Rats can transmit six serious diseases to dogs through a variety of ways. While not all of these transmissible diseases are fatal, they do carry serious health risks both for you and your dog. It is best to avoid any contact between rats and your dog, and to take extra precautions if interaction occurs.
Leptospirosis Can Be Deadly
Also known as "lepto," leptospirosis is a deadly and easily transmissible disease caused by a group of bacteria that persists in the kidneys of the infected animals. The process of transmission is called "shedding;" infected rats shed lepto by urination. Dogs become infected by sniffing this urine, licking or ingesting the urine or the infected rat and by drinking water contaminated with shed lepto bacteria. Open wounds are another pathway for the leptospirosis bacteria to enter your dog.
Potentially Fatal Toxoplasmosis
The parasite Toxoplasma gondii is responsible for the potentially fatal disease toxoplasmosis, and is transmitted when your dog eats an infected rat. Rats carrying toxoplasmosis develop cysts in their muscles; the parasite replicates and lives in these cysts. While dogs can contract toxoplasmosis and show no symptoms, puppies and pregnant dogs are more susceptible. Infection in puppies can lead to vomiting, fever and death. Pregnant mothers who are infected can lose litters due to abortion, stillbirth or puppies who die soon after birth.
Rat Bite Fever
Caused primarily by the bite or scratch of an infected rat, rat bite fever can infect your dog through interaction with a dead rodent or through ingesting anything contaminated by the diseased rat's feces. While dogs typically carry rat bite fever asymptomatic, they can pass the two strains of bacteria responsible for rat bite fever onto humans. These strains, Streptobacillus moniliformis and Spirillum minus can be fatal if left untreated, but usually are successfully treated with penicillin and ampicillin.
Tularemia or Rabbit Fever
Caught by eating infected rats or by drinking water contaminated by an infected rat, tularemia (also known as rabbit fever) is caused by the bacteria strain Francisella tularensis. Like rat bite fever, dogs are vectors for this disease, and can pass it to humans through open wounds or interaction with feces. Tularemia is fatal for dogs if left untreated; antibiotics administered quickly is the only defense post-infection. Tularemia is not isolated to any one climate, and can be found throughout most of the United States.
The Snacking Roundworm
Like toxoplasmosis, roundworm is another parasite contracted by consuming rats with roundworm larvae in their muscles. Not immediately life-threatening in adult dogs, the roundworm lives in the intestinal tract of your dog, competing with him for food. In young puppies, however, roundworms can affect their nutritional intake adversely to the point of death. Easily diagnosed by the spaghetti-like strands of worms found in your dogs feces, roundworms are treatable, preventable and quickly managed.
The Rare and Sometimes Deadly Plague
Perhaps the most renowned rat-transmitted disease, plague in dogs is also the most rare. Plague can be found in three forms: bubonic, pneumonic and septicemic, and is transmitted when your dog is bitten by or bites an infected rat. After infection, plague takes two to seven days to incubate before any symptoms appear. Symptoms of plague include difficulty breathing, vomiting and dehydration, and can be deadly. Fortunately, dogs have high natural resistance to plague, although they still can carry the disease to humans.
Prevention is Key
Sanitation is the No. 1 key to avoid your dog catching any rat-borne disease. Keep his water and food bowls clean and away from potential wildlife. Ensure that he does not hunt or catch wild or domestic rats: The rat's natural defensive bites and scratches as well as any consumed rat both pose high risk to your dog's health. Wash your hands between any interaction with pet rats before touching your dog, and upon any suspected infection take your dog immediately to his veterinarian.