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Black Fly Bites vs. Target Lesions

Dog scratching himself

Black flies are small, biting flies that are pests to people and animals living, working, or playing near running rivers and streams. Black flies are sensitive to weather conditions, and are most active on cloudy, humid days with low wind. Black fly bites are painfully itchy and are created when the fly cuts a hole in the skin to suck blood from animals and people. The flies attack around the eyes, ears, scalp and occasionally on the arms and exposed legs. The pain and swelling of the bite are due to the body’s allergic response to the fly’s saliva that they inject when feeding.

Fortunately, black flies do not transmit any diseases to humans in Washington state, but can cause discomfort and irritation. Black flies tend to bite our pet’s underbelly and groin regions or ears of critters whose ears stand up. The large welts that are left behind are quite distinctive. A bright red circle, about the size of a nickel are usually found in places where the fur is thinner.

At SouthCare, we’re happy to answer any questions you may have concerning these painful bites. One of the most common questions we hear is: “I think I’ve found a target lesion, does my dog have Lyme Disease?” The good news Lyme disease is not endemic to our area. Unless you and Frankie the Fluffball have traveled to the Northeastern, mid-Atlantic or limited regions in California, you are unlikely to have been exposed to Lyme disease. Click here to view the CDC Lyme Disease Map

While a “bull’s eye” rash at the site of the tick bite is common with human Lyme disease infection, dogs have no such indicator. In fact, a dog infected with Lyme disease may show few if any signs, but some of the more common symptoms of this disease can include any of the following: • Spontaneous and shifting leg lameness that lasts 3–4 days, sometimes accompanied by loss of appetite and depression • Reluctance to move • Fatigue

If you find black fly bites on your pet, the good news is most pets don’t mind them. Even though these welts may look irritated and sore, they do tend to disappear over time. Some pets may be more sensitive to these bites than others and can develop a skin infection. Signs of this may include irritation of the skin, and/or excessive licking and chewing at the site of the bite. If Frankie the Fluffball has extensive bites and is uncomfortable please do not hesitate to call us! We’re always happy to help you and your pets!

More information can be found at:

Spokane Regional Health District

Fly Bites in Dogs

Dogs and Ticks

CDC- Lyme Disease