Monday, April 27, 2009

A question of malaria

There is alot of angst out there in travel land, or at least on travel forums, about the question of malaria. What countries have malaria and what should a visitor do to prevent getting the disease?

There's also alot of advice given, much of it misleading, from other travellers. Some push the paranoid and erroneous view that everyone should take antimalarial prophylaxis and all will be safe, others scoff and debunk all the pills as capable of causing severe side effects, and anyway, they never got malaria despite taking nothing. Information from a visit a few years back can quickly become irrelevant as public health measures make more areas, especially in Asia, malaria free. There's quite a few well balanced remarks, but the poor punter who asked the question has now been bombarded with so many opposing opinions that he/she is pretty confused. My advice? See a doctor.

But it's not that simple, because many of your average GPs don't have much experience of travel medicine and may need to do a bit of research themselves to determine malarial risk. They also need to find out about the latest medications, potential side effects and discuss all this with their patient. Something many GPs just don't have the time to do when a client turns up wanting advice within a couple of weeks of the departure date.

Following is a general guide to all things antimalarial. If your doctor is not asking these questions then you should seriously consider going elsewhere. A travel medicine clinic is a good option, but even so a healthy dose of scepticism is in order, because doctors also aren't immune to having fixed ideas about what plan of "medical action" should take place. A little bit of your own research therefore helps.

So let's start with a comprehensive travel interrogation. Where are you going and for how long? Will you be spending most of your time in larger cities and what sort of accommodation will you be staying in? Will you be spending much time in rural areas and will you be staying overnight there or simply doing day trips? Are you a keen birdwatcher/photographer/nature lover who spends their dawns and dusks out in the elements or are you usually safe and sound in your bed or a bar at those times?

It's not simply a matter of looking up a particular country and determining its malaria risk and applying that to all travellers to that country. A typical example is Thailand, where Bangkok and most of the rural areas are now considered malaria free. There are still some areas of Thailand where malaria prevalence is quite high (though only moderate risk) and knowing this information usually involves a little more detailed research.

We've touched on a couple of epidemiology terms here. One of them is prevalence. This is a measure of how much disease is present in a given community. To determine the level of risk of acquiring malaria there needs to be both a presence/absence of the mosquito which transmits the disease and a reservoir of infected individuals to maintain a source. Australia, for instance, is considered malaria free because although there are plenty of anopheles mosquitos in the tropical climes, there is very little, if any, untreated malaria in the community to provide a reservoir for further spread. That's the advantage of a well funded public health system.

If your stay is mostly in large cities in malaria prone countries, risk is considered quite low. This risk assessment assumes that you will be staying in modest accommodation, with air conditioning or perhaps just a fan, rather than staying with local people in substandard conditions. Both aircon and moving air from a fan will reduce mosquito numbers in a room, and the use of a permethrin impregnated mossie net, and/or spraying the room with insect repellant prior to leaving for your evening meal will further reduce your risk of being bitten whilst sleeping or at dawn. Light coloured clothing that limits skin exposure during the anopheles' active times of dusk and dawn, and the use of repellants with DEET, also prevent you being bitten.

Where do you stand if you have determined that you will be spending time in an area which is not malaria free? This is where it gets tricky, because there are low risk, moderate risk and high risk areas. Then there's the actual amount of time you will be spending there, and then your medical history as to whether the use of antimalarials would be harmful for you.

The general rule is the longer you take an antimalarial medication, the higher the risk of significant side effects. This is why most expats living in a malaria prone country rarely take them. But as a short term traveller in an area, your risks are different. And if you are travelling to many places, some with high prevalence, others low or no risk, it all starts to get quite bewildering. Particularly as some of the available medications need to be commenced prior to entering the malaria zone, and must be continued for up to a month after leaving it.

It's a bit of a no brainer to work out that if you are going to a high risk area for a short period of time then it makes sense to take antimalarials. The rest of the scenarios however are less black and white. There is in fact no right answer to the question: should I take antimalarials? And the reason: because no medical evidence to this day has proven, categorically, that the taking of antimalarial prophylaxis actually prevents you contracting malaria. In fact there is some evidence that it may mask symptoms and delay diagnosis and appropriate treatment. But it's still recommended that travellers to malaria prone places take it, so you wonder why you're so confused?? No, it's not the Larium!!

Your doctor and you should now have a fairly good idea about where you are going, what sort of activities you are planning, and therefore what your risks are. Then you will probably be given a choice of a number of scenarios. 1. take antimalarials for your entire trip and for the appropriate tailing off period on your return. 2. take antimalarials just during the times when you are going to be in moderate or high risk areas, and for the ensuing time period afterwards. 3. take no prophylaxis but carry a course or two of treatment should you be in an area where medical help is unreliable.

For short trips, up to a month, I'd tend to favour option 1. Option 2 is a bit of a headache, as the tailing off times can mean alot of time on a drug with potential side effects. It also gets very expensive. Doxycycline, much cheaper than Malarone, can degrade quickly in the heat, so carrying large supplies may not be such a good idea, and purchasing it from local pharmacies is fraught with risks of poor quality or substitution. My favoured option is number three, particularly useful now that Malarone is more easily available and can be taken as a treatment course over four days. But the real message is:


Preventing getting bitten requires planning, execution and consistency. A long day out in the country may mean returning after dark, when your sleeveless top and shorts now offer no protection from the beasties. Or an afternoon session with some new friends turns into evening and you've left the DEET in your bag in your room. Remember, antimalarials don't prevent you getting bitten, and only not getting bitten prevents you getting malaria.

So plan early to see your doctor, you may even need to catch up on a few immunisations too. Then both you and your doctor will have time to be so well informed that you too can start answering those antimalarial questions on your favourite travel forum!!

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