Published: 18 Jun 2025

ICD9: 088.81      ICD10: A69.20      ICD11: 1C1G

Lyme disease is a bacterial infection transmitted to humans through the bite of infected blacklegged ticks (also known as deer ticks).
It's a serious illness that can cause a wide range of symptoms if left untreated, affecting the skin, joints, heart, and nervous system.

Here's a breakdown of key aspects of Lyme disease:

Cause:

Bacteria: The disease is caused by the bacteria *Borrelia burgdorferi* and, less commonly, *Borrelia mayonii*.
Vector: Blacklegged ticks (deer ticks) become infected by feeding on infected animals, such as mice, chipmunks, and deer. They then transmit the bacteria to humans when they bite.

Transmission:

Tick Bite: The bacteria enter the bloodstream through the tick's saliva during a bite.
Time: It typically takes 36-48 hours of attachment for a tick to transmit the Lyme bacteria. So, removing a tick promptly significantly reduces the risk of infection.
Tick Size: Nymphal (young) ticks are very small (about the size of a poppy seed) and are most commonly responsible for transmitting Lyme disease because they are easily overlooked.

Symptoms:

Symptoms of Lyme disease can vary widely and appear in stages:

Early Localized Lyme Disease (Days to Weeks after Bite):
Erythema Migrans (EM) Rash: A characteristic bullseye-shaped rash that expands outward from the site of the tick bite. However, it's important to note that not everyone develops the rash (estimates range from 60-80% of infected individuals). The rash is usually not painful or itchy.
Flu-like Symptoms: Fever, chills, fatigue, headache, muscle and joint aches, swollen lymph nodes.

Early Disseminated Lyme Disease (Weeks to Months after Bite):
More EM rashes may appear at other locations on the body.
Severe headaches and neck stiffness.
Facial palsy (drooping of one or both sides of the face).
Arthritis pain in large joints, such as the knees.
Heart problems (Lyme carditis) such as an irregular heartbeat.

Late Disseminated Lyme Disease (Months to Years after Bite):
Severe joint pain and swelling (Lyme arthritis), often affecting the knees.
Neurological problems: Cognitive difficulties, numbness or tingling in the hands or feet, nerve pain.

Diagnosis:

Clinical Evaluation: Based on symptoms, history of tick exposure, and geographic location.
Blood Tests: Two-tiered testing is typically used:
ELISA (Enzyme-Linked Immunosorbent Assay): A screening test to detect antibodies against Lyme bacteria.
Western Blot: A confirmatory test to identify specific antibodies.

Treatment:

Antibiotics: Lyme disease is treated with antibiotics, usually doxycycline, amoxicillin, or cefuroxime. The duration of treatment depends on the stage of the disease and the severity of symptoms.
Early Treatment: Early treatment with antibiotics is highly effective in curing Lyme disease.
Late-Stage Treatment: Treatment of late-stage Lyme disease can be more challenging and may require longer courses of antibiotics.

Prevention:

Avoid Tick-Infested Areas: Stay on cleared trails when hiking and avoid wooded areas with high grass and leaf litter.
Use Insect Repellent: Apply insect repellent containing DEET (20-30%) or picaridin to skin and clothing.
Wear Protective Clothing: Wear long sleeves, long pants tucked into socks, and closed-toe shoes.
Check for Ticks Regularly: Perform thorough tick checks after spending time outdoors, paying close attention to areas such as the scalp, groin, and armpits.
Shower Soon After Being Outdoors: Showering within two hours of coming indoors has been shown to reduce your risk of getting Lyme disease and may be effective in reducing the risk of other tickborne diseases.
Remove Ticks Promptly and Correctly: Use fine-tipped tweezers to grasp the tick as close to the skin's surface as possible. Pull upward with steady, even pressure. Don't twist or jerk the tick, as this can cause the mouthparts to break off and remain in the skin. After removing the tick, clean the area with soap and water or an antiseptic.
Tick-Proof Your Yard: Clear brush and leaf litter around homes and along stone walls. Keep grass mowed. Consider using tick-control products.

Important Considerations:

Not Everyone Gets a Rash: Remember that not all people with Lyme disease develop the characteristic bullseye rash.
Co-infections: Ticks can carry other pathogens besides *Borrelia burgdorferi*, leading to co-infections like Anaplasmosis, Babesiosis, and Ehrlichiosis.
Post-Treatment Lyme Disease Syndrome (PTLDS): Some people experience persistent symptoms (fatigue, pain, cognitive difficulties) after treatment with antibiotics, even when the infection is eradicated. The cause of PTLDS is not fully understood, and treatment focuses on managing symptoms.

If you suspect you may have Lyme disease, it's essential to consult with a doctor for proper diagnosis and treatment. Early diagnosis and treatment significantly improve the chances of a full recovery.