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Can malaria infection in man ever be eliminated?

October 15, 2010 - 10:50 -- Wallace Peters

In her excellent recent book "The fever" and in at least one newspaper interview, Sonia Shah has queried whether it will be possible truly to eliminate (a polite synonym for 'eradicate') malaria.

The current generous outpouring of funds on a previously unimaginable scale, in my humble opinion too will never achieve this goal, novel drugs, mosquito nets, vaccines notwithstanding, until adequate weight is brought to bear on the one factor that Macdonald and his colleagues omitted from the ingenious epidemiological formula that it was believed would underpin the road to global freedom from this family of diseases.

This factor was not the possible role that zoonotic malaria might remain as a reservoir for reinfection, but the role of human behaviour. Nothing I have experienced in over half a century of personal involvement in the struggle against malaria has shaken my belief in this problem.

I was interested to see that at least one other malariologist, William Jobin whose book was recently reviewed here, shares this view.

Comments

Bart G.J. Knols's picture
Submitted by Bart G.J. Knols on

Thanks for this thought-provoking contribution. What exactly do you mean when you say 'human behaviour'?

Although I appreciate your concerns ref zoonotic malaria, what about the success of the Chinese on the island of Moheli (Comores) with mass drug administration that led to the elimination of the parasite reservoir?

Are you suggesting that we should not proceed with such campaigns?

Submitted by Wallace Peters on

Thank you Bart for your very pertinent comments. I composed a longish and erudite reply but, in my amateurish way, failed to post it in the correct manner as I am finding is not unusual in the blogosphere! Could my draft possibly be hidden somewhere on one of your computers in a recoverable form? If not, I will have to reassemble my thoughts and start again. At least let me reassure you and all the readers of MalariaWorld that I am NOT advocating the abandonment of campaigns to eliminate malaria.

Wallace Peters

Bart G.J. Knols's picture
Submitted by Bart G.J. Knols on

I checked your contribution but this was all the text uploaded. Better to first write it off-line in a word document and then enter it when completed. I look forward to seeing your full contribution.

Submitted by Wallace Peters on

It is suprising how well writing goes when you do it correctly! Thank you again Bart.

Let me comment first on the question of eradicating malaria in a geographically isolated site such as an island, or in a fringe area of distribution such as the highlands of East Africa or New Guinea. The example of Moheli illustrates very well that it is possible completely to eliminate the parasite reservoir in some islands, the challenge then being to ensure that the infection is not reintroduced. Highland malaria is an entirely different proposition, ie, highly unstable. In the highland valleys of Papua New Guinea, for example, at about 2,000m altitude, malaria could assume epidemic proportions if (1) the climatic situation at a given time offered satisfactory conditions for malaria transmission and (2) a core of infective parasites were present. The latter was in the 1950’s provided by the return home of non-immune highland labourers from their temporary places of work in often holoendemic parts of the coast. It was reported that as many as 1% of the population of certain highland villages was decimated by epidemic outbreaks of falciparum malaria on a number of occasions.

As regards zoonotic malaria and, very recently, the question of the trans-host passage of simian-specific Plasmodium species to humans which may well have occurred, the time scale is such (thousands if not millions of years) that I cannot see this posing a major obstacle to eliminating transmission in man. The case of P.knowlesi may be an exception. Although only recently identified as a potentially serious and increasing problem, the lateral transfer of this macaque parasite to humans may be a recent phenomenon due, perhaps, to recent ecological changes in its natural habitat.

Let me now return to my original point, namely our failure to give adequate weight to the vital factor of human behaviour in the epidemiology of malaria in man and the evident implications that this can have in any programme to eliminate malaria from a potentially meso- or holoendemic area. It cannot be stressed too strongly to the individuals and organisations that currently, and very worthily, are producing an unprecedented pot of money and other resources, that no number of mosquito nets, new drugs, insecticides or vaccines will eradicate malaria (and I return to this word deliberately) in any but a few limited areas until it is accepted that the target human populations nearly always include a frighteningly large number of unscrupulous, corrupt and greedy individuals. Whether they wreak havoc by, for example, manufacturing and distributing fake antimalarial drugs, encouraging the consumption of good drugs in an incorrect manner (eg, the sale of artemisinin-type compounds for monotherapy instead of correctly manufactured and formulated combinations), the peddling of herbal or magical remedies of no proven efficacy, the end result can be the obstruction of rationally designed and executed control measures.

These examples of human failure do not take into account other problems imposed by the improper application of orthodox measures because of deficiencies in their administration for a variety of reasons, including those indicated by Jobin and Sonia Shah. Finally there is another factor that is frequently overlooked. The eradication of smallpox and now probably rindepest are rightly hailed as examples to be held on high as we plan to elimination yet other of the plagues of man and his animals. However, these diseases were caused by viruses. Malaria is caused by far more complex organisms with remarkably flexible genomes and complicated life cycles. Looking at the situation from just one point of view, the application of antimalarial drugs, in 1970 I concluded my book on this subject with the words “The best we can hope to do probably is to keep one jump ahead of nature. Malaria as a major public health problem is very likely to remain with us for the foreseeable future ”.

Seventeen years later I concluded the second edition of that book with the same words and added “In the final analysis, no country can afford not to fight the problem of malaria within its boundaries. The indications are that chemotherapy will play an increasingly important role in this fight. Let us hope that the next generation will prove that I am wrong.”

After a further thirteen years, what can I add?

Wallace Peters

Patrick Sawa's picture
Submitted by Patrick Sawa on

Coming from a high transmission area of Kenya, with the experience of seeing medics that modify malaria medicine dosages without any basis, people who get the medicine and go ahead to take them as they please usually without completing the dose.

Currently, the first two doses of Coartem should be taken 8 hours apart but to make our own work easier, the medical personnel prescribe it as a BD (take every 12 hourly) drug. Children have been given LLINs at antenatal clinics and at child welfare clinics but what proportion are using them? Some use them occasionally and yet more do not use them at all. The number of these LLINs being used to dry fish on the shores of the Lake Victoria is quite significant.

In Kenya, to date, you can still buy chloroquine over the counter. Who in their right mind could still be producing chloroquine and where is it passing through to get to the shops?

Just to tell a few of these behavioural reasons that will make eliminating malaria very difficult.

Castevill, I feel where you are coming from and I agree with your assertions that to deal with malaria we need to learn more on the motivators of human behaviour as relates to malaria control measures....

Submitted by Wallace Peters on

You have provided some excellent examples of the types of human behavioural problems that you and I know are at the root of the problem we are airing.

Thank you for your important contribution.

Wallace Peters