Symptoms & Treatment of Feline Upper Respiratory Infect

Symptoms:

Conjunctivitis, nasal and ocular discharge, sneezing, oral and tongue ulcers, drooling, coughing, loss of appetite, depression, fever, lameness, and vascular diseases.

1. Feline Calicivirus (FCV):

A positivesense RNA virus, with a single serotype capable of harboring multiple strains, each with varying antigenicity and crossreactivity. It possesses a highly mutable genome, making vaccines largely ineffective (with the exception of vaccines targeting the two most primitive strains). FCV is a common cause of infectious mortality in kittens, typically seen from 1 to 14 days postinfection.

Transmission Routes: Airborne, contact, and contaminated surfaces; it can survive outside the body for 810 days, and sometimes up to 28 days.

Excretion: 100% of cats shed the virus for 30 days, 75% for 75 days, and 25% may shed it chronically. Due to the RNA nature of the virus, it is highly mutable, and vaccines are nearly useless. It's crucial to note VSFCV, a malignant strain that can lead to vascular diseases such as subcutaneous edema, distal limb swelling, and involvement of the ears, nose, mouth, and eyes. It can also cause jaundice, liver disease, vomiting, diarrhea, multiorgan failure, and vasculitis. It's important to remember that VSFCV can present with different wild strains, and routine testing may not diagnose it.

VSFCV:

Hematological Tests: Decreased protein, elevated total bilirubin, increased creatine kinase, neutrophils, anemia, and severe coagulation issues.

Autopsy: Severe pancreatitis, bronchopneumonia, necrosis of stem cells, lymphocytes, and spleen cells, and peripheral and systemic vasculitis.

Treatment: Fluid therapy, symptomatic treatment; Oseltamivir 2mg/kg, twice daily for 5 days; highdose interferon for 3 days; antibiotic therapy.

It's important to note that Oseltamivir can also be used for common FCV, and the first choice of antibiotic is doxycycline. VSFCV requires medical guidance, as parents cannot manage it on their own.

2. Feline Herpesvirus (FHV):

A doublestranded DNA virus that does not survive outside the body. Cats start shedding the virus from the first day of infection and can continue for 14 weeks.

Transmission Routes: Aerosols and contact. Severe cases can lead to nasal and pharyngeal necrosis. 80% of cats carry the virus, with 45% resolving symptoms spontaneously and harboring the virus in the trigeminal nerve. Stress can reactivate the infection, and corticosteroids can reactivate 45% of the virus. Pregnancy can reactivate 80% of the herpes virus in cats.

Feline herpesvirus is one of the weakest sources of upper respiratory infections. If your cat becomes infected (with symptoms like rhinitis), you must hope for the best, as the herpesvirus vaccine is almost meaningless. It may only produce one type of cellmediated or humoral immunity. If administered before the kitten is exposed to the virus, it can alleviate symptoms upon subsequent exposure. However, in reality, most kittens are infected with the herpesvirus within 10 days, carry it for life. This is why vaccines are so popular.

However, the prevalence of herpesvirus infections remains unchanged. Treatment: The only safe and effective systemic antiviral drug is valacyclovir (be very careful, do not misspell it; valacyclovir can cause liver and kidney necrosis, and bone marrow suppression). 90mg/kg, taken 23 times daily for 13 weeks. However, upper respiratory infections caused by herpesvirus are not primarily treated with antivirals. The breakdown of tissue cell integrity during herpesvirus outbreaks often leads to secondary bacterial infections, which are the real cause of persistent symptoms. Therefore, treatment should focus on antibiotics.

Antibiotics of choice are doxycycline, 10mg/kg, once daily for at least two weeks. If severe symptoms lead to loss of appetite, nutritional and fluid support, warm food, appetite stimulants (mirtazapine or lurasidone), intravenous fluid administration, and multivitamin B supplementation are recommended.

Be aware that amoxicillinclavulanate potassium, also known as Augmentin, and similar drugs are highly prone to resistance in upper respiratory infections. Therefore, they can be used to suppress the infection in kittens under 4 months of age, while doxycycline is the preferred choice for kittens over 4 months. If veterinary drugs become more available in the future, kittens can also be treated with piroxicillin. Currently, it is difficult to obtain. For severe ocular symptoms caused by herpesvirus, a slit lamp fundus examination is recommended, and veterinary guidance should be sought, especially for conditions like corneal ulceration and keratitis.

3. Bordetella bronchiseptica:

Shared between cats, dogs, rabbits, humans, and pigs, it causes persistent infection and shedding. This Gramnegative bacterium does not survive well outside the body and can be killed by extreme temperatures and pH levels. It can lead to lymphadenopathy, and treatment requires medical guidance.

4. Chlamydia:

A obligate intracellular bacterium that typically causes conjunctivitis and persists in a carrier state. Due to its systemic nature, doxycycline 10mg/kg once daily for 68 weeks is recommended.

5. Mycoplasma:

Common and difficult to diagnose, often requiring PCR for detection. If mycoplasma is isolated from the lower respiratory tract or asthma, it is generally diagnosed as the cause. Treatment is doxycycline for 28 days, 10mg/kg, once daily.

6. Pasteurella multocida:

Can cause secondary infections due to foreign bodies or narrowing of the respiratory tract, and is more common in flatfaced cat breeds. If flatfaced cats have symptoms like a few sneezes, treatment may not be necessary.

When discussing feline upper respiratory infections, it's important to note that vaccines have little effect on herpes and calicivirus. Therefore, during antibody testing, focus on feline distemper virus antibodies. Over the years, this has not affected profitability, so the calicivirus vaccine still targets the two oldest strains. Herpesvirus itself does not have a significant impact, unlike human influenza vaccines, which are updated in realtime. A word of complaint: cats may be considered less valuable, which is why vaccines are still popular.

Then, doxycycline is widely used in upper respiratory infections not only for its antibacterial properties but also for its immunomodulatory effects. Therefore, even if drug resistance is detected in sensitivity tests, it should still be used due to its immunomodulatory effects. The reasons are: 1) immunomodulatory effects, and 2) the low dosage in sensitivity tests is not sufficient to prove its ineffectiveness in routine treatment.