A TECHNIQUE FOR THE DETECTION OF MINIMAL NUMBERS OF MALARIA PARASITES; ITS APPLICATION IN THE DETECTIN OF SUPPRESSED VIVAX MALARIA 123

It has been demonstrated, by the subinoculation of large volumes of blood, that malaria parasites are present in the peripheral circulation of indi- viduals who have been bitten by infected mosqui- toes but whose disease is suppressed with adequate treatment (1).Since each examination by this procedure requires the use of an additional volunteer subject, a substitute method which yields the same information without necessitating a cor- responding utilization of recipients should be highly desirable.Whereas not less than 10 malaria parasites per mm.8 or 10,000 per cm.3 of blood are required to be uniformly detectable by the usual thick smear examination, the method of Ferrebee and Geiman (2) for the preparation of concentrates of parasitized red blood cells is applicable, with slight modification, to the demonstration of Plas- modium vivax at parasite densities far below those required for detection by the routine laboratory method.The modified concentration technique permits the demonstration of parasites when they are present in concentrations of less than 100 per cm.8 of blood.1 The work described in this paper was done under