Barnyen Permpanich

White Blood Cell Counts and Malaria

White blood cells (WBCs) were counted in 4697 individuals who presented to outpatient malaria clinics in Maesod, Tak Province, Thailand, and Iquitos, Peru, between 28 May and 28 August 1998 and between 17 May and 9 July 1999. At each site and in each year, WBC counts in the Plasmodium falciparum-infected patients were lower than those in the Plasmodium vivax-infected patients, which, in turn, were lower than those in the uninfected patients. In Thailand, one-sixth of the P. falciparum-infected patients had WBC counts of <4000 cells/microL. Leukopenia may confound population studies that estimate parasite densities on the basis of an assumed WBC count of 8000 cells/microL. For instance, in the present study, use of this conventional approach would have overestimated average asexual parasite densities in the P. falciparum-infected patients in Thailand by nearly one-third.

GAMETOCYTEMIA IN PLASMODIUM VIVAX AND PLASMODIUM FALCIPARUM INFECTIONS

Two expert research microscopists, each blinded to the others reports, diagnosed single-species malaria infections in 2,141 adults presenting at outpatient malaria clinics in Tak Province, Thailand, and Iquitos, Peru, in May–August 1998, May– July 1999, and May–June 2001. Plasmodium vivax patients with gametocytemia had higher fever and higher parasitemia than those without gametocytemia; temperature correlated with parasitemia in the patients with gametocytemia. Plasmodium falciparum patients with gametocytemia had lower fever than those without gametocytemia, but similar parasitemia; temperature correlated with parasitemia in the patients without gametocytemia. Hematologic data in Thailand in 2001 showed lower platelet counts in P. vivax patients with gametocytemia than in the P. vivax patients without gametocytemia, whereas P. falciparum patients with gametocytemia had similar platelet counts but lower red blood cell counts, hemoglobin levels, hematocrit levels, and higher lymphocyte counts than patients without gametocytemia.

Fever in Patients with Mixed-Species Malaria

BACKGROUND Clinical symptoms of mixed-species malaria infections have been variously reported as both less severe and more severe than those of single-species infections. METHODS Oral temperatures were taken from and blood slides were prepared for 2308 adults who presented at outpatient malaria clinics in Tak Province (Thailand) during May-August 1998, May-July 1999, and May-June 2001 with malaria infections diagnosed by 2 expert research microscopists, each of whom was blinded to the others reports. RESULTS In each year, temperatures of patients with mixed Plasmodium vivax-Plasmodium falciparum infections were higher than temperatures of patients with P. vivax or P. falciparum infections. In every mixed-species case, P. falciparum parasitemia was higher than P. vivax parasitemia, but patient temperature was not correlated with the parasitemia of either species or with the total parasitemia. CONCLUSIONS Among adults who self-report to malaria clinics in western Thailand, patients with mixed P. vivax-P. falciparum infections have higher fevers than patients with single-species infections, a distinction that cannot be attributed to differences in parasitemia. This observation warrants more detailed investigations, spanning wider ranges of ages and transmission environments.

Comparison of antibody responses to the circumsporozoite protein repeat region and to intact sporozoites during acute falciparum malaria

Most acute falciparum malaria patients mount an antibody response to the circumsporozoite (CS) protein which contains a dominant B-cell epitope. In order to investigate whether antibodies against other epitopes on the sporozoite surface may be important during a particular phase of infection or convalescence, we longitudinally studied the antibody responses of 13 Thai patients with acute falciparum malaria. Antibody comparisons were made using intact Plasmodium falciparum sporozoites in an indirect fluorescent antibody test and the recombinant peptide, R32tet32, as capture antigen in an enzyme-linked immunosorbent assay. Antibody response curves derived using the 2 methods were similar, and adsorption with R32tet32 greatly (greater than 95%) diminished anti-sporozoite activity in sera. Thus, peptide constructs containing the CS repeat region epitope, (NANP)n, can be used with confidence to assay anti-sporozoite antibodies, independent of both the time of infection and prior malaria history.

Effect of anti-coagulants on cold-reactive anti-lymphocyte activity in the blood of patients with malaria.

The effect of three different anti-coagulants on the level of cold-reactive anti-lymphocyte activity (ALA) in the peripheral blood (PB) of malarious individuals was assessed to determine if plasma could be substituted for serum in assays designed to characterize ALA. Results show that plasma obtained by treating PB with acid-citrate dextrose or ethylenediamine tetraacetic acid can be used instead of serum in these assays but that plasma obtained from heparin-treated blood cannot.