Nyasa Raymond Babila, Zofou Denis, Kimbi Helen Kuokuo, Kum Karin Mbei, Ngu Roland C, Titanji Vincent P K
Biotechnology Unit, Faculty of Science, University of Buea, Buea, Cameroon.
Department of Zoology and Animal Physiology, Faculty of Science, University of Buea, Buea, Cameroon.
BMC Public Health. 2015 Nov 6;15:1105. doi: 10.1186/s12889-015-2463-1.
Global malaria has been on the decline over the past decade due to expansion of interventions. The present study aimed at determining the current status of malaria epidemiology in the context of sustained interventions and seasonal variations in Bolifamba, which represents a typical semi-urban malaria endemic community in the Cameroonian rainforest.
A monthly cross-sectional survey was carried out in Bolifamba, a multi ethnic semi-urban locality on the eastern flanks of Mt Cameroon, for a year during which blood samples were collected from participants and examined for malaria parasites by microscopy. Correlation analysis of seasonal/monthly malaria prevalence was done with weather data from Ekona, a nearby village with a meteorological station. Intervention strategy such as use of Insecticide Treated Bed Net (ITBN) and risk factors such as duration of stay in the locality, age and housing type were also investigated.
The results revealed a malaria prevalence of 38.3 % in the rainy season, which was significantly higher than 24.4 % observed in the dry season (P < 0.0001). A high prevalence of asymptomatic malaria which was more than double the prevalence of symptomatic malaria on a monthly basis was observed, 30.7 % vs 17.8 % in the rainy and dry season respectively (p < 0.0001) and asymptomatic malaria was significantly associated with anemia (p < 0.005). April was the peak month of malaria prevalence and coincided with peak periods of both asymptomatic and symptomatic malaria. The Plasmodium falciparum parasite rates in the 2- up to 10-years age group (PfPR(2-10)) was 40.8 %. The regular use of ITBN was significantly associated with low prevalence of 31.7 % as opposed to irregular or non-usage of ITBN 38.2 % (p < 0.05). Log of parasite load was found to initially increase to 2.49 with less than 5 years of stay, and decreased gradually with increasing duration of stay in the locality (p = 0.046). Climatic factors were significantly and positively associated with monthly malaria prevalence and the strongest predictors of malaria prevalence were rainfall and minimum temperature with r values of 0.563 and 0.6 respectively.
The study highlights the role of seasonal change in modifying malaria prevalence during the year and the beneficial effect of ITBN. It also underscores a sublime problem of asymptomatic malaria associated with anemia, and indicates that partial immunity is acquired with prolonged stay in Bolifamba. This preliminary result is the basis of ongoing work to identify the antigens involved in acquired immunity.
由于干预措施的扩大，全球疟疾在过去十年中呈下降趋势。本研究旨在确定在持续干预措施和季节性变化背景下，博利方巴的疟疾流行病学现状。博利方巴是喀麦隆雨林中一个典型的半城市疟疾流行社区。
在喀麦隆山侧翼的一个多民族半城市地区博利方巴进行了为期一年的月度横断面调查，在此期间从参与者身上采集血样，并通过显微镜检查疟原虫。对季节性/月度疟疾患病率与来自附近有气象站的埃科纳村的天气数据进行了相关性分析。还调查了干预策略，如使用经杀虫剂处理的蚊帐（ITBN），以及风险因素，如在当地的停留时间、年龄和住房类型。
结果显示雨季疟疾患病率为38.3%，显著高于旱季观察到的24.4%（P < 0.0001）。观察到无症状疟疾的高患病率，每月无症状疟疾患病率是有症状疟疾患病率的两倍多，雨季和旱季分别为30.7%和17.8%（p < 0.0001），且无症状疟疾与贫血显著相关（p < 0.005）。4月是疟疾患病率的高峰月，与无症状和有症状疟疾的高峰期重合。2至10岁年龄组的恶性疟原虫寄生虫率（PfPR(2 - 10)）为40.8%。经常使用ITBN与低患病率31.7%显著相关，而不规律或不使用ITBN的患病率为38.2%（p < 0.05）。发现寄生虫负荷的对数最初在停留时间少于5年时增加到2.49，随着在当地停留时间的增加逐渐下降（p = 0.046）。气候因素与月度疟疾患病率显著正相关，疟疾患病率的最强预测因素是降雨量和最低温度，r值分别为0.563和0.6。
该研究突出了季节变化在一年中改变疟疾患病率的作用以及ITBN的有益效果。它还强调了与贫血相关的无症状疟疾这一严重问题，并表明在博利方巴长期停留可获得部分免疫力。这一初步结果是正在进行的确定获得性免疫中涉及的抗原的工作的基础。
