|
TRAVEL NEWS 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. 
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 world’s 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:
The possibility of adverse reactions to DEET will be minimized if the following precautions are taken:
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;
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)
You have now weighed up the pros and cons of using malaria prevention drugs (chemoprophylaxis) as well as mosquito avoidance measures.
In consultation with us or a doctor experienced in travel medicine you must now decide whether there is justification for use of a medication for some,
or all, of your trip. The next decision is which one to use. The available prevention drugs are not necessarily suitable for all individuals and so you should
choose carefully.
Discuss this with the doctor when you visit. POPULAR MISCONCEPTIONS ABOUT MALARIA “But if I catch malaria won’t 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.
|
Login    |
|
|
 |