Tick-Borne Diseases

Understanding the diseases transmitted by ticks and their symptoms

Understanding Tick-Borne Diseases

Ticks can spread many different diseases to people and animals. These diseases are caused by tiny germs (bacteria, viruses, or parasites) that live inside the tick. When a tick bites you and feeds on your blood, it can pass these germs into your body.

The good news is that most tick-borne diseases can be treated successfully, especially if caught early. That's why it's so important to know the symptoms and see a doctor quickly if you get sick after a tick bite.

💡 Key Point

Not all ticks carry diseases, and not all tick bites result in illness. However, it's important to be aware of the symptoms so you can get help quickly if needed.

Lyme Disease

Lyme disease is the most common tick-borne disease in the United States. It's caused by bacteria called Borrelia burgdorferi and is spread by black-legged ticks (also called deer ticks).

Quick Facts:

  • How common: Most common tick disease in the U.S. - about 476,000 people are diagnosed and treated each year
  • Where it's found: Northeastern, mid-Atlantic, and upper midwestern United States; also parts of Europe and Asia
  • Which tick: Black-legged tick (deer tick)
  • How it spreads: Tick must be attached for 24-36 hours to transmit
Lyme disease bull's-eye rash (erythema migrans)

The characteristic "bull's-eye" or erythema migrans rash of Lyme disease. Image: Wikimedia Commons (CDC, Public Domain)

Early Symptoms (3-30 days after tick bite):

  • The "Bull's-Eye" Rash:
    • Appears in 70-80% of people with Lyme disease
    • Starts at the tick bite site
    • Usually appears 3-30 days after the bite (average 7 days)
    • Expands slowly, can reach 12 inches or more
    • May look like a target or bull's-eye
    • Usually doesn't itch or hurt
    • Can appear anywhere on the body
  • Flu-like symptoms: Fever, chills, headache, fatigue, muscle and joint aches, swollen lymph nodes

Later Symptoms (if not treated):

If Lyme disease isn't treated early, it can cause more serious problems:

  • Severe headaches and stiff neck
  • Arthritis (joint pain and swelling), especially in the knees
  • Facial drooping (facial palsy)
  • Heart problems (irregular heartbeat, dizziness)
  • Nerve problems (shooting pains, numbness, memory problems)

Treatment:

Lyme disease is treated with antibiotics. Early treatment is very effective. Common antibiotics used include doxycycline, amoxicillin, or cefuroxime.

References: CDC - Lyme Disease | Kugeler, K.J., et al. (2021). Estimating the frequency of Lyme disease diagnoses. Emerging Infectious Diseases, 27(2), 616-619.

Rocky Mountain Spotted Fever (RMSF)

RMSF is a serious tick-borne disease that can be life-threatening if not treated quickly. Despite its name, it's found throughout the United States, not just in the Rocky Mountains.

⚠️ Serious Disease

RMSF can be fatal if not treated promptly. Early treatment is critical - don't wait for test results if your doctor suspects RMSF.

Quick Facts:

  • How serious: Can be fatal if not treated
  • Where it's found: Throughout the U.S., most common in southeastern and south-central states
  • Which ticks: American dog tick, Rocky Mountain wood tick, brown dog tick
  • Treatment: Doxycycline (must start treatment immediately when suspected)

Symptoms (2-14 days after bite):

  • Fever
  • Headache
  • Rash (usually appears 2-5 days after fever starts)
  • Nausea and vomiting
  • Muscle pain
  • Loss of appetite

Reference: CDC - Rocky Mountain Spotted Fever (RMSF)

Anaplasmosis

Anaplasmosis is caused by bacteria and is spread by the same black-legged ticks that carry Lyme disease. It's often found in the same areas as Lyme disease.

Quick Facts:

  • Which tick: Black-legged tick (same as Lyme disease)
  • Where found: Same areas as Lyme disease
  • Treatment: Doxycycline

Symptoms:

  • Fever and chills
  • Severe headache
  • Muscle aches
  • Nausea, vomiting, diarrhea
  • Loss of appetite

Reference: CDC - Anaplasmosis

Babesiosis

Babesiosis is caused by tiny parasites that infect your red blood cells. It's spread by black-legged ticks and can be especially serious for people with weakened immune systems.

Quick Facts:

  • What causes it: Microscopic parasites (not bacteria)
  • Which tick: Black-legged tick
  • Where found: Northeastern and upper midwestern United States
  • Who's at risk: Can be severe in people with weakened immune systems

Symptoms:

  • Fever and chills
  • Heavy sweating
  • Headache
  • Body aches
  • Loss of appetite
  • Nausea
  • Fatigue

Treatment: Combination of medications (atovaquone + azithromycin, or clindamycin + quinine)

Reference: CDC - Babesiosis

Ehrlichiosis

Ehrlichiosis is caused by bacteria and is spread by lone star ticks. It's most common in the southeastern and south-central United States.

Quick Facts:

  • Which tick: Lone star tick
  • Where found: Southeastern and south-central United States
  • Treatment: Doxycycline

Symptoms:

  • Fever and chills
  • Severe headache
  • Muscle aches
  • Nausea, vomiting, diarrhea
  • Confusion
  • Rash (more common in children)

Reference: CDC - Ehrlichiosis

Other Tick-Borne Diseases

In addition to the diseases above, ticks can also spread:

Powassan Virus Disease
  • Rare but serious
  • Can cause brain infection
  • No specific treatment
  • Found in northeastern U.S. and Great Lakes region
Tularemia
  • Also called "rabbit fever"
  • Can be spread by several tick species
  • Treatable with antibiotics
  • Found throughout the U.S.

Co-Infections: Multiple Diseases from One Tick

A single tick bite can transmit more than one disease at the same time. This is called a "co-infection." For example, a black-legged tick can carry both Lyme disease and anaplasmosis, and you could get both from one bite.

⚠️ Important

Co-infections can make symptoms worse and may require treatment for multiple diseases. Always tell your doctor about any tick bites, even if you removed the tick quickly.

Recognizing Symptoms

Many tick-borne diseases start with similar symptoms, which can make them hard to tell apart:

Common Early Symptoms (Many Diseases):
  • Fever and chills
  • Headache
  • Fatigue
  • Muscle and joint aches
  • Nausea

When to see a doctor: If you develop these symptoms after a tick bite or spending time in tick areas, see a healthcare provider right away. Early treatment is key to preventing serious complications.

Reference: CDC - Signs and Symptoms of Tickborne Illness

Prevention is the Best Medicine

While it's important to know about these diseases, remember that prevention is your best defense. See our Tick Prevention guide for comprehensive strategies to avoid tick bites.

For more detailed information on specific diseases affecting humans, see our Human Diseases page.

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