity. FCV can infect cats of all ages, breeds, and health statuses. However, it's important to note that FCV can also infect other members of the Felidae family, including wild felids such as lions, tigers, and cheetahs.

Transmission

The predominant means of FCV transmission involves direct contact with infected cats, encompassing exposure to nasal and oral secretions, saliva, and urine. Additionally, indirect transmission can occur through contaminated objects like food bowls, bedding, and grooming tools. Aerosol transmission of the virus is also a viable route, especially in densely populated environments.

Risk Factors of FCV Infection

Various risk factors can contribute to the spread and severity of FCV infection, including,

• Overcrowding: Higher population density increases the likelihood of transmission in multi-cat households or shelter environments.
• Poor Hygiene Practices: Inadequate cleaning and disinfection of living areas, litter boxes, and communal spaces can facilitate viral persistence.
• Lack of Vaccination: Failure to adhere to appropriate vaccination schedules leaves cats vulnerable to infection.
• Stress and Immunosuppression: Cats experiencing stress or those with weakened immune systems are more susceptible to severe forms of FCV infection.

Pathogenesis

FCV exhibits a pathogenic mechanism involving various aspects. The oropharynx serves as the primary site for viral replication, with transient viremia occurring a few days later, allowing the virus to spread to different tissues. FCV induces necrosis of epithelial cells, resulting in the formation of vesicles and subsequent ulcers, particularly on the tongue. FCV can affect not only the oral cavity but also other tissues such as the lungs and joints.

VS-FCV strains are rare but cause severe disease, including vasculitis, multiorgan involvement, and high mortality rates. The pathogenesis of VS-FCV remains unclear, potentially involving viral evolution, immune-mediated components, and environmental or management factors.

Signs and Symptoms

Clinical signs linked to FCV infection exhibit variability in both severity and duration. Typical symptoms encompass painful oral ulcers affecting the tongue, gums, and oral mucosa. Additionally, upper respiratory tract signs such as sneezing, nasal discharge, coughing, and conjunctivitis are common. Lameness and joint pain may manifest due to joint inflammation, resulting in limping and reluctance to move. Systemic signs include fever, anorexia, lethargy, and depression.

Diagnosis

Laboratory diagnosis is the most accurate method for identifying respiratory symptoms caused by FCV, feline herpesvirus, Chlamydia felis, and other pathogens. We possess the expertise to offer comprehensive diagnostic kit development services for FCV, ensuring robust specificity and high accuracy in our solutions.

• Virus Isolation: FCV can be isolated and cultured in specialized laboratory settings.
• RT-qPCR: This technique is employed to detect FCV genetic material, confirming the presence of the virus.
• Indirect ELISA: Indirect ELISA is effective in detecting antibodies against FCV, indicating exposure to the virus.
• Veterinary Colloidal Particle-based Immunoassay: This method is capable of detecting the FCV antigen in the sample.

Treatment

Though no specific antiviral therapy exists for FCV, effective management of clinical signs and recovery promotion relies on supportive care. Treatment options encompass,

• Pain Relief: Administering analgesics to alleviate pain associated with oral ulcers and joint discomfort.
• Hydration and Nutrition: Ensuring sufficient fluid intake and offering palatable, easily digestible food.
• Antibiotics: Prescribing antibiotics to address potential secondary bacterial infections arising from compromised immune defenses.

Prevention and Control

Preventing FCV infection is crucial in maintaining feline health and minimizing its spread. Effective prevention and control strategies include,

• Vaccination: Regular vaccination using suitable vaccines plays a pivotal role in mitigating the intensity and duration of clinical symptoms. At BioVenic, we specialize in the development of advanced FCV vaccines meticulously crafted to deliver optimal protection against the virus.
• Hygiene Practices: Regular cleaning and disinfection of living areas, litter boxes, and grooming tools can help limit viral persistence and transmission.
• Isolation and Quarantine: Separating infected cats from healthy individuals, especially in multi-cat environments, prevents the spread of FCV.

At BioVenic, our commitment to feline health drives us to continually improve our understanding of FCV and help animal health researchers develop innovative diagnostics solutions. Additionally, through continued research and development of advanced vaccines, we work to protect cats from the devastating effects of FCV. If you need our technical support, please feel free to contact us.

References

1. Hofmann-Lehmann, Regina, et al. "Calicivirus infection in cats." Viruses 14.5 (2022): 937.
2. Image retrieved from Figure 2 "(A) Genomic organisation of FCV genomic RNA with open reading frames (ORF) 1 to 3, (B) Schematic representation of the viral structure of FCV." Hofmann-Lehmann, Regina, et al., 2022, used under [CC BY 4.0], the image title was changed to "Schematic diagram of the open reading frames and genome structure of FCV."