Graduate Programme in Infectious Diseases, Federal University of Espírito Santo, Vitória, Brazil.
Protozoology Laboratory, Institute of Tropical Medicine, University of São Paulo, São Paulo, Brazil.
Malar J. 2017 Nov 9;16(1):452. doi: 10.1186/s12936-017-2103-6.
Regions with residual transmission are potential obstacles to the elimination of malaria. It is, therefore, essential to understand the factors associated with the maintenance of endemic malaria in these areas. The objective was to investigate whether the status of asymptomatic carriers of Plasmodium spp. DNA is maintained in the long term in an extra-Amazonian region of Brazil with low incidence, residual malaria transmission.
Asymptomatic carriers of Plasmodium DNA detected in a survey carried out between 2001 and 2004 were reassessed between 2010 and 2011 using questionnaires, PCR and thick and thin blood smear tests three times at 3-month intervals.
Of the 48 carriers detected between 2001 and 2004, 37 were located. Of these, only two had positive PCR results and, as in the first survey, Plasmodium malariae DNA was detected.
The findings suggest that untreated dwellers from this extra-Amazonian region, who initially harbour malaria parasites, may become negative without ever developing apparent symptoms of the disease. Although the possibility of re-infection cannot be ruled out, the finding of two individuals harbouring P. malariae, both in the first and in the second survey, may be compatible with a long-term carrier state for this parasite. Since most clinical cases of malaria in the region are a consequence of infection by Plasmodium vivax, the epidemiological impact of such long-term carriage would be limited.
存在传播残留的地区是消除疟疾的潜在障碍。因此，了解这些地区维持地方性疟疾的相关因素至关重要。本研究旨在调查在巴西一个低发病率、存在疟疾传播残留的亚马孙河以外地区，是否长期维持无症状携带有疟原虫 DNA 的状况。
2001 年至 2004 年间进行的一项调查中检测到无症状携带有疟原虫 DNA 的个体，于 2010 年至 2011 年期间采用问卷调查、PCR 和厚血涂片及薄血涂片 3 次检测，每 3 个月 1 次进行重新评估。
2001 年至 2004 年间共检测到 48 例携带个体，其中 37 例可以联系到。在这些个体中，仅有 2 例 PCR 结果阳性，与首次调查一样，检测到疟原虫疟疾 DNA。
这些发现表明，来自这个亚马孙河以外地区的初始携带有疟原虫的未经治疗的居民可能会在没有出现明显疾病症状的情况下转为阴性。虽然不能排除再次感染的可能性，但在首次和第二次调查中都发现携带疟原虫的两个人，可能与该寄生虫的长期携带状态相符。由于该地区大多数疟疾临床病例是由间日疟原虫感染引起的，因此这种长期携带的流行病学影响将是有限的。
