Adaptive immunity selects against malaria infection blocking mutations

Malaria among the elderly in five communities of Osun East district, Southwest Nigeria: Prevalence and association with non-communicable diseases

Objective:

The level of immunity against pathogens decreases with old age. As a result, the elderly may be regarded to be at increased risk of malaria morbidity and fatality. There is paucity of studies on malaria among the elderly population in Osun East district, Southwest Nigeria. This study aimed to determine the prevalence of malaria and its association with medical comorbidities among the elderly.

Methods:

A descriptive cross-sectional study was carried out, which involved 972 adult residents of five communities in Osun State, who were selected using a multistage random sampling technique. Data was collected with aid of a structured questionnaire. The medical history of respondents and anthropometric measures were obtained. The presence of malaria parasitaemia in the respondents was determined by rapid diagnostic test (RDT). Appropriate descriptive and inferential analyses were done.

Results:

Out of the 972 respondents, 504 (51.9%) were 60 years and above. The overall prevalence of malaria RDT positivity was 4%. The positivity rate was higher among the elderly (4.6%) compared to those less than 60 years (3.4%), albeit not statistically significant ( p = 0.36). Among these elderlies, 52.6% and 16.1% used insecticide-treated nets and insecticide sprays, respectively. There was no association between the prevalence of malaria positivity and comorbid conditions, such as hypertension ( p = 0.37), overweight/obesity ( p = 0.77), or diabetes ( p = 0.15). Malaria positivity rate was also not significantly associated with the use of insecticide-treated nets ( p = 0.64) or insecticide sprays ( p = 0.45).

Conclusion:

The malaria positivity rate was higher among the elderly in the study area, although not statistically significant. The prevalence was not associated with comorbid medical conditions.

The erythrocyte membrane properties of beta thalassaemia heterozygotes and their consequences for Plasmodium falciparum invasion

Malaria parasites such as Plasmodium falciparum have exerted formidable selective pressures on the human genome. Of the human genetic variants associated with malaria protection, beta thalassaemia (a haemoglobinopathy) was the earliest to be associated with malaria prevalence. However, the malaria protective properties of beta thalassaemic erythrocytes remain unclear. Here we studied the mechanics and surface protein expression of beta thalassaemia heterozygous erythrocytes, measured their susceptibility to P. falciparum invasion, and calculated the energy required for merozoites to invade them. We found invasion-relevant differences in beta thalassaemic cells versus matched controls, specifically: elevated membrane tension, reduced bending modulus, and higher levels of expression of the major invasion receptor basigin. However, these differences acted in opposition to each other with respect to their likely impact on invasion, and overall we did not observe beta thalassaemic cells to have lower P. falciparum invasion efficiency for any of the strains tested.