Sensitivity of Plasmodium falciparum to antimalarial drugs in Colombia.

Sensitivity of Plasmodium falciparum to several antimalarial drugs was determined by in vitro and in vivo tests. Chloroquine resistance in vitro was detected in 97 of 101 patients from different geographic areas of Colombia. Sensitivity to amodiaquine in vitro was observed in 29 of 30 P. falciparum isolates. In vitro sensitivity to amodiaquine was observed in 16 patients infected with chloroquine-resistant P. falciparum. In vitro sensitivity to quinine was demonstrated in 57 P. falciparum isolates. Two infections from the Amazon base (2/24) were resistant to mefloquine in vitro at concentrations of 5.7 and 16 pmol/well. Resistance to Fansidar, a sulfadoxine-pyrimethamine combination, was described in 9 patients from the Amazon region. One patient showed recrudescence of the infection 41 days after treatment. The current distribution and degree of resistance of P. falciparum to widely used antimalarial drugs requires the evaluation of therapeutic schemes based on combinations of fast blood schizontocides with slow acting drugs. These associations may reduce the development of multidrug-resistant isolates and retard the spread of resistant populations of P. falciparum parasites.

Indirect ELISA test for malaria in blood donors.

To determine the potential risk of transfusion malaria at the Hospital Militar Central in Bogota, Colombia, sera from 3114 blood donors were tested for malaria antibodies by the indirect ELISA technique. Positive results were found in 8.6 per thousand of the serum samples using P. falciparum antigen containing more than 60% mature forms as substrate. Three cases of transfusion-induced malaria were confirmed during the study. The first patient developed a P. vivax infection one week after the administration of one unit of infected blood. The other two patients received a red blood cell concentrate and a platelet preparation, respectively, derived from a single donor and developed a P. falciparum infection eight days after transfusion. The application of the ELISA technique would be of use in attempts to control transfusion-induced malaria.

Specific identification of Plasmodium sporozoites using an indirect fluorescent antibody method.

The specific identification of plasmodial sporozoites is not possible on morphological grounds. This study presents a serological method for the identification of sporozoite species, indicating the suitability of this approach for detection and determination of sporozoites in wild vectors collected from malaria endemic areas. Specific antisera and monoclonal antibodies prepared against each of two species of rodent malaria (Plasmodium berghei or P. yoelii) were evaluated for their ability to discriminate among sporozoites of different malaria species (P. vivax, P. gallinaceum, P. berghei, P. yoelii) from varied host types. Antisera produced by intravenous immunization of rabbits or mice and hybridoma-produced monoclonal antibodies reacted only with homologous sporozoites in an immunofluorescent antibody test. Antisera produced by intravenous challenge showed no significant difference in reactivity with fresh sporozoites as compared with sporozoites frozen at -80 degrees C for up to six months, whereas antisera produced by infective mosquito bites showed reduced sensitivity to frozen-stored homologous sporozoites and some cross-reactions with heterologous sporozoites. Antisera prepared against the erythrocytic stages of P. berghei or P. yoelii also cross-reacted with sporozoites of all four plasmodia tested, indicating that it is advantageous to use anti-sporozoite antibodies for the identification of malaria sporozoite species by means of serological tests.