Hospital for Tropical Diseases, Mortimer Market Centre, Capper Street, London WC1E 6JB, UK.
Malar J. 2013 Jan 24;12:31. doi: 10.1186/1475-2875-12-31.
Gametocytes are the sexual stage of Plasmodium parasites. The determinants of gametocyte carriage have been studied extensively in endemic areas, but have rarely been explored in travellers with malaria. The incidence of gametocytaemia, and factors associated with gametocyte emergence in adult travellers with Plasmodium falciparum malaria was investigated at the Hospital for Tropical Diseases in London.
Clinical, parasitological and demographic data for all patients presenting with P. falciparum malaria between January 2001 and December 2011 were extracted from a prospective database. These data were supplemented by manual searches of laboratory records and patient case notes.
Seven hundred and seventy three adult patients with laboratory-confirmed P. falciparum malaria were identified. Four hundred and sixty five (60%) were born in a country where malaria is endemic. Patients presented to hospital a median of four days into their illness. The median maximum parasite count was 0.4%. One hundred and ninety six patients (25%) had gametocytes; 94 (12%) on admission, and 102 (13%) developing during treatment. Gametocytaemia on admission was associated with anaemia and a lower maximum parasitaemia. Patients with gametocytes at presentation were less likely to have thrombocytopenia or severe malaria. Patients who developed gametocytes during treatment were more likely to have had parasitaemia of long duration, a high maximum parasitaemia and to have had severe malaria. There was no apparent association between the appearance of gametocytes and treatment regimen.
The development of gametocytaemia in travellers with P. falciparum is associated with factors similar to those reported among populations in endemic areas. These data suggest that acquired immunity to malaria is not the only determinant of patterns of gametocyte carriage among patients with the disease.
配子体是疟原虫的有性阶段。配子体携带的决定因素在流行地区已被广泛研究，但在患有疟疾的旅行者中很少被探索。在伦敦热带病医院，研究了成人间日疟原虫疟疾病人的配子体携带率及其与配子体出现相关的因素。
从 2001 年 1 月至 2011 年 12 月期间所有因恶性疟原虫疟疾就诊的患者前瞻性数据库中提取了临床、寄生虫学和人口统计学数据。通过手工搜索实验室记录和患者病历补充了这些数据。
确定了 773 例经实验室证实的恶性疟原虫疟疾病例。其中 465 例（60%）出生在疟疾流行的国家。患者发病中位数为 4 天。中位数最大寄生虫计数为 0.4%。196 例（25%）患者有配子体；94 例（12%）入院时，102 例（13%）在治疗期间发生。入院时的配子体血症与贫血和较低的最大寄生虫血症有关。出现配子体血症的患者血小板减少症或严重疟疾的可能性较低。在治疗期间出现配子体血症的患者更可能出现长时间的寄生虫血症、高最大寄生虫血症和严重疟疾。配子体的出现与治疗方案之间似乎没有明显的关联。
在恶性疟原虫感染的旅行者中，配子体血症的发展与在流行地区人群中报告的因素相似。这些数据表明，对疟疾的获得性免疫并不是疾病患者配子体携带模式的唯一决定因素。
