What are the symptoms and treatment options for tick-borne illnesses?

Tick-Borne Illness Symptoms and Treatment

Primary Symptoms by Disease Type

The most critical early symptoms of tick-borne illnesses are fever, headache, and malaise—often appearing 5-14 days after tick bite—with specific rash patterns and laboratory abnormalities helping distinguish between diseases. 1

Rocky Mountain Spotted Fever (RMSF)

• Fever (nearly universal), headache (86%), and myalgia (76%) typically appear first 1
• Rash develops in 90% of patients but often appears AFTER the first 2-4 days of illness, making early diagnosis challenging 1
• The rash begins as small pink macules on wrists, forearms, and ankles, spreading centrally and becoming petechial 2
• Palms and soles involvement is characteristic but may not appear until day 5-6 1, 2
• Gastrointestinal symptoms (nausea, vomiting) are less common than in ehrlichiosis 1
• RMSF is the most lethal tick-borne disease in the United States—delay in treatment is the most important factor associated with death 1

Ehrlichiosis (E. chaffeensis)

• Fever (96%), headache (72%), malaise (77%), and myalgia (68%) are predominant 1
• Gastrointestinal manifestations are prominent: nausea (57%), vomiting (47%), diarrhea (25%) 1, 3
• Rash occurs in only 20-40% of patients, making it less reliable for diagnosis 1
• Symptoms appear median 9 days (range 5-14 days) after tick bite 1, 3
• Case-fatality rate is approximately 3% 3

Anaplasmosis (A. phagocytophilum)

• Fever, headache, and myalgia are typical; rash is RARE (occurs in <10% of patients) 1
• Patients typically seek care 4-8 days after fever onset 3
• Case-fatality rate is <1%, but 7% of hospitalized patients require ICU admission 1
• Serious opportunistic viral and fungal infections can occur during acute illness 1

Rickettsia parkeri Rickettsiosis

• Nearly all patients develop an inoculation eschar (90%) 1
• Rash primarily involves trunk and extremities, with palms/soles involvement in approximately 50% 1
• Fever, headache (86%), and myalgia (76%) are common 1
• Illness is typically milder than RMSF; no deaths have been reported 1

Critical Laboratory Findings

Laboratory abnormalities provide crucial diagnostic clues when symptoms are nonspecific: 1

Common Findings Across Tick-Borne Diseases

• Thrombocytopenia (low platelets) occurs in 40-50% of cases 1
• Leukopenia (low white blood cells) occurs in approximately 50% 1
• Elevated hepatic transaminases occur in 78% of R. parkeri cases and commonly in other tick-borne diseases 1
• Mild hyponatremia is frequently present 1

Disease-Specific Laboratory Features

• Anaplasmosis: Morulae may be visible within granulocytes on blood smear 1
• Ehrlichiosis: Morulae may be visible within monocytes 1
• Lymphocytosis can appear during recovery period in ehrlichiosis and anaplasmosis 1

Treatment Approach

Doxycycline 100 mg twice daily (adults) or 2.2 mg/kg twice daily (children <45 kg) should be initiated IMMEDIATELY when tick-borne rickettsial disease is suspected, without waiting for laboratory confirmation. 1, 4

Critical Treatment Principles

• Treatment must begin empirically based on clinical suspicion—diagnostic tests are not helpful during initial illness stages 1
• Fever typically resolves within 24-48 hours if doxycycline is started during the first 4-5 days of illness 1
• Doxycycline is the drug of choice for ALL ages, including children <8 years and pregnant women when RMSF is suspected 1, 4
• Oral therapy is appropriate for early-stage disease in outpatients; IV therapy for severely ill hospitalized patients 1

When to Hospitalize

Hospitalize patients with: 1, 2

• Evidence of organ dysfunction
• Severe thrombocytopenia
• Mental status changes
• Need for supportive therapy

Empiric Treatment for Multiple Diagnoses

When meningococcemia cannot be ruled out, administer both doxycycline AND ceftriaxone (or other appropriate antibiotics for N. meningitidis) pending culture results 1

Diagnostic Pitfalls and Key Clinical Pearls

The "Classic Triad" Myth

The classic triad of fever, rash, and tick bite is RARELY present when patients first seek care 1

• Most patients do not recall a tick bite 1
• Rash appears late in RMSF (after 2-4 days) 1
• Early symptoms are nonspecific and easily mistaken for viral illness 1

Common Misdiagnoses

Tick-borne diseases are frequently mistaken for: 1

• Viral gastroenteritis (especially ehrlichiosis with prominent GI symptoms)
• Upper respiratory tract infection
• Urinary tract infection
• Viral meningoencephalitis

Coinfection Considerations

The Ixodes scapularis tick transmits multiple pathogens; coinfection with Lyme disease (B. burgdorferi) or babesiosis (B. microti) occurs in <10% of anaplasmosis cases 1

• If patient fails to respond to doxycycline within 48 hours, consider coinfection or alternative diagnosis 1
• Leukopenia or thrombocytopenia in a Lyme disease patient should raise suspicion for A. phagocytophilum coinfection 1

Geographic and Seasonal Clues

• Most cases occur during spring and summer months, but year-round transmission is possible 1, 2
• Recent outdoor activities in wooded or grassy areas increase risk 2
• Geographic location helps narrow differential (e.g., RMSF more common in southeastern US) 5

Follow-Up Requirements

Close outpatient follow-up is essential—patients must return within 24-48 hours if substantial improvement is not observed 1

• Emphasize to patients that these diseases can progress rapidly 1
• Reevaluate if fever persists beyond 48 hours of appropriate doxycycline therapy 1