Concurrent helminthic infection protects schoolchildren with Plasmodium vivax from anemia

Abstract

Background: Plasmodium vivax is responsible for a significant portion of malaria cases worldwide, especially in Asia and Latin America, where geo-helminthiasis have a high prevalence. Impact of the interaction between vivax malaria and intestinal helminthes has been poorly explored. The objective of this study was to evaluate the influence of intestinal helminthiasis on the concentration of hemoglobin in children with Plasmodium vivax malaria in rural areas in the municipality of Careiro, in the Western Brazilian Amazon.

Methodology/principal findings: A cohort study was conducted from April to November 2008, enrolling children from 5 to 14 years old in two rural areas endemic for malaria. A cross-sectional evaluation was performed in April to actively detect cases of malaria and document baseline hemoglobin and nutritional status. Children were followed-up for six months through passive case detection of malaria based on light microscopy. Throughout the follow-up interval, hemoglobin value and stool examination (three samples on alternate days) were performed on children who developed P. vivax malaria. For 54 schoolchildren with a single infection by P. vivax, hemoglobin during the malaria episode was similar to the baseline hemoglobin for children co-infected with Ascaris lumbricoides (n = 18), hookworm (n = 11) and Trichuris trichiura (n = 9). In children without intestinal helminthes, a significant decrease in the hemoglobin during the malarial attack was seen as compared to the baseline concentration. In the survival analysis, no difference was seen in the time (in days) from the baseline cross-sectional to the first malarial infection, between parasitized and non-parasitized children.

Conclusion/significance: For the first time, a cohort study showed that intestinal helminthes protect against hemoglobin decrease during an acute malarial attack by P. vivax.

Figure 1. Algorithm of the study, describing the details of eligible, enrolled and analyzed children.

Figure 2. Mean (± standard error of the mean) hemoglobin concentration before (baseline Hb) and during (malarial Hb) the first P. vivax acute attack in 54 schoolchildren followed from April to November 2008, in an endemic area for malaria (Municipality of Careiro, Amazonas, Brazil), according to the helminth detected at stool examination.

Figure 3. Correlation between parasitemia and hemoglobin.

Correlation between parasitemia and hemoglobin during the first malarial attack in children without helminthes (A) and with helminthes (B).

Figure 4. Survival analysis of the time for the first malarial episode.

Kaplan-Meier survival analysis showing the time elapsed from the baseline cross-sectional to the first malarial infection (in days) in 54 schoolchildren followed from April to November 2008, with and without Ascaris lumbricoides (A), hookworm (B) and Trichuris trichiura (C).