[00:00.100]This is the Agriculture Report.
[00:03.050]Irrigation systems can make a big difference
[00:06.930]in agricultural production.
[00:09.070]Irrigation can also improve the lives of farm families.
[00:14.710]However, the addition of water to the land or soil
[00:19.090]may cause problems in some areas.
[00:22.820]A new study describes how irrigation water
[00:27.260]can lead to an increase in malaria cases
[00:30.990]that could last for ten years or more.
[00:35.170]Malaria is spread by mosquitoes,
[00:38.800]the insects like to reproduce in standing water.
[00:43.280]So when a dry area is irrigated,
[00:47.420]the disease can appear and spread.
[00:51.600]Mercedes Pascual is a scientist at the University of Michigan.
[00:57.580]She and her team studied areas in northern India
[01:02.600]where irrigation systems were built over a number of years.
[01:08.380]They compared how malaria progressed with the spread of irrigation.
[01:15.600]"What happens is that when you irrigate, there is more,
[01:18.590]in a sense, more breeding habitats for the mosquito."
[01:22.270]She and the other scientist found
[01:25.890]that after farmers began irrigating their crops,
[01:29.820]the risk of malaria rose sharply.
[01:33.560]At first, her team thought maybe the number of cases rose
[01:39.440]because there was little effort to control the mosquitoes
[01:44.420]that spread the disease. But they were wrong.
[01:47.800]"In fact, we saw the opposite.
[01:49.440]This transition stage was characterized not just
[01:55.910]by heightened malaria risk,
[01:58.350]but also by more intervention to control the mosquito vector."
[02:03.430]Even after the mosquito control efforts were in place,
[02:08.110]the researchers found high rates of malaria
[02:12.010]continued for ten years or longer.
[02:15.990]Mercedes Pascual suggests that the irrigation project supervisors
[02:22.860]need to work more on reducing places
[02:26.050]where mosquitoes might reproduce.
[02:29.380]She also says health officials may need to try other methods of
[02:35.410]malaria prevention that would work for long periods of time.
[02:40.290]"And what we are saying is that those measures have to be sustained,
[02:44.820]and sustained and also planned for, for the long term."
[02:48.660]In the words of the researchers,
[02:51.700]irrigation offers considerable rewards in areas with low rainfall.
[02:58.670]But as Mrs Pscual and her team discovered irrigation
[03:03.690]also can bring years of high rates of malaria.
[03:08.480]The only way to avoid the problem
[03:11.960]is through better planning and control measures.
[03:15.410]A report on the study was published
[03:18.940]in the Proceedings of the National Academy of Sciences
[03:22.470]of the United States of America.
[03:25.460]And that's the Agriculture Report from VOA Learning English.