Lyme disease is an illness that affects both humans and animals. It is a vector-borne illness, meaning a specific organism transmits infectious diseases between humans, or from animals to humans. The primary vector or organism that transmits Lyme disease is a bloodsucking insect called a tick. People cannot get Lyme disease directly from their dog. Although the disease was once limited to the Northeastern region, the West Coast, and the north-central states of the U.S., health officials have reported cases across the country.
According to the Centers for Disease Control, health officials report about 30,000 cases of Lyme disease in humans each year across the U.S. However; the CDC estimates the number may be closer to 300,000. The number of dogs that contract Lyme disease is harder to estimate. Between 50-75% of dogs in New England alone have been bitten by a tick infected with Lyme disease, according to research numbers. Canine Lyme disease doesn’t exhibit symptoms of the illness for weeks or even months after the infection. Unlike humans, however, the infection seldom causes life-threatening illness in dogs. Only about 10% will become seriously ill from the infection.
Lyme disease concerns pet owners for a number of valid reasons. Separating the myths from the facts is key to understanding the disease and protecting your pet and household.
Around 50% of adult black-legged ticks carry Lyme disease. These parasitic arthropods wait for victims in tall grass or on the tips of vegetation. Ticks don’t fly, and they don’t jump. They crawl onto their mammal hosts. Ticks are attracted to warmth, motion, and carbon dioxide. When an infected tick finds its host, it crawls around on the skin until it finds a place to bite. Ticks prefer a crevice, skin folds, or places on the body with little or no hair. They usually choose canine ears, neck, face, and limbs. The tick bites its host, attaching its mouthparts to the skin and feeding on the host’s blood until engorged. This bite releases the pathogens into the body through the tick’s saliva. An infected tick’s bite releases a bacterium called Borrelia burgdorferi. This worm-like, spiral-shaped bacterium transmits Lyme disease.
Most dogs show no signs of the disease. Those that do may have a fever, a loss of appetite, painful or swollen joints, and swollen lymph nodes. Some dogs experience lameness in their legs that shifts from one to the other. They may seem depressed and lethargic. A small percentage of dogs experience edema with decreased levels of a protein called albumin in their blood. This may indicate kidney issues, but can also be signs of other infections or conditions.
Most veterinarians consider a diagnosis of Lyme disease or other tick-borne illnesses if the owner reports finding a tick on their pet. Some owners remove the tick and take it to the vet for analysis. If the dog has a low-grade fever, swollen lymph nodes, and suddenly develops an inability to use one or more of their limbs properly, the vet will likely suspect the cause is Lyme disease. Standard blood tests won’t identify Lyme disease. Tests cannot detect the antibodies that fight against the disease-causing bacteria for several weeks after the infection. However, these tests can help the vet rule out other causes. Mixed infections may also complicate the diagnosis. A newer test, the C6 test, is an immunological test that detects antibodies to the spirochetes’ peptides. Because of this, it is cheaper and more sensitive, making it more accurate.
Once infected, the spirochetes spread through the dog’s connective tissue. This may cause infections in the joints and heart and long term damage. The infection can also affect the dog’s neural tissue, the main component of the nervous system, which includes the brain, spinal cord, and nerves. Veterinarians have reported facial paralysis and seizure disorders due to nervous system damage from the disease. Some dogs may show no symptoms, but they have a long-term presence of the infection in their bodies. The dog’s immune system works overtime to remove the invading spirochete. Eventually, the antibodies may deposit in the dog’s kidneys leading to severe damage.
About 90% of dogs never show symptoms, and owners don’t seek out vet advice or treatment for their pet unless symptoms appear. For dogs that show symptoms, vets prescribe antibiotics, usually a two-to-four week course. If Lyme disease is a possibility, some vets start antibiotic therapy whether or not the dog is exhibiting symptoms. The antibiotics don’t eliminate the spirochete organism. Instead, they bring the dog into what animal biologists and vets call a premunitive state. This means the organism is still in the dog’s body, but it’s not causing an infection. After starting antibiotics, most dogs start to improve within 48 hours.
Ticks do not die off during the colder months or after a freeze, contrary to popular opinion. Black-legged ticks start to become active as the season changes from summer to fall. They remain active in their adult stage from fall to spring, when the temperatures are above freezing. They are generally most abundant early in October when they begin their feeding activity. However, each of the tick’s life stages has a specific period when they search for a host. Nymphal ticks, the middle stage, are most active in late spring and early summer. The temperatures must drop below 10 degrees for an extended time period before ticks begin to die. Heavy snow can provide a layer of insulation for ticks through the winter. Once the temperatures reach near or above freezing, they’re hunting for a host.
There are a variety of tick prevention products on the market, including shampoos and collars. However, these preventatives are not always 100% effective. Checking your dog frequently after they’ve been outdoors is the best way to ensure the ticks don’t feast on your pet for the 48 hours it takes to transmit the Lyme disease infection. Removing ticks quickly also prevents them from falling off inside your home and latching on to a household member or pet. If you have a recurring tick problem in your yard, you may want to seek out a professional pest service to spray it.
Although Lyme disease can occur anywhere in the U.S., most black-legged tick infections occur in the Northeast and mid-Atlantic states, the north-central states of Wisconsin and Minnesota, and northern California. There are several types of vaccines available on the market. These vaccinations work on puppies or dogs who have never had exposure to Lyme spirochetes. Vets recommend an annual booster to continue the vaccination’s immunity. Although most dogs show no symptoms and the vaccination doesn’t seem necessary, some vets recommend it anyway to minimize the sources of Lyme disease. Dogs who become infected with Lyme disease may also become sources for human infection as well. The tick feeds on the infected dog, then bites and infects a human. Pet owners should discuss vaccination with their veterinarian.
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