**Question:** The following are recognized infectious causes of eosinophilia EXCEPT-

A. Parvovirus B19 infection
B. Tuberculosis
C. Leishmaniasis
D. Strongyloides stercoralis infection

**Core Concept:**
Eosinophilia is an increase in the number of eosinophils, a type of white blood cell, in the bloodstream. Eosinophilia can be caused by various infectious agents or conditions. Recognized infectious causes of eosinophilia include parasitic infections, bacterial infections, viral infections, and fungal infections.

**Why the Correct Answer is Right:**
Option A (Parvovirus B19 infection) is not typically associated with eosinophilia. Parvovirus B19 infection commonly presents with symptoms such as fever, arthralgia, and a non-specific rash. Eosinophilia is less common in this infection.

Option B (Tuberculosis) can lead to eosinophilia, particularly during the active phase of infection. Eosinophilia is relatively common in tuberculosis due to the involvement of eosinophils in the immune response against Mycobacterium tuberculosis.

Option C (Leishmaniasis) is known to cause eosinophilia, especially in the visceral form of the disease. Eosinophils are involved in the immune response against Leishmania parasites, leading to increased eosinophilia.

Option D (Strongyloides stercoralis infection) is a common cause of eosinophilia, especially in endemic regions. Strongyloides stercoralis, a nematode (roundworm), triggers an immune response involving eosinophils, resulting in increased eosinophils and eosinophilia.

**Why Each Wrong Option is Incorrect:**
Option A (Parvovirus B19 infection) is less likely to cause eosinophilia compared to the other options.
Option B (Tuberculosis) can cause eosinophilia but is less common than Leishmaniasis and Strongyloides stercoralis infections.
Option C (Leishmaniasis) is a specific cause of eosinophilia due to the involvement of eosinophils in the immune response against Leishmania parasites.
Option D (Strongyloides stercoralis infection) is a common cause of eosinophilia due to the nematode parasite triggering an immune response involving eosinophils.

**Clinical Pearls:**
Eosinophilia is a useful clinical marker for diagnosing parasitic infections, particularly when associated with clinical signs and symptoms. A high suspicion index for parasitic infections should be maintained in endemic regions, especially in patients presenting with eosinophilia, to initiate appropriate diagnosis, treatment, and management.