Institut de Recherche en Sciences de La Santé, Direction Régionale de L'Ouest (IRSS-DRO), Bobo-Dioulasso, Burkina Faso.
Institut Des Sciences Et Techniques (INSTech Bobo), Bobo-Dioulasso, Burkina Faso.
Malar J. 2024 May 6;23(1):135. doi: 10.1186/s12936-024-04969-0.
The direct membrane feeding assay (DMFA), whereby gametocyte-infected blood is collected from human donors and from which mosquitoes feed through a membrane, is proving essential for assessing parameters influencing Plasmodium transmission potential in endemic countries. The success of DMFAs is closely tied to gametocyte density in the blood, with relatively high gametocytaemia ensuring optimal infection levels in mosquitoes. As transmission intensity declines with control efforts, the occurrence of asymptomatic individuals with low gametocyte densities, who can significantly contribute to the infectious reservoir, is increasing. This poses a limitation to studies relying on the experimental infection of large numbers of mosquitoes with natural isolates of Plasmodium. A simple, field-applicable method is presented for improving parasite infectivity by concentrating Plasmodium falciparum gametocytes.
Anopheles gambiae received one of the following 5 blood treatments through DMFA: (i) whole blood (WB) samples from naturally-infected donors; (ii) donor blood whose plasma was replaced with the same volume of Plasmodium-naive AB + serum (1:1 control); (iii) plasma replaced with a volume of malaria-naïve AB + serum equivalent to half (1:1/2), or to a quarter (1:1/4), of the initial plasma volume; and (v) donor blood whose plasma was fully removed (RBC). The experiment was repeated 4 times using 4 distinct wild parasite isolates. Seven days post-infection, a total of 1,095 midguts were examined for oocyst presence.
Substituting plasma with reduced amounts (1:1/2 and 1:1/4) of Plasmodium-naive AB + serum led to a 31% and 17% increase of the mosquito infection rate and to a 85% and 308% increase in infection intensity compared to the 1:1 control, respectively. The full removal of plasma (RBC) reduced the infection rate by 58% and the intensity by 64% compared to the 1:1 control. Reducing serum volumes (1:1/2; 1:1/4 and RBC) had no impact on mosquito feeding rate and survival when compared to the 1:1 control.
Concentrating gametocytic blood by replacing natural plasma by lower amount of naive serum can enhance the success of mosquito infection. In an area with low gametocyte density, this simple and practical method of parasite concentration can facilitate studies on human-to-mosquito transmission such as the evaluation of transmission-blocking interventions.
直接膜喂食检测（DMFA）通过从人类供体收集感染配子体的血液，并通过膜让蚊子吸食，这对于评估在流行地区影响疟原虫传播潜力的参数非常重要。DMFA 的成功与血液中的配子体密度密切相关，相对较高的配子体血症可确保蚊子获得最佳的感染水平。随着控制工作的推进，传播强度下降，携带低配子体密度的无症状个体（他们可以显著增加传染性储存库）的出现越来越多。这对依赖于用天然疟原虫分离株实验性感染大量蚊子的研究构成了限制。本文提出了一种简单、适用于现场的方法，通过浓缩恶性疟原虫配子体来提高寄生虫感染力。
通过 DMFA，冈比亚按蚊接受以下 5 种血液处理之一：（i）来自自然感染供体的全血（WB）样本；（ii）用相同体积的无疟原虫 AB 血清替代供体血浆（1:1 对照）；（iii）用相当于初始血浆体积一半（1:1/2）或四分之一（1:1/4）的无疟原虫 AB 血清替代血浆；以及（v）用全血（RBC）替代血浆。该实验重复了 4 次，使用了 4 种不同的野生寄生虫分离株。感染后 7 天，共检查了 1095 个中肠以确定卵囊的存在。
用疟原虫 AB 血清替代部分血浆（1:1/2 和 1:1/4）分别导致蚊子感染率增加 31%和 17%，感染强度分别增加 85%和 308%，与 1:1 对照相比。与 1:1 对照相比，完全去除血浆（RBC）导致感染率降低 58%，感染强度降低 64%。与 1:1 对照相比，降低血清体积（1:1/2；1:1/4 和 RBC）对蚊子的取食率和存活率没有影响。
用较低量的无经验血清替代天然血浆浓缩配子血可以提高蚊子感染的成功率。在配子体密度较低的地区，这种简单实用的寄生虫浓缩方法可以促进人类向蚊子传播的研究，如评估阻断传播的干预措施。
