Tularemia, a zoonotic, bacterial disease that affects dogs and their people is yet another in a succession of serious tick-borne illnesses.
Ticks have crawled the Earth since the Oligocene Epoch 33.9 million to 23 million years ago when one lone tick hitched a ride and grabbed a meal inside a woolly rhino's ear and fossilized to tell the story. First recognized for the damage they cause to their hosts as early as 850 B.C., when Homer found ticks on Ulysses' dog, it was not until the end of the 19th century with the discovery of the Texas fever pathogen that people understood the full magnitude of the devastating effects of a tick bite.
Today, we know that ticks exist for one purpose only — to wreak havoc on their hosts and spread multiple diseases, among them, tularemia, which can be fatal. Early detection and medical intervention may improve the prognosis.
What causes tularemia in dogs?
Like fleas and lice, ticks are ectoparasites, which means they live on or in the skin but not within the host's body. In the United States, tularemia in dogs is spread by the bite of an infected dog tick, wood tick, or lone star tick carrying the Francisella tularensis (F. tularensis) bacteria.
Often referred to as rabbit fever, tularemia infects cottontail and jackrabbits, muskrats, prairie dogs, meadow voles, beavers, field mice, and other animals. The bacteria survive by creating tumor-like masses and abscesses in the animal's liver.
Tularemia in dogs is the result of a cycle that begins when a tick bites a rabbit or rodent that is infected with the blood-borne F. tularensis bacteria, then slowly sucks their blood for several days, absorbing the bacterium to become a carrier. Moving on, the tick crawls to the tip of a long blade of grass waiting for a host, then, when a dog walks by, grabs on for a meal. The tick may crawl through the dog's fur to a warm spot under a dog's leg, for example, where it latches on and bites by burrowing its head into the skin. Now firmly attached, the tick sucks the dog's blood for sometimes several days if undetected and transmits the bacterium to the dog in the process.
Another way that dogs become infected with tularemia is through direct contact with bodily fluids and tissues of an infected rabbit or rodent through the skin or by killing and eating it, ingesting an infected carcass, or drinking contaminated water. And if a dog inhales the bacteria, it causes a more severe form of the illness called pneumonic tularemia.
The symptoms, diagnosis, and treatment of tularemia.
After exposure or ingestion of the bacteria, the lymph nodes in the dog's head, neck, and GI system collect the bacteria and systemic infection follows. This acute illness presents with the following clinical symptoms:
- High fever from 104- to 106-degrees Fahrenheit
- Swollen, painful lymph nodes in the head and neck.
- Jaundice which causes yellowing of the skin, whites of the eyes, and mucous membranes.
- Abdominal pain.
- Failure of the organs.
To rule out bubonic plague and other diseases with similar symptoms such as high fever and swollen lymph nodes, your veterinarian will run diagnostic tests such as a complete blood count (CBC), a blood chemistry panel, and a urinalysis. In tularemia, these tests reveal a high white blood cell count, low blood sodium, low blood sugar, an elevated level of bilirubin, and blood in the urine.
Once diagnosed, dogs are at once hospitalized, and an aggressive course of treatment begins. Antibiotics and supportive care with intravenous fluid therapy can save many dogs' lives, however, even with early detection and treatment, the death rate for dogs with tularemia is high.
Identification of ticks and prevention of tularemia.
The importance of protecting your dog and your family from tick bites cannot be overemphasized. Today, ticks are second only after mosquitoes as vectors of human diseases and are the most important vector of pathogens in North America. Tick medications are crucial if you live in a tick-infested region or if your dog is often outdoors. Ticks occur throughout the U.S., so regular tick control is your first line of defense against them. Furthermore, you should regularly groom your dog after a walk to find and remove ticks.
Some areas where your dog is most susceptible to ticks are on trails or in wooded areas, dense undergrowth, scrubland, wildlife habitats such as forests, and grassy fields. Keep in mind that ticks will still latch on to your dog's fur even if he is protected by medication. Once transported inside the house, ticks can crawl onto human members of the family and bite them. To give you peace of mind, consider treating your dog with a topical spray or spot-on tick control product that kills ticks on contact to reduce the chances of ticks getting loose in your house.
Different species of ticks carry different germs. If your dog is bitten, take him to the vet at once to have the tick removed and identified. If you have experience removing ticks, capture the specimen in a container to take with you to the vets for identificatioin. The three species responsible for tularemia — dog tick, wood tick, and the lone star tick — look similar but have distinguishing characteristics. Check out Tick Encounter for photos of the different tick species in their various life stages — larva, nymph, the adult female, and adult male — and see how they become unrecognizable as they morph into balloons when fully engorged with a blood meal.
Making the prevention of tularemia and other tick-borne diseases a priority on the homefront is easy, affordable, and just takes a little work:
- Keep lawns clipped short.
- Remove debris, woodpiles, and garbage.
- Reduce leaf litter by raking and removing leaves.
- Create a tick-free zone for your dog to hang out in while in the backyard by erecting protective fencing around his space to keep out wildlife that may carry ticks. Or consider fencing your entire property to keep out deer and other tick-carriers.
- Hire an exterminator to spray or apply granulated pesticide to the perimeter of your property to keep ticks at bay.
- Tick-proof mice — inevitably, they will live in the surrounding areas, if not on your property — tick-free by installing Thermacell Tick Control tubes in stone walls and other areas where mice reside. The tubes are stuffed with nesting material treated with permethrin and keep mice that nest in it relatively tick-free.