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Question

Difficulty: MediumInfectious Diseases

Match each clinical exposure scenario with the most appropriate post-exposure prophylaxis or management strategy.

  • A 40-year-old man in an endemic area who presents to the clinic after safely removing an engorged Ixodes scapularis tick that was attached to his abdomen for approximately 48 hours.Administration of a single dose of oral doxycycline
  • A 28-year-old pregnant woman, with no prior history of varicella infection or vaccination, who had significant face-to-face contact with a child with active chickenpox 2 days ago.Administration of varicella-zoster immune globulin (VZIG)
  • A 32-year-old unvaccinated medical resident who sustains a deep needlestick injury from a patient known to be hepatitis B surface antigen (HBsAg) positive.Administration of hepatitis B immune globulin (HBIG) and hepatitis B vaccination series
  • A 14-year-old boy who sustains a provoked bite on the hand from a vaccinated, healthy-appearing neighborhood dog that is available for quarantine.Thorough wound cleansing and 10-day observation of the animal

Answer

The tick bite meets criteria for single-dose doxycycline. The pregnant woman exposed to varicella requires VZIG. The unvaccinated healthcare worker exposed to HBV requires both HBIG and the HBV vaccine series. The provoked bite from a healthy domestic dog requires wound care and 10-day observation of the animal.
Each clinical scenario presents a distinct infectious exposure requiring a targeted preventive strategy. Tick bites meeting specific attachment criteria require single-dose doxycycline. Pregnant patients exposed to varicella require passive immunity with VZIG because live vaccines are contraindicated. Unvaccinated healthcare workers exposed to Hepatitis B require both active and passive immunity. Bites from healthy domestic animals available for quarantine do not require immediate rabies PEP, only observation and wound care.

Step-by-Step Solution

1
Analyze the tick bite exposure in the 40-year-old man.
The patient meets criteria for prophylaxis: Ixodes tick, endemic area, attachment time >36 hours (48 hours).
Single-dose oral doxycycline is highly effective at preventing Lyme disease when administered under these specific criteria.
2
Evaluate the varicella exposure in the pregnant patient.
The patient lacks immunity and faces a high-risk exposure, but live vaccines are contraindicated.
Varicella-zoster immune globulin (VZIG) provides immediate, safe passive immunity for pregnant individuals to prevent congenital and maternal complications.
3
Assess the needlestick injury in the medical resident.
An unvaccinated host was exposed to a known HBsAg-positive source.
Optimal prevention of Hepatitis B infection requires immediate passive immunity via HBIG and the initiation of long-lasting active immunity via the HBV vaccination series.
4
Determine the rabies risk for the dog bite.
The dog is a domestic animal, healthy-appearing, and available for quarantine.
Immediate rabies PEP is unnecessary; observing the dog for 10 days ensures it was not shedding the rabies virus at the time of the bite.

Key Concept

Appropriate selection of post-exposure prophylaxis based on pathogen, host immune status, and exposure characteristics.
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Topics

Infectious Diseases

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