[Reactive hypereosinophilia in parasitic diseases]

Hypereosinophilia is often linked to the presence of pluricellular parasites in host tissues. Polynuclear eosinophils are sprung from the bone marrow. After multiplying and maturing, they are thrown into the blood flow and from the blood to the tissues where they are found in immediate contact with the parasite. Eosinophils are major components of the parasitic granuloma. Parasitic diseases are a major cause of hypereosinophilia and eosinophilia is mainly due to helminths. Protozoa do not produce hypereosinophilia, except for toxoplasmosis in which a low and discontinuous eosinophilia may be seen. Subsequently, maggots producing myiasis yield to hypereosinophilia too. In helminthiasis, the action of the eosinophil granulocyte is double. In tissues, it destroys the parasite and plays a regulatory role in mastocytes degranulation. Eosinophils which participate in the inflammatory reaction secrete factors which neutralize mediators liberated by mastocytes, histamine mainly, destroyed by histaminase. In a practical point of view, blood hypereosinophilia is a very useful tool for diagnosis. Eosinophilia reach early a high value, this before the parasitic infection becomes detectable by means of resources other than immunological. The eosinophils rates decreases rapidly as an effect of the anthelmintic drug, this confirming the efficacy and specificity of the prescribed treatment.