Malaria is a killer. According to Jeffrey Sachs and Pia Malaney (see below) "there are 300 to 500 million clinical cases every year, and between one and three million deaths, mostly of children, are attributable to this disease. Every 40 seconds a child dies of malaria, resulting in a daily loss of more than 2,000 young lives worldwide."
Malaria also slows economic growth in developing countries. Gallup and Sachs look at The Economic Burden of Malaria (The American Journal of Tropical Medicine & Hygiene, January/February 2001). Sachs and Malaney examine: The Economic and Social Burden of Malaria (Nature, February 2002). Jeffrey Sachs has a web page on his work on malaria at the Earth Institute: Prof. Jeffrey D. Sachs on Malaria . The page provides access to published and unpublished papers, datasets, and general background.
According to Sachs and Malaney, bottom-up estimates of the costs of malaria cases, obtained by summing estimates of the costs of medical care and lost income for individual cases, are generally much smaller than the top-down estimates from looking at patterns in aggregate national data. They argue that the gap is created by behavioral responses to life in a malarious environment that are counter-productive for growth. These behavioral responses create costs beyond the care costs and income losses for individual cases. While the empirical evidence on how these behavioral responses work themselves out sounds relatively limited, they speculate that the following processes may be relevant:
- Malaria hits kids especially hard. Parents who view children as old-age insurance and as a labor force on the family farm, are likely to have more children than they would otherwise, if child mortality was less.
- Families with lots of children may invest less in the human capital of the average child, reducing the child's future productivity. Since large families are likely to leave mothers less time for labor force participation, parents may stint especially on investments in education for girls.
- Persistent exposure to malaria carrying mosquitos in a particular area creates an immunity in survivors. This immunity can be lost if a person leaves a malarial region. Immunity may be local - spatially restricted to the mosquitos and parasite in a particular spot. These considerations may reduce productivity enhancing within country migration.
- Foreign direct investment from non-malarious nations may be inhibited because of the potential health and mortality risks to foreign employees.
- Foreign tourism may be inhibited.
- Malaria may predispose its victims to other - productivity dehancing - health problems.
- Families struggling with malaria may experience lower savings rates.
The southern Indian Ocean island nation of Mauritius had an extremely good growth record following independence in 1968 (What made Mauritius grow?, Ben Muse, Dec. 27, 2005; More on Mauritian Growth, Ben Muse, January 6, 2006; Mauritius: A Case Study, Subramanian, Finance & Development, December 2001). Average growth rates were quite high for an African nation from the 1970s through the 1990s (Subramanian and Roy estimate GDP growth per capita of 3.25% per annum for Mauritius, as opposed to 0.7% for Africa as a whole, between 1973 and 1999). Rates have moderated more recently.
map from www.isla-mauricia.com
Mauritius has an environment that is relatively hospitable to malaria. But, despite this, the incidence of malaria in recent years has been very low. The figure below compares an index of ecological suitability for malaria, with a measure on incidence in the population. Only one other country with an ecology index over five has an incidence rating under 35% (Singapore).
The figure (based on one in David Weil's introductory growth text - Economic Growth), exploits a malaria ecology index prepared by Kiszewski et al. (A Global Index Representing The Stability Of Malaria Transmission). The data set is here: Datasets. The ecology index is an index of climatic suitability for malaria. Higher values of this index identify more congenial environments for malaria. The vertical axis shows the percentage of the population living in areas of high malaria risk in a country in 1994. Only one observation with an ecology index value as high as Mauritius' (Singapore) is associated with a risk value as low as that for Mauritius.
Malaria wasn't always a concern in Mauritius. Once there were no malaria carrying mosquitos... or people:
...Part of the three-island Mascarene archipelago, Mauritius has been separated from Africa for millions of years, and was not inhabited either by humans or anophelines until relatively recently. The first human inhabitants of the island were probably slaves transported by the Dutch from Madagascar in the middle of the 16th century. Owing to the ravages of periodic hurricanes, however, the island defied continuous habitation and served primarily as a temporary resting place for malarial travelers on the way back to Europe, until control of the island devolved to Britain in 1810. The British deforested much of Mauritius in order to establish sugar cane plantations, and despite the importation of laborers from malaria-endemic regions, malaria was not transmitted due to the absence of anopheline vectors. Over the course of the next half century, An.gambiae and An.funestus were imported via ship traffic and, owing to the previous deforestation and irrigation of the island, became indigenous. The combination of malaria vectors and malarial humans set off a series of massive epidemics... (Hamoudi and Sachs, The Changing Global Distribution of Malaria: A Review)
In December 1865, heavy rains ended a long drought. In 1866 malaria broke out on a sugar plantation to the south of the capital of Port Louis. By the end of 1866 an area of 40 to 50 square miles around the plantation had become malarious, and the fever had reached into Port Louis. (Harrison, page 199-201)
In 1867, all hell broke loose. The epidemic lasted through 1868 and covered almost all of the island, except for high ground inland. Almost 32,000 people died in 1867, and over 10,000 more in 1868. This is out of a population of about 300,000: over 10 percent. (Harrison, page 199-201). At this point, and for almost 100 years after, malaria was endemic, killing people each year, but leaving survivors immune. (Harrison, page 199-201)
At this time, no one knew what caused malaria. The malaria parasite itself was identified for the first time in 1880. In 1898, Ronald Ross, a British military doctor, figured out that it was transmitted by mosquito bites. A cure for malaria - quinine - had been available since the 17th Century. DDT wouldn't be identified as an insecticide until 1939.
In 1908, Mauritius began a sustained effort to control the mosquitos - building on Ross' recent discovery of the importance of mosquitos in transmitting malaria. John Roberts:
In 1908 a campaign was started to eradicate the breeding grounds for the mosquito and its larvae which had some impact in controlling the disease below epidemic levels, based upon methods developed by Dr Ronald Ross, a British Army doctor who was invited to the island following his successful identification of the causative factors in malaria and his development of procedures for reducing the breeding of mosquitoes.... This reduced the mortality and morbidity in the island. But in the period 1941-1948 there were still on average over 2,500 annual deaths from malaria in Mauritius and in 1948 over 46,000 reported cases from hospitals and local dispensaries.
This control effort had its fits and starts, its ups and downs. Brookfield notes that in the period 1916-1922, "anti-malarial works were prosecuted with fresh energy, and an anti-hookworm campaign was instituted in 1922..." In the mid-1930s,
Malaria and other diseases took a great toll, and, largely through financial stringency, the anti-hookworm campaign was abandoned as a failure, while anti-malaria works were restricted to the immediate environs of the upland towns. (Brookfield, page 105)
In 1935... malaria measures below 600 feet were abandoned as "not useful"...In fact the restriction was even greater than this, and until 1943 new work was confined to the immediate vicinity of the towns in Plaines Wilhems... (Brookfield, page 105, footnote 4)
The war didn't help:
...After 1942, however, food became very short and health deteriorated. Malaria incidence rose and undernourishment was common. A nutrition survey team reported a close connection between malnutrition and the incidence of malaria, hookworm, and other diseases. The survey found a general deficiency in calories, particularly in the intercrop season, and very marked vitamin deficiencies. Deficiencies, and their symptoms, were of serious dimensions among the poor and were greater in the malarial coastal zone than in the higher country. Generally they were more marked among Hindus than among Muslims and Christians. (Brookfield, page 106)
This period of stringency culminated in a year of very high mortality in 1945, when the second most devastating cyclone in the island's history halved the sugar crop, wreaked immense destruction, and led to greatly increased incidence of disease among a weakened population. In 1946 there was a further malaria peak, but it was the last. (Brookfield, page 106)
The colonial administration began to get things under control in the late-1940s:
During the war British forces stationed in the island had carried out efficient anti-malaria works around their camps, and, with a guarantee of finance, the government began a campaign of unprecedented vigour in 1945. By 1948 malaria incidence had been reduced by half; the death rate began to fall sharply in 1947 and the infant mortality rate fell below 120 for the first time on record in the same year. In 1946 preliminary experiments with residual insecticides were carried out, and in 1949 residual spraying of habitations was extended to the whole island. This was successful in eliminating the main carrier, A. funestus, in two seasons; the chain of transmission was broken and after 1951 new infection virtually ceased. In 1950 the crude death rate stood at only 13.9, while the infant mortality rate fell to 76.3. (Brookfield, page 106)
Sada J. Reddi wrote about malaria eradication efforts in the 1940s: Fighting malaria in the 1940s (Mauritius Times, 2005). Reddi provides a lot more detail on the developments prior to the introduction of DDT, and on the introduction of DDT itself. His essay puts heavy emphasis on the organizational dimensions of the efforts in the 1940s. This is a very good essay.
Malaria rates were really knocked down in the 1950s. Roberts:
In 1949 the first programme of eradication using DDT was launched. By 1957 deaths from Malaria had been eliminated and there were only 94 reported cases in that year. Following a WHO expert visit that promoted better case finding, there was an increase in reported of cases in 1959-1961, with a new peak of reported cases in 1960. But this was more an artefact of better surveillance than a true resurgence of disease. So effective were the new combined measures that by 1973 WHO declared Mauritius officially free from Malaria.
There was a resurgence in the late 1970s and early 1980s. The circumstances are interesting. Roberts again:
...Two years later [two years after the WHO declaration - Ben], after the serious cyclone Gervaise in Mauritius in 1975/6, there was a real resurgence of Malaria. This was probably caused by the combination of four factors.
First there was an increase in standing water from the tropical cyclone itself providing more breeding grounds for mosquitoes.
Second economic growth in the country resulted in the building of many new houses with flat concrete roofs which trapped the storm water and created a new type of breeding ground for mosquitoes. (Previously most dwellings had pitched roofs. More recent designs for concrete roofs provide better drainage for the storm water.)
Third malaria was, by chance, imported from countries where the disease was endemic. This happened, when, after the tropical storm Gervaise, technical help was brought in from countries with endemic malaria. The migrant workers included army engineers, to assist in post cyclone emergency relief and reconstruction. These migrant workers were not fully checked by the public health officials to see if they were malaria carriers. When unaffected mosquitoes bite a person carrying malaria, the mosquitoes themselves become infected by the parasites and then pass the parasites on to the next person they bite.
Finally local malaria controls were relaxed following the apparent success of eradication in 1973. Fewer people were being checked than before. The annual blood examination rate... declined as the health services were lulled into a false sense of security. Less work was being done in clearing streams and stagnant water. Thus the new early cases of malaria were not detected creating a growing pool of people carrying the parasites, which were then readily re-transmitted through the population by the increasingly present and active mosquitoes.
In this period of resurgence 1975-1984 there were 2,580 reported Malaria cases, with a peak of 668 reported cases in 1982.... In response to this resurgence, a further intensified programme of control was launched in 1982 with WHO assistance. From then on cases declined and by 1985 there were fewer than one hundred reported cases a year. Since 1996 in Mauritius there have been no reported indigenous Malaria cases and on average fewer than 50 imported cases a year. There have been only six malaria deaths in Mauritius since 1955.
Malaria control requires ongoing effort by the government. Roberts:
...The national communicable disease control unit in Mauritius co-ordinates and monitors the activities of five regional teams each headed by a public health doctor. Intervention includes vector control of the malaria mosquito and its larvae, using DDT for control of adult mosquitoes and Temephos for larvae control; continued environmental control to maintain water flows in rivers and canals, to reduce stagnant water and maintain stocks of larva eating fish in ponds and lakes; surveillance through immigration points and follow-up of all persons coming from countries with endemic malaria; free early diagnosis, treatment and follow-up of all active cases by public health staff; free anti-malarial drugs for those travelling to countries with endemic malaria; and public education and health education and information.... Insecticide treated bed-nets (ITBNs) have not been a routine part of the programme and are generally not used by people in Mauritius, although there is a growing support for the use of ITBNs as part of an integrated and effective programme of control in other parts of the world....
Gopaul provides another view of efforts in the mid-1990s:
The entomological surveillance is an essential link in the fight against malaria in Mauritius. Because of the large number of malaria-infected travellers in Mauritius and the presence of the vector Anopheles arabiensis, the risk of local transmission is very real. The medical entomology division together with the malaria control unit and the health appointees exert a rigorous entomological surveillance of malaria. Field agents make entomological investigations of pilot villages and around the harbor and airport, where there have been cases of malaria, in addition to a few randomly chosen regions. All of the inhabited regions are accessible because of a good highway infrastructure, which enables a complete coverage for the entomological prospectives. Entomological controls are also conducted in the airplanes and the ships. All of the captured mosquitos and the harvested larva are transferred to a laboratory for identification, dissection or sensibility tests, etc. The larva of A. arabiensis have not yet developed resistance to Temephos and the adults are still sensitive to DDT. Thus, the larval habitats are treated with Temephos and DDT is sprayed in the residences where there have been native cases of malaria. The entomology division studies the ecology and the evolution of the larval habitats, as well as the impact of the anti-larval fight on the anophelene density. In addition to the chemical fight, a biological control is being tried with larva-eating fish such as Lebistes and Tilapia. In general, the anophelene density in Mauritius is low, but after the big summer rains, especially during a period of cyclones, there is a considerable increase of larval habitats and consequently a higher number of A. arabiensis. Therefore during this season, it is necessary to make an even more rigorous entomological surveillance. A. arabiensis has a strong exophile tendency even if it is endophage and exophage. This mosquito is zoophile, mostly towards cattle, and the zooprophylaxis must have a significant role in the regions with herds of cattle such as the western part of the island. However, the favorite larval habitat of A. arabiensis seems to be water on the flat roofs of solid houses. Therefore, the availability of such larval habitats across the country facilitates the vector-human contact. On the other islands forming part of the state of Mauritius, such as Rodriguez and Agalega, there are no anopheles and therefore no risk of transmission of malaria. There still are entomological investigations on these islands periodically to assure that there is no accidental introduction of anopheles mosquitos. (Entomological surveillance in Mauritius, Sante, 1995 - this is an English abstract of an article in French)
Why was Mauritius so lucky:
...First, once controlled, the population of a vector species is less likely to grow quickly in a relatively isolated island context. When new vectors are imported, for example through international travel on airplanes or ships, it is generally in small numbers. In the presence of an intact infrastructure, efficient entomological surveillance can identify and eliminate foci before a vector population grows unwieldy (as, for example, with Mauritius’ success in keeping An.gambiae and An. funestus populations very small). Second, importation of cases is less likely to occur as a result of mass migration. Mass migration, either in the presence or absence of infrastructural collapse, has accounted for malaria outbreaks throughout history, including for example those of Mauritius in the 19th century, or more recently, the reestablishment of endemic transmission in Tajikistan in 1990, or epidemics in the Dominican Republic in 1994 (32). Thirdly, they are less susceptible to infrastructural collapse in neighboring countries. Malaria outbreaks often result from civil strife or economic crisis (as, for example, in central Asia), and these outbreaks inevitably have repercussions in the border regions of neighboring countries, particularly when these regions do not provide a natural barrier against vector migration. (Hamoudi and Sachs, The Changing Global Distribution of Malaria: A Review)
The Roberts and Gopaul extracts point to the importance of organizational capital in fighting malaria. Effective government efforts implemented over a long period of time, appear to be important. The Reddi piece on the efforts in the 40s also highlights the importance of coordinated organization at different spatial scales (national, regional, and local):
In 1943 C.R Harrison of the Ross Institute visited Mauritius and mounted a vast campaign for malaria control. A Malaria Control Committee was set up which included members of the Mauritius Chamber of Commerce; regional committees were set up in various localities and public meetings were organised in various societies and clubs...
...Harrison‘s approach was comprehensive.... According to him although Ross, Mac Gregor and others had done essential work in Mauritius , what Harrison was able to do in Mauritius was to convert all the knowledge acquired over malaria into an island-wide organisation for the control of the disease. As Watson remarked, in many places control of malaria failed because doctors, entomologists and laboratory workers knew only a part of the subject and knew nothing about drainage and the management of labour.
Drawing from his experience on labour management in the rubber plantations of Malaya, Harrison prepared his policy both for the long-term and the short term. In the short term Harrison wanted to make people malaria-conscious and advised on measures that would encourage individuals to act themselves and in their own interests. More importantly, a vast project for the drainage of various localities was undertaken. Harrison visited villages and explained his policy to sugar estate owners. People responded positively and took their own initiatives to fight malaria. In Long Mountain and Pamplemousses, health leagues were formed and voluntary work was carried out in connection with malaria and soil conservation. Estate owners appointed two full-time medical officers to look after the health of their workers. Anti- malaria laws and forest laws were amended and Government voted 1.5 million pounds to carry out the various projects.
"Brookfield" is Brookfield, H.C. "Mauritius: Demographic Upsurge and Prospect." Population Studies, 11(2): 102-122. Nov., 1957. "Harrison" is Harrison, Gordon. Mosquitoes, malaria, and man: a history of the hostilities since 1880. 1978. John Roberts and Roberts is John Roberts, "Malaria Control: A Case Study from the Republic of Mauritius." A case study prepared for UNEP. Nairobi, 2002. Subramanian and Roy is "Who Can Explain the Mauritian Miracle? Meade, Romer, Sachs, or Rodrik?" by Arvind Subramanian and Devesh Roy in In Search of Prosperity. Analytic Narratives on Economic Growth, edited by Dani Rodrik, Princeton, 2003. The idea for the post was suggested by a related discussion in David Weil's text on Economic Growth.