Kennel Cough could be one of the obvious possibilities.
Here is something I read about the condition from
Kennel Cough Prevention, Diagnosis, and Treatment | kennelcough.com
"Kennel cough is characterized by a dry, hacking cough often followed by gagging or coughing up mucus. Many people describe it as a hoarse sound or a loud "honking," which occurs because of laryngitis, or swollen vocal cords. Usually the coughing comes on in a sudden (acute) attack. Coughing can be induced when the dog becomes excited, exercises, or in response to changes in temperature or humidity. Nasal discharge is also a common finding in dogs with kennel cough. Usually dogs with mild cases of kennel cough are still active and maintain a good appetite, and usually don't have a fever. However in very severe cases, the symptoms may progress to include inappetance, vomiting, diarrhea, fever, lethargy, a moist productive cough, discharge from the eyes and nose, and exercise intolerance, and can even develop into pneumonia."
Hope this helps.
