Which finding in a peripheral blood smear is especially associated with tissue-invading helminths?

Which finding in a peripheral blood smear is especially associated with tissue-invading helminths?

• A. Eosinophilia
• B. Leukopenia
• C. Lymphocytosis
• D. Neutropenia

Answer: (A)

Eosinophils rise in response to tissue-invading helminths because these parasites trigger a Th2-driven immune reaction that promotes eosinophil production and recruitment. Eosinophils are specialized for attacking large parasites, releasing cytotoxic granule proteins such as major basic protein that damage the worm’s surface, and they participate in antibody-dependent cellular cytotoxicity via IgE. On a peripheral blood smear, this shows up as eosinophilia—an increased number or percentage of eosinophils. The other options don’t specifically reflect a helminth invasion: leukopenia is a general reduction in white blood cells, lymphocytosis is more typical of certain viral infections, and neutropenia is often seen with bacterial infections or bone marrow suppression.