A 4-year-old child from a rural area develops dry cough, wheeze, low grade fever, and marked eosinophilia one week after playing in soil contaminated with human faeces. Chest radiograph shows transient migratory infiltrates. Which event produced these pulmonary findings?

• A Hypersensitivity reaction to third stage larvae breaking into the alveoli ✓
• B Direct injury by adult worms lodged in the bronchial tree
• C Embolic spread of ingested ova to the pulmonary vasculature
• D Secondary bacterial pneumonia following mucosal invasion by ova

Explanation

Third stage larvae of Ascaris lumbricoides hatch in the small intestine, enter the portal circulation, and break out of pulmonary capillaries into the alveoli roughly a week after ova are swallowed. This transit triggers an IgE mediated hypersensitivity response, Loeffler syndrome, with cough, wheeze, migratory infiltrates, and striking eosinophilia. Adult worms reside in the small intestine where they cause obstruction or biliary ascariasis, and ova do not embolise to the lung.

Reference: Paniker's Textbook of Medical Parasitology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.