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Patient Case: Loiasis

Patient Case: Loiasis

Discussion

Chief Complaint: “I noticed a worm moving under my skin, and it’s been bothering me for a few weeks.”

History of Present Illness:
A 34-year-old man presents with a complaint of visible, moving swelling under the skin on his right forearm. He reports first noticing the swelling about two weeks ago, which has since grown larger and has become increasingly painful. The swelling is accompanied by intermittent itching. The patient recalls that during a recent trip to a rural area, he was bitten multiple times by mosquitoes, but he didn’t think much of it at the time.

The patient denies fever, joint pain, or any other systemic symptoms but mentions that the swelling appears to move slowly from one location to another under his skin. He has no significant medical history and is otherwise healthy.

Physical Examination:

  • A 2 cm long, raised, serpiginous, and slightly erythematous lesion located on the right forearm
  • The lesion is tender, and the patient can feel a worm moving beneath the skin
  • No lymphadenopathy, fever, or other systemic symptoms
  • No other active lesions or skin abnormalities

Diagnosis:
Based on the clinical presentation of a moving subcutaneous worm and a history of mosquito bites, loiasis is suspected. The disease is caused by Loa loa, a parasitic worm transmitted by the bite of infected deer flies (Chrysops), which leads to the migration of the adult worms under the skin. This condition is often characterized by the appearance of "calabar swellings," which are transient, localized reactions to the migration of the worm.

Management Plan:

  • Antiparasitic treatment: Diethylcarbamazine (DEC) to kill adult worms and microfilariae
  • Symptomatic relief: Pain management with NSAIDs
  • Patient education:
    • Preventing further mosquito bites using insect repellent and sleeping under insecticide-treated nets
    • Informing the patient about the importance of completing the DEC course for effective parasite elimination

The patient is scheduled for follow-up to monitor treatment response and ensure the complete removal of the parasite.

Questions
1. What is the most likely causative organism responsible for this patient’s symptoms?

a) Loa loa
b) Onchocerca volvulus
c) Wuchereria bancrofti
d) Dracunculus medinensis

2. How is loiasis most commonly transmitted to humans?

a) By drinking contaminated water
b) Through mosquito bites carrying infected larvae
c) By direct contact with infected animals
d) Through consumption of undercooked meat

3. Which of the following is a typical sign of loiasis?

a) Subcutaneous, moving worm causing swelling
b) Severe headaches and fever
c) A sudden, painful eye infection
d) Skin ulcers with pus-filled lesions

4. What is the most appropriate treatment for loiasis?

a) Oral albendazole
b) Diethylcarbamazine (DEC)
c) Topical antibiotics
d) Oral doxycycline

Reveal answers

Answers

  1. (a) Loa loa – Loiasis is caused by the parasitic worm Loa loa, which is transmitted by the bite of infected deerflies and causes the classic symptom of a moving subcutaneous worm.
  2. (b) Through mosquito bites carrying infected larvae – Loiasis is transmitted by the bite of infected deerflies (Chrysops), which introduce larvae into the human bloodstream.
  3. (a) Subcutaneous, moving worm causing swelling – A characteristic feature of loiasis is the migration of adult worms under the skin, often referred to as "calabar swellings," which can be visually identified as moving lesions.
  4. (b) Diethylcarbamazine (DEC) – Diethylcarbamazine is the treatment of choice for loiasis, as it is effective in killing both adult worms and microfilariae. It is important for eliminating the parasite from the body.

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