These two conditions have a common cause and thus often occur together. In fact, sore throats usually do not occur in dogs as isolated infections, the way they do in people. Most sore throats are associated with infections in the mouth, sinuses, or respiratory tract. They can also occur with systemic diseases such as parvovirus, distemper, herpesvirus, and pseudorabies. Dogs with an anal gland infection may also have a sore throat from spreading the infection while licking at their glands.
The signs of sore throat are fever, coughing, gagging, pain on swallowing, and loss of appetite. The throat looks red and inflamed. A purulent drainage may be seen coating the back of the throat.
Canine leptospirosis is caused by an order of bacteria called spirochetes-slender, spirally undulating bacteria. There are at least four species of the leptospira bacteria (or serovars) that can infect dogs: canicola, icterohemorrhagiae, grippotyphosa, and pomona.
Leptospira are found in wild and domestic animals. The bacteria are spread in the urine, often making their way into water sources and remaining infective in the soil for up to six months. Rats, pigs, raccoons, cattle, skunks, and opossums...
The group A streptococcal sore throat (commonly known as strep throat) that occurs in young children can produce mild or unapparent sore throat in dogs and cats, who may then harbor the bacteria in the respiratory tract. Although dogs usually get the infection from human members of their family, and not vice versa, to eliminate the bacteria in households with recurrent strep throat, consider treating pets as well as family members.
The tonsils are aggregates of lymph tissue located at the back of the throat in dogs, as they are in people. They may not be visible unless they are inflamed. This generally occurs as a secondary symptom of a sore throat.
Primary bacterial tonsillitis is rare. It occurs in young dogs of the smaller breeds. Symptoms are similar to those of a sore throat, except that fever is more pronounced (over 103°F) and the dog appears depressed. The tonsils are bright red and swollen. Localized abscesses may be visible as white spots on the surface of the tonsils.
Chronic tonsillitis with tonsil enlargement is caused by persistent infection or by mechanical irritation from prolonged coughing, retching, or regurgitation of stomach acid into the throat. Any dog showing signs of tonsillitis should also be checked for anal gland problems, as grooming and licking the anal glands can spread the infection to the mouth.
Treatment: Acute pharyngitis and tonsillitis respond to treatment of the underlying condition. When a primary cause cannot be identified, treatment involves giving a broad-spectrum antibiotic for 10 days. Feed a soft diet consisting of canned dog food mixed with water to make a mush.
Enlarged tonsils must be distinguished from lymphoma and squamous cell carcinoma-the most common cancers of the tonsil. This is done by biopsy. Tonsillectomy for chronically inflamed tonsils is seldom necessary.
WebMD Veterinary Reference from "Dog Owner's Home Veterinary Handbook"