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

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.

This proposal aims to deliver substantial and lasting impact by providing mechanistic understanding of one of the more elusive yet fundamental aspects regarding the mechanisms of spreading of Vibrio diseases. Results of the project will address key aspects regarding 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 major epidemics. As this research is multidisciplinary in nature, research will be of relevance to a wide variety of stakeholders with interests in microbial ecology, bacterial genomics, food safety, epidemiology and oceanography, among others. In addition to diverse scientific communities, the research will therefore have a wider impact in relation to understanding of the long-distant routes of migration of marine organisms through the open ocean and how the introduction of new populations through this mechanisms can impact the ecological equilibrium of local communities.

Although we will engage directly with a variety of stakeholders (in academic, industry and policy areas), a key goal of the proposed research is to build pathways to enable the connection of basic scientific knowledge with policy and decision makers with a clear aim of applying the results of this research proposal to design intervention strategies to anticipate risks associated with the arrival of El Niño waters to Peru.

The economic and societal impacts of the research are broad as the results may affect many aspects of society that rely on marine ecosystems. In Peru, the implementation of surveillance programs resulting from the proposed research would contribute to an early detection of the arrival of pathogens to coastal areas, which provides to the local authorities of an effective tool to design strategies and implement measures directed to minimize the potential impacts of the introduction of new pathogens on health. These measures may be particularly useful to provide protection to coastal populations and low income groups with a diet primarily based on seafood consumption, mainly raw and undercooked seafood, and main target of previous Vibrio epidemics. Fishing industry in Peru. Peru has a coastal belt of over 3,000 km fishing more than 50 species of commercial interest. Secondly, due to importance of fish activities in Peru (154 millions of tons in 2011 and more than 120,000 jobs), results of the present research would help to competent authorities for the seafood safety to implement measures for an early detection of potentially pathogenic Vibrio arriving to coastal areas of Peru, which will contribute to minimise further risks associated with the commercialization of contaminated seafood and infection of consumers. These measures will be instrumental in preventing the dramatic impacts that have occurred during previous epidemics, such as the closure of the borders for exportation and affecting local coastal populations with a primary economic sector based on small-scale fisheries.

Outside Peru, non-academic stakeholders include policy forming bodies such as Governmental Health and Environment Departments (e.g. the European Union, UK Government Departments, US Food and Drug Administration, NOAA). All of these groups have a potential interest in human marine pathogens and the impact climate and ocean dynamics on human health. Results from the proposed research will not affect to our understanding of the role of the El Niño in the dissemination of pathogenic bacteria in the Pacific, but also will built up a new framework for the study of the ocean dynamics as major driver for microbial communities and pathogenic bacteria with consequences for ecology and epidemiology on a global scale.