From what you are describing, I am very concerned that your dog has pneumonia secondary to having Kennel cough. Let me explain a bit more...
Kennel Cough (Bordetella Bronchiseptica, infectious trachebronchitis) is a highly contagious cough. It is transmitted by saliva or through an aerosol when a dog coughs. With kennel cough, dogs have a cough that sounds like something is stuck in their throat, and after coughing a few times they have what is called a "terminal gag" which means that they sound like they are bringing up phlegm. If you watch closely, you will often see dogs swallow after this final gag - they are in fact swallowing phlegm. Some dogs will even cough up a puddle of clear, whitish, or slightly yellow mucoid fluid.
Kennel cough is highly contagious so dogs that have this should be kept isolated from other dogs for 2-3 weeks until it resolves. You asked if it would be contagious to your cats. The short answer to your question is YES kennel cough can be transmitted from the dog to your cats, and NO it doesn't happen very often.
Clinical signs of Bordetella infection aren't common in cats. Coughing and mild upper respiratory tract infection signs are typical (a lot like "kennel cough" with a little eye and nose discharge thrown in). Cats may also run a low grade fever. They usually get better without any treatment, and then would be immune for at least 6 months.
Unless your cat has health problems like feline leukemia or feline immunodeficiency virus, I would not expect her to have any serious health consequences on the off chance that she did catch this from your dog.
Most cases of canine kennel cough resolve without medications, but in some cases patients are put on antibiotics and/or cough suppressants. Antibiotics are used in dogs who are at risk for a secondary pneumonia (very young or very old dogs, or those with a suppressed immune system). Cough suppressants are used when the cough is so severe that the dog cannot sleep. There can be quite a bit of phlegm with kennel cough, and it is better that the dog DOES cough that up, rather than leave it in the lungs by suppressing the cough. However, there has to be a balance where it's possible for the dog and his human companions to sleep.
Amoxil is not my favourite antibiotic choice for kennel cough. Penicillins (like amoxicillin) do not penetrate well into the respiratory tract. Bordetella organisms attach to ciliated epithelial cells that line the trachea and bronchi. Many drugs do not attain therapeutic concentrations in respiratory secretions. It's not common to spread to pneumonia but as you've found out it does happen from time to time. So generally I find amoxil is a poor choice. Doxycycline (or tetracycline) and quinolones (such as enrofloxacin or ciprofloxacin) are better. Chloramphenicol has been used in the past and historical data shows good susceptibility. Macrolides (clindamycin, azithromycin) are worth checking into. Maybe the best treatment is nebulization with gentamicin or amikacin. Intratracheal injections with gentamicin have also been described.
Furthermore, your dog is on a fairly conservative dose of Amoxil. Here is more about this drugm including dose range:
And more about Baytril (enrofloxacin) which would be my first choice of drug to put her on:
So, in summary, from what you are describing, I am very concerned that your dog has pneumonia. If she came in to my clinic and we did not have to worry about money at all, I would recommend blood work and x-rays to see what is going on with her chest. If these tests supported a diagnosis of pneumonia, I would start her on Baytril and possibly nebulize her (using an inhaler and mask) with gentamicin if she was in serious condition. This could be done at home. I do think it is very important to get her seen by a veterinarian as soon as possible! If you are in a time zone where a vet is open, it would be best to have her seen tonight as I do feel she is quite sick!
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