Ecological characterisation and infection of Anophelines (Diptera: Culicidae) of the Atlantic Forest in the southeast of Brazil over a 10 year period: has the behaviour of the autochthonous malaria vector changed?

BACKGROUND In southeastern Brazil, autochthonous cases of malaria can be found near Atlantic Forest fragments. Because the transmission cycle has not been completely clarified, the behaviour of the possible vectors in those regions must be observed. A study concerning the entomological aspects and natural infection of anophelines (Diptera: Culicidae) captured in the municipalities of the mountainous region of Espírito Santo state was performed in 2004 and 2005. Similarly, between 2014 and 2015, 12 monthly collections were performed at the same area of the study mentioned above. METHODS Center for Disease Control (CDC) light traps with CO2 were set in open areas, at the edge and inside of the forest (canopy and ground), whereas Shannon traps were set on the edge. FINDINGS A total of 1,414 anophelines were collected from 13 species. Anopheles (Kerteszia) cruzii Dyar and Knab remained the most frequently captured species in the CDC traps set in the forest canopy, as well as being the vector with the highest prevalence of Plasmodium vivax/simium infection, according to molecular polymerase chain reaction techniques. CONCLUSIONS P. vivax/simium was found only in abdomens of the mosquitoes of the subgenus Nyssorhynchus, weakening the hypothesis that this subgenus also plays a role in malaria transmission in this specific region.

背景：巴西东南部的大西洋森林（Atlantic Forest）碎片周边区域，可发现本土疟疾病例。由于疟疾传播循环尚未完全阐明，需对该区域潜在媒介昆虫的行为开展观测。2004年与2005年，研究团队针对在圣埃斯皮里图州（Espírito Santo）山地地区各市县捕获的按蚊（Anophelines，双翅目：蚊科Culicidae）的昆虫学特征及自然感染情况开展了相关研究。2014年至2015年间，研究团队在上述同一区域完成了12次月度采样。

方法：设置搭载二氧化碳的疾病预防控制中心（Center for Disease Control, CDC）诱蚊灯，分别布置于开阔区域、森林边缘及林内（林冠层与地面层）；同时在森林边缘设置香农诱捕器（Shannon traps）。

结果：本次研究共捕获按蚊1414只，分属13个物种。经分子聚合酶链反应（polymerase chain reaction, PCR）技术检测，在森林林冠层CDC诱捕器中捕获频次最高的物种为克鲁兹按蚊（Anopheles (Kerteszia) cruzii Dyar and Knab），同时该物种也是间日疟原虫/猿疟原虫（Plasmodium vivax/simium）感染率最高的媒介昆虫。

结论：仅在尼氏按蚊亚属（Nyssorhynchus）蚊虫的腹部中检测到间日疟原虫/猿疟原虫，该结果削弱了"该亚属在本区域疟疾传播中亦发挥作用"的假说。