Malaria is one of the world's most serious tropical diseases and imposes very significant economic costs on some of the poorest nations on earth. This study estimates the direct and indirect costs of malaria to South Africa and examines the issues surrounding the use of DDT as an anti-malaria insecticide.

Early records of malaria cases by Europeans in the late 19^th and early 20^th centuries show that malaria was a severe inhibitor of economic development and caused large economic costs. The current malarial areas in South Africa today are about one fifth of the size they were at the beginning of the 20^th century. The historical success in controlling malaria is due in very large part to the use of DDT in malaria vector control.

In recent years, however, there has been a sharp rise in the number of malaria cases in South Africa, and indeed throughout Southern Africa. This rise is due to a number of factors, such as high rainfall in recent years, increased migration and a reduction in the use of DDT in vector control. The rise in malaria cases imposes heavy costs on the local and national economies. The economic cost (direct costs include the costs of care and control of malaria, and indirect costs include the losses in productivity and lost future earnings from death) of malaria in South Africa is conservatively estimated to be around R124 million (US$20 million) in 1997/98. Malaria in selected Southern African countries could cost as much as US$1,000 million, or 4% of GDP in 1998. In South Africa, malaria usually occurs in rural areas with agricultural and labour intensive industries. The incidence of malaria in these areas has severe economic impacts and as in the past, continues to hamper economic development

For a number of reasons, DDT is being phased out of the malaria control programmes in South Africa. Numerous environmentalist organisations have lobbied strongly for the banning of DDT, despite the success of the insecticide in saving lives and preventing disease in developing countries. While DDT is not an ideal insecticide, it does have numerous advantages over the alternative insecticides and has a proven track record. Although DDT is currently used by a number of Southern African countries in malaria control programmes, the UNEP Governing Council is pressing for the banning of DDT and eleven other persistent organic pollutants (POPs).

The potential banning of DDT highlights a trend whereby environmental pressure from mostly developed countries imposes standards on developing countries where they are neither accepted nor appropriate. While there are alternatives to DDT, these are all more expensive and frequently more complicated to use than DDT. The banning of DDT would not only remove an important anti-malaria weapon, but will result in countless deaths and very significant economic costs (perhaps as much as US$480 million) on countries that can ill afford it.

Donald R. Roberts, Ph.D., has worked in the area of malaria vector ecology and malaria control for 32 years. He has conducted field studies in Southeast Asia, the Middle East and in several countries of the Americas. He has published over 80 peer-reviewed papers and holds one patent. In recent years his research has focused on applications of remote sensing and geographical information system technologies to the study and control of malaria. His research also has emphasised studies to elucidate actual functions of insecticide residues in controlling malaria. Dr. Roberts created the project and directed the early phase of research at the Walter Reed Army Institute of Research on enzyme-linked imunosorbent assays for detecting malaria sporozoites in Anopheles mosquitoes. He was also a principal participant in the research that led to incrimination of Culicoides paraensis as the vector of Oropouche virus in urban areas of the Amazon Basin.  

The United Nations Environment Programme (UNEP) is negotiating a legally binding agreement for global elimination of DDT (UNEP, 1998), along with other persistent organic pollutants (POPs). Reports in the popular press suggest that global elimination of DDT is a lofty and desirable goal (Kirby 1999, Denyer 1999). However, modern trends of increasing malaria that accompanies decreasing numbers of DDT-sprayed houses reveal a devastating cost for DDT elimination (Mouchet et al 1997, Roberts et al 1997).

As will be shown later, DDT elimination has been an important goal of certain environmental groups and in the foreign policies of developed countries and in the politics of many UN organisations. The result of these policies and politics is that many developing countries have already been forced to abandon their public health use of DDT. Almost without exception, where this has occurred, malaria rates have increased (Figure 1). Today, if UNEP negotiations are successful in the unconditional banning of DDT, which is the intent; even more millions will suffer increased death and disease from malaria.

As stated by Heppner and Ballou (1998), "More cases of malaria are expected to occur in 1998 than in 1958.." This is a sobering assessment of our backward march to the pre-DDT era of rampant, uncontrolled malaria. The re-emergence of this highly preventable disease speaks to the limited role of poor countries and poor people in international politics. Even the fact that this disease has been allowed to re-emerge with limited international notice attests to the political invisibility of threatened populations.

The re-emergence of malaria in the Americas and declining use of DDT for control are illustrated in Figure 2. In 1959, the house spray rate of DDT for 21 countries of the Americas was 71.55 houses per 1,000 inhabitants. This rate was reduced 81% by 1989. Since 1989, most countries of the Americas have stopped using DDT and numbers of malaria cases are growing at unprecedented rates. The relationship between reduced numbers of houses sprayed with DDT and increased numbers of malaria cases is irrefutable (PAHO, 1991, 1994, 1997, Mouchet et al 1997, Roberts et al 1997).

Just as the pressures on developing countries to stop using DDT are diverse and multi-layered (discussed below), the arguments for and against DDT are diverse and multi-layered (see Taverne 1999). Some environmentalists argue that there are effective alternative insecticides and DDT is no longer needed. This argument ignores hopes of environmental groups to even stop the use of potential DDT alternatives, e.g., organophosphate and pyrethroid insecticides (Congressional Research Service Report, 1993 and World Wildlife Fund, 1998). As warned by the American Crop Protection Association in 1998 (Kenworth 1999), "..sooner or later, virtually all pesticides and pesticide uses will be jeopardised." Additionally, the environmentalist argument does not account for prohibitive costs of the alternative insecticides. The more naïve even argue that integrated vector management should replace use of all insecticides for malaria control (World Wildlife Fund, 1998). Unfortunately there are no cost-effective, broadly applicable methods of environmental management for malaria control. So, in reality, promoting the application of these methods is like promoting the use of a malaria vaccine when there is no vaccine. Some DDT opponents propose that predictions of increased disease are expected and are consistent with the unrealistic predictions that accompanied actions to eliminate other toxic substances, e.g., freon, Alar, chlordane, and use of DDT in agriculture. However, as shown in Figure 2, we do not need to wait for global elimination of DDT in order to know the end result. DDT elimination has been underway since the late 1970s and we know with certainty that numbers of malaria cases spiral out of control when endemic countries stop spraying internal house walls. In a recent US Environmental Protection Agency (EPA) Risk Assessment Forum Project (Crisp et al 1998), it was determined that "in a risk assessment paradigm for human health, relevant and adequate epidemiological studies and case reports for the agent(s) are preferable." Well, in the case of DDT and malaria control, the studies and case reports have been performed. Most endemic countries have experimented with alternatives to DDT and countries generally increase use of alternative insecticides when DDT is banned. Despite their use of alternative insecticides, rapidly increasing malaria is the legacy of DDT elimination. Increased malaria is probably due to some combination of factors, e.g., countries not being able to afford to spray a sufficient number of houses with more expensive insecticides and/or alternative insecticides not being as effective or not lasting long enough to bring about adequate levels of control.

Without doubt, the insecticide and pharmaceutical industries have received direct benefits from DDT elimination. The former industry has benefited because countries purchased more expensive insecticides and the latter benefited from selling more drugs to treat an ever-increasing number of malaria cases. Regardless of benefits that accrue to these industries, the wealthy multinational environmental groups, such as the World Wildlife Fund (WWF); Physicians for Social Responsibility (PSR); International Pesticide Action Network (PAN); International Organisation of Consumer Unions (IOCU); and the Environmental Liaison Center (ELC), who influence foreign policies of industrialised countries and UN organisations are the primary proponents for global DDT elimination (World Wildlife Fund, 1998 and Pan American Health Organisation, 1993). Additionally, United Nations organisations such as UNEP, the World Health Organisation (WHO), and Food and Agriculture Organisation (FAO) are full participants in this environmental agenda.

Although most knowledgeable people are concerned about environment issues, when the environmental agenda eliminates a critical public health tool, it is time to ask a number of questions, to include how large a public health price and who pays? Of the world's estimated 6.8 billion people, 4.4 billion live in developing countries. Within developing countries, 2.64 billion have no access to basic sanitation and 1.45 billion are without safe drinking water (United Nations Human Development Report of 1998). Unfortunately, a large proportion of these poor and disadvantaged people live in malaria endemic countries. The price for DDT elimination is already enormous and it is being paid in daily instalments of lost health and lost lives for hundreds of millions of the world's poorest and most disadvantaged people.

Over the years, WHO experts, WHO Expert Committees and WHO statistical reports have consistently shown that DDT is the most cost effective, and time-tested tool for preventing transmission of human malaria. These reports document, in the clearest of terms, how DDT freed 32% of the world's population from the risk of malaria, and for most of the last 50 years, how DDT continued to protect hundreds of millions of people in malaria endemic countries (Brown 1976, WHO 1984).

As unequivocally stated in a statistical report (WHO 1992) "...annual cost of programmes based on intradomiciliary spraying as the main intervention ranged from US$ 0.5-5 per capita of actually protected population. In most of these countries, DDT was the insecticide used, and a shift to alternative, more toxic and costly insecticides could lead to considerable increases." Also, WHO safety evaluations, as recent as 1993, have uniformly and consistently concluded that DDT is safe for humans and acceptable for use in malaria control (WHO 1994).

Yet, since 1979, WHO strategies have specifically de-emphasised use of house spraying for malaria control (Roberts et al . 1997). Discussions with malariologists in developed and developing countries alike and publications of prominent health workers suggest that a scientific explanation of the global strategies does not exist. Likewise there appears to be no consensus of support for WHO's de-emphasis of house spray programmes (Farid 1991 and Mouchet et al 1997).

In 1969, the great Venezuelan malariologist, Dr. Arnoldo Gabaldon, argued for establishing a WHO strategy that emphasised residual spraying of houses to maintain the successes of the eradication programme.

Changes in strategy are necessary - general public-health activities in hyperendemic areas are not effective in the presence of malaria; the funds they use might be better designated for efficient indoor residual spraying. (Litsios 1996)

Unfortunately, Dr. Gabaldon's arguments to WHO's Malaria Expert Committee were ignored and he subsequently disassociated himself from the 1969 report (Litsios 1996). In 1979 WHO adopted a new Control Strategy with four tactical variants. The causal link between decreasing numbers of sprayed houses and increasing malaria was ignored. The new strategy defined WHO's emphasis on curative measures and its unambiguous de-emphasis of preventive measures (WHO 1979, and Gilles and Warrell 1993). This strategy sent a clear and erroneous message to national programmes that DDT was not needed. De-emphasis of vector control measures was even more strongly worded in WHO's Global Malaria Control Strategy (GMCS) of 1992 (WHO 1993).

Pressure from WHO for changes in the organisational structure of malaria control programmes also obstructed continuation of house spray activities. The idea of placing malaria control in a primary health care organisational framework was formally presented to the World Health Assembly (WHA) in 1979 (WHO 1979). In 1985 the WHA adopted resolution 38.24 for incorporating vertically structured malaria control programmes into horizontally structured primary health care (PHC) systems (World Health Assembly 1985, and Gilles and Warrell 1993). A recent study by Thomson et al (1999) showed no significant difference in amount of malaria in children in villages with PHC services versus children in villages without PHC services.

International assistance and political acceptability of malaria control programmes are generally contingent on compliance with WHO's global strategies. In other words, if a developing country wants external assistance, its proposal should comply with the WHO strategy and this means that vector control must be de-emphasised. Beyond this, assistance is often contingent on the specific non-use of DDT. For example, the US Agency for International Development (USAID) has invoked sections of the Foreign Assistance Act and USAID Regulation 16, published at 22 Code of Federal Regulations, Part 216 and USAID's pesticide procedures in section 216.3(b) for making decisions about foreign assistance to programmes in developing countries that used DDT for malaria control. The rationale is that DDT is not registered by the Environmental Protection Agency (EPA) for use in the US, consequently foreign assistance is not available to programmes that use DDT. This registration issue ignores the fact that DDT would not be registered by EPA because malaria is not a problem in the US. Also this interpretation ignores WHO's ruling that DDT is safe and effective for use in malaria control. Similar restrictions are employed by other industrialised countries to prevent continued use of DDT in developing countries.

The impact of these conditions is partly defined in the pace of countries abandoning DDT and, in some cases, all house-spray activities. In 1993, 8 of 11 malaria endemic countries of South America reported some low-level use of DDT for malaria control. French Guiana, Suriname and Guyana reported no spraying and were the most highly malarious countries of the Americas (PAHO 1994). In 1996, only Ecuador, Venezuela and Argentina reported use of DDT (PAHO 1997).

We should note that the early (pre-eradication) patterns of malaria response to house spray programmes in the Americas did not change during the eradication era. Where DDT had shown an ability to stop transmission, disease was eradicated, e.g., southern Brazil; but where transmission was not stopped, only variable levels of control were achieved, e.g., some countries of Central America and regions of the Amazon Basin.

We should also note that, just as the patterns of malaria response to DDT-sprayed houses did not change during the eradication programme, the same patterns held steady after eradication. So as house spray programmes declined, malaria rates increased and transmission reappeared in areas previously cleared of malaria. We should further note that these occurrences reflect a failure to use the chemical, not a failure of the chemical itself. During this time of increasing malaria, Mexico, Ecuador and Belize still used DDT to exert spectacular control over burgeoning malaria rates (Roberts et al 1997). Control was achieved in Mexico despite problems of vector resistance to DDT.

Reduced malaria rates in Mexico, Belize and Ecuador are in contrast to the increased numbers of malaria cases in many other countries of the Americas. In spite of their successes, Mexico and Ecuador were specifically identified for non-compliance with the GMCS in PAHO's 1997 report (PAHO 1997). Countries of Africa have also used DDT to exert renewed control over increasing malaria rates (Mouchet et al 1998).

One might argue that change has occurred; so now it is time to get on with the job of making WHO's global strategy a success. Unfortunately, the global strategy includes no broadly applicable and cost-effective preventive measures, so success is simply not possible. Emphasis on case treatment (the core tenet of the global strategy and the new 'roll back malaria' initiative) is laudable; but case treatment is basically curative, not preventive. Without doubt, de-emphasis of preventive measures has allowed the numbers of cases to increase in many rural and even urban environments.

Prior to the mid-1940s malaria was endemic in urban areas of the Amazon Basin. With the advent of DDT and organised house spray programmes, urban malaria largely disappeared. Unfortunately, persistent urban malaria is once again becoming a major health burden (Sandoval et al 1998, Guarda et al 1999).

The dichotomy of WHO's Malaria Expert Committee's consistent support for use of DDT versus WHO strategies that worked against use of house spray programmes suggest that global strategies have been political formulations unrelated to the opinions of malariologists or to health interests of people living in malaria endemic countries. In the international arena, defence of DDT for public health use is a WHO/PAHO responsibility. Overall, it is disappointing to examine how these organisations fulfil their responsibilities.

WHO's GMCS de-emphasises vector control measures. The more recent 'Role Back Malaria' initiative does not even mention the house spray approach to malaria control. The key negotiator for WHO's position on the DDT controversy is with the Panel of Experts on Environmental Management for Vector Control (PEEM). The PEEM was established in 1980 by FAO, UNEP and WHO to promote environmental management for vector control, i.e., to de-emphasise use of insecticides.

The Pan American Health Organisation has worked to obtain compliance of countries in the Americas with the GMCS. Unlike the WHO, PAHO has actually called for prohibition of continued DDT use for malaria control (PAHO, Division of Health and Environment 1994) and recommended that countries prohibit the purchase, distribution and use of DDT (PAHO 1993).

In 1995, a North American Commission for Environmental Cooperation (CEC) agreement forced Mexico to stop producing DDT and discontinue use of DDT for malaria control. The PAHO participated in the CEC meeting; but proceedings of that meeting reveal no PAHO defence for continued production or use of DDT. On the other hand, the Ministry of Health (MOH) of Mexico declared openly that DDT was an important and valuable component of its malaria control programme (Commission for Environmental Cooperation 1995). In spite of this, the government of Mexico signed the agreement. The signed agreement attests to the economical and political power of environmental movements within developed countries. The CEC agreement brings an end to the use of DDT for malaria control in Mexico and, more importantly, low cost availability of DDT for malaria control programmes throughout the Americas.

For certain, DDT is still needed for control of malaria. This does not mean that we should return to the wide scale use of DDT as employed during the eradication programme. Even today, formal WHO guidance for spraying houses is the same as employed in the eradication era (2 g of DDT/m² of wall surface at intervals of 6 months). With research support, new and improved approaches to malaria control could have evolved from the wreckage of the eradication programme. For example, an annual or even semi-annual (bi-annual?) versus the standard 6-month spray cycle might have produced adequate levels of control in many environments (Rozendaal 1990, Roberts and Alecrim 1991). If effective, this change alone would have reduced amount of insecticide used in some control programmes by 50% or more. Partial spraying of houses might have produced control comparable to complete wall coverage (Casas et al 1998). Today, geographical information system and remote sensing technologies can be used to more accurately define risk factors and categorise houses by risk of malaria (Beck et al 1994, Pope et al 1994, Rejmankova et al 1995, Roberts et al 1995, Rejmankova et al 1998, Thomson et al 1999). Even in rural endemic areas, not all households are at equal risk of malaria transmission and we now have the technologies for accurately prioritising spray operations to increase the cost-effectiveness of limited malaria control resources.

In summation, there is hope for more cost-effective uses of DDT and other insecticides for malaria control. However, we are presently confronted by a global environmental agenda that opposes a major public health need. On the environmental side there is a clearly defined plan for DDT elimination through UNEP negotiations. On the public health side, there is no operable plan for controlling the current global epidemic of malaria or for controlling malaria once DDT is eliminated. So today, with malaria control positioned in organisational structures that are not compatible with vector control programmes; guided by strategies that de-emphasise vector control measures; pressured economically and politically by environmental groups and developed countries to eliminate use of DDT; combined with the political force of ongoing UNEP negotiations, the malaria endemic countries are experiencing an unmitigated disaster as numbers of malaria cases increase at unprecedented rates.

Public health advocacy is needed to bring about an open debate of the DDT and malaria control issues. The outcome of such a debate is critical to hundreds of millions of people in malaria endemic countries. Public health professionals should not accede these issues to the exclusive domain of UN organisations, environmental groups and foreign policies of industrialised countries.

Figure 1. Standardized annual parasite indexes (IPAs) and house spray rates (HSRs) for 21 countries of the Americas, 1959-1995. Major changes in global malaria control strategies are depicted with arrows along the x-axis (WHA 31.45 for 1979; WHA 38.24 for 1985; and the Global Malaria Control Strategy for 1992). Block A represents a period of malaria control by spraying adequate numbers of houses with insecticide residues (primarily DDT). Block B represents a period of increasing malaria as the house-spray rates declined below effective levels. Open circles represent house-spray rates and solid squares represent standardized annual parasite indexes. (Graph copied from Roberts et al 1997)

Figure 2. Increases in annual parasite indexes for four categories of countries, South America, 1993-1995. For each country, the populations at moderate to high risk for malaria were adjusted to midyear (1994) values. (Graph copied from Roberts et al 1997)

I am indebted to the following for their kind support, advice and information, without which this report would not have been possible: Roger Bate, Henk Bouwman, Ian Cooper, Colleen Fraser, Frank Hansford, Kelvin Kemm, Kobus La Grange, Danette Lombard, Lorraine Mooney, Jotham Mthembu, and Justin Wilkins. 

Richard Tren is an economist, specialising in environmenal and natural resource issues. He was born and grew up in South Africa, but received most of his higher education in the UK. After reading economics at St.Andrews University in Scotland he went on to study at L'Universita Luigi Bocconi in Milan in 1993 and then worked in financial sector in London for two years. Mr. Tren then obtained his MSc in Environmental and Resource Economics from University College London and then returned to South Africa where he has since worked on a wide range of research projects. Mr. Tren has worked on several water resource projects for research institutions and for the South African government. He has recently become a Research Fellow of the Environment Unit at the institute of Economic Affairs. 

Malaria is one of the most serious tropical diseases in the world and has been a health risk to humanity for many generations. Diseases referred to as deadly fevers, likely to be malaria, have been documented for thousands of years. Malaria was a very widespread disease, covering many areas of Europe, North America, South America, Asia and Africa.

It was only in 1897 that Dr. Ronald Ross of the British army, discovered the complex life cycle of the malaria parasite. Ross proved the link between the parasite of the genus Plasmodium that causes malaria and the Anopheles mosquito. Prevention of malaria had until this time concentrated mainly on the treatment of malaria patients, usually with the quinine. The discovery of the role that the Anopheles mosquito plays in the lifecycle of the malaria parasite led to arguably the most effective way of dealing with the disease - attacking the malaria vector, the Anopheles mosquito.

Vector control programmes began in earnest in the 1950s and saw the eradication of malaria in Europe and North America and dramatically reduced the incidence of malaria in many tropical countries in Asia, Africa and South America. These vector control programmes relied mainly on the pesticide, DDT, which proved to be remarkably effective in controlling the disease. In 1969 however, WHO abandoned its attempts to eradicate malaria globally, leaving many developing countries, particularly those in Sub-Saharan Africa with considerable problems associated with the disease.

Currently, malaria burdens mainly poor countries and causes between 300 and 500 million episodes of acute illness globally every year. Not only does malaria affect the poor, it is an important factor in ensuring that many countries and communities remain poor and is a major impediment to progress, particularly in Africa. This paper estimates some of the economic costs of malaria in South Africa and assesses the potential impacts of a ban of one of the most effective weapons against malaria, DDT. 

An outbreak of malaria carries with it two categories of costs or damages. The first category consists of morbidity and mortality costs, which are made up of productivity losses through lost time and in the case of death, lost future earnings. The second category consists of the costs associated with taking action to avert and to treat the illness. This paper will attempt to measure each of these categories of costs in order to arrive at an estimate of the economic costs of an outbreak of malaria.

Perhaps the most rigorous economic method of valuing the economic costs of an illness is to measure the willingness to pay (WTP) to avoid illness, or the willingness to accept compensation (WTAC) as a result of the illness. Social benefits, or social welfare is made up of the sum of individual's willingness to pay for (or to avoid) change. Illness affects social welfare through the individual's inability to work and to contribute to social welfare. The impact of lost work affects not only the individual, but also the employer, the customers and the rest of society.

To estimate the different impacts on employers, individuals and customers would be extremely complicated, therefore it will be assumed that the interests of the individual are identical to that of the employer and customer. It will be assumed that each malaria sufferer is self-employed and therefore the losses in pre-tax income will be an adequate estimation of the social value of lost work.

Evaluating individuals' preferences towards illness may be a more rigorous approach to establishing the economic costs of a disease, however it relies on detailed information and primary data collection. Because of the time limits to this paper, no attempt will be made to estimate the WTP or WTAC to avoid disease. Rather a cost of illness (COI) approach will be adopted. This will estimate the social losses through lost work and the cost of treating malaria.

These costs will consist of:

• Direct costs of medical resources used in the treatment of the disease, including costs of self-treatment to individuals (or households) and government expenditure;
• Indirect costs for households associated with lost economic opportunities caused by illness or death, due to reduced productivity of the victim or family care-providers, in both the short and long term;
• Other direct costs, such as transportation to health services and household costs to accommodate the needs of the affected person;
• Social costs, such as both short and long-term quality of life reductions associated with the pain and suffering from illness or death caused by the disease;
• Overall costs to the economy reflecting the impact on the gross national product due to reductions in productivity and allocation of limited resources to health care.

(Paul and Mauskopf, 1991 - quoted in Pegram, G.C., Rollins, N., Espey, Q. 1998)

Lack of data will preclude the estimation of all of these costs, however as far as possible, all of these costs will be taken into account.

Nineteenth century European pioneers and travellers into the Northern Province, Mpumalanga and northern Kwazulu Natal soon recognised the threat and serious impact that malaria could have. Little data is available on the incidence of malaria at this time, however specific studies into the disease in the early twentieth century has shown the devastating effect that the disease had on the economy.

In South Africa, malaria is now only found in the low altitude areas of the Northern Province, Mpumalanga and the north east of Kwazulu Natal Province. The fact that the disease is contained to these areas is due in large part to the vector control programmes, which began in earnest after the Second World War. Prior to this, malaria occurred in much of the North West Province, areas of Gauteng (including Pretoria), much of Kwazulu Natal and even in the Northern Cape - an area five times larger than the area of its present distribution.

In 1905 a malaria epidemic in Durban alone resulted in 4 177 cases and 42 deaths and subsequent epidemics in Kwazulu-Natal and the lowveld (low altitude areas) of the Northern Province and Mpumalanga frequently brought economic activities to a standstill. Because of the changing socio-economic conditions of the country at the time, the impact of malaria was extremely severe. At this time, many labourers were brought into malarial areas to work on railway lines and to develop agricultural areas. Many of these labourers came from non-malarial areas and therefore had no immunity to the disease.

In 1932, malaria incidence extended as far south as Port St. Johns on the Eastern Cape coast, with a reported 22 132 deaths of malaria in Kwazulu Natal for 1932 alone when the population was only 1 819 000, representing a mortality rate of 1.2%. Malaria incidence in the Northern Province and Mpumalanga (then the Transvaal Province) was equally severe during this period. During April 1928 a survey found that 62% of Europeans and 74% of Natives (original terminology) in Rustenburg and Nylstroom were suffering from malaria (Dept of Health, 1997). Heavy rains in 1939 caused a number of outbreaks of malaria, one of the most severe occurring in the Oliphants valley and Sekhukhuneland (Northern Province). This outbreak led to the deaths of 9 311 people out of a population of 1 108 800 (0.8% mortality rate) which devastated farming and economic activities. (Dept. of Health, 1997)

Since the advent of the use of DDT in the vector control programmes (to be described in more detail below) after the Second World War, outbreaks of malaria have not been as serious, nor have they led to the number of deaths as witnessed prior to this period. The combination of agricultural and industrial development in the malarious areas during the 1960s and 70s with the increased concentrations of people in the homeland areas caused a general increase in the number of malaria cases.

A number of severe outbreaks in South Africa occurred following wet summers. One such outbreak in 1953 in the then Transvaal caused the number of infections to increase to 700 and varied from 104 to 251 during the three subsequent years. (Dept of Health, 1997)

Specific data for the number of cases and deaths as a result of malaria have only been kept since 1971 and are presented below. Of the approximate 40 million population of South Africa, 10%, or 4 million people live in a malaria risk area.

There has been a noticeable increase in the number of cases of, and deaths from malaria in recent years. Heavy rains have been experienced throughout South Africa and particularly in the low altitude malarial areas in the last three years. A study performed in the malarial areas showed that for one research station, Makatini, the rainfall and malaria cases were well correlated (r = 0.913, P<0.001), however the relationship for another research station, Ndumu, was far less well correlated (r = 0.643, P>0.05). (Sharp B. et al, 1988). While anecdotal evidence would suggest that the incidence of malaria and rainfall are very closely correlated, research suggests that this relationship is more complex.

Sharp et al, 1988 estimated that for the period between 1976 and 1985, imported malaria cases (mostly from Mozambique) accounted for 19% of the total cases. With the democratic changes in South Africa and the more relaxed policy towards border control, imported cases could account for a significant proportion of the total number of cases. Geographic Information Systems (GIS) for Kwazulu-Natal show markedly increased levels of malaria along the main corridors travelled by Mozambicans through Kwazulu-Natal from the southern border of Mozambique. (pers. comm. Jotham Mthembu, Kwazulu Natal Dept. of Health) Migration from other Southern African countries, such as Zimbabwe, Botswana and Malawi could account for some of the increase in malaria cases in recent years.

A change in the vector control programme, away from the use of DDT, which historically has been extremely successful in malaria control, towards synthetic pyrethroids could also account for some of the increase in malaria cases. A more detailed discussion of DDT and the vector control programme is given below. It is not within the scope of this paper to model the changes in malaria incidence with these factors, however it is accepted that the increases in malaria incidence in South Africa is due to a combination of them. (pers. comm. Danette Lombard, National Dept. of Health)

In order to accurately estimate the economic impacts of malaria, it is important to know the age groups of malaria sufferers. If malaria occurs mainly in the working population (between the ages of 15 and 65) the disease is likely to incur far higher economic costs than if the disease affects only small children or only the elderly.

Table 2 gives a summary of the percentages of malaria cases within each age group for 1996, 1997 and 1998. In each case, the majority of the malaria cases were in the economically active age group of 15 years to 64 years. The percentages range from a low of 58.02% in 1997 to 62.75% in 1996. A large proportion (as much as 40.51% in 1998) of malaria cases was found in patients below the age of 15 indicating the heavy burden the disease places on children of school going age. Approximately 2.5% of malaria cases were found in people over the age of 65 in 1997 and 1998 and a slightly lower figure of 2.05% in 1996.