Being proactive with tick prevention does more than stop your stomach from churning when you discover a tick on your pet. It helps protect your dog (and your whole family) from contracting tick-borne diseases. In addition to Lyme disease, ticks spread conditions like the infectious disease ehrlichiosis, which can be life-threatening for dogs. Thankfully, there are measures you can take to recognize ehrlichiosis in dogs, as well as to prevent it.
What Is Canine Ehrlichiosis, and How Is it Spread?
Ehrlichiosis is an infectious bacterial disease transmitted by tick bites that lives in white blood cells throughout the body. When ticks are infected with bacteria belonging to certain bacterial groups, it can cause ehrlichiosis. Ehrlichia canis is the most common bacterial species to cause canine ehrlichiosis. Across North America, dogs are primarily exposed to Ehrlichia canis through the bites of brown dog ticks (Rhipicephalus sanguineus). The bites of Lone Star ticks (Amblyomma americanum), which are common to the eastern, southeastern, and south-central United States, can expose dogs to the bacteria Ehrlichia ewingii, which can also cause ehrlichiosis.
“Ehrlichiosis is a widespread problem in the United States, as dogs can be infected with at least five Ehrlichia species that are transmitted by at least three different tick species, which are distributed widely throughout the country,” says Dr. Edward B. Breitschwerdt, professor of medicine and infectious diseases at North Carolina State University College of Veterinary Medicine.
Ticks can transmit the disease after just a few hours of attaching themselves to a dog, so promptly removing these tiny parasites as soon as you find them is very important.
What Are the Symptoms of Ehrlichiosis?
When caused by Ehrlichia canis bacteria, ehrlichiosis is associated with three sequential phases, known as acute, subclinical, and chronic. The acute phase usually lasts two weeks to a month, with visible symptoms that often appear one to three weeks after the infected tick attaches to your dog. It can be tricky for your veterinarian to diagnose the disease in this phase, as dogs will often display non-specific symptoms, such as lethargy, lack of appetite, and fever, and antibody evidence of ehrlichiosis won’t show in tests for those first couple of weeks.
“The most common symptoms an owner might see in their dog at home are lethargy, malaise—a general feeling of being unwell—or possibly limping,” says Dr. Barbara Qurollo, DVM and associate research professor at North Carolina State University College of Veterinary Medicine. “In more severe cases, they might see petechiae, [which are] pinpoint areas of bleeding just under the skin’s surface.” Symptoms sometimes disappear within a few weeks, but without treatment, an infected dog will usually pass into the subclinical phase. Even if a dog is asymptomatic during the subclinical phase, they can still carry the infection for months or years.
Not all dogs progress to the chronic phase, but if they do, ehrlichiosis can in some cases be life-threatening. During the chronic phase of canine ehrlichiosis, it can be challenging to make a diagnosis because there can be such a wide range of serious symptoms. “These can range from uveitis (eye inflammation), to bleeding, to localized edema (swelling because of fluid buildup), to severe bone marrow pathology, to kidney, liver or lung injury,” Dr. Breitschwerdt says.
Dogs bitten by ticks infected with Ehrlichia ewingii are more likely to be asymptomatic or display milder symptoms, typically swollen joints and a fever.
How Do Vets Diagnose Ehrlichiosis?
In areas where ticks are more common, your vet will likely be on high alert for this infection. “Many veterinarians screen annually for antibody evidence of infection with an Ehrlichia species,” says Dr. Breitschwerdt. If your dog seems to be sick, after conducting clinical observations and taking down their medical history to evaluate tick exposure and symptoms, your vet will take a blood test for antibodies as the initial step in diagnosing your pet.
If your dog comes back positive for antibodies, your vet may start treatment immediately. Alternatively, they may recommend additional PCR testing to confirm the presence of the bacteria through DNA detection.
How to Treat Ehrlichiosis in Dogs
“The good news is that most Ehrlichia infections are effectively treated with antibiotics, typically doxycycline,” Dr. Qurollo says. Antibiotics kill off the bacteria in all strains of ehrlichiosis that dogs can catch, and, with treatment, the prognosis for complete recovery is very good. “If an infected dog isn’t treated, and depending on the Ehrlichia species, a few outcomes are possible. One, the dog’s immune system may clear the organism. Two, the dog could remain chronically infected but become asymptomatic, [with] no signs of disease. Or three, they could be chronically infected and develop a more severe form of ehrlichiosis.”
Treatment usually lasts for one month. But for chronic infections, your vet will likely extend the treatment duration and give a more guarded prognosis. It’s important to complete the full course of antibiotics when treating any infection. Dr. Breitschwerdt explains that this is especially true for ehrichliosis, since research shows shortening the duration of doxycycline treatment can make that treatment ineffective.
Dr. Breitschwerdt always recommends testing for other tick-borne diseases in dogs diagnosed with chronic ehrlichiosis, especially babesiosis and bartonellosis. Both of these diseases can cause complications and are treated differently from canine ehrlichiosis.
How to Prevent Ehrlichiosis in Dogs
Dr. Qurollo encourages owners to discuss the range of dog-specific tick preventatives with their dog’s veterinarian. “Depending on where you live, ticks are still active even in the winter months, so I strongly encourage keeping animals on [tick] preventives year-round.“
Any dog in an area with tick populations is at risk. But dogs that spend a lot of time outside, especially in heavily forested areas or in densely populated dog parks or kennels where infected ticks can easily pass between dogs, carry an even greater risk of contracting ehrlichiosis.
Inspecting your dog for ticks daily is important, especially after walks in long grass or wooded areas. Prompt daily tick checks are the safest and best way to prevent tickborne disease. Speedy and careful tick removal can prevent transmission of the infection. Be sure to wear gloves and wash your hands after touching ticks.
“Diagnosis and treatment of ehrlichiosis, particularly the chronic phase of illness, can be extremely expensive,” Dr. Breitschwerdt says. “And, despite treatment, some dogs will not respond and will die of the disease,” he adds.
Is Canine Ehrlichiosis Contagious to Humans?
By reducing the risk of tick-borne illnesses, you are also helping to protect people. While dogs with ehrlichiosis can’t transmit the disease to people, the ticks they bring in on their bodies carry Ehrlichia species and other harmful bacteria that can infect humans. This includes Ehrlichia ewingii, borrelia (responsible for Lyme disease), and the parasite babesia. So when you inspect your dog for ticks and use preventatives, you’re protecting everyone in your home.