Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale, BP288, Yaoundé, Cameroon.
UMR MIVEGEC, Institut de Recherche pour le Développement, 911 Avenue Agropolis, BP64501, 34394, Montpellier Cedex, France.
Malar J. 2017 Aug 17;16(1):345. doi: 10.1186/s12936-017-1978-6.
The measure of new drug- or vaccine-based approaches for malaria control is based on direct membrane feeding assays (DMFAs) where gametocyte-infected blood samples are offered to mosquitoes through an artificial feeder system. Gametocyte donors are identified by the microscopic detection and quantification of malaria blood stages on blood films prepared using either capillary or venous blood. However, parasites are known to sequester in the microvasculature and this phenomenon may alter accurate detection of parasites in blood films. The blood source may then impact the success of mosquito feeding experiments and investigations are needed for the implementation of DMFAs under natural conditions.
Thick blood smears were prepared from blood obtained from asymptomatic children attending primary schools in the vicinity of Mfou (Cameroon) over four transmission seasons. Parasite densities were determined microscopically from capillary and venous blood for 137 naturally-infected gametocyte carriers. The effect of the blood source on gametocyte and asexual stage densities was then assessed by fitting cumulative link mixed models (CLMM). DMFAs were performed to compare the infectiousness of gametocytes from the different blood sources to mosquitoes.
Prevalence of Plasmodium falciparum asexual stages among asymptomatic children aged from 4 to 15 years was 51.8% (2116/4087). The overall prevalence of P. falciparum gametocyte carriage was 8.9% and varied from one school to another. No difference in the density of gametocyte and asexual stages was found between capillary and venous blood. Attempts to perform DMFAs with capillary blood failed.
Plasmodium falciparum malaria parasite densities do not differ between capillary and venous blood in asymptomatic subjects for both gametocyte and trophozoite stages. This finding suggests that the blood source should not interfere with transmission efficiency in DMFAs.
新的药物或疫苗控制疟疾方法的衡量标准是基于直接膜喂养检测（DMFA），通过人工喂养系统向蚊子提供感染有配子体的血液样本。配子体供体通过在使用毛细血管或静脉血制备的血膜上进行显微镜检测和疟原虫血液阶段的定量来识别。然而，寄生虫已知会在微血管中隔离，这种现象可能会改变对血膜中寄生虫的准确检测。血液来源可能会影响蚊子喂养实验的成功，因此需要进行研究以在自然条件下实施 DMFA。
在四个传播季节期间，从喀麦隆姆福附近小学的无症状儿童身上采集的血液中制备厚血涂片。从毛细血管和静脉血中对 137 名自然感染配子体携带者的寄生虫密度进行了显微镜检测。然后，通过拟合累积链接混合模型（CLMM）评估血液来源对配子体和无性阶段密度的影响。进行 DMFA 以比较来自不同血液来源的配子体对蚊子的感染力。
4 至 15 岁无症状儿童中恶性疟原虫无性阶段的流行率为 51.8%（2116/4087）。恶性疟原虫配子体携带的总流行率为 8.9%，且在不同学校之间存在差异。毛细血管和静脉血中的配子体和无性阶段密度没有差异。尝试用毛细血管血进行 DMFA 失败。
在无症状人群中，配子体和滋养体阶段的寄生虫密度在毛细血管和静脉血之间没有差异。这一发现表明，血液来源不应干扰 DMFA 中的传播效率。
