Lyme Disease

The western black-legged tick is much smaller than common dog and cattle ticks. In their larval and nymphal stages, they are no bigger than a pinhead. Adult ticks are slightly larger. Larvae and nymphs take in spirochetes as they feed on infected mice. Infected larvae molt to infected nymphs and infected nymphs molt to infected adults.

In the United States, the disease is mostly localized to states in the northeastern, mid-Atlantic, and upper north-central regions, and to several counties in northwestern California.

The number of annually reported cases of Lyme disease in the United States has increased about 25-fold since national surveillance began in 1982, and a mean of approximately 12,500 cases annually were reported by states to the Centers for Disease Control and Prevention (CDC) from 1993-1997.

Most B. burgdorferi infections are thought to result from exposure to infected ticks during property maintenance, recreation, and leisure activities. Thus, individuals who live or work in residential areas surrounded by woods or overgrown brush infested by vector ticks are at risk of getting Lyme disease.

A red rash usually appears an average of 1 to 2 weeks after disease transmission. The early symptoms of Lyme Disease can be mild and easily overlooked. Although a majority of the infected develop the classic red rash, many do not. 

People who are aware of the risk of Lyme Disease in their communities and who don’t ignore the sometimes subtle early symptoms are most likely to seek medical attention and treatment early enough to be assured of a full recovery.

Early Symptoms

The first symptom is usually an expanding rash called erythema migrans, or EM, in medical terms. It is thought to occur in only about 50-60% of all Lyme Disease cases, and is characterized by the following:

• Usually (but not always) radiates from the site of the bite
• Appears a solid red expanding rash or blotch, or a central spot surrounded by clear skin that is ringed by a red rash (bullseye).
• Average diameter of 5″ to 6″
• Persists for about 3 to 5 weeks
• May or may not be warm to the touch
• Is usually painful or itchy

EM rashes appearing on brown-skinned or sun-tanned patients may be more difficult to identify because of decreased contrast between darker skin tones and the red rash. A dark, bruise-like appearance is more common on dark-skinned patients.

Around the time the rash appears, other symptoms such as joint pains, chills, fever, and fatigue are common, but they may not seem serious enough to require medical attention. These symptoms may be brief, only to recur as a broader spectrum of symptoms as the disease progresses.

There is no test that can determine if a patient is infected with the Lyme Disease bacterium and then demonstrate that the patient has become bacterium-free.

Therefore, Lyme Disease is a clinical diagnosis based on signs and symptoms, with the patients travel history to endemic areas and test results being additional pieces of information in the complete picture. No test can “rule-out” Lyme Disease.

Certain tests, both indirect and direct, can aid in a proper diagnosis.

Indirect (Antibody) Tests

Antibodies are the immune system’s response to combat infection. Tests strive to be both sensitive (detecting any Lyme Disease antibodies) and specific (detecting just Lyme Disease antibodies).

Test Interpretation

• False negative tests occur due to defects in test sensitivity; too low an antibody level to detect (e.g. they are bound to the bacteria, with too few free-floating; the patient taking antibiotics or other drugs; naturally low antibody production); the bacterium has changed, limiting recognition by the immune system; or bacterial strain variations.
• False positive tests occur due to test failure or cross-reacting antibodies (e.g. syphilis, periodontal disease, ANA or RF).

Types of Tests

• Titer (ELISA, EIA, IFA) tests measure the level of Bb antibodies in fluid, with labs using different detection criteria, cut-off points, types of measurements, and reagents.
• Western blot tests produce bands indicating the immune system’s reactivity to Bb, with labs differing in their interpretation and reporting of these bands.

Cats

Cats may show lameness, fever, loss of appetite, fatigue, eye damage, unusual breathing, or heart involvement. Many cats do not show noticeable symptoms, despite being infected.

Dogs

Infected dogs may be lethargic, have a poor/loss of appetite, or a fever (103° – 105 ° F). Dogs may also experience lameness shifting from one joint to another, fatigue, kidney damage or failure, heart disorders, or neurologic involvement (e.g. aggression, confusion, overeating, seizures). Dogs can be infected with the Lyme bacterium but not exhibit any noticeable symptoms. Dogs appear to have the same expression of disease as humans, therefore, humans have been considered an animal model for dogs. Transplacental transmission has occurred in dogs.

Tick Checks & Removal

Conduct frequent tick checks. Examine animals closely in order to detect embedded ticks.

Tick Removal

• Remove attached ticks properly and promptly to reduce the chance of transmission of the Lyme bacterium.
• Place fine point tweezers around the tick’s mouthparts (the place where the tick is attached) and gently pull upwards until the tick detaches.
• Do not use your bare fingers!
• Disinfect the bite site and tweezers after removal.
• Wash your hands.
• Place the tick, along with several blades of grass, into a small container (e.g. a clean screw-cap pill bottle or a zip-lock bag) for later examination.
• Label the container with: the date, name of pet, type of animal, owner’s name, address and phone number.
• Call your veterinarian to determine if there is a local place where the tick can be tested.
• Have your animal(s) examined as soon as possible if you notice any symptoms of disease; the sooner a disease is diagnosed, the easier it is to treat.