聖多美普林西比共和國五歲以下兒童惡性瘧疾的治療與惡性瘧原蟲抗藥性調查

Abstract

於2003~2004年，我們在西非聖多美普林西比共和國，針對258位五歲以下罹患惡性瘧之孩童投以Artesunate+Sulfadoxine/Pyrimethamine (Fansidar)取代Chloroquine作為惡性瘧的治療計劃。結果發現五歲以下孩童在醫療人員的監督下接受Artesunate+Fansidar治療後的 day 3、 day 7、 day 14、 day 21和day 28的血液抹片陽性率分別為 7.87%、 5.51%、 2.81%、 6.1%和7.26%。相較於治療前day 0的100%，顯見Artesunate+Fansidar治療惡性瘧疾的效果良好。我們繼而利用在前述的臨床試驗中所收集到濾紙血片的血液檢體，進行分子生物學的研究，藉以找出聖國在投以Artesunate+Fansidar之前的抗藥基因存在情形。但由於目前為止，惡性瘧原蟲對Artesunate尚未出現抗藥性蟲株，故本研究主要是篩選對Fansidar之抗藥性基因，以及感染者在接受Artesunate+Fansidar藥物治療後對於Fansidar的抗藥基因出現的情形。因此，本研究設計針對惡性瘧原蟲蟲株DHFR及DHPS基因的引子，經nested PCR篩選並純化PCR產物送定序後，發現對Pyrimethamine出現中高程度抗藥性的惡性瘧原蟲有61%，而出現中等程度程度抗藥性的惡性瘧原蟲有35%；另外，對Sulfadoxine出現中等程度抗藥性的惡性瘧原蟲有12%，而出現低程度抗藥性的惡性瘧原蟲有80%。此外，本研究使用PCR-RFLP genotyping來分辨經過Artesunate+Fansidar治療後還出現寄生蟲血症的惡性瘧原蟲為復發或再感染。我們發現59人中有35人為再感染；另外24人無法由此法來判讀。最後，經由本研究的結果，期望可供該國在未來抗瘧疾藥物治療和預防選擇上和定期追蹤抗藥基因演變作為參考。

We aimed to assess the efficacy of an antimalarial combination therapy with artesunate (A) and sulfadoxine/pyrimethamine (SP) for children aged less than 5 years (258 persons, 124 males and 134 females; median age, 37 months) who were inhabitants of selected farm villages and diagnosed with falciparum malaria; and to analyze the prevalence of SP resistant gene of P. falciparum and its incidence after treatment with SP in the Democratic Republic of San Tome and Principe. Treatment regimens were administered on a directly-observed-therapy basis. In the study, blood specimens were collected from children infected with malaria on day 0 (before the initiation of A/SP), day 1, day 2, day 3, day 7, day 14, day 21, and day 28 for microscopic examinations. The rate of parasitemia on day 3, day 7, day 14, day 21, and day 28 of antimalarial therapy was 7.87%, 5.51%, 2.81%, 6.1%, and 7.26%, respectively, on an as-treat analysis. The regimen was well tolerated. In addition, we designed primers specific to the DHFR and DHPS genes of P. falciparum for nested PCR；then, we purified the PCR products and sequence them. At baseline, we found that 61% of P. falciparum demonstrated intermediate-level resistance to pyrimethamine, 35% of P. falciparum low-level resistance to pyrimethanine, 12% of P. falciparum intermediate-level resistance to sufadoxine and 80% of P. falciparum low-level resistance to sulfadoxine. Furthermore, we used PCR-RFLP genotyping method to distinguish recrudescence from reinfection. We found that 35 of 59 children had reinfection；among the other 24 children we were not able to distinguish the two by this method. We concluded that A plus SP was effective as a antimalarial combination treatment for children aged less than 5 years who developed falciparum malaria in the Democratic Republic of San Tome and Principe. Prevalence of P. falciparum resistant to SP was high, other antimalarial combination regimens should be investigated.