Protection for individuals
Personal protection measures for preventing malaria infection fall into two categories:
- Protecting people from being bitten by vector mosquitoes and,
- Using a course of chemoprophylaxis (malaria prevention drugs) so that if a person is bitten by an infected mosquito, the malaria parasites will not multiply in their body.
Repellents are an excellent option for deterring mosquitoes. The most effective repellents contain at least 50% DEET (diethyltoluamide) and these should be used in areas of high transmission. In moderate to low transmission settings slightly lower DEET concentrations may be preferred.
Repellents should be applied to all uncovered skin in the early evening hours. Wearing long trousers and sleeves may be useful. However, since mosquitoes can bite through many fabrics, it is useful to apply repellent underneath the clothes or spray it on them, as well as on exposed areas of skin.
Repellents can provide effective personal protection when used regularly and properly by short to medium term visitors to a malarious area.
Unlike the primary vectors of malaria in Africa, which tend to bite late at night, several key vectors in the Asia-Pacific region tend to start biting earlier in the evening, before people reach the protection of their insecticide treated bed-nets (ITNs). Thus ITNs alone cannot provide full protection. It had been hoped that community-wide use of repellents might provide the solution to this early vector biting but findings from recent research in Lao PDR¹ and elsewhere in the GMS have been disappointing, showing that repellents given to families who also had access to long lasting insecticidal nets, did not provide significant additional protection. It may be that the repellents were not applied well, did not persist long enough to protect from bites, or that mosquitoes that bite indoors later in the night contribute more to malaria transmission in these areas than thought.
Long lasting insecticidal nets
Insecticide treated nets provide about twice as much protection as nets with no insecticide. This is because mosquitoes do not bite through insecticide treated nets, are unlikely to pass through small tears or holes, and if a mosquito gets trapped inside they are likely to be knocked out or killed before they can bite the sleeping person. Long lasting insecticidal nets have insecticide incorporated within the net fibres, or bound around them, meaning the insecticide does not easily wash off. They should withstand 20 washes and remain effectively insecticidal. The effective lifespan of an LLIN usually ranges from 3-5 years depending on the type of material used for the net (polyester/polyethylene) and the process used for incorporating the insecticide.
In sub-Saharan Africa, where mosquitoes bite predominantly late at night and indoors, LLINs provide an ideal means of protecting people from malaria. In the Asia-Pacific region however many important vector species start biting outdoors earlier in the evening. As a result LLINs are somewhat less effective, than in Africa, although studies have demonstrated that they do still have a significant protective effect and therefore an important role to play in malaria prevention in these settings.
While LLINs are primarily a personal protection measure, high coverage rates (in excess of 80%) can also provide a ‘community effect’ reducing overall transmission so that people without nets gain some level of protection.
LLIN hammocks and hammock nets
In a number of areas in the Asia-Pacific, particularly in the Greater Mekong Sub-region, there are high risk groups who temporarily spend time sleeping outdoors in high transmission areas, particularly forested areas visited for personal or employment related work. Given the temporary nature of the exposure and the practice of sleeping outdoors or in crudely constructed shelters; indoor residual spraying and LLINs tend to be inappropriate. Insecticide treated hammock nets, insecticide treated bed-sheets and repellents can all however provide some level of personal protection. In forested areas of central and southern Vietnam, for example, insecticide treated hammocks nets have been shown to provide good protection.
Other methods of bite prevention
Electric vaporizers that emit insecticide from a liquid or tablet and can be easily installed in rooms have been shown to reduce biting. However these are far less effective than an LLIN and should only be used as a complementary measure. Repellent coils can also be effective in deterring mosquitoes indoors provided they burn throughout the night. They are less effective outdoors where any breeze reduces their effect.
Window and door screens provide protection against mosquitoes by preventing them from flying through open doorways and windows. The mesh must be small enough to prevent mosquitoes flying through them, and if they are on windows that can be opened it is important to be disciplined about closing them around dusk.
Malaria chemoprophylaxis works by raising the levels of specific malaria drugs in a person’s blood to a level that ensures that if an infective mosquito bite is received, the parasites are destroyed before an infection can take hold.
Chemoprophylaxis must be taken throughout the period of potential exposure but also prior to travel and after returning. This is because prior to travel the drug level needs to be built up in the blood to ensure maximum protection on arrival in the malarious area. Following travel, optimal levels of the drug in the bloodstream need to be maintained as the malaria parasite may still be developing in the liver and yet to emerge. The frequency and the duration of treatment pre- and post-travel varies according to the drug used. There are three recommended prophylactic drugs that are currently prescribed in areas where falciparum malaria is present: atovoquone-proguanil, mefloquine and doxycycline (various brand names exist). The choice of drug depends on the drug resistance profile of malaria parasites in the area in question. Click here to see the list of countries with recommended chemoprophylaxis drugs.
In the Korean peninsula and parts of China, where only vivax malaria is found, chloroquine can provide effective chemoprophylaxis provided parasites are not resistant to it. Where chloroquine resistance is present primaquine may be used provided recipients are not G6PD deficient.
Choice of prophylactic drug should be made by a doctor after discussion with the individual concerned. Each has different pros and cons and will have different effects on different people. For example:
- Mefloquine should be started 2–3 weeks prior to travelling and continued for 4 weeks after leaving the endemic area. It can cause unpleasant psychological side effects in a small minority of people. These side effects range from mild to more serious. Serious neuropsychiatric disturbances may occur but are very rare (1 in 10,000). The early start of treatment prior to travelling is important both for the effectiveness of the drug but also to enable prescription of an alternative drug if severe side effects are seen.
- Doxycycline should be started 2 days prior to travelling and continued for 4 weeks after leaving the endemic area. Side effects include excessive sensitivity to sunlight in some users.
- Atovoquone-proguanil needs to be taken 1-2 days prior to travelling and continued for 1 week after leaving the endemic area. It is well tolerated, and side effects are rare. The most common adverse reactions reported are stomach pain, nausea, vomiting, and headache. It must be taken at the same time each day and to minimise side effects it should be taken with food or a milky drink.
Other measures to protect individuals
Intermittent presumptive treatment of malaria in pregnancy (IPTp)
This approach sees women taking 2-3 doses of an anti-malaria drug at specific points during their pregnancy to clear any parasites and reduce the chances of low birth weight and maternal or new-born anaemia. This approach is only appropriate in high transmission settings where women are semi-immune. The treatment doses are given without a malaria test on the assumption that most women will be carrying low levels of the malaria parasite in the blood long-term, which will need to be cleared to improve pregnancy outcomes. This approach has not been used widely in the Asia-Pacific as in most countries intense transmission is restricted to a few malaria hotspots. It is however used extensively in Papua New Guinea where transmission remains sufficiently high and the approach has been shown to be effective.
Stand-by Emergency Malaria Treatment
For travellers to malarious areas who also travel to areas with poor access to high quality health services, stand-by emergency malaria treatment may be provided. Individuals carry this with them, and are given instructions on when, why and how to use it. If they become ill with suspected malaria and are unable to promptly present themselves to a good quality health provider, they can take the emergency treatment.
There is currently no commercially available malaria vaccine.
A number of vaccine candidates for falciparum malaria are being developed or trialed and the most advanced of these – RTS,S – could be used operationally in the medium term (WHO predicts making a policy recommendation in 2015)² . RTS,S has however been designed for the vaccination of children living in highly endemic areas. It will not be appropriate as a vaccine for international travellers and there are currently no vaccines in the later stages of development that would be appropriate for this target group.
There is currently no vaccine candidate being tested for use in the Asian setting.
There are currently no vaccine candidates for any other species of malaria.
¹ Chen-Hussey, V., Carneiro, I., Keomanila, H., Gray, R., Bannavong, S., Phanalasy, S. and Linday, S.W. (2013) Can Topical Insect
on the prevention of malaria