there are some bacteria that are contagious from dog to dog. the most notable of these are "bordetella bronchiseptica", one of the causes of kennel cough, "leptospira" sp, which cause leptospirosis, and "brucella canis", cause of brucellosis in dogs. there are also common tick-borne bacterial diseases, including lyme disease, ehrlichiosis, and rocky mountain spotted fever.