Lyme disease (Lyme borreliosis) is an illness that affects both animals and humans -- what is known as a zoonotic disease -- and is the most commonly reported vector-borne illness in the United States, according to the U.S. Centers for Disease Control and Prevention (CDC). Transmitted through tick bites, the disease can be difficult to detect and can cause serious and recurring health problems. Therefore, it is best to prevent infection by taking appropriate measures to prevent tick bites and, for dogs, possibly vaccinating against the disease. 
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The bacterium that causes Lyme disease - a worm-like, spiral-shaped bacterium called Borrelia burgdorferi - is carried and transmitted primarily by the tiny black-legged tick known as the deer tick.  Deer ticks are found in forests or grassy, wooded, marshy areas near rivers, lakes or oceans.  People or animals may be bitten by deer ticks during outdoor activities such as hiking or camping, or even while spending time in their back yards. 
Named after numerous cases were identified in Lyme, Connecticut in 1975, the disease has since been reported in humans and animals across the United States and around the world.  Within the U.S., it appears primarily in specific areas including the southern New England states; eastern Mid-Atlantic states; the upper Midwest, particularly Wisconsin and Minnesota; and on the West Coast, particularly northern California.  The CDC maintains a map detailing confirmed cases of Lyme disease throughout the years. 
Lyme disease is a reportable disease -- which means that health care providers and laboratories that diagnose cases of laboratory-confirmed Lyme disease are required to report those cases to their local or state health departments, which in turn report the cases to the CDC. 

How to prevent Lyme disease
The best way to protect pets from Lyme disease is to take preventive measures to reduce the chance of contracting the disease.  Even during the last weeks of summer, it's important to remember that pets and people are at greater risk of being infected with Lyme disease and other tick-borne diseases such as anaplasmosis, ehrlichiosis, or Rocky Mountain Spotted Fever. 

People with pets should:

• Use reliable tick-preventive products.  Speak with your veterinarian about what tick preventive product is right for your pet.
• Work with your veterinarian to decide whether to vaccinate your dog against Lyme disease.  Your veterinarian's advice may depend on where you live, your pet's lifestyle and overall health, and other factors. 
• When possible, avoid areas where ticks might be found. These include tall grasses, marshes and wooded areas.
• Check for ticks on both yourself and your animals once indoors. 
• Clear shrubbery next to homes.
• Keep lawns well maintained. 

​As noted above, there are preventive Lyme disease vaccines available for dogs, but they aren't necessarily recommended for every dog.  Consult your veterinarian to see if the vaccination makes sense for your pets.  If your veterinarian does recommend that your dog be vaccinated against Lyme disease, the typical protocol will involve an initial vaccination followed by a booster 2-4 weeks later and annual boosters after that. 

Lyme disease in pets - symptoms & treatment
Pets infected with Lyme disease may not show any signs for 2-5 months.  After that time, typical symptoms include:

• Fever
• Loss of appetite
• Lameness
• Joint swelling
• Decreased activity

Recurrent lameness also is possible, and the involved extremity may be tender.  Inflammation of the joint can last from days to weeks, and may migrate from one extremity to another.
Horses with Lyme disease can develop lameness, joint pain, neurologic disease, eye problems and dermatitis.
Symptomatically, Lyme disease can be difficult to distinguish from anaplasmosis because the signs of the disease are very similar, and they occur in essentially the same areas of the country.  Lyme disease is diagnosed through a blood test that shows whether an animal has been exposed to the bacterium.  
Antibiotics usually provide effective treatment for Lyme disease.  However, it's important  to follow your veterinarian's advice regarding follow-up care after your pet has been diagnosed with and treated for the disease. 
Lyme disease is not communicable from one animal to another, except through tick bites.  However, if you have more than one pet and one is diagnosed with Lyme disease, your veterinarian might recommend testing for any other pets who may have been exposed to ticks at the same time.  In fact, because people and their pets often can be found together outdoors as well as indoors, a Lyme disease diagnosis in any family member - whether human or non-human - should serve as a flag that all family members might consult their doctors and veterinarians, who can advise about further evaluation or testing.  ​

It's a "One Health" problem
Because people and their pets often spend time in the same environments where Lyme and other disease-transmitting ticks are found, the American Veterinary Medical Association (AVMA) and the American Academy of Pediatrics (AAP) are working together to offer advice to households with both children and pets.  People who have been diagnosed with Lyme disease should consult their veterinarian to determine their pet's risk based on the animal's lifestyle and possible environmental exposures.  Likewise, people whose animals have been diagnosed with Lyme disease may want to consult their physician about their own or their children's risk if they have concerns that the animals and family members might have been exposed to similar environmental risks.  
Thousands of cases of Lyme disease have been reported in humans and animals across the United States and around the world.  By knowing about Lyme disease and how to prevent it, you can help keep all members of your family - human and animal - safe.  

Lyme disease in people
In humans, often the earliest indication is a "bullseye" rash at the site of the tick bite - so named because it resembles a target.  As the infection develops, symptoms include fever, headache, fatigue, and muscle and joint pain.  The disease can progress to cause chronic joint problems as well as heart and neurological problems.  As with pets, Lyme disease is not contagious from one person to another.  
There are many things people can do to avoid exposure to tick bites.  These include:

• Avoid areas where ticks are found
• Cover arms, legs, head and feet when outdoors
• Wear light-colored clothing
• Use insecticides
• Checking for ticks once indoors

The AAP has more information about Lyme disease in people.