Lyme disease is caused by a bacteria called Borrelia burgdorferi and is spread by ticks. Ticks become infected with the bacteria by feeding on infected mice and other small animals. When an infected tick bites other animals, it can transmit the bacteria to these animals. Lyme disease is transmitted by the deer tick (black-legged tick) and a small group of other closely related ticks. The deer tick is small and may bite animals and people without being detected. Lyme disease affects a variety of species, including dogs, cats, and people. Up to 95 percent of dogs infected with B. burgdorferi do not develop symptoms (people are much more likely to become ill with Lyme disease).
There is no evidence that Lyme disease is spread by direct contact with infected animals. However, keep in mind that ticks can hitch a ride home on your pets and move on to the humans in the household.
Dogs that spend a lot of time outdoors, especially in the woods, bush, or areas of tall grass are most commonly infected with Lyme disease. However, ticks can be carried into yards on other animals, and dogs can become infected anywhere ticks are found.
Infections occur during tick season (usually spring through early fall), but the time between infection and the appearance of Lyme disease symptoms can be up to 2-5 months.
Lyme disease is seen across the US and in many other parts of the world. In the US. Lyme disease is most common in the northeastern US, along with the Pacific coast, and in the midwest.
Signs of Lyme Disease
When clinical signs do develop, they may be transient or recurrent, and can include:
- Decreased appetite.
- Swollen, painful joints (dogs may be reluctant to move).
- Lameness — limping which may be mild at first, then worsen, and may also shift from one leg to another.
- Swollen lymph nodes.
Some dogs with Lyme disease may develop kidney disease.
Signs of kidney disease may include depression, vomiting, loss of appetite, and increased thirst and urination (sometimes a lack of urination will develop). Dogs who develop kidney disease can become very ill and may not respond to treatment.
Neurological disease (behavioral changes, seizures) and heart complications, which are sometimes seen in humans, are rare in dogs.
Diagnosis of Lyme Disease
The diagnosis of Lyme disease must be based on a combination of factors, including history (tick exposure), clinical signs, finding antibodies to B. burgdorferi bacteria, and a quick response to treatment with antibiotics.
A positive antibody test is not enough to make a diagnosis on its own, because not all dogs that are exposed to B. burgdorferi get sick, and antibodies can persist in the blood for a long time after exposure.
Other diagnostic testing, such as blood and urine tests, x-rays, and sampling of joint fluid, may be done to check for signs of kidney disease and to rule out other conditions with similar signs and symptoms.
Treating Lyme Disease
Treatment with antibiotics usually produces rapid improvement in symptoms (antibiotics will be continued for a few weeks). Treatment may not be completely clear the bacteria, but produces a state where no symptoms are present (similar to the condition in dogs that don't have symptoms from infection).
Kidney disease may develop some time after the initial infection, so is it a good idea to regularly check for excess protein in the urine of dogs that have had Lyme disease. Catching the kidney disease early in its course offers the best prognosis. If kidney disease is present, a longer course of antibiotics along with additional medications to treat the kidney disease is usually necessary.
Preventing Lyme Disease
- Tick Control is extremely important for the prevention of Lyme disease (and many other diseases that can be transmitted by ticks). Check your dog daily for ticks and remove them as soon as possible, since ticks must feed for at least 12 hours (possibly 24-48 hours) before transmitting the bacteria causing Lyme disease. This is especially important in peak tick season and after your dog spends time in the bush or tall grass (consider avoiding these areas in tick season). Products that prevent ticks such as monthly parasite preventatives (e.g., Frontline®, Revolution®) or tick collars (e.g., Preventic®) can be used; be sure to follow your veterinarian's advice when using these products. Keep grass and brush trimmed in your yard, and in areas where ticks are a serious problem, you can also consider treating your yard for ticks.
- Vaccines for Lyme Disease: Vaccination against Lyme disease is a controversial topic and is something that should be discussed in depth with your veterinarian. Many specialists do not recommend routine vaccination because so few dogs develop symptoms of Lyme disease, and when Lyme disease does occur in dogs, it is usually readily treated. Additionally, because arthritis and kidney problems associated with Lyme disease are at least partly related to the immune response to the bacteria (rather than the bacteria itself), there is concern that vaccination may contribute to problems. Vaccination is also not 100 percent effective, and it's only helpful in dogs that have not already been exposed to B. burgdorferi. However, vaccination before exposure can help prevent dogs from getting Lyme disease and also prevent them from becoming a carrier of the bacteria. Where vaccines are used, it is usually recommended to start vaccinating dogs as young puppies (e.g., at around 12 weeks, with a booster 2-4 weeks later). The vaccine does not provide long-lasting immunity, so annual re-vaccination (ideally before tick season) is necessary. The recombinant form of the vaccine is considered to have less potential for side effects than the bacteria form of the vaccine.
Please note: this article has been provided for informational purposes only. If your pet is showing any signs of illness, please consult a veterinarian as quickly as possible.