Subclinical Malaria Research Articles

A field study on malaria prevalence in southeastern Laos by polymerase chain reaction assay.

A detection survey for malaria infection by routine microscopy and polymerase chain reaction (PCR) assay was conducted on 336 inhabitants of two villages in Khammouane Province, Lao People's Democratic Republic (Lao PDR), in July 1997. Malaria infection was demonstrated in 58 (17.3%) subjects by microscopy and in 117 (34.8%) by PCR assay. Specimens positive by both methods were frequent in young villagers, suggesting the presence of many subclinical infections in older persons. The most common species of malaria parasite was Plasmodium falciparum (82.9%). Polymerase chain reaction assay detected mixed infections with 2-4 species in 27 specimens (23.1%). The results demonstrate that there are many subclinical malaria infections with low parasite level and infection with all four human malaria species in Lao PDR.

Whole Blood Chloroquine Concentrations with Plasmodium vivax Infection in Irian Jaya, Indonesia

Whole blood concentrations of self-administered chloroquine (CQ) and its metabolite desethylchloroquine (DCQ) were measured in 168 patients with microscopically confirmed infection by Plasmodium vivax in northeastern Irian Jaya, Indonesia. The study consisted of both survey and passive case detection in four separate villages between 1992 and 1994. The subjects were Javanese people 4-51 years old who had lived in the Arso region for up to two years. The sum of CQ and DCQ ranged from 0 to 8,342 ng/ml of whole blood, and 122 subjects (73%) had > or = 100 ng/ml of CQ plus DCQ, the estimated minimally effective concentration (MEC) in whole blood against chloroquine-sensitive P. vivax. Among 56 subjects reporting to a clinic with symptoms of malaria, 53 (95%) had ordinarily effective levels of chloroquine in blood. Among 109 largely asymptomatic malaria patients found by survey case detection, 69 (63%) had chloroquine blood levels greater than the MEC. Virtually all clinical and most subclinical vivax malaria in this region occurs despite ordinarily effective levels of chloroquine in blood.

Suppression of Cell-Mediated Immune Responses to Malaria Antigens in Pregnant Gambian Women

In malaria endemic areas, pregnancy predisposes previously immune women to clinical and subclinical malaria infection. While parameters of humoral immunity do not seem to be affected by pregnancy, suppression of cellular immunity has been demonstrated for a number of antigens. In this study of women from a rural area of the Gambia where falciparum malaria is holoendemic, we show that lymphoproliferative responses to Plasmodium falciparum antigens are depressed in pregnant women compared to parity matched non-pregnant women, and that this effect is particularly marked in primigravidae. The data also indicate that malaria antigen induced gamma-interferon production may be depressed in pregnant women. There was no significant difference in antimalarial antibody titers between the 2 groups.

Mass therapy of subclinical vivax malaria with primaquine.

This report deals with the problem in mass therapy presented by the large number of cases of vivax malaria occurring in the United Nations forces in Korea since 1950. Because malaria is not a single disease but instead is a complex of diseases all caused by a member of the genus plasmodium the unique properties of the members of the various species and strains of the organism must be considered in any given therapeutic problem. On morphologic grounds, four distinct species of plasmodia are recognized. One species, Plasmodium ovale, is rare and of little clinical importance; two species, P. malariae and P. vivax, have many properties in common. For therapeutic purposes, they may be considered together. The remaining species, P. falciparum, has special properties and must be considered separately. On physiologic grounds, each species is made up of several strains, each with idiosyncrasies that modify response to treatment. It is