[NEW DELHI] Irrigating arid regions may result in raising the risk of malaria epidemics for more than a decade unless public health interventions are integral to project planning, a study conducted in the Indian state of Gujarat has found.
Based on earlier experiences in the states of Rajasthan and Punjab, the central government has already made mitigation measures mandatory, but these cover only areas adjacent to dams and canals and are limited to the initial years.
"The cost of public health should be considered for the long term and cover infrastructure to distribute water in areas well beyond the big dams," says an author of the study Mercedes Pascal, professor of ecology and evolutionary biology at the University of Michigan and a Howard Hughes Medical Institute Investigator.
The study, published in the Proceedings of the National Academy of Sciences this month (12 August), tracked irrigation-based development in Gujarat over a decade using satellite imagery and compared it with malaria incidence in the districts of Kutch, Banas Kantha and Patan.
Mapping the intensity of malaria incidence in these areas over time, the researchers from the University of Michigan and National Institute of Malaria Research, New Delhi, found that newly irrigated areas adjacent to the main canal were at highest risk.
In contrast, a sustained low disease burden was found in neighbouring areas that have been irrigated for at least three decades.
With time, factors including changes in the environment that eventually transform the ecology of the main vectors and better socio-economic and living conditions of the people residing in the area, along with their ability to afford better health care and prevention measures, brought down disease incidence.
Previous studies have shown the correlation between rainfall and malaria incidence and how it was modified by land use and irrigation. Pascal said the enormous data and indications from earlier studies opened the door for the present study.
The researchers have called for long-term commitment by health authorities and international agencies supporting irrigation schemes, to monitor health impacts and sustain control measures.
India's National Vector Borne Disease Control Programme (NVBDCP) assesses the health impact of irrigation projects and checks mitigation measures before granting clearance for projects. But actual enforcement is left to respective state governments.
"Stringent measures should be instituted by all states to ensure compliance," G. S. Sonal, additional director at the NVBDCP, tells SciDev.Net.
Link to abstract
Malaria dogs newly irrigated areas for decades
Irrigation projects must cover malaria control costs
Malaria plans must be long-term and cover wider areas
Irrigation can build capacities to fight malaria