A parasitological and serological malária survey in Amazonas, 1971

Abstract

Thick blooã film s anã malaria indirect fluorescent antiboãy testM alaria due to Plasmoãium falciparum aud P. vivax, was formerly hyperendemic in Amazonas. In 1967-1968 the spraying of houses with the residual insecticide DDT, on a regular cycle, was started and this has been very effective against the m ain vector, Anopheles ãarlingi, which has alm ost disappeared from houses. There has also been widespread distribution of an tim alaria drugs. This resulted in a dram atic decrease in the incidence of m a laria in m an although passive surveillance figures for 1970 still showed a parasite index of from 0.3 to 15% in different m unicipalities of this vast area.In July-August 1971 a survey for m a laria antibodies was done in four different regions in order to compare serological and parasitological data, and to see wheth er the form er could give fu rth er Inform ation about the am ount of m alaria tra n s mission which m ight still be occurring. METHODSDrops of blood were collected on pieces of W hatm an No. 3 chrom atography papel, 5 sets of drops from different individuais being collected o,n one piece of paper measuring about 14 x 9 cms -a convenient size to h a n d le . W hen fully dried these were sealed into polythene bags and protected from extrem es of h eat before being tested. In the laboratory a disc, or discs, of paper equivalent to 50 /il. of blood was cut out and eluted in 0.4 ml. of phosphate buffered saline (PES) to give an approxim ate 1/16 dilution of serum and this, and subsequent dilutions of positive sera made by the 'M icrotitre' method, were used to test for antibodies in the m alaria indirect fluorescent antibody test (IFAT) . The latter was done with thick blood films of Plasmoãium falciparum and P. vivax by the m ethod of Sulzer et al. in 1969, (3) as