Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Climatic variations influence the emergence of cholera in Africa

06.09.2007
Cholera is an infectious disease caused by a bacterium, the bacillus Vibrio cholerae. In 2004, 101 383 cases, including 95 000 solely for the African continent, and 2 345 deaths were reported to the World Health Organization.

Global climate change has for several years been contributing greatly to the spread of cholera through associated increase in the frequency of torrential rain, floods and periods of drought. It is now established that the spread of zooplankton which harbours the Vibrio cholerae bacterium follows that of phytoplankton, whose growth is directly related to climate variations.

However, a host of factors act on the climatic conditions and they are difficult to study. Certain parameters vary depending on the regions of the world whereas others act on the global scale. The interactions between the climate and emergence of cholera must therefore be studied region by region. Research has been ongoing in Bangladesh and also in South America for many years, but up to now few studies have been conducted in Africa. Yet it is on that continent that the public health situation is giving the most cause for concern.

A study published by research scientists of the Laboratoire de Génétique et Evolution des Maladies Infectieuses (GEMI), mixed research unit IRD/CNRS (2), is the first to yield evidence of the correlations between the outbreak of cholera epidemics and climatic data in 5 West African countries (Togo, Ivory Coast, Ghana, Benin and Nigeria). The research team set up an epidemiological database founded on cases recorded by the WHO over a 20-year period, between 1975 and 1995, in each of these countries. Comparison of these figures with parameters of local and global climate variations showed the factors particularly involved to be the volume of rainfall and the Indian Oscillation Index (IOI), an indicator of the global climate variability constructed from variations in atmospheric pressure in the Indian Ocean. Values of this index lower than –1 showed an association with a warm event such as an increase in sea surface temperature. In contrast, values above +1 coincided with cold events.

The annual rainfall regime and the IOI act on the aquatic environment in which Vibrio cholerae develops (estuaries, sea shores, river beds and so on). In the wild, the cholera bacillus lives in contact with small aquatic crustaceans, copepods, are a component of the zooplankton. These microscopic animals, which constitute the principal reservoir of the bacterium, feed on phytoplankton. They therefore have a tendency to congregate in the zones where the density of microscopic algae is highest. This relationship is fundamentally important. It provides a means to monitor the areas rich in plankton by remote sensing, and therefore to detect from space the potential reservoirs for Vibrio around the coasts.

Outbreaks of cholera appear irregular and, in order better to understand the epidemic pattern dynamics, the GEMI researchers used an adapted statistical tool that favours a wavelet analysis method. This novel process allows comparison of the frequencies of epidemic outbreaks with a range of climatic or environmental parameters (climate variability index, volume of precipitation, phytoplankton concentration near the coasts). This approach also takes into account the random variation of frequencies of emergence of epidemic foci.

The research team thus successfully linked the number of new cases of cholera first to the global climate variability index and then to monthly rainfall readings between 1989 and 1994. For that period, a frequency of epidemic occurrence of 2 to 3 years was indicated for the countries studied, except for the Ivory Coast. A significant correlation was also observed between the IOI and the annual rainfall regime for these same four countries. Furthermore, analysis of the interannual variability of rainfall between 1975 and 1996 indicated the existence of a 3 to 5–year long cycle in the appearance of the disease for the whole of the areas covered by the study. The IOI and volume of precipitation are therefore two climatic variables that appear to be strongly correlated with the appearance of epidemic foci of cholera. The latter usually develop during seasonal periods but their rhythm period can also exceed the annual cycle (between 2 to 5 years). In other words, indirect relationships between climatic variations or variations in rainfall volume and emergence of foci of infection can persist for several years. These results agree with those obtained previously in Bangladesh and South America.

Over the coming years, the results of this research work should contribute to the creation of an early warning system that takes climatic parameters into account for prediction of cholera epidemic dynamics. That should facilitate the organization of prevention actions, such as drinking water filtration schemes, and the planning of care provision for people by supplying medical kits and rehydration kits. This kind of approach could also be applied to the understanding and prevention of other climate-sensitive illnesses such as malaria, dengue and other vector-borne diseases.

Grégory Fléchet -IRD

Grégory Fléchet | alfa
Further information:
http://www.ird.fr/fr/actualites/fiches/2007/fas271.pdf

More articles from Studies and Analyses:

nachricht Rutgers-led innovation could spur faster, cheaper, nano-based manufacturing
14.02.2018 | Rutgers University

nachricht New study from the University of Halle: How climate change alters plant growth
12.01.2018 | Martin-Luther-Universität Halle-Wittenberg

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: In best circles: First integrated circuit from self-assembled polymer

For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.

In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

Im Focus: Hybrid optics bring color imaging using ultrathin metalenses into focus

For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.

But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...

Im Focus: Stem cell divisions in the adult brain seen for the first time

Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.

The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...

Im Focus: Interference as a new method for cooling quantum devices

Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters

Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

'Lipid asymmetry' plays key role in activating immune cells

20.02.2018 | Life Sciences

MRI technique differentiates benign breast lesions from malignancies

20.02.2018 | Medical Engineering

Major discovery in controlling quantum states of single atoms

20.02.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>