| > | | | | the problems they have encountered. Surmounting |
| Scientists at Imperial College, London, point the way | | | | these difficulties would make possible not just a |
| to stopping malaria at its source: the mosquito | | | | malaria-free future but would also allow similar |
| Malaria remains one of the world's most intransigent | | | | techniques to be applied in fighting yellow fever and |
| diseases, causing suffering and posing serious threats | | | | dengue. |
| to development in some of the world's poorest | | | | The obstacle race |
| countries. Transmitted through the bite of a female | | | | Professor Andrea Crisanti, who has recently jointly |
| mosquito (Anopheles stephensi), it affects more than | | | | published a paper on these studies, acknowledges |
| 300 million people and causes more than one million | | | | that further work is needed on the molecular |
| deaths each year, 90 percent of which occur in | | | | genetics of the problem: 'an increasingly important |
| Africa. According to the World Health Organisation | | | | challenge is to study the population biology of |
| (WHO), most of these deaths are among children | | | | transformed mosquitoes and understand how a |
| under the age of five. Pregnant women are also | | | | beneficial gene can be driven through a wild |
| especially vulnerable to this disease, which is | | | | population,' he says. |
| increasingly resistant to the drugs used to treat it. | | | | He recognises too that public concern over genetic |
| Malaria is characterised by the WHO as 'both a | | | | modification in general means that the environmental |
| disease of poverty and a cause of poverty'. As no | | | | and bio-safety aspects of the work will play an |
| effective vaccination been developed and none is on | | | | important role. The population studies being |
| the horizon, the situation seems to hold little promise | | | | undertaken by himself and his team will be essential |
| for those whose lives and livelihoods are threatened | | | | to the regulatory processes associated with such |
| by the disease. | | | | issues. |
| Now progress in the field of genetics has led | | | | Mathematical modelling, carried out by Professor |
| scientists from Imperial College, London, to map the | | | | Charles Godfray also at Imperial College is helping the |
| means by which it could be eradicated - not by | | | | scientists to understand more about how the GM |
| treatment but by prevention. Genetically modified | | | | mosquitoes react in mixed populations. Already it |
| mosquitoes that do not transmit malaria were first | | | | seems as if one problem has been identified. As the |
| bred under laboratory conditions three years ago. | | | | GM mosquitoes have been bred from a single |
| The hope has been that such a strain, if released into | | | | ancestor, it may be that inbreeding is causing the |
| the wild, would become absorbed into the native | | | | introduced gene to become associated with |
| population and spread the gene that stops the | | | | detrimental mutations. While these do not actually kill |
| transmission of the malaria parasite, thus transforming | | | | the mosquito, they impair its competitiveness with |
| the insects from 'disease carriers to disease fighters.' | | | | unmodified insects. Fortunately such effects can be |
| Unfortunately this hope has so far been thwarted. It | | | | overcome by cross-breeding. |
| seems that the transgenic mosquitoes do not have | | | | Hope for the future |
| the clout to dominate over their wild relatives. On the | | | | While current weapons against malaria remain |
| contrary, they quickly die out if they breed freely | | | | inadequate to protect the thousands of very young |
| with their unmodified counterparts. The Imperial | | | | children who die each year from this cruel disease, |
| College Study, in which the transgenic mosquitoes | | | | the research being conducted by the Imperial College |
| were mated with unmodified insects showed that | | | | team holds real hope that the end is in sight. |
| the beneficial gene was lost over the course of | | | | References: |
| between 4 and 16 generations. Given the short | | | | Catteruccia, F., Godfray, C. J. & Crisanti, A. Impact of |
| life-cycle of the insects, this represents only a very | | | | genetic manipulation on the fitness of Anopheles |
| slight time span. Infinite numbers of mosquitoes | | | | stephensi mosquitoes. Science, 299, 1225 - 1227, |
| would therefore need to be released in a particular | | | | (2003). |
| place to give them a hope of replacing the wild, | | | | Catteruccia, F. et al. Stable germline transformation of |
| parasite-riddled varieties - meaning that the scale and | | | | the malaria mosquito Anopheles stephensi. Nature, |
| cost of such an activity would probably be prohibitive. | | | | 405, 959 - 962, (2003). |
| However, the scientists involved in the project, which | | | | For further information, please contact: |
| is funded by the Wellcome Trust, are confident that | | | | Judith Moore |
| what has been learnt points the way ahead. Now | | | | Imperial College of Science, Technology and |
| they have to carry out feasibility studies and look at | | | | Medicinej.h.moore@ic.ac. |
| the costs involved to see if they can find solutions to | | | | |