Sneezing, Wheezing, Mucus, Chronic Respiratory Disease in Cats, Try Doxycycline

Symptoms of Upper Respiratory Disease (URI)
Cats with Upper Respiratory Disease (URI) look ill. They have nasal mucus, sneezing, loud breathing, and frequently have poor appetites. Many lose weight. They may become constipated, with small, firm stools because they aren’t eating or drinking normally. Because cats with URI don’t feel well, they don’t groom themselves; their coats become unkempt, often oily with dander.  Fur on the face may matt around the eyes and nose.

 Why are cats prone to develop URI?

Unfortunately, several diseases infect cats affecting their lungs, sinuses, eyes, and nose:

• Feline Herpes Virus (FHV)
• Feline Immunodeficiency Virus (FIV)
• Chlamydophila
• Mycoplasma

Feline viruses weaken the immune system and make it easy for bacteria, chlamydia, and mycoplasma to invade. These viruses are exceptionally difficult to eradicate and once infected, many cats are infected for life. Viruses can safely escape the immune system because they hide within the cat’s cells. Intracellular viruses remain quiescent until the cat is stressed, at which time they multiply with a flourish, reappear, and cause URI, ocular, and systemic symptoms.

Antiviral Drugs Famciclovir and Azidothymidine

Two antiviral drugs have been researched in cats. The antiviral drug famciclovir may help clear FHV, but does not improve the cat’s respiratory symptoms. The antiviral drug Azidothymidine (AZT) may cause severe side effects so it has not been used to treat viruses causing respiratory disease.

Antibacterial Drugs: Doxycycline, Amoxicillin-clavulanic acid, Pradofloxacin, Cefovecin

Doxycycline is the best antimicrobial medication for cats with chronic URI because it eliminates mycoplasma and has some anti-inflammatory benefit that soothes respiratory cartilage. Amoxicillin-clavulanic acid and azithromycin both clear chlamydia, but do not have anti-inflammatory effect  to soothe the damaged respiratory cartilage. If the infection were acute rather than chronic, amoxi-clav would be a wise choice.

Pradofloxacin clears mycoplasma but takes six weeks of treatment to clear 75% of cats of chlamydia, and extended use may have serious, even life-threatening side effects; Pradofloxacin is not a wise choice for most cats. Cefovecin, although a convenient antibiotic because it only needs to be given once rather than daily for two or three weeks, is not effective against chlamydia or mycoplasma respiratory infection.

Precautions and Potential Concerns with Doxy

The good news is that when cats with chronic URI are given doxycycline for two weeks, a mycoplasma infection clears completely. The bad news is that doxy must be given once or twice a day for two weeks.

Doxy should be given as a suspension, mixed with a delicious flavouring agent, and should not be given as a tablet unless the cat swallows water or food immediately after being medicated. Fluoroscopic studies of cats swallowing pills has shown that the majority of the time, the pill remains in the lower esophagus and does not travel on to the stomach. Left in the esophagus, doxycycline (and the other forms of tetracycline) erodes the mucosa leaving an esophageal ulcer. The ulcerated area heals with scar tissue that constricts the esophagus. Cats with esophageal strictures have difficulty swallowing, lose weight, and waste away. Avoid esophageal ulcers and strictures by medicating with doxy compounded as a liquid or by ensuring the cat swallows water or food immediately after being given doxy tablets.  

 

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