The fight is of David and Goliath proportions - humankind against the mosquito. As in the Biblical tale, the little guy is winning. But while the moral of the battle between the poorly armed David and the well-weaponed giant, Goliath, was one of faith, the war against mosquito-borne diseases is down to earth. Mosquitoes carry diseases that kill millions of people around the world each year and affect hundreds of millions more. The financial resources being devoted to mosquito eradication and drugs to ward off the diseases transmitted - malaria and dengue fever among them - is miniscule in comparison to the problem. Put simply, it is a case of rich versus poor. Mosquitoes are most prevalent in tropical and sub-tropical regions, where the poorest people in the world generally live. There are enough resources globally to control and eradicate mosquitoes and the diseases they carry, but those in wealthy countries mostly lack the will to help. Humanitarian workers often give HIV/Aids as an example that the will exists. The virus kills about the same number of people annually as malaria and afflicts a tenth the number of people, yet attracts massive funding and wide-ranging research by pharmaceutical companies in North America and Europe to develop a vaccine. In contrast, observers estimate that US$200 million goes to malaria annually, while research on drugs to replace the increasingly-ineffective drugs available is being carried out by a handful of scientists, mostly in China. The human and economic costs of disease transmitted by mosquitoes can be as devastating as HIV/Aids. Malaria is the No1 killer of children in Africa. No vaccine has been developed for dengue fever and treatment, usually involving four or five days in hospital, can put families in countries such as Cambodia or Indonesia two years in debt. From the perspective of drug companies, there is no argument - HIV/Aids affects rich people as much as it does poor and putting funds into research and development of drugs can therefore be profitable. Less incentive exists for putting hundreds of millions of dollars into creating treatments for people who cannot afford to pay. Scientists do not doubt that HIV/Aids is potentially more devastating than malaria, although there is one important difference. While no cure has been found for HIV/Aids, malaria, dengue, West Nile fever and the dozens of other diseases and viruses mosquitoes carry can be prevented. Hong Kong is a prime example, according to legislator Lo Wing-lok. Malaria and dengue were endemic until the 1970s when the health-care system was strengthened. Only when vigilance fell, such as with the current dengue outbreak, was there a recurrence. 'Malaria is under control because of a well-developed public health system,' said Dr Lo, an infectious diseases expert and medical representative on the Legislative Council. 'There are cases of dengue fever in almost all of our neighbouring countries and regions. Hong Kong was spared for many years until 2002 when there was a lapse of control.' Last year, the Health Department reported 49 cases of dengue fever and 28 of malaria. The majority of the dengue sufferers and all of those with malaria were infected while travelling overseas. Hundreds of thousands of people elsewhere in Southeast Asia suffer from the diseases. Cambodia, one of the world's poorest countries, has an estimated 300,000 malaria victims, while each year 100,000 are treated in China. No accurate figures are available for dengue, although the figure is thought to be in the tens of thousands. Different varieties of mosquito transmit the diseases. The Anopheles genus carries malaria and favours rural areas where there is flowing water and forests. Aedes varieties, which transmit dengue, favour urban settings and are less selective about the cleanliness of water and the size of the source they breed in. World Health Organisation infectious diseases adviser Kevin Palmer said last week that warmer, wetter weather in the region as a result of global warming and increasing urbanisation meant that dengue was spreading at an alarming rate. The biggest problem was that the threat was unrecognised. 'Nobody seems willing to put money into supporting any big initiatives on dengue,' Dr Palmer said from his office in Manila. 'Politicians seem willing to accept it - there is an outbreak and things get done and in the interim period, nobody does anything for prevention.' He said that while his budget for malaria was US$10 million, just US$50,000 had been allocated for dengue. This was despite 10 per cent of some island nations in the Pacific Ocean being affected. Outbreaks occurred in Singapore despite stringent checks and spraying for mosquitoes. Because of the number of potential breeding places in Hong Kong, the possibility of a major outbreak was ever-present, he suggested. 'The only way of bringing dengue completely under control is a vaccine,' Dr Palmer said. 'Some are about to go to clinical trials, but until we get one, the reliance will be on mosquito control. Singapore is small in area and they still have a problem, so what happens with Malaysia where there are millions of breeding places?' He advocated high-pressure media advertising campaigns to convince people to eliminate potential breeding sources as the most effective interim solution. Sufferers of malaria are more fortunate in that drugs 95 per cent effective in treating the disease are available. The problem is a matter of resistance and affordability. Biological systems evolve and the inexpensive, decades-old treatments are now mostly ineffective in Asia and Africa. Mosquitoes build immunity to insecticides. But Guangzhou University of Traditional Chinese Medicine scientist Li Guoqiao is among a small number of researchers at the forefront of the fight to produce better, cheaper drugs. Using a Chinese herb, qinghaosu, as the basis for a compound known as artemisinin, his team is working on the fourth generation of a combination therapy. The third generation, under the brand name Artekin, is available in China and has been under trial with 95 per cent success in Cambodia. In partnership with a western pharmaceutical company, international trials are under way which, if successful, could lead to it being available internationally within five years. Professor Li's assistant, Song Jianping, said Artekin was available in China for about US$1.20, but older drugs such as Chloroquine cost just 10 cents per treatment. 'Professor Li's objective is that the world's poorest sufferers of malaria can use artemisinin-based combinations,' Mr Song said. 'He will continue developing new drugs until this objective has been achieved.' The cheapest artemisinin-based drugs recommended for use by the WHO under its Roll Back Malaria programme cost governments and humanitarian organisations about US$2.50 per treatment. The head of the programme, Allan Schapira, said from Geneva that Artekin was a promising treatment based on initial test results. 'Because its potential is so great, we need to have everything in order around it so that quality and documentation issues can be resolved,' he said. But Dr Schapira and scientists warned that despite the high number of deaths caused by mosquito-borne diseases, such drugs could not be pushed on to the market without proper measures being taken. The director of the malaria programme at Columbia University's Earth Institute, Awash Teklehaimanot, believed that no matter what the price, funding was available. 'You cannot fast-track these sorts of drugs at the expense of people's lives,' he said. 'There are effective drugs that are available, but US$2 or US$2.50 for them is not expensive if there is an international will.' That was a problem, given that for malaria US$2 billion to US$3 billion was needed annually to tackle the disease and only a fraction of that was being donated, he said. The Geneva-based Global Fund for Aids, Malaria and Tuberculosis was by far the biggest donor, ahead of the World Bank and UN Children's Fund. 'But a lack of financial resources is only part of the problem,' Dr Teklehaimanot said. 'Nor are new malarial drugs the magic bullet. There needs to be integrated tools where houses need to be sprayed, bed nets need to be distributed, and there needs to be education.' Despite the seemingly bleak outlook, though, optimism is high among some observers that new drugs and a changed attitude will deal with malaria, dengue and other diseases carried by mosquitoes. Global Fund spokesman John Liden said that when compared to HIV/Aids, the outlook for malaria, in particular, was extremely promising. 'There are spectacular results with fighting malaria that you would never see with Aids,' he said. 'With Aids, we're at most able to stop an increase in the epidemic. That is not the case with malaria, so investing in it makes a lot of sense.'
