What is the recommended prophylaxis for a 9-year-old child after a tick (Ixodes scapularis) bite in a Lyme disease endemic area?

Pediatric Lyme Disease Prophylaxis After Tick Bite

For a 9-year-old child with an Ixodes scapularis tick bite in a Lyme disease endemic area, a single dose of doxycycline (4 mg/kg, maximum 200 mg) is recommended as prophylaxis if specific criteria are met. 1

Prophylaxis Decision Criteria

Prophylactic treatment should only be given when ALL of the following conditions are met:

1. The tick is identified as an adult or nymphal Ixodes scapularis (deer tick)
2. The tick was attached for ≥36 hours (based on engorgement or known time of attachment)
3. Prophylaxis can be started within 72 hours of tick removal
4. The local rate of tick infection with Borrelia burgdorferi is ≥20% (typically only in parts of New England, mid-Atlantic states, Minnesota, and Wisconsin)
5. Doxycycline is not contraindicated for the child 2, 1

Dosing for Children

• For a 9-year-old child (≥8 years of age): Single dose of doxycycline at 4 mg/kg (maximum 200 mg) 2, 1, 3
• This single-dose approach has been shown to be approximately 87% effective in preventing Lyme disease after a tick bite 4

Important Timing Considerations

• Prophylaxis must be administered within 72 hours of tick removal to be effective 1
• The efficacy decreases significantly if administered later than 72 hours post-tick removal 5
• The risk of Borrelia transmission increases dramatically during the third day (>48 hours) of tick attachment, with 50% transmission probability occurring at approximately 68 hours of attachment 6

When Prophylaxis is NOT Recommended

• If the tick was attached for less than 36 hours
• If prophylaxis cannot be started within 72 hours of tick removal
• If the local infection rate of ticks is below 20%
• If the tick cannot be reliably identified as Ixodes scapularis 2, 1

Monitoring After Tick Bite

If prophylaxis criteria are not met or prophylaxis is not given:

• Monitor for symptoms of Lyme disease for 30 days after tick removal
• Watch for erythema migrans (bull's-eye rash), which typically appears 7-14 days (range 3-30 days) after tick detachment
• Seek medical attention if symptoms develop such as expanding red rash, fever, headache, fatigue, or muscle/joint pain 1

Safety Considerations for Doxycycline in Children

• Doxycycline is now considered safe for short-term use in children under 8 years old
• Previous concerns about dental staining have been largely disproven for short courses of treatment 7
• The single-dose prophylactic regimen has minimal risk of significant adverse effects 4, 7

Prevention of Future Tick Bites

• Use EPA-registered repellents containing DEET, picaridin, or permethrin on clothing
• Wear protective clothing (long-sleeved shirts, pants, socks, closed-toe shoes)
• Perform regular tick checks after outdoor activities
• Limit exposure to tick-infested habitats when possible 1, 8

Proper Tick Removal Technique

• Use fine-tipped tweezers to grasp the tick as close to the skin as possible
• Pull upward with steady pressure
• Clean the bite area thoroughly with soap and water, alcohol, or iodine scrub 1

Remember that prophylaxis is only one component of Lyme disease prevention, and the decision to use prophylactic antibiotics should be based on careful assessment of the specific risk factors for each tick bite incident.