Australian and American researchers announced last week the results of their work into modifying and releasing mosquitoes into people’s gardens in a bid to combat dengue fever.
The World Health Organisation ranks dengue as the most important mosquito-borne viral disease in the world. In the last 50 years, incidence has increased 30-fold and there are multiple outbreaks in many areas of the world, including Laos, each year.
hese Archeulean hand axes from a European site have a characteristic pear shaped typical of Homo erectus tools. Some examples are extremely refined and manufactured. Image - creative commons
There is currently no specific treatment, no vaccine and no easy way to control the mosquitoes that spread the disease. However, an innovative programme currently being trialled in Australia is shaping up to be an important weapon in the fight against the disease.
The scientists have enlisted the help of a bacterium called Wolbachia pipientis. They had previously shown that mosquitoes infected with Wolbachia cannot carry the virus. More important they also found the bacterium is easily passed on to other mosquitoes and their offspring.
Dengue viruses are found throughout the tropics and sub-tropics and appear annually in northern Australia. The researchers released mosquitoes infected with the bacterial parasite Wolbachia, which suppresses the virus, and looked to see if the Wolbachia parasite spreads through the wild mosquito population.
Wolbachia is transmitted by female mosquitoes to their offspring. A pair of infected mosquitoes produces slightly fewer eggs than an uninfected couple, but when an infected male mosquito mates with an uninfected female, she produces no eggs at all.
That provides a big reproductive advantage to the spread of Wolbachia – infected mosquitoes, generation by generation.
While it was easy to show this in the laboratory the results of field tests where infected mosquitoes were released into the wild have only just been analysed.
Infected insects were released at two sites in Queensland and within a couple of months 100 percent of mosquitoes at one site were infected and 98 percent at a second site. This meant they could no longer carry the virus and infect humans.
“It’s natural selection on steroids,” Turelli, one of the researchers says.
The results show that local populations can be transformed in a few months and provides a cheap and effective means to control the disease.
Oldest tools found
A new study reported in the Journal Nature has pushed back the date of the oldest known tools to about 1.76 million years ago. Previously the oldest tools discovered were estimated to have been made around one and a half million years ago.
The tools were found from a site near Lake Turkana in Kenya.
Although no hominid fossils were found with the tools, Homo erectus fossils had previously been found in similar sediments nearby.
The age of the tools was determined by dating the surrounding mudstone with a paleomagnetic technique. When layers of silt and clay hardened into stone, the orientation of earth’s magnetic field at the time is preserved. An analysis of the periodic polarity reversals and other records then yielded the age.
Richard Leakey, who discovered the Turkana Boy, made the valley where the tools were found famous. Turkana Boy was a young Homo erectus who lived about 1.5 million years ago and is the most complete early hominid skeleton found so far.
