Feline Viruses

Feline Viruses

• Feline Viruses includes FIP lecture regarding cat breeds, history, physiology and health, plus Feline Parvovirus is similar to dog parvovirus.

Feline Calicivirus

• A highly contagious pathogen spreads through cat populations
• Virus prevalence: 25-40% of cats are infected in larger households or shelters.
• Virus prevalence: 50-90% infection rate within large colonies of cats.
• Virus prevalence: less than 10% infection rate in small cat households.
• A +ve single-stranded RNA virus enabling rapid mutations.
• It is difficult to develop long-term protective immunity.
• Infection occurs via oral, nasal, or conjunctival routes.
• The primary infection route is through the oropharynx.
• Transient viremia (virus in blood) lasts 2-4 days.
• Virus is later found in distant tissues
• The virus kills epithelial cells, resulting in epithelial cell necrosis.
• Tongue, mouth, eyes, lungs, and synovial membranes (joints) are affected.
• Vesicles (blisters) initially appear on the tongue and rupture into ulcers.
• Tissue healing takes 2-3 weeks post-injury.
• Most acute infections lead cats to recover within 30 days.
• Some cats shed the virus for life.
• The virus is localized in palatine tonsils, but tonsillectomy will not clear it.
• Clinical signs include acute oral and upper respiratory tract disease.
• Disease manifestation depends on the animal's health, age, husbandry, and the virus's virulence (infectivity).
• Often appears in kittens.
• Symptoms include sneezing, watery eyes, coughing, and lethargy.
• In some cases, it can lead to Calicivirus Pneumonia
• Limping syndrome causes transient lameness in cats.
• Limping occurs a few weeks post-acute infection or after vaccination.
• Eye problems includes ulcers of the cornea.
• Can also cause inflammation of the conjunctiva and excessive tearing.
• Chronic stomatitis symptoms includes chronic inflammation of the mouth caused by an immune-mediated problem (autoimmunity) and large amounts of lymphocytes invading the tissue.
• Highly Virulent Feline Calicivirus, a new disease described in Europe and the USA within the last decade.
• The disease infects adults more than kittens and is characterized by systemic inflammatory response syndrome (hyperinflammation).
• It can cause disseminated intravascular coagulation (DIC) and multi-organ failure.
• The mortality rate is around 67% of incidence.

Calicivirus Diagnosis & Management

• Diagnose by virus isolation.
• Serology requires that all cats who test positive should be considered carriers.
• Molecular techniques includes PCR to detect single copy of the virus's nuclear material.
• Management includes supportive care for acute upper respiratory disease
• NSIAD (ketoprofen) or ibuprofen-like drugs can treat discomfort.
• Antibiotics for secondary bacterial infections.
• Antivirals are either toxic or unavailable.
• Vaccination is very important and effective; all healthy cats should be vaccinated.
• When managing the virus in shelters, always vaccinate new arrivals.
• Disinfect with a 5% bleach solution as the virus can survive for 1 month in the environment.
• In catteries, vaccinate queen and kittens.

Feline Leukemia Virus

• It is gamma-retrovirus infecting domestic and wild cats like lynx.
• The retrovirus is an enveloped RNA virus with four subtypes: A, B, C, and T.
• Subtype A is involved in every infection.
• The virus doesn't survive well in the environment (heat, disinfectants, and drying destroy it).
• It can live in moist areas and easily transmit from cat to cat, or iatrogenically via contaminated needles, surgical equipment, or blood transfusions.
• Infections have been identified worldwide and depends on cat population density.
• Prevalence is less than 1% in individual cats.
• Prevalence is over 20% in unvaccinated multiple-cat households.
• Viremic cats are the source of that infection and the virus sheds in saliva, milk, nasal secretions, and feces.
• Transmission occurs through friendly contact like grooming and bites.
• Pregnant queens may experience stillbirth/abortions, or viremic kittens may succumb to illness quickly in utero or during nursing.
• Infections typically start in the oropharynx.
• Virus infects lymphocytes that travel to the bone marrow, leading to rapid marrow cell division and viremia.
• With large amounts of virus present, it infects salivary glands and the intestine, shedding virus in saliva and feces.
• Some cats develop protective immunity, while others persistently infected develop the disease, leading to death within 18 months to 3 years.
• Immune suppression occurs when granulocytes (neutrophils) and lymphocytes are infected by the virus, impairing or destroying them.
• Diseases caused by the virus lead to leukemia and lymphoma.
• These disorders involve the Thymic, Alimentary tract, peripheral form (multi-centric lymph nodes)
• Extra-nodal locations includes: non-lymph node sites (skin, kidneys, brain, etc.) and odd tumors (fibrosarcoma).
• The virus can cause Lymphoma in the thorax, skin, and intestinal lymph nodes and is non-regenerative.

Feline Leukemia Virus Disease Management

• Diagnose by:
• Elisa test for antibody to p27
• Immunochromatography and immunofluorescence.
• Virus isolation with molecular techniques includes PCR
• Includes separating infected cats from uninfected ones.
• Test and remove all virus-positive cats in multi-cat households or in catteries.
• Preventing exposure by keeping cats indoors
• Supportive care includes antibiotics for secondary bacterial infections.
• Blood transfusions and stimulating agents (erythropoietin to stimulates red blood cell production) can aid anemic animals
• Antiviral agents are not very effective
• Vaccination can be administered (but is not 100% successful).

Feline Immunodeficiency Virus (FIV)

• It is a retrovirus (Lentivirus) closely related to HIV and has 5 subgroups (A-E)
• Subtypes A and B are most common.
• Subtype important for PCR diagnosis.
• FIV mutates rapidly, resulting in variability and making it hard to mount and effective immune response.
• First discovered in 1986 and is endemic worldwide in domestic cats.
• Infects sick, male, and roaming cats most often.
• Most often transmitted by oronasal and venereal spread.
• Though less common, can be tramitted vertically from mother to kittens (70% of fetuses via in utero) and via nursing
• The infection often appears later in life (4-6 years).
• Pathogensis targets CD4 T cells and macrophages/dendritic cells which directs/orchestrates immune responses.
• Macrophages can initiate immune functions and destroy pathogens and involved in healing.
• gp120 binds to CD 134 protein on CD4 T cells to invade the cells.
• Virus part (proviral genome) integrates into host cell genome in period of latency upon cell activation, produces virus, which is thus hard for immune system to remove

FIV Pathogenesis & Clinical Signs

• Initially replicates in CD4 T cells, macrophages, and dendritic cells.
• Identifiable in blood (viremia) after 2 weeks but can also experience peak infection 8-12 weeks post-exposure, leading to anorexia, fever, and depression.
• Following this the cat recovers with enlarged lymph nodes for up to several months.
• Enters asymptomatic phase, where cats remain healthy or could slowly lose CD 4 T cells or develop macrophage dysfunction.
• Immunological impairment includes AIDS or acquired immunodeficiency syndrome that could lead to death.
• Most clinical signs causes secondary infection leading to sickness, such as bacteria, fungal or viral infections
• Tumors can develop (lymphosarcoma, bone marrow cell hyperproliferation).
• In rare cases, FIV can induce brain injury itself; behavioral changes, seizures, and changes in sleep patterns can occur.
• Clinical signs and symptoms that can manifest include stomatitis, as well as Hemorrhagic necrotizing enteritis-intestinal injury with bleeding and mucosal sloughing

FIV Disease Management

• Diagnose via:
• Virus isolation
• Molecular techniques: PCR
• Serology for detection of antibodies for FIV
• T cell function tests
• By Decontamination, the virus can only survive minutes outside the animal and disinfectants can destroy it
• Isolation is primary protection.
• Isolation keeps the FIV cat safe from pathogens via isolation.
• Multi-cat households require well-adjusted cats to reduce bite wounds and isolated/terminate positive animals.
• Shelters should test all sick cats and terminate positive animals due to possibly feral or aggressive behaviours
• Breeding catteries should rarely occur, if so new cats must be tested before entering. In this case quarantine the cats for up to 3 months as a possibility
• Routine health checks
• Consider neutering infected male cats to help stop aggression and roaming
• Offer Supportive treatment for nursing care and antibiotics.
• Administer Antiviral therapy for AZ, ADM 3100 (CXCR4 on T cells blocking drug), interferons
• Consider Vaccination

Test your knowledge of feline viruses, including Feline Calicivirus and Feline Parvovirus. This quiz covers prevalence, transmission, and related viruses. Learn about the factors influencing the spread of these infections in cat populations.