New more invasive strains of streptococci have recently appeared, resulting in frightening new diseases in both humans and dogs. Both humans and dogs can develop streptococcal toxic shock syndrome, with the rapid development of symptoms of shock, high fever (104 to 107 degrees Fahrenheit), cough, abnormalities of coagulation and rapid death. In humans, the mortality rate is estimated at between 60-80%. In dogs, it may be even higher as the course of the disease is so rapid that a dog may be killed in as little as 1 to 4 hours from development of the first symptoms, so that some dogs are simply found dead in their runs, houses or yards. It’s entirely possible to leave a healthy dog in the morning and find it dead when you come home from work. Necropsy, if done, frequently fails to reveal the cause of death in dogs found dead, further skewing the statistics.
Treatment of acute CSTSS is often unsuccessful. One veterinarian in Canada has noted a 50% mortality rate, which seems to be unusually successful. Those dogs who survive have been treated with IV antibiotics to which streptococci are susceptible, particularly Penicillin G and Clindomycin. Clindomycin seems to be particularly useful in acute cases because it halts the metabolism of the streptococci, stopping the cascade of toxins responsible for the high fever, shock and Disseminated Intravascular Coagulation (DIC).
Dogs can be infected by canine strains of streptococci and sometimes by human strains. A dog handler with pharyngitis (sore throat) was thought to be the source of infection in a Greyhound kennel epidemic in Florida, and a human strain was isolated from an infected dog in Canada. There are certainly human “carriers” of streptococci, and according to Brad Fenwick, D.V.M. of Kansas State University Veterinary School, there are also canine carriers of virulent streptococci who never show a symptom.
The portal of entry in dogs usually seems to be the throat and lungs. The reproductive tract of bitches in season is an open invitation to bacteria as well. Oddly, streptococcal skin infections in dogs don’t seem to be a problem although this is a frequent site of entry in humans. This could be because canine skin is better protected by the fur, because canine skin is simply more resistant to infection, or because minor wounds or cellulitis are overlooked because of being covered by fur.
The severe symptoms typical of CSTSS seem to result when the bacteria invade the bloodstream, producing septicemia and toxemia, with a cascade of toxins. In humans, the invasion follows the pattern of classical “blood poisoning” from streptococcal cellulitis or septicemia from “strep throat,” except for being much more toxic and much quicker. In humans, the disease is about as contagious as bacterial meningitis, and antibiotic prevention is recommended for both diseases.