Influence of water temperature and salinity on seasonal occurrences of Vibrio cholerae and enteric bacteria in oyster-producing areas of Veracruz, México

The influence of temperature and salinity on the occurrence of Vibrio cholerae, Escherichia coli and Salmonella spp. associated with water and oyster samples was investigated in two lagoons on the Atlantic Coast of Veracruz, Mexico over a 1-year period. The results indicated that seasonal salinity variability and warm temperatures, as well as nutrient influx, may influence the occurrence of V. cholera. non-O1 and O1. The conditions found in the Alvarado (31.12 °C, 6.27‰, pH = 8.74) and La Mancha lagoons (31.38 °C, 24.18‰, pH = 9.15) during the rainy season 2002 favored the occurrence of V. cholera O1 Inaba enterotoxin positive traced in oysters. Vibrio alginolyticus was detected in Alvarado lagoon water samples during the winter season. E. coli and Salmonella spp. were isolated from water samples from the La Mancha (90–96.7% and 86.7–96.7%) and Alvarado (88.6–97.1% and 88.6–100%) lagoons. Occurrence of bacteria may be due to effluents from urban, agricultural and industrial areas.     

清代（1816—1911年）霍乱流行的时空特征、危险模拟与边界探测

霍乱是清代1820年左右传入中国的新型烈性传染病,迄今仍是人类生命健康安全的重大威胁之一。本文运用ArcGIS时空分析、MaxEnt生态位模拟、BoundarySeer边界探测等方法对清代的霍乱流行进行分析,结果表明：① 清代霍乱的流行频度为77%,对整个清代疫灾的流行贡献了约21.32%的广度。② 霍乱在中国的适生范围广,东部沿海为最佳适生区;中国不同区域霍乱流行的危险等级差异显著,并呈现自东向西递减、南方高于北方的总体特征;距海距离、海拔高程、日照时数、最高气温是影响霍乱流行的主要因素,贡献率分别为29.3%、22.4%、16.1%和7.7%。③ 霍乱流行的边界性特征明显,第一边界是以凤阳为圆心,以凤阳-夹江直线距离为半径（约1300 km）与国界线或海岸线围合的圆弧圈,界内包含97.65%的霍乱流行事件;第二边界参照霍乱高适生度分布线,该线迤东包括中国东、中部省份;第三边界是由霍乱主要网络构成的围合区,总体上掩及环渤海、长三角和珠三角等东部沿海一线。     

霍乱发病率与气象因素关系的探讨

对北京市西城区1994～1998年人群霍乱发病率与月平场气温、气压、降水量的关系进行Spearman等级相关分析，结果表明：发病率与月平均气温呈显著正相关，与月平均气压无显著相关，与月平均降水量无显著相关，高温可能提高霍乱发病率。对1994～1998年的霍乱发病率、月平均气温分别做月和年的显著性检验，结果支持气温与霍乱发病率的相关关系，同时提示气象因素只是影响霍乱发生的因素之一。     

Global warming, rising sea level, and growing risk of cholera incidence: a review of the literature and evidence

The survival of Vibrio cholerae -the pathogen agent of cholera- in aquatic environments is linked to both abiotic and biotic ecological factors, which are likely to be influenced by global climate changes and the resulting rise in sea level. Yet little attention has been paid to the possible impacts of these predicted global environmental changes on water-borne diseases such as cholera. The probable ecological mechanisms to explain why cholera may increase if predicted global warming and sea level rise do occur have, as yet, not been addressed. The objective of this paper is to argue the hypothesis that the survival of Vibrio cholerae in aquatic environments may be favoured by global warming and flooding of low-lying coastal areas due to rising sea level. Those changes may enhance primary and secondary transmission of cholera in developing nations, particularly among populations settled in low-lying coastal areas of tropical regions. Primary transmission is also likely to increase in developed nations, mainly among populations living in low-lying coastal areas of subtropical and temperate regions, where new foci of hypoendemic cholera may appear. Nevertheless, if current high levels of hygienic standards in developed nations are relaxed, secondary transmission of cholera may also increase. The prediction and assessment of the potential impact of global climate change on cholera epidemic and endemic potential and its geographical distribution should consider the role of the aquatic reservoirs of Vibrio cholerae in the transmission and endemicity of cholera. The geographical distribution of cholera depends not only on social and cultural factors, but also on ecological variables. On the other hand, global climate changes may cause different impacts in different ecosystems and geographical landscapes. Hence it would be useful to calculate and map future cholera incidence rates for areas defined by natural boundaries, such as ecosystems and geographical landscapes, in search of space-time associations between cholera incidence rates and environmental changes. This revised version was published online in August 2006 with corrections to the Cover Date.