Sunday, July 15, 2007
Good science does get done in Africa, though it tends to go unnoticed
African science: Local heroes
Feb 1st 2007
From The Economist print edition
Good science does get done in Africa, though it tends to go unnoticed
AFRICA is where researchers go to carry out exotic fieldwork—at least, that is a common presumption in rich countries. It is a useful place for studying elephant behaviour and discovering early hominid remains; then the scientists return home, write papers and enjoy the kudos of getting them published in oft-cited journals.
This, however, is only part of the picture. Nigeria, for instance, has about 40% of the world's sickle-cell-anaemia patients. Last July, a drug company called Xechem Nigeria started selling a new medicine for the disorder. This medicine, Nicosan, had been developed by the country's pharmaceutical research institute. And, at a more esoteric level, the Southern African Large Telescope, located in South Africa's semi-desert Karoo region, is the joint-biggest such instrument in the world.
Despite these successes, many African scientists feel neglected by their politicians who, they suspect, do not understand that geeks as well as businessmen are crucial to economic development. That, however, might be about to change. For the first time, the theme of the twice-yearly African Union Summit (held on this occasion in Addis Ababa) was science, technology and climate change. Although not everything went to plan (“I have a crisis meeting with ministers to discuss how they got beaten by soccer on the agenda,” read one speaker's BlackBerry message to The Economist) such a high-level discussion of the role that science can play in Africa's development was long overdue.
Though the summit's conclusions were limited (many decisions were put off until a re-match next month), that Africa's politicians are taking any notice at all of their continent's science is encouraging. It is, of course, possible to free-ride on the science and technology of others. But in Africa, as elsewhere, no one knows better than the locals exactly what technology needs to be created, and no one has a greater incentive to create it. Nor need such technology be of the unsophisticated kind often badged as “appropriate” by well-meaning outsiders. Appropriate technology can be very sophisticated indeed.
Brothers in arms
The African Laser Centre, for example, is that most trendy of things, a virtual organisation. This means it can draw on talent from different countries without requiring people to move. One of its first projects is to design a laser-based gadget that can diagnose the condition of crops. For this project, the collaborators are a Ghanaian, Paul Buah-Bassuah, who works at the University of Cape Coast, and a South African, Hubertus von Bergmann, of the University of Stellenbosch.
Chlorophyll, the molecule that is at the heart of the process of photosynthesis, absorbs the short and long wavelengths of visible light (blue and red), and reflects the stuff in the middle (green). It is the absorbed wavelengths that are used for photosynthesis, so measuring the efficiency of that absorption gives an indication of a plant's health.
The device devised by Dr Buah-Bassuah and Dr von Bergmann contains a laser that produces blue light of the wavelength preferred by chlorophyll. In a healthy plant the energy from this light will, once it has been taken in by a chlorophyll molecule, be passed on to other molecules and used to make sugar. In a plant that is stressed by lack of water or nutrients, however, such a transfer of energy is harder to effect, and if the chlorophyll cannot pass its energy on, it simply re-radiates it—a process known as fluorescence.
When the laser in the device is shone onto a leaf or fruit through a fibre-optic cable, the light excites chlorophyll molecules inside the cells. Any fluorescent re-emissions travel back along the optical fibre to a detector that analyses both the amount and the nature of the fluorescence.
According to Dr von Bergmann, the amount of re-emitted light can vary by as much as 80% between a healthy and an unhealthy plant. The nature of the fluorescence is also important. The re-emitted light is not blue. Instead, it is a mixture of red and infra-red. The more infra-red light the mixture contains, the fewer functioning chlorophyll molecules there are in the leaf or fruit being examined.
Laser laboratories, virtual or otherwise, are still a rarity in Africa. The continent, however, does produce some of the world's top veterinary livestock research.
From the perspective of poor farmers, animal diseases can be placed into three categories. Some, such as Newcastle disease, for which H5N1 flu was first mistaken in Nigeria, reduce their assets by killing livestock. Others pose limits to their productivity. East Coast Fever, for instance, hits non-indigenous but meaty breeds of cattle harder than the scrawny, local zebu. That puts cattle farmers in the east and south of the continent, where the disease is endemic, on the horns of a dilemma when they choose which breeds to ranch.
It is the third category of disease, though, that is most economically devastating. This is the sort that shuts down farmers' access to their markets because the buyers are afraid of it spreading.
Rift-valley fever falls in this third category. For centuries, nomadic herders in areas now under the control of Djibouti, Eritrea, Ethiopia, Somalia and Sudan sold sheep and goats to customers across the Red Sea for sacrifice during the haj pilgrimage to Mecca. Until nine years ago, this trade involved millions of animals. But then, a massive outbreak of rift-valley fever led Saudi Arabia to impose a trade ban, and to buy more expensive Australian livestock instead.
Some scientists, such as Assaf Anyamba, from Kenya, are trying to tackle the problem by using satellite images to forecast how much rain will fall in various parts of the Horn of Africa. Eggs of the mosquito that transmits rift-valley fever must dry out and become wet once more if they are to develop into adults, so an accurate forecast of periodic flooding is the key to predicting where the disease will break out. That might help herders avoid those areas. But a vaccine would be better.
This is what Felicity Burt, of the University of the Free State, in Bloemfontein, South Africa, is trying to create. She has taken a virus called sindbis, which does not cause serious symptoms, and swapped the genes that code for its protein shell with a selection of those that do the same job for the rift-valley-fever virus. When her vaccine is injected into an animal, it causes the production of rift-valley viral proteins without the associated fever. The immune system can then learn to recognise those proteins, so that it can react rapidly if it encounters real rift-valley viruses.
So far, the vaccine seems to work well in mice—protecting them against infection. Whether it protects sheep has not yet been tested, although it certainly causes them to produce the appropriate antibodies. Unfortunately, that needs two inoculations, and an ideal vaccine would need only one. Nomadic herders, by definition, are rarely found in the same place twice, so tracking them down to give their animals a booster shot is difficult. One way to create a single-shot inoculation might be to insert extra or altered promoter elements–which switch genes on and off—into the sindbis virus's genetic material. That should increase the amount of rift-valley proteins made in an infected cell.
Such genetic modification is also finding a place in African crop science. Jennifer Thompson and Edward Rybicki, of the University of Cape Town, have developed a variety of maize that is resistant to maize-streak virus, another insect-borne disease (the culprits here are leaf-hoppers). Maize is not native to Africa, even though it now, for instance, occupies 90% of the cultivated land in Malawi. But since its arrival from the Americas in the early 1500s, a virus found in local grasses has evolved a way to attack it. In bad years, such as 2006, maize-streak virus can wipe out entire harvests. Plant breeders have tried for a quarter of a century to develop crops that are immune to the disease by crossing maize with partially resistant native grasses. Unfortunately, they have met little success. The pattern by which resistance genes are inherited has proved elusive.
Dr Thompson and Dr Rybicki's trick was to insert a modified viral gene into the maize. This gene encodes a mutated version of one of the proteins that the virus needs to copy itself. When expressed at high levels in a plant infected with maize-streak virus, the modified protein outcompetes the normal version, throwing a spanner into the works of viral assembly. That has been demonstrated in greenhouses, at least, by Panner Seeds, a seed supplier in Greytown, South Africa. And the trait has successfully passed itself down four generations of crop. If further crosses go well, field trials will take place later this year. Those would be the first such trials of a genetically modified crop in Africa, and if successful, this maize would be the first genetically modified crop created in a developing country—the first, it is to be hoped, of many.
Copyright © 2007 The Economist Newspaper and The Economist Group. All rights reserved.
Posted by lmurx at 5:56 PM