There is an interesting article in this week’s Science (Science 20 July 2007: Vol. 317. no. 5836, pp. 310 – 313) about a program to use sterile males to try to short-circuit breeding in the tse-tse fly:
“The scheme sounds simple. Produce as many as a million male flies a week, make them sterile by blasting them with radiation for a couple of seconds, then release them in tsetse-infested areas, making sure they outnumber wild males 10 to 1. Hapless females will mate with the lab critters, but their rendezvous will produce no offspring. Repeat the procedure several times, and the tsetse population will die out.”
A country that is not known for it’s financial resources is spending millions on this. Why? Because tse-tse flies transmit trypanosomiasis, a nasty disease caused by protozoan parasites. This is also known as Sleeping Sickness or Nagana. It’s a very sad story:
“Almost a quarter-million square kilometers of mostly fertile valley land in western and southwestern Ethiopia is infested with tsetse flies. Nagana, caused by a unicellular parasite of the Trypanosoma genus, makes keeping livestock difficult. That means fewer animals to plow the land, less milk, and less manure–in short, poverty. A large swath of Africa has the same problem. The U.N.’s Food and Agriculture Organization puts the bill for missed farming revenues in this “Green Desert” across Africa at about $4.5 billion annually.
Then there’s the human cost: Sleeping sickness, or human trypanosomiasis, is believed to infect some 50,000 to 70,000 people a year, although hard data are not available. No vaccine exists, and drugs–most more than 50 years old–are toxic and decreasingly effective. Melarsoprol, an arsenic-based drug, kills between 3% and 10% of patients. “
Use of sterile males has successfully worked in the past for several different species, and in one case, was able to remove tse-tse flies from an island. There is a great deal of discussion about this particular project, though, and it’s not certain it will work:
“the Ethiopian project is at the center of a divisive, often caustic, debate among entomologists. Critics believe that for a variety of reasons–such as the fact that there are five tsetse species in Ethiopia–it is likely to fail. And besides, it’s not a sustainable solution, they say, because flies may reinfest the country. The money–Ethiopia’s government spent $12 million on the factory alone–would have been much better spent on cheaper and simpler ways to fight tsetse, such as insecticide spraying, says Glyn Vale, a former head of tsetse research in Zimbabwe. “I hate to see a poor country waste so much money,” Vale adds. Veterinary entomologist Ian Maudlin of the University of Edinburgh, U.K., calls SIT Ethiopia’s “man-on-the-moon project.”
With experts not optimistic, why would Ethiopia spend resources this way? Interestingly, the project is funded by the IAEA:
“critics blast the International Atomic Energy Agency (IAEA), which is supporting the project, for seducing Ethiopia into trying sterile insects….. Best known for its wrangling with aspiring nuclear powers, the U.N. agency, headquartered in Vienna, Austria, also promotes the peaceful use of atomic energy, including the creation of sterile insects, and its lab in Seibersdorf, outside Vienna, is the world’s premier SIT research center…..IAEA doesn’t fund SIT projects; however, it provides technical assistance, with countries picking up most of the tab. “
The article goes on to detail why this probably isn’t a viable strategy for the rest of Africa, either, unfortunately. I hope the Sterile Insect project works, but I’m not very optimistic myself.
Image via Wikipedia