OFFICIAL ABP TOPIC:

Tick-borne Illness – Understand, evaluate, and manage a patient with possible tick-borne illness

BACKGROUND

Tick-borne diseases are a significant and growing public health concern in the United States, with the number of reported cases rising in recent decades. These infections can be life-threatening, making it critical for pediatricians to recognize the signs and symptoms early and promptly begin treatment.

RECOGNIZING TICK-BORNE ILLNESS

Most tick-borne infections occur during spring and summer when tick activity peaks and people spend more time outdoors. The most common ticks transmitting diseases to humans are:

• Blacklegged tick and Western blacklegged tick: Vectors for Lyme disease, Anaplasmosis, and Babesiosis. Found in the Northeast, mid-Atlantic, upper Midwest, and coastal Northern California.
• Lone star tick: Vector for Ehrlichiosis. Found in the Southeast and parts of the Midwest and Northeast.
• American dog tick (eastern, central, and western U.S.) and Rocky Mountain wood tick (Rocky Mountain states): Vectors for Rocky Mountain spotted fever (RMSF).

SPECIFIC TICK-BORNE DISEASES

LYME DISEASE

• Causative organism: Borrelia burgdorferi (spirochete)
• Rash: Erythema migrans (EM), the hallmark bull’s-eye rash, in ~70-80% of cases.
• Systemic symptoms: Fever, fatigue, headache, myalgias, and arthralgias are common in the early stage.
• Disseminated disease: Multiple EM lesions, Bell’s palsy, meningitis, carditis, and arthritis may occur if untreated.
• Lab findings: ↑ ESR, ↑ AST/ALT, microscopic hematuria, or proteinuria.

IMAGE: www.pbrlinks.com/ERYTHEMA-C1

RMSF

• Causative organism: Rickettsia ricketsii (bacterium)
• Rash: Maculopapular rash starts on wrists and ankles, spreads to trunk and palms/soles within hours, becoming petechial after day 6. Present in >90% of children.
• Other symptoms: High fever, severe headache, myalgia, periorbital edema, photophobia, abdominal pain, vomiting. Severe cases may lead to altered mental status, respiratory compromise, necrosis, and multiorgan failure.
• Severity: Can be severe and fatal if treatment is delayed.
• Lab findings: ↓ WBC, ↓ platelets, ↓ Hgb, ↓ Na, ↑ AST/ALT.

EHRLICHIOSIS

• Causative organism: Multiple bacterial species of Ehrlichia
• Rash: Maculopapular, petechial, or diffuse erythema on trunk and extremities. Appears in 30-40% of children.
• Other symptoms: Fever, headache, myalgia, abdominal pain, diarrhea.
• Severity: May rapidly progress to sepsis/shock and multiorgan failure if untreated.
• Lab findings: ↓ WBC, ↓ platelets, ↓ Hgb, intracellular bacterial clusters on peripheral smear (low sensitivity), ↓ Na, ↑ AST/ALT, CSF pleocytosis.

ANAPLASMOSIS

• Causative organism: Anaplasma phagocytophilum (same family as Ehrlichia)
• Rash: Occurs in <10% of cases.
• Systemic symptoms: Similar to ehrlichiosis but usually milder.
• Severity: Generally self-limited but can be severe in elderly or immunocompromised.
• Lab findings: ↓ WBC, ↓ platelets, intracellular bacterial clusters on peripheral smear (low sensitivity), ↓ Na, ↑ AST/ALT.

BABESIOSIS

• Rash: Typically no rash.
• Symptoms: Gradual onset of fatigue, malaise, anorexia, progressing to fever, chills, arthralgia, myalgia, and headache.
• Severity: Often asymptomatic or mild, but can be severe and life-threatening (DIC, renal failure, shock, respiratory distress, hypotension).
• Lab findings: Intraerythrocytic Babesia parasites on peripheral blood smear (“Maltese cross”), hemolytic anemia, ↑ retic, ↓ platelets, proteinuria, ↑ BUN, ↑ Cr, ↑ LFTs.

EVALUATION OF TICK-BORNE ILLNESSES

HISTORY

Ask about outdoor activity, travel to endemic areas, and known tick exposure. Elicit timing and progression of symptoms.

PHYSICAL EXAM

Inspect for rashes or embedded ticks. Assess for hepatosplenomegaly, jaundice, altered mental status, and any focal neurologic deficits.

DIAGNOSTIC TESTING

• Lyme disease: Two-tiered serologic testing with ELISA, followed by Western blot if ELISA is positive or equivocal. Antibody titers may be negative in the first 2 weeks.
• RMSF: Serologic testing of acute and convalescent samples to demonstrate rising antibody titers, PCR for rickettsial DNA in a skin biopsy.
• Ehrlichiosis/Anaplasmosis: PCR during the first week or serologic testing at least 2-4 weeks later.
• Babesiosis: PCR analysis or peripheral blood smear to visualize organisms. Antibody testing can help confirm.

Consider CBC, peripheral blood smear, LFTs, BMP, and U/A depending on clinical findings and which tick-borne illness is suspected. Hemolytic anemia is common in babesiosis.

MANAGEMENT OF TICK-BORNE ILLNESS

Lab serologies may sometimes take weeks to come back. Presumptive treatment may be needed depending on the specific tick-borne illness:

• Lyme disease: Presumptively treat patients with EM, regardless of serology. Also treat patients with positive Western blot who have other symptoms of Lyme disease. Do NOT treat seropositive patients who are asymptomatic or have nonspecific symptoms.
• RMSF: Start treatment as soon as diagnosis is suspected without waiting for serology results. Early treatment is associated with improved outcomes.
• Ehrlichiosis/Anaplasmosis: Start treatment if clinically suspected without waiting for diagnostic testing; delaying treatment may lead to severe disease.
• Babesiosis: Only treat symptomatic active babesiosis (positive blood smear or positive PCR). No treatment is needed for asymptomatic children, even if testing is positive.

SUMMARY OF TREATMENT FOR SPECIFIC TICK-BORNE ILLNESSES

Doxycycline dosing is 2.2 mg/kg/dose BID up to a max of 100 mg BID (PO or IV).

The AAP now supports the use of doxycycline in children <8 years old for up to 21 days. Consult ID if longer treatment needed for children <8 (e.g., Lyme arthritis).

REFERENCES

https://publications.aap.org/pediatricsinreview/article/40/8/381/35322/Tickborne-Diseases-in-Children-in-the-United

https://www.uptodate.com/contents/treatment-of-lyme-disease