Malaria – a growing threat

Box 2 | Controlling malaria

By far the most effective control for malaria has nothing to do with mosquitoes. As mosquitoes only carry the malaria parasite from one person to another, the risk of getting malaria is related to the number of people who have malaria. In countries that have eradicated or greatly reduced malaria, better treatment has been of paramount importance.

A little thought will show why better treatment of malaria is more important than mosquito control. A single malaria infection, if untreated, can last in a human for more than a year. Adult mosquitoes only live a very short time (on average 3-4 days), so it's unlikely that malaria can persist in the mosquito population for more than about 3 weeks. If you kill the mosquitoes but don't treat the people, you have to eradicate ALL the mosquitoes for more than a year. Total eradication is basically impossible at an acceptable environmental cost. On the other hand, you could eradicate malaria by treating all the people for about a month.

We have had outbreaks of malaria in Australia in the past, and we still have plenty of mosquitoes that can transmit malaria. An increased population density and a trend towards more outdoor living are factors that ought to make malaria more prevalent, and yet we have been officially malaria-free since 1981. The reason we no longer have malaria in northern Australia is an example of the effectiveness of prompt treatment. It takes about 10 days after you get sick from malaria before the gametocytes mature enough to infect mosquitoes. So if a person is treated in the first 10 days after getting sick, there is no chance of that person giving malaria to mosquitoes. In Australia, it is now highly unlikely that someone will be sick with malaria for 10 days and not be treated. Hence no malaria.

A particularly good example of the effectiveness of early detection and treatment of malaria has been the eradication program in China. Malaria in China has fallen from around 8,000,000 cases per year to about 50,000 in the last 15 years, almost entirely as a result of putting in place a case detection and treatment program. This involves checking everyone for malaria if they have a fever. If someone has malaria they get medicine for it; and if there are several cases in a village, then everyone gets medicine, regardless of whether they are sick or not.

Widespread spraying programs have rarely been used as a control program for malaria. They are costly and ineffective. By far the most common form of spraying has been to spray houses with a contact insecticide. This kills mosquitoes when they rest on the walls. Selective spraying like this has a relatively minor impact on the environment.

Boxes
Box 1. Life cycle of malarial parasite
Box 3. Antimalaria vaccine
Box 4. Australian research

Related sites
Malaria: What you should know (ABC Online's Special Lab Feature)
Malaria (ABC radio's The Health Report, 28 February 2000)
Control of malaria vectors in Africa and Asia (University of Minnesota, USA)
Malaria control measures (Wellcome Trust, UK)

External sites are not endorsed by the Australian Academy of Science.
Page updated January 2012.