Major differences in the two principal attacks on malaria during the Twentieth Century
It is fortunate that the international agencies responsible for attacking malaria are all in a state of self-examination this year, seeking better and more durable strategies. To this end, I have recently submitted suggestions to the World Health Organization, to the US Presidential Malaria Initiative and to the UN Roll Back Malaria Program, outlining how they could avoid repeating the collapse of the first Global Malaria Eradication Program, by broadening their current strategies.
In each case I started with my own understanding of the major differences in the two principal attacks made against malaria since the beginning of the Twentieth Century. In the hope that we all might better understand these historical events and thus might devise a new and better approach together, I have summarized my understanding of those histories for your review and criticism.
Historical comparison of the two principal attacks on malaria
There have been two principal and contrasting attacks on malaria; the first being the successful elimination of malaria from northern countries during the Twentieth Century under a holistic Environmental Approach, and the second being the unfortunate and narrow Specialist Approach of the WHO Global Malaria Eradication Program which began in 1955 and collapsed in 1969. Not only the outcomes, but the basic approaches of the two attacks were starkly different. Their differences should give us clues to what we should be doing now and in the future. Unfortunately the current WHO malaria strategy is largely a repetition of that used in the GMEP, with the addition of bednets which realistically offer serious protection only to infants and small children under their parents control.
The sequence of applying control measures was different in these two attacks, as were the natures of the control methods. These differences had serious technical, economic and social consequences, which played a large part in the success of the first attack, and failure of the second.
First Stage of the holistic Environmental Approach
The first large-scale measures used successfully against malaria in subtropical and temperate countries were largely environmental in nature; attacking swampy breeding sites by draining or filling them, and also by protecting sleeping people from adult mosquitoes by improving and screening houses.
In some areas such as the Tennessee River Valley in the southern USA and around the Pontine Marshes in western Italy, the suppression of malaria also stimulated agricultural and economic growth. This strong economic growth must have created a generally favorable economic situation in Tennessee and Italy in which the cost of the malaria program could be easily maintained by the health agencies. We have recently shown that suppression of malaria in areas of subsistence agriculture yields good economic returns on the investment, greater than 3:1. The economic growth would also have created a positive social and political atmosphere in which gradual improvements in housing, education, basic health services, communications, and transportation would all contribute to the holistic suppression of malaria, as described by Snowden in his book on the conquest of malaria in Italy.
After the Second World War, when DDT and chloroquine became available, the northern countries could easily afford to add them to their existing suppression programs, and quickly reduced malaria transmission to very low levels. This led to further economic development and social progress, including the ability to provide affordable electricity to most homes. Of course urbanization and industrial development further inhibited malaria transmission, but unfortunately by contaminating the air and the surface waters.
Third Stage and Elimination
The provision of affordable electricity was an intrinsic feature of malaria suppression in the Tennessee River Valley because the Tennessee Valley Authority was part of a program to promote rural development in the southern US during the Great Depression. This was done by constructing 17 large dams on the Tennessee River to produce hydro-electricity for the region. Once the people of Tennessee were able to sleep comfortably in enclosed or screened houses with electric fans, the malaria mosquitoes were doomed. Malaria disappeared from the US and from Italy by the early 1960’s.
A similar history occurred more recently in Turkmenistan when their malaria suppression program was accompanied by construction of multiple dams for producing hydro-electricity along the Amu Darya River. Fortunately the population in Turkmenistan is also clustered along the river, so now rural homes there have not only electric fans, but even air-conditioning. What mosquito could overcome that? WHO has declared Turkmenistan to be malaria free.
Reversed sequence of the GMEP
Unfortunately the sequence and nature of control methods in the narrowly conceived Specialist Approach of the GMEP was the reverse of that of the holistic Environmental Approach, with disastrous results. In the Environmental Approach, DDT and chloroquine were used in the Second Stage, after transmission had been drastically reduced. However the GMEP was initiated out of the hubris created by DDT and chloroquine, and thus Stage One of this attack was based on intensive annual applications of these dramatic - but ephemeral – synthetic chemicals, without permanently reducing the extent and intensity of transmission first.
Budget-wise, the use of these ephemeral chemicals was very demanding - especially in tropical countries - and required that the malaria control agencies maintain a high level of expenditures, just to keep transmission suppressed in the initial areas. While the decreases in malaria would be producing economic benefits, in this case they would be offset by the large and continuous costs of the suppression effort. This created a potential instability in malaria transmission, with the danger of rebounds in transmission in populations which had lost their immunity.
Note that this economic difficulty was in marked contrast to Stage One of the Environmental Approach, in which suppression would be maintained even if the budget and effort dropped to zero, because the environmental improvements were permanent. Thus there was no danger of a rebound in transmission with the Environmental Approach.
For national malaria control agencies following the Specialist Approach of the GMEP, this budgetary difference was an important weakness. The agencies had little flexibility to try new methods, nor could they easily adapt to the recurring resistance problems which required new and more expensive biocides and drugs. Thus the GMEP collapsed. Now international agencies are once again trying to suppress malaria in these same countries. However only the holistic Environmental Approach has succeeded, in the northern countries which are now free of malaria.
What does this tell us about revising the current strategies? Your criticisms and suggestions would be appreciated.