Lyme Disease: Comprehensive Study Notes

What Lyme Disease Is

• Lyme disease is caused by bacteria called Borrelia burgdorferi, and rarely, Borrelia mayonii.
• The bacteria are spread to people through bites of infected blacklegged ticks.
• Under a microscope, the Lyme disease bacteria are corkscrew-shaped.

Where Lyme Disease Is Found

• People can only get Lyme disease from ticks that carry the bacteria.
• In high-risk areas, about $10\% \text{ to } 50\%$ of blacklegged ticks carry the bacteria.
• High-risk areas include:
  • Eastern states, primarily New England and the mid-Atlantic
  • The Great Lakes Region and Northern Midwestern states, especially Wisconsin and Minnesota
  • West Coast, particularly parts of northern California and, less commonly, Oregon and Washington

How Lyme Disease Is Spread

• Transmission requires ticks to be attached for more than >24\ \text{hours} and to begin filling with blood before Lyme disease bacteria can be transmitted.
• Most people are infected through bites of immature ticks called nymphs.
  • Nymphs are tiny (less than $2\ \text{mm}$) and difficult to see; they most commonly bite in spring and summer.
• Adult ticks can also transmit Lyme disease bacteria.
  • Adults are larger and more likely to be found and removed; they most commonly bite during fall.
• There is no evidence that Lyme disease is transmitted person-to-person through touching, kissing, or having sex with a person who has Lyme disease.
• If untreated during pregnancy, Lyme disease can lead to infection of the placenta. Spread from mother to fetus is possible but rare. With appropriate antibiotic treatment, there is no increased risk of adverse birth outcomes. If you are pregnant and suspect Lyme disease, contact your healthcare provider.
• There are no reports of Lyme disease transmission through breast milk or blood transfusion.
• Blacklegged ticks don’t just have black legs; they are a different species than other common ticks (e.g., dog tick).
• In their life stages, blacklegged ticks are:
  • Larva and nymph: no bigger than a pinhead
  • Adults: about the size of a sesame seed
• Ticks can attach to any part of the human body but prefer hard-to-see areas such as the groin, armpits, and scalp.
• Embeded nymphal tick photo note (visual context in original material) — not reproduced here.
• Reported Lyme disease cases are counted by residence, not the location of infection; exposure can occur elsewhere.
• Surveillance data may be incomplete due to variability in state reporting and events such as the COVID-19 pandemic.
• For more information, see CDC Lyme data surveillance pages.

Tick Removal

• Grasp the tick firmly and as close to the skin as possible.
• With a steady motion, pull the tick’s body away from the skin.
• Do not be alarmed if the tick’s mouthparts remain in the skin.
• Cleanse the area with rubbing alcohol or soap and water.

Signs and Symptoms

• Early diagnosis and proper antibiotic treatment are important to prevent more serious forms of the disease.
• Contact your healthcare provider if you notice an expanding rash or other possible symptoms.
• Early signs and symptoms can include:
  • An expanding skin rash, called erythema migrans
  • Fatigue
  • Chills and fever
  • Headache
  • Muscle and joint pain
  • Swollen lymph nodes
• Erythema migrans (EM) details:
  • A reddish or purple-colored rash that appears $3-\ 30\text{ days}$ after the tick bite
  • Typically appears at the bite site; round or oval and expands over several days
  • Can appear on any area of the body
  • The center of the rash may clear as it enlarges, yielding a bull’s-eye appearance
  • EM occurs in over $70\%$ of people with Lyme disease
  • The rash may be warm but is rarely itchy or painful
• Not all rashes at the site of a tick bite are due to Lyme disease.
  • Allergic reactions to tick saliva can occur and be confused with EM; these usually appear within hours, do not typically expand over time, and disappear within days.
• A rash similar to EM has been described after bites from lone star ticks (Southern Tick-Associated Rash Illness, STARI); the cause is unknown but it is not due to Lyme disease.
• More severe forms of Lyme disease can appear weeks to months after a bite, including:
  • Arthritis with severe joint pain and swelling (usually in one or more large joints, especially the knees)
  • Nervous system symptoms: numbness, pain, facial palsy (often unilateral), meningitis (fever, stiff neck, severe headache)
  • Rare heart rhythm irregularities
• For a subset of people, fatigue, body aches, or difficulty thinking can persist after treatment.
• Reinfection is possible if bitten by another infected tick; protective measures are important.
• Key presentations include:
  • EM rash
  • Lyme arthritis (swollen knee)
  • Facial palsy (droop)

Diagnosis

• Clinicians should consider several factors:
  • Likelihood of exposure to infected blacklegged ticks (see geographic map)
  • Presence of signs/symptoms such as EM or arthritis
  • Other illnesses with similar symptoms
  • Laboratory test results, recognizing that serologic responses may take several weeks to develop
• FDA-cleared tests are recommended; most tests measure antibodies to infection, which may take weeks to appear in the blood.
• Antibodies, once produced, tend to remain detectable in the blood for months or years after recovery.
• Implications of testing:
  • A negative blood test result is possible if tested in the first few weeks after infection.
  • Providers should treat promptly if there is a history of recent tick exposure and signs of early Lyme disease (e.g., EM).
  • A negative test in a patient with arthritis or long-standing symptoms strongly suggests Lyme is not the cause.
  • Distinguishing reinfection from the original infection using a blood test is difficult; reinfection diagnosis relies on exposure history and symptoms.

Treatment

• People treated with appropriate antibiotics in the early stages usually recover rapidly and completely.
• Common antibiotics used include:
  • Doxycycline
  • Amoxicillin
  • Cefuroxime axetil
• Early diagnosis and proper antibiotic treatment can help prevent more severe disease.

Prevention: Tick Bite Prevention (People)

• Use EPA-registered insect repellents containing one of the following: $\text{DEET}, \text{picardin}, \text{IR3535}, \text{oil of lemon eucalyptus}, \text{para-menthane-diol}, \text{2-undecanone}$; always follow product instructions.
• Wear clothing treated with $0.5\%\text{ permethrin}$; re-treat clothing according to label instructions.
• Shower as soon as possible after spending time outdoors.
• Check for ticks daily; ticks can hide in armpits, behind the knees, in hair, and in the groin.
• Dry clothing in a dryer on high heat for $10\ \text{minutes}$ to kill ticks on dry clothing after coming indoors; if clothes are damp, dry completely and then run for another $10\ \text{minutes}$ on high heat.
• Vaccine status: There is not currently a vaccine for people to prevent Lyme disease, though clinical trials of new vaccines are underway.
• Post-Exposure Antibiotics: The CDC generally does not recommend antibiotics after tick bites to prevent tickborne diseases. In some circumstances, a single dose of doxycycline after a tick bite in areas where Lyme disease is common may lower the risk; consult your healthcare provider.

Tick Bite Prevention for Pets

• Use a tick preventive product on dogs; they are highly susceptible to tick bites and tickborne diseases.
• Discuss with your veterinarian about:
  • Lyme disease vaccination for your dog
  • The best tick prevention products for your pets
  • Tickborne diseases in your area
• Reduce tick exposure by:
  • Checking pets daily for ticks
  • Removing ticks from your pet promptly

Tick Control in the Yard (Environmental Management)

• Landscaping strategies to create tick-safe zones:
  • Blacklegged ticks require high humidity to survive and die quickly in drier environments.
  • Remove leaf litter and clear tall grass and brush around houses and at the edges of lawns to reduce tick numbers.
  • Placing wood chips or gravel between lawns/play areas and wooded areas creates a dry barrier difficult for ticks to cross.
  • Fences help keep deer away from homes.
• Zone definitions (based on a design diagram):
  • TICK ZONE: Avoid areas with forest and brush where deer, rodents, and ticks are common.
  • WOOD CHIP BARRIER: Use a $3\text{ ft}$ barrier of wood chips or rock to separate the “tick zone” from the lawn.
  • WOOD PILE: Keep wood piles on the wood chip barrier, away from the home.
  • TICK MIGRATION ZONE: Maintain a $9\text{ ft}$ barrier of lawn between the wood chips and areas such as patios, gardens, and play sets.
  • TICK SAFE ZONE: The area inside this perimeter where daily living activities occur.
• Garden planning: Plant deer-resistant crops; an optional $8\text{ ft}$ fence can keep deer out.
• Play sets should be kept in the “tick safe zone” in sunny areas where ticks have difficulty surviving.
• Diagram credit: Based on a diagram by K. Stafford, Connecticut Agricultural Experiment Station.
• For more information, contact CDC via telephone or web listed in the original material.

Miscellaneous and Practical Notes

• The material emphasizes practical, evidence-based tips for prevention, early detection, and treatment.
• The information reflects CDC guidelines and emphasizes that risk varies by geography, season, and tick activity.
• Always consult a healthcare professional for diagnosis and treatment, especially for pregnant individuals or pets.