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Mass murderers of the insect world
There is unquestionably one creature in Africa that is in a league
of its own when it comes to causing human deaths. The Anopheles
mosquito is Hitler, Stalin and Mao all tied up in one on its own. This
is of course a major concern to anyone who likes the bush, but as with
every other potentially deadly animal there are a lot of
misconceptions. So let’s look at this little mass murderer and its
Not every mosquito that bites is dangerous. The tiny ones that make
you itch round the feet and ankles around sunset are probably Aedes.
The bigger ones that drive you frantic in the small hours of the night
by sounding like a Stuka diving into your ear (and which also give the
itchiest bites) are probably Culex. Neither carries malaria.
The only carrier, and only under certain circumstances, is the female
Anopheles mosquito (the male is a harmless vegetarian), a silent
assassin and rather finicky in its habits. It only bites between dusk
and dawn. It apparently doesn’t like coming indoors, it likes shallow
puddles and is not usually found in deep, dirty or running water or
There are four species of malaria — Plasmodium falciparum is the only
one that can kill (contrary to popular belief, “cerebral malaria” is
not a different type) and unfortunately is also the most common.
If a non-immune person (that’s us) is bitten by a carrier mosquito,
about 15-20 sporozoites are injected into his or her blood. These end
up in the liver where they divide into thousands of little parasites.
After five days the infected liver cells burst and these are washed
out into the blood, where they look for a host red blood cell where
After two days (we’re now on day seven) these red cells become sticky
and stick in the capillaries in deep organs while the parasites divide
again and after a few hours the red cell bursts and another wave is
released. This is repeated every two days, each time releasing about
10 times as many parasites as well as toxins from their excreta, which
is what causes the fever, nausea and other malaria symptoms. This is
why the symptoms come every two days with increasing severity.
Initially you may have a mild fever for a few hours. Two days later
you will feel sick, have a fever and will experience vomiting but
malaria may still not show up in tests.
In two more days you will have become very sick and now tests will
show a clear positive. Another couple of days without treatment (12-14
days from the bite) and you could be in real trouble.
Once five percent of the red cells are infected they start sticking
together and blocking capillaries. This can cause deep organ failure
affecting the kidneys, lungs and brain resulting in death (this is
what is commonly known as “cerebral malaria” — not a separate strain
but normal falciparum which has gone untreated).
This time scale after five days applies to a non-immune adult from one
infected bite — with more bites, or in a baby, it could happen more
People who are repeatedly infected and survive — usually because of
treatment — can develop immunity. (If you were considering not taking
the prophylatics so you can do this, don’t even think about it. You
have to get sick several times a year for years on end.) In particular
breast-fed children of immune mothers start with some immunity, which
increases with each infection. Unfortunately, these people are the
source of the disease. The mosquito can’t be infected by biting a
non-immune person with malaria, only by biting an infected but immune
One of the big problems with malaria is identifying it, because there
are no specific symptoms. Fever, nausea, headaches and joint pains can
be due to other causes and many people are sometimes wrongly diagnosed
with malaria. The problem with this is you are treated for malaria and
don’t get better because you haven’t got it, so the doctor mutters
about resistant strains and puts you on quinine which can have nasty
side effects. In the mean time your gastro enteritis clears up and you
are pronounced cured. So how do you know if you’ve got malaria?
Firstly, think about how long ago it was when you first arrived in a
malarial area? If it was less than eight days, then it’s not malaria.
Secondly, are you taking a recommended prophylactic? If so, it’s
possible but very unlikely.
Finally, take a test and take another one a day or two later to be
sure. There are excellent self-administered rapid tests for falciparum
on the market that are sensitive to parasite counts well below the
danger level. But be warned: the test kits go out of date, they don’t
like excessive heat and they show positive for some time after you’re
cured (which at least confirms that you did have malaria).
The best treatment for malaria is Act — arthemether combination
treatments. The arthemether kills most of the parasites in about four
hours but itself only remains in the system a very short time. The
longer-acting combination drug looks after any relapse due to
parasites that are released later. What confuses people is that you
feel a lot worse after taking the Act.
Remember that the symptoms result from the toxins released when the
red cells burst and this is going to happen as the parasites die,
which means that the drug is working.
Much of this information was gleaned from a series of articles in The
Eye magazine by Dr Dick Stockley of Uganda.
• Roddy Smith works as a guide and conservationist in the lower