Wednesday, August 22, 2007

Malaria Eradication

Malaria is a shitty, piss-poor, easily-prevented, easily-treated, easily-eradicable disease that kills millions throughout the world every year.



Let’s talk about me (as usual) and malaria first. I’ve had it too many times to count – and, hey I’m still here! The very first time was 6 months after getting back to England from a year in China and 3 months in India. I spent two weeks with flu-like symptoms in a student house during the Easter holidays and “the flu” wasn’t clearing up so I eventually ... phoned Mum and Dad and said “I’m coming home”. I got home, they took one look at me, called the GP and I was sent to hospital.

Isolation. I could be contagious. In those days (1980s) a very very simple malaria test could only be executed at the two tropical medicine hospitals in the UK so the turn-around took a few days. Whilst we waited for the results and as my paternal grandfather had died from lymphoma, they had a cancer “specialist” come and look at me. Results came back, a course of Chloroquine and off-you-go – not that they didn’t invite me back to their Friday lunchtime general-meeting of interesting cases at which I was asked all about how I had felt. … like a long case of flu …

Six months later it recurred. Remember your father, uncle, grandfather who served in S.E. Asia during the war who always had bouts of fever for years and years? Well, nowadays and in the 1980s, there is a way of getting rid of recurring malaria. Just the doctors at the local general hospital didn’t know. I went to the local GP – she was Indian – I said I’ve got malaria, I want a prescription for chloroquine. She was very sympathetic, and knew, but she said “No … if you wanted it for arthritis, fine, but for malaria I have to have a blood-test result”.

Another four days of waiting … but this time, in addition to the Chloroquine to get the malaria out of my blood, she gave me Primaquine to get it out of its safe-storage in my liver and thus prevent it from recurring.

Malaria is caused by a parasite of the genus Plasmodium. In humans there are four species that cause malaria – P. falciparum, P. malariae, P. ovale and P. vivax. P. vivax is the one that remains dormant in your liver, if not treated. P. falciparum does not but is the most dangerous and can directly kill, if not treated. All these species are transmitted into human blood through the bite of vampiric Anopheles mosquitoes.

The malaria parasites have, over the recent past (let us say 150 years) developed resistance to the drugs used to destroy them (cunning buggers). Once upon a time P. falciparum could be treated with Chloroquine – now it is all but useless.

In our tiny African country, malaria has been a major killer ever since it was colonised (it was uninhabited at colonisation). The principle parasite is P. falciparum, although very small percentages of the other species do occur. As our country consists of two small islands at some distance from the continent, we are an ideal testing-bed for eradicating the disease – this has been achieved on other islands, for example, in the Pacific, the most notable and most relevant to this post being Taiwan which was certified as malaria-free in 1965. This is equally borne out by two outbreaks of the sleeping-sickness vector, the tse-tse fly, in the last century on the smaller of our two islands and which was eradicated twice.

Back in 1982 a WHO-sponsored initiative attempted to eradicate the malaria vector, Anopheles mosquitoes, using the notorious insecticide DDT. Although the incidence of malaria decreased, it also resulted in the death of much poultry and livestock. The campaign was “imposed”, was not integrated, was resented, was not sustained and malaria made a comeback with a vengeance.

In 2002-2003 another attempt began receiving a range of inputs from a range of donors. US and Portuguese research, education and promotion of impregnated mosquito nets by the Seventh Day Adventist development agency ADRA etc etc.

But the biggest input has been from the Taiwanese. They have some experience in its eradication.

The Taiwanese part of the programme has two main components:

  • prevention through the spraying of house interiors.
  • treatment with the latest anti-malarial medications.

The insecticide used is Alphacypermethrin. This does not require a general fumigation, as DDT, but is sprayed on the interior walls of houses. The mode of action is surprisingly simple - the mosquito bites an infected sleeping person, has a good meal and then goes off to have a fatal siesta on the nearest impregnated wall.

Supposedly, the effect of one application will last 400 days – but I am sure this will vary with the absorption capacity of the surface being sprayed. Untreated wood, varnished or painted wood or cement block, matt or gloss.

The Taiwanese claim that Alphacypermethrin is ecologically safe. However, there is no biodiversity impact evaluation as part of the study. I have certainly noticed a decline in butterflies in recent years – this could just as well be due to other factors (e.g. climate change) but monitoring could be worthwhile both for human health and biodiversity.

The second component of the Taiwanese programme is treatment. The traditional treatment, chloroquine, has been largely ineffective for several years as Plasmodium falciparum has become resistant to it. Various other drugs have been used here – Quinine, Fansidar, Mefloquine, Halfan etc – but there were no guidelines and each doctor would prescribe what s/he felt fit.

Now we are using in the first line a combination treatment of Amodiaquine and Artesunate. Clearly, the former is part of the quinine family (of which I haven’t studied the modes of action as I have with the chemotherapy drugs Kezia is taking). The latter has a fascinating history!

The mainland Chinese started studying the anti-malarial effects of the traditional anti-malarial medicine derived from the plant Artemisa anna back in the 1960s. For various reasons, including the upheavals of the Cultural Revolution, the positive results were not published internationally. When they were, in the 1990s, they were pretty much “poohed-poohed” by the developed world except … the pharmaceuticals who pricked up their ears and went for it big time! The plant’s active ingredient was Artemisin and soon the synthetic Artesunate was developed.

Artesunate is fast-acting but has a very short half-life (i.e. very quickly disappears from the blood). Amodiaquine has longer half-life. The tablets are marketed in packs of a pair a day. If there is still some residual malaria, then a second line of attack is used – the trade name Coartem, a combination of Artesunate and Lumefantrine (in turn developed from halofantrine, the basis of Halfan, which at the time of its recent development was revolutionary in its approach to killing malaria parasites).

Prophylaxis, if you are pregnant or a tourist, is more controversial and I won’t deal with here.

Anyway, the initial Taiwanese trial on our smaller island saw the hospital’s 21 beds in two months go from 100% occupation to 0% occupation. Two years later the hospital internment rates from malaria had maintained, indicating the mosquito had not developed resistance to the insecticide and the malaria parasite had not developed resistance to the treatment medications.

The programme has now been introduced to the larger island.

No comments: