Paired day and night blood specimens from 41 persons living in a hyperendemic Wuchereria bancrofti area of southwestern Ethiopia were examined for microfilariae by Nuclepore® filter, thick film, and counting chamber techniques. Filtering techniques were so highly sensitive that more infected persons were identified by filtering day blood than by examining night blood by conventional methods. Increasing the volume of blood filtered from 1 ml to 5 ml increased the number of positives identified during the day. Filtering 5 ml of day blood obviated the need for examining night blood, even though a high proportion of infected persons had very low numbers of circulating microfilariae.
Present address: NAMRU-2, Djakarta Detachment, A.P.O. San Francisco 96356.
NAMRU-5, Ethiopia, A.P.O. New York 09319.
Present address: Department of Entomology, British Museum (Natural History), London SW7 5BD, England.