Unravelling the impact of El Niño on waterborne diseases in South America

弧菌是一种在海洋环境中发现的多种革兰氏阴性菌属。除了在许多海洋生态系统中发挥关键的生态作用外，该属还包括人类的关键病原体。霍乱弧菌和副溶血性弧菌是源自海洋环境的最重要的人类致病菌。仅霍乱一项就影响到全世界约300万至500万人；副溶血性弧菌是世界上海产细菌性肠胃炎的主要原因。霍乱弧菌和副溶血性弧菌引起的感染在过去几十年中随着大流行克隆的出现而稳步扩大。第七次霍乱大流行于1961年在印度尼西亚开始，一直局限于亚洲，直到1970年才传播到非洲和欧洲。在很长一段时间没有任何新的传播证据之后，它于1991年在秘鲁北部重新出现，在短短三年内造成了100多万例霍乱病例。同样，副溶血性弧菌感染几乎局限于亚洲，直到1996年在加尔各答出现与单一克隆有关的病例。我们报告了1997年这种克隆在亚洲以外的第一次入侵，导致秘鲁沿岸的感染。1991年和1997年在南美洲西海岸出现的霍乱弧菌和副溶血性弧菌感染是仅有的两个报告的证据，表明这些病原体的亚洲变种向东漂移，这两个过程都与厄尔尼诺现象Niño取代的温暖赤道水域的到来同时发生。El Niño是一种气候模式，描述了南美洲热带西海岸地表水的异常变暖，对全球范围内的海洋和天气产生了显著影响。El Niño事件发生不规律，不能严格预测，最主要的表现之一是印度洋-太平洋暖池的纬向位移，该暖池拥有世界上最温暖的海洋海水。这一水体受到强烈东移到厄瓜多尔的影响，与El Niño水域的运动相一致。在南美洲太平洋沿岸，El Niño赤道海水进入美国海岸，引起了沿海岸向南移动的低盐度温暖海水的入侵，这已被证明将外来浮游动物种群运送到秘鲁和智利。由于在不利条件下弧菌在海洋环境中的生存和传播与这些细菌附着在浮游生物上的能力有关，我们假设浮游动物提供营养和保护，使弧菌能够穿越海洋。过去10年来，我们一直在秘鲁开展工作，分离和鉴定从环境和临床来源获得的弧菌菌株，目的是确定亚洲和南美洲太平洋沿岸人群之间联系的新证据。作为这些调查的结果，我们已经在秘鲁的环境来源中确定了弧菌的四种遗传变异的存在，这是以前在亚洲唯一报道过的，令人惊讶的是，所有这些变异在时间和空间上都出现了重大的El Niño事件。根据这些观察，被困在El Niño水域的入侵性浮游生物种群入侵秘鲁海岸可能提供了新的致病性弧菌变体的独特来源。在等待新的El Niño事件发生十多年后，这一活跃事件提供了一个独特的机会，可以检验与El Niño水域的地带性位移相一致的弧菌种群有效跨太平洋转移的假设。所有这些方面都将涉及浮游动物和弧菌生态学的关键方面，特别是浮游动物在推动弧菌通过主要海洋走廊在全球扩散方面的作用，这将特别有助于保护种群和预防未来的流行病。

Vibrio species are a diverse genus of Gram-negative bacteria found in marine habitats. In addition to playing a critical ecological role in many marine ecosystems, this genus also includes key pathogens of humans. V. cholerae and V. parahaemolyticus, are amongst the most significant human pathogenic bacteria originating from the marine environment. Cholera alone affects an estimated 3-5 million people worldwide; V. parahaemolyticus is the leading cause of seafood borne bacterial gastroenteritis in the world. Infections caused by Vibrio cholerae and V. parahaemolyticus have shown a steady expansion over the last decades associated with the emergence of pandemic clones. The seventh cholera pandemic began in Indonesia in 1961 and was confined to Asia until 1970 when it reached Africa and Europe. After a long time without any new evidence of dissemination, it re-emerged in northern Peru in 1991 causing more than 1,000,000 cases of cholera in just three years. Likewise, V. parahaemolyticus infections were almost confined to Asia until the emergence of cases associated with a single clone in Calcutta in 1996. We report the first incursion of this clone outside Asia in 1997 causing infections along the coast of Peru. The advent of V. cholerae and V. parahaemolyticus infections on the West coast of South America in 1991 and 1997 represented the two only reported evidences of an eastward drift of Asian variants of these pathogens and both processes were concurrent with the arrival of warm equatorial waters displaced by El Niño. El Niño is a climate pattern that describes the unusual warming of surface waters along the tropical west coast of South America causing a notable impact on the ocean and weather at global scale. El Niño events occur irregularly and are not strictly predictable and one of the most major manifestations is the zonal displacement of the Indo-Pacific Warm Pool, a body of water which holds the warmest oceanic seawaters in the world. This body of water is subjected to strong east migrations to Ecuador in phase with the movement of El Niño waters. In the Pacific coast of South America, the incoming of El Niño equatorial waters to the American coasts originate the incursion of warm waters of lower salinity moving southward along the coast, which has been shown to transport foreign zooplankton populations into Peru and Chile. As the survival and spread of vibrios in the marine environment under adverse conditions has been linked to the ability of these bacteria to attach to plankton, we hypothesize that zooplankton provide nutrients and protection to enable vibrios to travel across oceans. We have been working in Peru over the last 10 years isolating and characterizing Vibrio strains obtained from environmental and clinical sources with the aim of identifying new evidence of the link between populations in Asia and the Pacific coast of South America. As result of these investigations, we have identified in environmental sources in Peru the presence of four genetic variants of Vibrio which had been uniquely previously reported in Asia and, strikingly, all of these variants emerged both in time and space with significant El Niño events. According to these observations, the incursion of invasive plankton populations into the coasts of Peru trapped in the El Niño waters may provide a unique source of novel pathogenic variants of Vibrio.After more than ten years waiting for a new El Niño episode, the active event provides a unique opportunity to test the hypothesis of the existence of an effective trans-Pacific transference of Vibrio populations in phase with the zonal displacement of El Niño waters. All these aspects will address key aspects of the ecology of zooplankton and Vibrio, and specifically the role of zooplankton in driving the global dispersal of Vibrio through major oceanic corridors, which will be particularly useful protection of populations and prevention of future epidemics.