Lyme disease is a hot topic in general, and even more so in the northern Virginia area where many of us know someone personally who has been adversely affected by it, sometimes devastatingly so.
Lyme disease is also a hot topic in dogs. The classic symptoms in dogs are a “shifting leg” lameness (more than one limb affected) with general lethargy and malaise. Rarely, it can cause a quickly progressive and often fatal kidney failure called “Lyme nephritis.” While we do not know definitively, there is some thought that Lyme disease may contribute to chronic lameness and joint issues as well.
Because the Ixodes scapularis tick (aka: deer tick or black-legged tick - which carries the bacteria Borrelia burgdorferi, the causative agent of Lyme disease) is so small, even when engorged we often do not know that we, or our dog, has been bitten. Additionally, dogs do not get the characteristic bull's-eye rash that people do.
Fortunately, many dogs in our area are screened for exposure to the Lyme bacteria (Borrelia burgdorferi) on a yearly basis as part of the annual screening for heartworm disease. This blood test checks for antibodies (the dog’s immune response) to the Borrelia (in addition to two other tick-borne organisms: Anaplasma and Ehrlichia). If positive, it indicates that the dog has been exposed but not necessarily infected; the dog may have mounted an effective immune response and eliminated the organism, or the organism could be “hiding out” in the body ready to rear its ugly head down the road.
Whether or not to treat asymptomatic dogs that test positive on this yearly screening test is a huge topic of debate among veterinarians, especially since a small percentage (~5%) of dogs who test positive ever have any symptoms (compared to humans, where ~90% of exposed develop some degree of symptoms). A positive test warrants reevaluation of the tick prevention strategies being used in the pet and possibly looking into co-infections (i.e. OTHER tick-borne infections the dog may have been exposed to). Treatment typically consists of a four-week course of the antibiotic doxycycline. Some argue that it’s better to treat than take a chance of actual disease; others argue that we need to be more judicious with our use of antibiotics and only treat dogs that are symptomatic, or those that are showing other markers of infection. There is no one perfect test for determining which dogs those are, but other tests that your pet’s veterinarian may recommend to determine if treatment is necessary are a urinalysis to screen for protein loss through the kidneys (which can be a potential indicator of the more severe form of the disease that affects the kidneys) or the C6 antibody test (which gives a quantitative antibody number to go with the positive result and may be more useful in symptomatic dogs and with serial measurements). Each case is unique, and we always recommend talking with your pet’s veterinarian about what further testing might be indicated and whether treatment is indicated for your pet.
We are fortunate that there are several good options for prevention of Lyme Disease, and other tick-borne diseases, in dogs. A good, regular and year-round flea and tick preventative is likely the best prevention. Many experts are recommending the newer generation of oral flea/tick preventatives over the topical preventatives because they are extremely effective and kill the ticks faster - before they have a chance to transmit disease (they do still need to bite to receive the drug). There is also a vaccine for Lyme in dogs that may be considered for dogs with a lifestyle that may put them at high tick exposure, despite good flea/tick prevention. While neither is 100% effective, when combined together they do offer a very high level of protection.
A few side-notes:
Dogs cannot transmit Lyme disease directly to us, but they do act as sentinels for the disease (as usually wherever your dog has been you have been also) and can bring ticks into the home!
A special note on cats -- cats, while they can certainly pick up ticks, appear to be quite resistant to Lyme disease. There is one tick-born disease called Cytauxzooanosis that can be fatal in cats, but fortunately is not found in Northern Virginia, at least at this point.
http://natcaplyme.org/ -> the National Capital Lyme Disease Association
http://tickspotters.org/ -> you can submit pictures of ticks you find for identification (both type of tick, life stage, and what diseases it may carry)
http://www.tickencounter.org/ -> you can send your ticks in for testing for tick borne diseases!