Effect of pregnancy on exposure to malaria mosquitoes

Abstract

Pregnant women attracted twice the number of Anopheles gambiae complex--the predominant African malaria-carrying mosquito--than did their non-pregnant counterparts. We postulate that physiological and behavioural changes that occur during pregnancy are responsible for increased attractiveness, which could be important in intervention strategies aimed at protecting this high-risk group against malaria.

PIP: In Africa, malaria has been the major cause of illness and an indirect cause of death among pregnant women. It is also an important cause of stillbirths, low birth weight and early infant mortality. A comparative study was conducted in Gambia to examine the relative attractiveness of pregnant and nonpregnant women to mosquitoes. For 3 consecutive nights, 12 groups of women consisting of 3 pregnant and nonpregnant women in each group were studied. After adjusting for variation between huts and trials, Anopheles gambiae (main malaria vectors in Africa) were found to be more attracted to pregnant women (mean, 6.33 per night [95% confidence interval, 4.5-8.7]) than to nonpregnant women (3.1 [2.1-4.5]; p = 0.0002). Similar findings were also found with Mansonia spp. (7.6 [5.8-10.0] vs. 5.7 [4.1-7.8]; p = 0.0008), but differences were of borderline significance with other culicines. Two physiological factors underlying increased attractiveness during pregnancy were increased heat and increased release of volatile substances from the skin surface. Overall, this study confirms the increased risk of malaria and other mosquito-born diseases among pregnant women, and underlines the importance of protecting these women through immunity and nutrition.