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Feline Calicivirus (FCV) has host specificity for feline animals and has not yet been found to have zoonotic potential. As an RNA virus, FCV exhibits significant genetic plasticity in feline populations. The viral RNA relies on the low fidelity and high error rate of RNA polymerase, making it highly susceptible to mutations during replication, resulting in the emergence of multiple new strains. Feline calicivirus (FCV) is a viral respiratory infectious disease caused by feline calicivirus, belonging to the genus Calicivirus in the family Calicividae. The virus is resistant to lipid solvents, stable at pH 4-5, and can be inactivated at 50 ℃ for 30 minutes. It often occurs in kittens, with high incidence rate and low mortality. The virus is transmitted through the secretions of sick and infected cats, with asymptomatic infected cats being the main source of infection. The host range is limited to feline animals, and kittens are susceptible. The virus reproduces within the host cytoplasm and can form crystalline structures. The clinical manifestation is upper respiratory tract infection, with a latent period of 2-3 days. ccurate diagnosis is critical for disease management, with serological assays utilizing the Feline Calicivirus Antigen—typically the recombinant VP1 capsid protein—playing a central role in the sensitive detection of FCV-specific antibodies.
Figure 1. Two general models for calicivirus genome organization.
| Host Cellular Process / Pathway | Key Host Genes / Factors Involved | Mechanism & Role in FCV Pathogenesis |
| Innate Immune Evasion (Interferon Antagonism) | MDA5, IRF3 | FCV actively suppresses the host's type I interferon (IFN) response. The virus can inhibit the signaling cascades initiated by cytoplasmic RNA sensors (MDA5/RIG-I), preventing the activation of IRF3 and subsequent IFN-β production. It also interferes with JAK-STAT signaling, impairing the nuclear translocation of STAT1/STAT2 and blocking the expression of interferon-stimulated genes (ISGs). |
| Inflammatory Response & Tissue Damage | TNF-α, IL-1β, IL-6 | Infection activates the NF-κB pathway, leading to a potent but often dysregulated production of pro-inflammatory cytokines (TNF-α, IL-1β, IL-6). This "cytokine storm" is a key driver of systemic inflammation, vascular leakage, and the severe tissue damage seen in VS-FCV infections, including widespread edema and organ failure. |
| Cellular Stress & Death Pathways | PERK, eIF2α | The massive synthesis of viral proteins induces Endoplasmic Reticulum (ER) stress, activating the PERK-eIF2α-ATF4-CHOP axis of the Unfolded Protein Response (UPR). Sustained ER stress can push cells towards apoptosis, executed by caspase-3/7. FCV may modulate the timing of this response to benefit its replication cycle. |
Feline Calicivirus is a positive stranded single stranded RNA belonging to the Vesivirus genus of the Caliciviridae family. It has 32 cup-shaped capsids arranged on its capsid surface, hence the name calicivirus. Feline calicivirus is one of the main infectious disease pathogens in cats. Although feline calicivirus has rich antigenic differences and multiple strains, it is currently still a single serotype. FCV can survive for weeks to days at room temperature, months in low temperature and humid environments, and can be stored for a long time after freeze-drying. Not sensitive to organic solvents such as ether and chloroform. FCV cannot agglutinate red blood cells. Interestingly, FCV can grow on primary cells such as cat kidney cells and cat fetal lung cells, and can also proliferate on diploid cat tongue cell lines and thymocyte lines. Generally, it can cause pathological effects such as cell shrinkage, shedding, and aggregation into grape clusters or clustered cells within 48 hours.
| Etiology | Details |
| Cause of Disease | The main cause of feline calicivirus disease is FCV infection, which is non enveloped and has strong environmental stability. The virus is transmitted through direct contact with infected cats' saliva, nasal secretions, or pollutants, and can also rapidly spread in dense environments through aerosol routes. |
| Inducing factors | This includes environments with multiple cats (such as shelters, cat houses), weak immunity of kittens, lack of vaccination, stress events (such as transportation, environmental changes), and co infection with other pathogens (such as feline herpesvirus). |
| Pathogenesis | After FCV invades the body, it first infects oral and respiratory mucosal epithelial cells, and through the binding of viral capsid proteins to host cell receptors, initiates the replication process. Virus replication leads to cell lysis and local inflammatory reactions, causing oral ulcers and respiratory symptoms. In highly virulent strains of infection, the virus can enter the bloodstream, causing endothelial cell damage, leading to vasculitis, subcutaneous edema, and necrosis of multiple organs (such as the liver and pancreas), which can be life-threatening in severe cases. |
Feline Calicivirus disease has a high incidence rate in the global cat population, with an infection rate of 25% -40%, especially in multi cat environments. The intensity of epidemics is influenced by environmental factors such as temperature, humidity (viruses survive longer in humid environments), and cat population density. Kittens (<1 year old) and unvaccinated cats are high-risk groups, while vaccinated cats may alleviate symptoms but still be susceptible to infection and detoxification.
Figure 2. Classification of caliciviruses based on the nucleotide sequences of the complete capsid protein. (Nørrung, Birgit,et al, 2008)
Due to various factors such as differences in FCV strains, differences in host immune responses, and the presence of mixed infections, diseases induced by FCV infection often have multiple manifestations, including ulcerative diseases, gingivitis, claudication syndrome, and toxic systemic diseases.
Ulcerative upper respiratory disease is the most common type of disease caused by FCV infection, with clinical symptoms including oral ulcers, gingivitis, fever, and drowsiness. However, in more cases, FCV often forms mixed infections with feline herpesvirus (FHV), feline chlamydia, and feline mycoplasma, leading to upper respiratory tract diseases, and co infections can affect the presentation of clinical symptoms. Research has shown that FHV and feline chlamydia mainly cause eye diseases, accompanied by conjunctivitis and keratitis. In addition, FHV can reduce the clearance rate of lung mucosa and impair local immune defense, leading to the development of focal alveolar inflammation into exudative, proliferative, and interstitial pneumonia.
The characteristic of chronic FCV infection is the occurrence of chronic, progressive, plasma cell/lymphocyte proliferative or ulcerative gingivitis and stomatitis. Clinical symptoms may include bad breath, difficulty swallowing, excessive salivation, anorexia, and weight loss. At present, the cause of chronic gingivitis in cats is still uncertain, but there is evidence to suggest that viruses/bacteria are the main pathogenic microorganisms.
Another but relatively rare clinical manifestation caused by FCV is claudication syndrome, characterized by stiffness, mild joint pain, and muscle soreness. Some cases have appeared after receiving live FCV vaccines with modified strains, but claudication caused by vaccine strains is an accidental and rare event.
The treatment is mainly supportive therapy, without specific antiviral drugs.
Drug therapy includes broad-spectrum antibiotics (such as amoxicillin clavulanic acid) to prevent secondary bacterial infections, anti-inflammatory drugs (such as corticosteroids) to reduce inflammatory reactions, and interferons (such as feline interferon) to inhibit viral replication.
Support treatment includes intravenous rehydration to correct dehydration, nutritional support (such as high-energy liquid food) and oral care (such as chlorhexidine spray to alleviate ulcers).
Physical therapy such as fog chemotherapy can help alleviate respiratory symptoms. In severe cases, oxygen therapy and inpatient monitoring may be necessary.
The pathogenesis of feline calicivirus is a complex interaction between virus replication and targeted host cell manipulation. By hijacking entry mechanisms, antagonizing interferon signaling, inducing inflammation and cellular stress pathways, and reprogramming host metabolism, FCV creates an environment favorable for its transmission, while driving the immunopathology that leads to disease. Understanding these host centered mechanisms is key to developing more effective antiviral drugs and immunomodulatory therapies.
References
| Target | Cat. No. | Product Name | Host | |
| FCV | DAGC065 | Native Feline Calicivirus Antigen | FC 3TG Cells | Inquiry |
| DAG-WT5871 | Feline calicivirus (FCV) Stock (Qualitative) | N/A | Inquiry |
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