Predictive value of the eosinophil counts in the biological diagnosis of lymphatic filariasis in French Polynesia.

SETTINGS: Lymphatic filariasis is common in many tropical and subtropical areas and is a major public health issue in south Pacific islands. In endemic areas, most infected individuals are asymptomatic but may harbor microfilariae or filarial antigens in their peripheral blood. Microscopy remains the reference diagnostic tool for the identification of microfilariae but is weakly sensitive. The diagnosis of Wuchereria bancrofti infection was dramatically altered by the development of filarial antigen tests, which are easy to perform but expensive for routine use. Lymphatic filariasis is responsible for acquired eosinophilia and blood eosinophil count is commonly used as a screening tool in endemic areas.

METHOD: We retrospectively analyzed all the results of eosinophil counts, antigen and microfilariae detection performed in our laboratory over a 24-month period. We calculated the prevalence of antigenemia for various eosinophilic cut offs.

RESULTS: The prevalence of antigenemia was estimated at 25.78% with eosinophilia defined as a count eosinophilic PMN above 500 per mm(3).

DISCUSSION: Our prevention strategy against lymphatic filariasis is based on annual mass drug administration, vector control, and systematic treatment of antigenemic and microfilaremic patients. Antigenemic and microfilaremic detection cannot be routinely performed because of their cost. Current treatments used for lymphatic filariasis are safe and cheaper than antigenic detection. A possible additional strategy to decrease the prevalence of antigenemia would be the systematic treatment of patients with hypereosinophilia.