Scientists quantify El Niño's effect on malaria
The well-known link between El Niño and the incidence of malaria has been measured by scientists in Colombia.
A rise in sea surface temperature of one degree Celsius equates to a 20 per cent increase in malaria cases in Colombia, they have found. They say that their new technique may make seasonal malaria forecasting possible.
Research has already shown that malaria infection rates in South Asia and Latin America are affected by the El Niño Southern Oscillation (ENSO) — a periodic warming and cooling of the Pacific Ocean with associated changes in air pressure.
But now scientists have applied a mathematical tool that other countries could use to better understand fluctuations in malaria rates, make predictions based on climate forecasts, and unravel the different factors involved.
The researchers used the model to investigate ENSO's role in all five of Colombia's geographical regions, including the Pacific and Atlantic coasts. They studied climate data for 1960—2006 and annual malaria statistics.
ENSO was found to have no influence on malaria cases inland but a discernable effect on the coasts, which was more pronounced on the Pacific side.
The link between the one degree rise in temperature, which indicates a weak to moderate ENSO event, and the increase in malaria rates persisted even when other factors were accounted for, such as changes in the population and prevention and control policies.
Although Colombia is a challenging test case in view of its geographical contrasts, annual cycle of rainfall and temperature and low endemic malaria condition, the team from the US-based Earth Institute at Columbia University and Econstat, Colombia, says malaria prediction using seasonal climate forecasts may be feasible.
"'From the health management and policy-makers' perspective, it is very useful to have a regional differentiation of how ENSO changes could increase or decrease the number of malaria cases," say the researchers.
"Ultimately probabilistic forecasts of the ENSO state could be used to form probability forecasts of temperature and precipitation, which in turn could lead to predicted malaria levels together with their uncertainties throughout Colombia."
Author Hugo Oliveros, of Econstat in Colombia, told SciDev.Net that the next step would be to look for additional understanding of the dynamics of the problem so it can be used by people undertaking malaria campaigns.
Although malaria remains a serious problem in Colombia the number of cases appears to have decreased since the late 1990s, peaking at 187,000 in 1998.
The research was published last month (8 January) in Malaria Journal.