[00:00.00]This is the Agriculture Report.
[00:03.05]Irrigation systems can make a big difference
[00:06.93]in agricultural production.
[00:09.07]Irrigation can also improve the lives of farm families.
[00:14.71]However, the addition of water to the land or soil
[00:19.09]may cause problems in some areas.
[00:22.82]A new study describes how irrigation water
[00:27.26]can lead to an increase in malaria cases
[00:30.99]that could last for ten years or more.
[00:35.17]Malaria is spread by mosquitoes,
[00:38.80]the insects like to reproduce in standing water.
[00:43.28]So when a dry area is irrigated,
[00:47.42]the disease can appear and spread.
[00:51.60]Mercedes Pascual is a scientist at the University of Michigan.
[00:57.58]She and her team studied areas in northern India
[01:02.60]where irrigation systems were built over a number of years.
[01:08.38]They compared how malaria progressed with the spread of irrigation.
[01:15.60]"What happens is that when you irrigate, there is more,
[01:18.59]in a sense, more breeding habitats for the mosquito."
[01:22.27]She and the other scientist found
[01:25.89]that after farmers began irrigating their crops,
[01:29.82]the risk of malaria rose sharply.
[01:33.56]At first, her team thought maybe the number of cases rose
[01:39.44]because there was little effort to control the mosquitoes
[01:44.42]that spread the disease. But they were wrong.
[01:47.80]"In fact, we saw the opposite.
[01:49.44]This transition stage was characterized not just
[01:55.91]by heightened malaria risk,
[01:58.35]but also by more intervention to control the mosquito vector."
[02:03.43]Even after the mosquito control efforts were in place,
[02:08.11]the researchers found high rates of malaria
[02:12.01]continued for ten years or longer.
[02:15.99]Mercedes Pascual suggests that the irrigation project supervisors
[02:22.86]need to work more on reducing places
[02:26.05]where mosquitoes might reproduce.
[02:29.38]She also says health officials may need to try other methods of
[02:35.41]malaria prevention that would work for long periods of time.
[02:40.29]"And what we are saying is that those measures have to be sustained,
[02:44.82]and sustained and also planned for, for the long term."
[02:48.66]In the words of the researchers,
[02:51.70]irrigation offers considerable rewards in areas with low rainfall.
[02:58.67]But as Mrs Pscual and her team discovered irrigation
[03:03.69]also can bring years of high rates of malaria.
[03:08.48]The only way to avoid the problem
[03:11.96]is through better planning and control measures.
[03:15.41]A report on the study was published
[03:18.94]in the Proceedings of the National Academy of Sciences
[03:22.47]of the United States of America.
[03:25.46]And that's the Agriculture Report from VOA Learning English.
[03:31.68]You can download transcripts and MP3s of all of our programs
[03:37.36]at our website, 51voa.com.
[03:43.73]You can also find captioned videos
[03:48.16]at the VOA Learning English channel on YouTube.
[03:51.80]I'm Christopher Cruise.