Malaria Prevention.

Malaria still remains one of the most common causes of fever in returned travellers. Approximately 30,000 cases of travel-related malaria are reported annually throughout the world. The majority come from Africa. Between 600 and 800 cases of malaria are reported in travellers after returning to Australia each year.

Malaria still remains one of the most common causes of fever in returned travellers. Approximately 30,000 cases of travel-related malaria are reported annually throughout the world. The majority come from Africa. Between 600 and 800 cases of malaria are reported in travellers after returning to Australia each year.

Most of the deaths that do occur are preventable. It is important for travellers to malaria-endemic areas to have a good understanding of the disease. Preventing mosquito bites and recognising symptoms are as important as an antimalarial medication.

The story of malaria is one of interaction between a tiny blood parasite, a delicate female anopheles mosquito that feeds on human blood to grow her eggs, and humans.

The Parasite: Four species of Plasmodia infect humans. Plasmodium falciparum is the most feared because it causes the red blood cells it has invaded to stick to the lining of small blood vessels. Left untreated, broken cells begin to clog up the small blood vessels in vital organs such as the brain and kidneys. Without early diagnosis and treatment, this can kill quickly, especially the very young and older people with no immunity.

The Mosquito: There are hundreds of species of anopheles mosquitos, each with their own behaviours. About 20 of these transmit most of the worldӳ malaria. Their efficiency at transmitting malaria depends on many factors.

The Human: In areas where there is constant risk of malaria, the locals, after many years in childhood, acquire a degree of immunity. They will have circulating parasites without feeling unwell. Many children die while in the process of acquiring this immunity. Travellers are non immune and at high risk of serious illness if exposed.

PREVENTION:

Primary Prevention Methods

Measures to minimise mosquito contact are the first line of defence. Risk is highest between dusk and dawn because the anopheles mosquitoes feed at night.

Personal anti- mosquito measures should be routinely used. These should include:

• Stay in air-conditioned or well-screened areas
• Avoid strong perfumes and dark clothing
• Use mosquito nets
• Wear clothes that cover most of your body
• Apply flying-insect spray that contains pyrethroid to living and sleeping areas during evening and night time hours
• For added protection against mosquitoes, bednets and clothing can be soaked in or sprayed with permethrin. When used according to directions, permethrin can be effective on clothing for several weeks
• When outside, apply repellents that contain 30-35% DEET to clothing and exposed skin

The possibility of adverse reactions to DEET will be minimized if the following precautions are taken:

• Avoid applying products containing more than 35% DEET to the skin.
• Always use repellent according to label directions.
• Apply repellent sparingly only to exposed skin or clothing.
• Do not inhale or ingest repellents or get them in the eyes.
• Avoid applying repellents to portions of children's hands that are likely to have contact with their eyes or mouth.
• Never use repellents on wounds or irritated skin.
• Wash repellent-treated skin after coming indoors if there is no risk of exposure to insects.
• If a suspected reaction to insect repellent occurs, wash treated skin and seek medical attention.

Antimalarial Medications

Although no antimalarial is 100% effective, the use of anti malarials is an important component of any malaria prevention strategy.

When advice on antimalarials is sought from a medical practitioner certain factors must be considered;

• The actual risk of the disease and the benefit of taking a prophylactic drug.
• The risk of taking the drug (ie potential side effects).

Assuming that there is a reasonable risk of exposure, then taking a drug will make malaria a lot less likely.

Even effective anti-malarials do not always prevent an individual becoming infected from an infective mosquito bite. They do, however, prevent multiplication of the parasite to levels that cause clinical illness. (If the drugs fail, symptoms will occur and these need to be acted upon)
Well-chosen preventive drugs reduce the amount of malarial illness that a non-immune person will suffer in an endemic area. They also reduce that chance of serious, life-threatening malaria and the risk of hospitalisation in a remote area.

POPULAR MISCONCEPTIONS ABOUT MALARIA

"But if I catch malaria wont it keep coming back?"

Two malaria species, P.vivax and P.ovale, do have latent liver forms called hypnozoites which are not killed by the currently available prevention drugs. It is possible for these to come out from the liver into the circulation causing illness or relapse at a later date. It is very uncommon for this to happen more than 6 months after leaving the malarial area. If this does occur, the patient is usually treated with chloroquine and another drug called primaquine. While unpleasant, the illness caused by these strains is rarely life-threatening.

"Why take antimalarials when the parasite is resistant anyway?"

No one pretends that antimalarials are 100% effective. Drug resistance is only partial and varies from place to place. Mefloquine, Malarone and Doxycycline offer very good protection over and above using mosquito protection measures. Until a vaccine can be developed, they are all we have against a potentially fatal disease. Most antimalarial drug Failures are due to failure to use them as instructed.

"Taking antimalarials masks the disease."

If you are bitten by an infected mozzie, you are infected. The drugs treat the infection by destroying the parasites before they multiply in your red blood cells, and before this causes you to get symptoms. They do not destroy the early liver cycle of the parasite and that is why you are instructed to take them for a period after leaving the malaria area. When the parasites emerge from your liver, the drug will be in your circulation waiting to kill them. If the drug fails, you will get symptoms and then you must get diagnosed and treated with other medication.

"I don't need to take tablets for malaria prevention because I grew up there."

This is a very wrong and dangerous assumption. Statistics from non-malarial developed countries show that those most likely to contract as well as die from malaria are folks returning home to visit friends and relatives (VFR). Natural immunity is only acquired by living continuously in a bad malaria area and is lost within a few months of leaving it. Natural immunity is only partial, and immune adults in these areas are nonetheless often sick with malaria. The parasite has a very complicated cycle and this is why a vaccine has proved so difficult to develop.