Piyaratne M K, Amerasinghe F P, Amerasinghe P H, Konradsen F
International Water Management Institute, PO Box 2075, Colombo, Sri Lanka.
J Vector Borne Dis. 2005 Jun;42(2):61-7.
BACKGROUND & OBJECTIVES: Selected physico-chemical characteristics of flowing and pooled water in a stream that generated two malaria vectors, Anopheles culicifacies s.l. Giles and Anopheles varuna Iyengar, were investigated during August-September 1997 and July 1998 at the Upper Yan Oya watershed in north-central Sri Lanka.
The physico-chemical parameters measured were: temperature, dissolved oxygen, pH, conductivity, total dissolved solids, alkalinity, ammonia nitrogen, nitrate nitrogen, calcium, magnesium, carbondioxide, ferrous iron, phosphate, colour and turbidity. In total, 75.5% of 151 samples analysed were mosquito-positive. Logistic regression was used for statistical analysis.
Among physico-chemical parameters, An. culicifacies (the major malaria vector in the country) was positively related only to temperature, and An. varuna (a secondary malaria vector) to calcium. Among habitat characteristics, An. culicifacies was associated with light and vegetation, and negatively associated with the presence of potential predators. An. varuna was positively associated with other aquatic fauna.
INTERPRETATION & CONCLUSION: Surprisingly this detailed study did not find an association between An. culicifacies and dissolved oxygen as previously found in the few studies that have looked at physico-chemical characteristics of malaria vector breeding habitats in south Asia. This study, along with existing information from other studies indicate that most of the physico-chemical parameters measured under natural conditions within the same habitat type is insufficient to explain the distribution of vectors within such habitats. However, it seems likely that both An. culicifacies and An. varuna follow a strategy whereby ovipositing females scatter their eggs over most of or all of a highly temporary and only transiently available stream bed pool habitat, in order to optimise breeding success.
1997年8月至9月以及1998年7月，在斯里兰卡中北部的上亚诺亚流域，对一条滋生了两种疟疾媒介——嗜人按蚊复合组（Giles）和瓦氏按蚊（Iyengar）的溪流中流动水和积水的选定物理化学特征进行了调查。
所测量的物理化学参数包括：温度、溶解氧、pH值、电导率、总溶解固体、碱度、氨氮、硝酸盐氮、钙、镁、二氧化碳、亚铁、磷酸盐、颜色和浊度。总共分析的151个样本中，75.5%的样本检测出蚊子呈阳性。采用逻辑回归进行统计分析。
在物理化学参数中，嗜人按蚊（该国主要的疟疾媒介）仅与温度呈正相关，而瓦氏按蚊（次要的疟疾媒介）与钙呈正相关。在栖息地特征方面，嗜人按蚊与光照和植被有关，与潜在捕食者的存在呈负相关。瓦氏按蚊与其他水生动物呈正相关。
令人惊讶的是，这项详细研究并未发现嗜人按蚊与溶解氧之间存在关联，而此前在少数研究南亚疟疾媒介滋生地物理化学特征的研究中曾发现过这种关联。这项研究以及其他研究的现有信息表明，在同一栖息地类型的自然条件下所测量的大多数物理化学参数不足以解释这些栖息地内媒介的分布情况。然而，嗜人按蚊和瓦氏按蚊似乎都遵循一种策略，即产卵的雌蚊会将卵散布在大部分或整个高度临时性且仅短暂存在的河床水洼栖息地，以优化繁殖成功率。
