 |
|
|
 |
From parasite to saviour |
| |
 |
 |
 |
 |
|
The fruit fly, Drosphila simulans, is a common insect used to model diseases.
Photo: Dr Andrew Weeks. Supplied courtesy of CESAR Genetics
|
|
 |
 |
|
|
 |
|
|
This bacterium, found in the stomach of insects, may hold the key to controlling Malaria. The Wolbachia bacteria (red) inside fruit fly cells.
Photo: David Clancy. Supplied courtesy of CESAR Genetics |
|
|
|
|
In the 1900s the mosquito net was considered the key to marital bliss. There is nothing more distracting than hearing that annoying buzz around your head at night: Knowing the dreaded mozzie is after your blood and that scratching furiously at the bite could prelude an infection or worse. Like an unhappy marriage, a mozzie in the bedroom is something most of us would like to avoid.
Although this annoying little creature is one aspect of summer that we could do without, we are lucky in Australia that a red welt for a couple of days is all we receive. Malaria carrying mosquitoes are responsible for around 5.3 million deaths annually. But now scientists have found a possible new treatment using the bacteria of other insects, such as the common fruit fly.
Treatment for Malaria has been challenging. The one time miracle cure, quinine, found in the bark of the Peruvian cinchona tree, has now lost its potency as a cure. The Plasmodium falciparum mosquito that transmits Malaria has developed a resistance to quinine and some of the alternative drugs developed since the 1940s, such as chloroquine.
These days, the best way to avoid Malaria is to prevent a mosquito from biting you. The mosquito net, covering water to stop breeding and the common insect repellent are the most effective ways of avoiding a Malaria outbreak.
New Malaria research has taken a different approach and focused on the mosquito itself. It is thought that controlling the spread of Malaria could be achieved in two ways: by varying the mosquito's genes, making it unable to bite people, and creating a virus that will only kill the plasmodium falciparum variety of mosquito.
Now another solution is on the horizon. Scientists at the University of Melbourne have discovered a bacterium that may reduce the fertility of the dreaded Malaria carrying mosquito. Interestingly, they found the bacterium in the most unlikely of places - in the stomach of insects.
Professor Ary Hoffmann and Dr Andrew Weeks from the department of Genetics at the University of Melbourne used the Californian fruit fly (Drosophilia) as a model in their experiments to study a bacterium that commonly infects insects but has evolved from being parasitic to becoming a fertility aid.
"In the Wolbachia bacteria, we have found that they had rapidly changed from being parasitic and therefore detrimental to their insect host, to engaging in a mutualistic relationship where both bacteria and insect benefit because the insect gains enhanced fertility," said Andrew.
"We believe this bacterium could be an option for pest control in order to kill the common human disease carriers, mosquitoes.
"Wolbachia is spread from an infected male to an uninfected female," Andrew explained. "We found that within 20 years, the infected females had gone from having reduced fertility with a 15-20 per cent reduction in egg production, to a 10 per cent increase in egg production under laboratory conditions. Our results suggest a small reduction, but similar changes are occurring in nature.
"This is the fastest rate of evolution for this relationship so far as we know of no previous examples where an evolutionary shift towards mutualism has been observed in a period of decades in nature.
"Because this increased fertility seems to provide an advantage in nature, we predict that the bacteria will continue to be present in the insects for future generations and they may even evolve to become essential to the host.
"We could take advantage of this evolving situation by killing off the bacteria in the stomachs of insects such as mosquitoes. Because the bacteria increases fertility, by taking it away this strategy could reduce mosquito numbers and their ability to spread disease," Andrew concluded.
The research, funded by the Australian Research Council and published in PLos Biology, is a breakthrough for Malaria treatment. Let's also hope that in the near future when in places like Africa, were Malaria is prevalent, when laying in bed on a hot humid night, you will not need to worry as you hear that irritating buzz when trying to sleep!
Author - Nerrisa Hannick
University of Melbourne
|
|
 |
|
|
 |
|
|
 |
 |
 |
Drosophila simulans is the latin name for a type of fruit fly.
|
 |
 |
|
The term "drosophila", meaning "dew-loving", is a modern scientific Latin adaptation from the Greek language.
|
|
|
|
Wolbachia is a bacterium which infects arthropod species, including a high proportion of insects. It is one of the world's most common parasitic microbes and is potentially the most common reproductive parasite in the biosphere; for example more than 16% of neotropical insect species carry this bacterium.
|
|
|
|
About 75% of known human disease genes have a recognisable match in the genetic code of fruit flies and 50% of fly protein sequences are similar to those of mammals.
|
|
|
|
Drosophila is being used as a genetic model for several human diseases including the neurodegenerative disorders Parkinson's, Huntington's, spinocerebellar ataxia and Alzheimer's disease. The fruit fly is also being used to study mechanisms underlying immunity, diabetes, and cancer, as well as drug abuse.
|
|
|
|
|
 |
|
Get it delivered
Learn how Australia's science in motion makes a difference to daily lives. Sign up today.
|
|
|
 |
|
