Which statement about eosinophilia is true?

• A. It is always present in helminth infections
• B. It is often associated with helminth infections but not always present
• C. It is a marker for protozoan infections only
• D. It is never associated with parasitic infections

Answer: (B)

Eosinophils rise in response to many helminth (worm) infections because these parasites trigger a strong type 2 immune response. IL-5 drives eosinophil production and recruitment, and eosinophils release cytotoxic granules that can damage the parasite. This is why eosinophilia is commonly seen with helminth infections.

But the presence of eosinophilia is not universal. Depending on the parasite species, the stage of the infection, the parasite burden, and the host’s immune status, circulating eosinophil levels can be normal or only mildly elevated. Some helminths or certain clinical scenarios may not produce a noticeable eosinophilic response. Protozoan infections, by contrast, typically do not cause eosinophilia. So, while eosinophilia is often associated with helminth infections, it is not always present.