We are now on the last lap of our Malaria marathon. This month and the next article are about prevention. The first 5 articles have looked at what is malaria, how we get it, what happens to us, and why a schoolboy in Pakwatch gets bitten by an infected mosquito every night yet is perfectly well, while a Muzungu bitten only once is sick after 8 days, very sick in 10 days and without treatment dies after 2 weeks in multiorgan failure.

The key to understanding malaria is immunity, and without consideration of the immune status of the mosquito’s dinner option, you will not understand malaria. Last month we looked at the different treatment options, and why the treatment that works for the Pakwatch schoolboy may not work for the traveller. This month we are looking at prevention and why what works for our famous schoolboy may not work for you.

I am writing this from the Kenya coast, that well known literary venue that has inspired most of Kampala’s annual pantomimes! This year I am not taking prophylaxis. At least not yet. I haven’t seen a single mosquito, it is too windy, and the local anophylene doesn’t like salt air. 100 metres inland and I am sure the situation changes. Those who live out of the range of the sea breeze may enjoy sitting out on the veranda in the evening but so does our friendly female mozzy. And that is the first consideration of prevention. Where are you? Are you going to get bitten, and is your dinner guest likely to be infected?

Location
Malaria has to develop inside a malaria mosquito that has bitten a semi immune human and ingested the male and female gametes. They meet and mate in the mozzy tummy, usually while she rests on the house wall, and the babies, called sporozoites migrate to the salivary gland. When she has digested her meal and her eggs are ready, she goes off to look for a puddle to lay her eggs in. On coming off the water, she is met by the males who hang around the pools waiting for the girls. So she is pounced on by the male, and starts to grow eggs. This is energy consuming (the egg growing I mean, not the mating which is over in seconds.) So she needs a blood meal, and goes looking for you. The male meanwhile has a much easier life and so is vegetarian. So he goes off to look for a nice juicy plant shoot, then straight back to the gutter again to look for another nice juicy female. Sound familiar?

The female if the timing is right bites you just when the sporozoites are mature enough to infect you and start off another cycle of malaria. This timing is temperature dependent: over 15 degrees centigrade, the malaria can develop insisde the mozzy within her breeding cycle. If not, it can’t. You either get another species that can develop at slightly lower temperatures, Vivax, or no malaria at all.

Half of southern Europe could have Malaria, and indeed used to in the past, and half the southern USA. But there are no semi-immune humans to infect the Italian or Californian mosquito. So no malaria. The Kenya coast within a few metres of the sea has no mosquitoes. Nairobi is above 6,000 feet so too cold at night. Kampala is perfect, but some of the hills are too steep for the shallow puddles that anophylenes prefer to breed in, and less than 1% of the mosquitoes in some areas are infected.

So prevention no.1. Live on Makindye! No one ever gets malaria on Makindye (except one family and we made them move.) Other peculiarities of our local anophylene, photophobia, preferring to bite after 10.00pm and before dawn, an odd preference for puddles rather than lakes, tin cans, toilet cisterns and dirty ditches, and they don’t like heights. More than 10 feet above ground and they get dizzy, so there is no malaria above the second floor of hotels. That is why we never see malaria from people living in the Golf Course Apartments. (Unless your mother is a doctor).

So that is the first option for prophylaxis. Nothing.
If you live in Kampala, or above 6,000 feet, or are always on the second floor after dark, this is a legitimate option. It is tasteless, no side effects, cheap and you never forget to take it. However it certainly is not 100% effective, and we see about half a dozen bazungu a year who have slept only in Kampala and have got malaria.

Up country it is not a sensible option! Many of the old eye readers will remember the fishing trip to Murchison about 10 years ago. One couple took prophylaxis, but 7 out of 10 of the Old Kampala boys who took nothing got malaria, most of them for the first time in their lives. Murchison is rightly notorious. And Entebbe airport night flights are high risk too: most of the patients I know who have died or have needed intensive care and renal dialysis flew out of Entebbe 2 weeks earlier! One evening in Entebbe seems to be as much a risk as 2 years in Kampala.

A lot of people tell me they don’t take prophylaxis because they are here for a long time. First of all a "long time” is 5 years not 2. Next the mozzy doesn’t care how long you have been here, you may smell pretty bad to the rest of us but you still smell like dinner to one interested female! Immunity takes at least half a dozen attacks of malaria in a year to be of any use at all, plus a bite at least once a week to keep it boosted. How much of your short time in Africa do you want to spend vomiting to develop any useful immunity?

Others tell me they don’t take prophylaxis because they don’t work. I hope the last 5 articles have explained why. Someone takes malarone or mephloquin and they get an acute fever and diarrhoea, and the local expert, perhaps the garden boy or their favourite IT specialist, tells them they have malaria. He knows of course, because he has had malaria 100 times in the past year and recognizes it immediately. Or perhaps you are not that gullible, and go to the local clinic for a blood test.

There your blood is put on an old scratched slide, stained with old reagents that haven’t been filtered for hours and looked at down a microscope that hasn’t been cleaned for a week. Someone may see a squashed platelet that looks a little bit like a parasite and may report it as “MP + seen” or but even if reported as negative the doctor then calls it “clinical malaria” and treats you anyway. Meanwhile your acute gastroenteritis that caused the fever gets better on its own. Every honest microscopist is bound to miss malaria sometimes on the first day of fever because there are simply too few to be seen in a blood slide. The right thing to do is repeat the slide, or the malaria rapid test, the next day, NOT say my prophylaxis doesn’t work and stop taking it.

So nothing is an option in Kampala, perhaps in other places where malaria really is rare, but not a sensible option for travellers and 2 year wonders living up country.

Other options

Homeopathy
Homeopathy is perfectly safe because it contains only water or inert powder. The active ingredient is diluted by a factor of 10 at least 16 times, and shaken so that the “life force” of the drug goes into the water or inert powder. Of course anyone is welcome to believe in life forces, but unfortunately malaria parasites do not! Amazing how few people use homeopathy to prevent pregnancy, isn’t it?

Boiling and filtering your water.
Wrong disease. Doesn’t prevent pregnancy either. As effective as the first 2.

Nets, mozzy repellent, long sleeves etc.
Your choice. Like most men my age I have to get up to pee every night and can’t stand mosquito nets. And I forget the repellent. And the little b….s get my ankles anyway. So I use option 1. Live on Makindye.

Next month we look at the various drug options. The full article is available on the web site.