Lyme disease can cause a number of mood and demeanor changes in affected dogs, as noted in "The Clinical Textbook for Veterinary Technicians." It is unclear whether these changes are caused by chemical fluctuations within the brain or simply caused by the dog's feeling unwell. Dogs experiencing illness caused by Lyme disease can react to normal stimuli with increased aggression and irritability. Other dogs display depression and a lack of interest in their surroundings. Still others exhibit confusion and the inability to function normally. A dog with Lyme disease may exhibit one, more than one, or none of these symptoms, according to "The Veterinarians' Guide to Your Dog's Symptoms."
When left unchecked, the bacteria that causes Lyme disease causes permanent nerve damage, up to and including total paralysis. Early symptoms of the disease include joint pain and weakness, typically manifesting as lameness or the refusal to use one or more legs, according to "Veterinary Microbiology and Microbial Disease." This early manifestation of nerve pain is typically reversible, provided proper treatment is obtained. Related advanced neurological symptoms include partial or total facial paralysis and permanent nerve damage throughout the body. The likelihood of nerve damage and paralysis increases the longer treatment is delayed.
There may be a link between Lyme disease and seizures in dogs already prone to them. Dogs with seizure-causing disorders such as epilepsy can experience an increase in seizure activity after suffering a bout with the disease. According to "A Practical Guide to Canine and Feline Neurology," the link is unclear. More research is needed to establish a solid link between Lyme and other diseases.
Humans and dogs experience Lyme disease differently, for the most part, but there are also a number of similarities. "The Clinical Textbook for Veterinary Technicians" postulates that dogs may experience the human symptoms of hallucinations, problems sleeping, memory loss and a lack of concentration or decreased attention span. It's tough to judge whether or not these symptoms occur in our canine companions---they're unable to tell us directly whether these distinct neurological symptoms occur in the presence of Lyme disease.