World Malaria Day

I have written several posts on this blog concerning the historical impact of disease. Many diseases continue to ravage modern populations. Malaria is the most prolific killer. As average global temperatures rise, the regions hospitable to the parasites that cause malaria will grow. Much can be done to protect those in affected regions.

Read more of the following at the website for World Malaria Day.

World Malaria day--A Day to Act

25 April 2010 is a day of unified commemoration of the global effort to provide effective control of malaria around the world. This year's World Malaria Day marks a critical moment in time. The international malaria community has less than a year to meet the 2010 targets of delivering effective and affordable protection and treatment to all people at risk of malaria, as called for by the UN Secretary-General, Ban Ki-Moon.

World Malaria Day represents a chance for all of us to make a difference. Whether you are a government, a company, a charity or an individual, you can roll back malaria and help generate broad gains in multiple areas of health and human development.

Origins of Malaria

Agriculture and Malaria

In July 2001, The Economist notified its readers of two articles in Science published that month concerned with the origins of malaria. Both articles, the news magazine noted, employed studies in genetics to explore a hypothesis put forth more than forty years earlier by Frank B. Livingstone in American Anthropologist. In “Anthropological Implications of Sickle Cell Gene Distribution in West Africa,” Livingstone suggested that the development of agriculture in western Africa brought Plasmodium falciparum as a parasite into human populations, and “the spread of this agriculture is responsible for the spread of the selective advantage of the sickle cell gene” (555). He concludes:

The agricultural revolution has always been considered an important event in man's cultural evolution, but it also seems to have been an important event in man's biological evolution. … [Disease became a significant limiting factor in population growth.] Two results of the agricultural revolution seem to account for this change in the role of disease in human evolution: (1) the great changes in the environment, and (2) the huge increase in the human population. Both of these seem to be involved in the development of holoendemic malaria. First, when man disrupts the vegetation of any area, he severely disrupts the fauna and often causes the extinction of many mammals, particularly the larger ones. When this happens, there are many known instances of the parasites of these animals adapting to man as the new host. It is thus possible that the parasitization of man by P. falciparum is due to man's blundering on the scene and causing the extinction of the original host. Second, concomitant with the huge increase in the human population, this population became more sedentary and man also became the most widespread large animal. Thus, he became the most available blood meal for mosquitoes and the most available host for parasites. This change resulted in the adaptation of several species of the Anopheline mosquito to human habitations and the adaptation of many parasites to man as their host.
Livingstone, “Sickle Cell Gene Distribution,” 556.

One of the Science articles presented research by the Harvard-Oxford Malaria Genome Diversity Project. Sarah K. Volkman, Alyssa E. Barry, and the others on the team analyzed “25 introns from eight independent isolates” (482) which they found deficient in single-nucleotide polymorphisms (SNPs). Their data led to an estimated age of 3200 to 7700 years for the most recent common ancestor (MRCA) of extant P. falciparum, and 9500 to 23,000 for the age of MRCA when two “suspect SNPs” are included.

[T]he establishment of slash-and-burn agriculture in the African rainforest less than 6000 years ago … could have provided suitable expansion conditions for the mosquito vectors of P. falciparum and adequate human population size to maintain transmission.
Volkman, et al., “Recent Origin of Plasmodium falciparum,” 483.

The other article examined “genetic defense mechanisms … for resisting infection by Plasmodium” (455). Estimating the ages of two glucose-6-phosphate dehydrogenase (G6PD) alleles that “are restricted to specific geographic regions,” Sarah A. Tishkoff and her co-authors note the ages correspond with the development of agriculture. They estimate that G6PD “A- mutation arose in the past 3840 to 11,760 years” (459) and the Med allele 1600 to 6640 years ago. They note that the age of the A- allele partly supports the hypothesis of Frank Livingston, but that “an increase in both temperature and humidity between 12,000 and 7000 years ago” in Africa may have contributed to malaria’s spread earlier in the Sahara and east Africa (460). They note that malaria had been present in human populations much longer, but that “more severe malaria did not become hyperendemic until the past 10,000 years” (460). They also state:

It is possible that the recent and rapid spread of the Med allele across a broad geographic region may correspond with the spread of agriculture during a Neolithic expansion and migration across Europe from the Middle East 10,000 to 5000 years ago.
Tishkoff, et al., “Haplotype Diversity and Linkage,” 460.

These two articles were not published without skepticism from other researchers in genetics, epidemiology of malaria, and related subjects. In “Malaria's Beginnings: On the Heels of Hoes?” in the same issue of Science, Elizabeth Pennisi outlined some aspects of the controversy. The “prevailing view has long favored ancient origins,” she notes, but several studies in recent years have supported the “link between malaria and agriculture” (416-417).

Two years after the flurry of articles in Science in 2001, another article offered additional support both for the ancient origin and for the more recent expansion of P. falciparum. Deidre A. Joy and her co-authors “reject the claim that the parasite originated 6000 years ago,” but suggest that the population of the parasite likely remained small for a long period. Their data “provide[s] strong evidence for a recent and rapid population expansion in Africa followed by migration to other regions” (321).

Historical Significance

If P. falciparum, the parasite that causes the most virulent form of malaria, expanded in concert with agriculture, it joins many other maladies that have made gatherings of humans into towns and cities unhealthy places for most of human history.

As the development of agriculture made possible the rise of cities, food became cheaper but often less varied. The rise of towns and cities with the expansion of agriculture reduced the overall health of human populations. Deleterious effects of the Neolithic revolution included sedentary lifestyles, repetitive physical tasks (swinging a scythe, for example, or pounding grain into flour), ecological degradation, and new illnesses. Cities were terribly unhealthy abodes for humanity until the twentieth century developments of modern water and sewage treatment, plumbing, and garbage disposal. These themes are central to the arguments in The Backbone of History: Health and Nutrition in the Western Hemisphere (2002), edited by Richard H. Steckel and Jerome C. Rose, and of Jared Diamond, Guns, Germs, and Steel: The Fates of Human Societies (1997).

In general, the healthiest populations were hunter-gatherers, and the least healthy lived in large settlements supported by systematic agriculture. Our statistical analysis of the health index identifies settlement size and use of domesticated plants as the two most important factors associated with the long-term decline in pre-Columbian health.
Steckel and Rose, “Conclusions,” The Backbone of History, 587.

Sedentary farmers became surrounded not only by their own feces but also by disease transmitting rodents, attracted by the farmers’ stored food. The forest clearings made by African farmers also provide ideal breeding habitats for malaria-transmitting mosquitos.
Diamond, Guns, Germs, and Steel, 205.

Civilization made us sick, but it also made us more numerous so we could impose our will on those otherwise more fortunate. The maladies that afflicted Europeans contributed in significant measure to their global expansion.

Death in Jamestown

Fyndeinge of fyve hundrethe men we had onely Lefte aboutt sixty, The reste beinge either sterved throwe famin or Cutt of by the salvages.
George Percy, “A Trewe Relacyon”

In early 1610, sixty English colonists remained from the previous year’s population of five hundred. After two years, the colony at Jamestown had not yet established itself as a viable settlement. Approximately 90% of the colonists to Virginia had died—killed by Indians, starved, fallen to disease—or run away and disappeared into the wilds of America. Conditions were so grim that the surviving remnant prepared four boats and set out to return to England. Some considered burning the small fort where they had suffered, but were persuaded that it might yet be occupied by others who would follow them. As they sailed downriver, they met Lord De La Ware’s ship loaded with supplies and more than three hundred additional colonists. They returned to Jamestown.

The colonists would continue to die. Each ship that arrived in Virginia brought more colonists and most died within two years. Of the many thousands who arrived year after year, perhaps 900 occupied Jamestown and the surrounding area in 1620 (Gately, 73). So many colonists died that an investigation by the Royal Council in 1624—the year that John Smith published his Generall Historie—asked, “What has become of the five thousand missing subjects of His Majesty?” (Morison, 54).

John Smith described the conditions in 1607. Food consisted of meager rations from the common store.

… halfe a pinte of Wheat, and as much Barly boiled with water for a man a day, and this having fryed some six and twenty weekes in the ships hold, contained as many wormes as graines
Smith, “Description,”

Hunger was aggravated by thirst. The colonists were reduced to drinking water from the river.

… when they [Captain Newport and the ships] departed, there remained neither Taverne, Beere-house, nor place of reliefe but the common kettell. … our drinke was water.
Smith, “Description”

George Percy noted the abysmal conditions of the water.

… our drinke cold water taken out of the River, which was at a floud verie salt, at a low tide full of slime and filth, which was the destruction of many of our men.
Percy, “Observations”

Earlier in this paragraph, Percy gives us the earliest diagnosis of the maladies that would continue to devastate the Virginia colony for more than a decade.

Our men were destroyed with cruell diseases as Swellings, Flixes, Burning Fevers, and by warres, and some departed suddenly, but for the most part they died of meere famine.
Percy, “Observations”

Flixes seems most likely a reference to dysentery, but what caused the fevers?


Malaria?

In A Patriot’s History of the United States, Larry Schweikart and Michael Allen clearly identify one of the principal causes of death.

Disease also decimated the colony. Jamestown settlers were leveled by New World diseases for which they had no resistance. Malaria, in particular, proved a dreaded killer, and malnutrition lowered the immunity of the colonists.
Schweikart and Allen, A Patriot’s History, 17.

The identification of malaria as a principal malady killing the settlers is neither surprising nor original. The textbook I read in my first college course in early American history also identified malaria, which the authors linked to the poor choice of location for the settlement.

The town was located on marshy ground where mosquitoes flourished during the summer, and a hundred of the first settlers died from malaria.
Weinstein and Wilson, Freedom and Crisis, 63.

An article in The Pilgrim Newsletter published in recognition of the 400th anniversary of the founding of Jamestown continues this common assertion, “Malaria and other mosquito born illnesses were rampant in the colony” (Stacy, 17). School children at Jamestown Elementary School in Virginia incorporated this idea into a Rap song written as part of a school project.

Although the identification of malaria as a killer of colonists is not uncommon, Schweikart and Allen's add a new twist with their assertion that it was a “New World disease” against which the English lacked immunities. In contrast to this original idea, a statement from the Johns Hopkins Bloomberg School of Public Health reflects the current state of knowledge concerning malaria in the New World.

Plasmodium vivax stowed away with the English going to Jamestown, while P. falciparum rode along with slaves from Africa.
“Background History on Malaria”

P. vivax thrived in northern Europe for centuries, but it killed very few. P. falciparum is far more deadly. Indeed, it is one of the world's leading killers even today. If the English colonists succumbed to malaria, it came with them. But they were unlikely to succumb until a more virulent strain was brought in with imported servants from Africa. The first of these arrived in 1619 by which time the English population at Jamestown was growing and reasonably healthy.


If not Malaria?

The common assertion that malaria killed the Jamestown settlers rests on a weak foundation. In Malaria: Poverty, Race, and Public Health in the United States (2001), Margaret Humpheys suggests that the English colonists might have brought malaria with them. The strain of malaria they brought—P. vivax—was less virulent than that likely brought sometime after 1619 from Africa—P. falciparum. Humphreys earned a medical degree from Harvard as well as her Ph.D. in the history of science. Her qualifications for assessing the epidemiology of colonial Virginia would seem more than adequate. It thus comes as no surprise that her book is thorough and well argued, and offers only tentative conclusions in recognition of the absence of the sort of medical data required to make a definitive diagnosis.

Humphreys leaves Schweikart and Allen’s novel allegation in shambles: there is no credible reason to believe that malaria was a New World disease. She also offers good reasons to doubt their commonplace assertion that malaria was the cause of the fevers about which Percy and Smith wrote.

The Jamestown settlers came from England, including parts of England where vivax malaria was common. They certainly could have brought it with them. But one would not expect such a nonvirgin population, however malnourished, to experience a major outbreak of vivax malaria with that level of mortality.
Humphreys, Malaria, 24.

Humpreys suggests that the level of mortality is more consistent with typhoid fever than malaria. Typhoid fever had been put forth as an explanation in the work of Wyndham Blanton in the first half of the twentieth century and by Carville Earle in the second half of the century. Earle notes that the parasites Salmonella typhi and Endamoeba histolytica were present in the “slime and filth” that Percy observed in the water.

Ironically, most of them died needlessly, for on at least two occasions, Virginians understood the nexus between site and mortality, and they eliminated that link through the preventative medicine of settlement dispersal only to have their costly insights overturned by company agents freshly arrived in Virginia.
Earle, “Pioneers of Providence,” 482.

Of course, settlement dispersal rendered the colonists more vulnerable to Indian attack. It was bad enough that the English were economically dependent upon the Natives for many of their provisions, whether through trade or abundant theft. The Indians frequently found cause for hostilities—Percy mentions for example an accidental shooting of a Native when a “pistoll suddenly fyered and shotte the salvage” (Nicholls). Moreover, archaeological excavations and “tree-ring analysis of cypress trees” suggest that the Natives were already suffering scarcity of crops due to a severe drought during the years 1606-1612 (Sheler). The additional burden of feeding the helpless English during hard times did not bode well for peaceful relations.


Plausible Deniability

Schweikart and Allen’s statement that malaria killed the Virginia colonists could be true, but more than likely it is false. Their original claim would merit consideration if they offered some evidence in support. The most convincing scholarship available when they were writing their book suggests an alternate hypothesis that seems more likely. They ignore Humpreys' text. Perhaps the belief that malaria killed the colonists should go the way of Smith’s alleged rescue at the hands of an eleven year old Indian child—a useful myth that is probably false but cannot be proven false beyond all doubts.

Their identification of malaria as a New World disease, on the other hand, is absurd. Even so, they do not state unequivocally that it was. The transition from “New World diseases” to “[m]alaria, in particular” in the next sentence certainly implies that malaria was a New World disease, but they do not list it among those “diseases thought to be ‘transmitted’ from Europe” several pages earlier (Stripes). The relationship between the two sentences could be a misleading non sequitur conferring plausible deniability. It could be clever politics; it could be incompetent editing.


Citations

“Background Information on Malaria.” Johns Hopkins Bloomberg School of Public Health. http://www.jhsph.edu/Malaria/Malaria_Background.html. Accessed 4 February 2008.

Earle, Carville. “Pioneers of Providence: The Anglo-American Experience, 1492-1792.” Annals of the Association of American Geographers 82, no. 3 (1992), 478-499.

Gately, Iain. Tobacco: A Cultural History of How an Exotic Plant Seduced Civilization. New York: Grove Press, 2001.

Humpheys, Margaret. Malaria: Poverty, Race, and Public Health in the United States. Baltimore: Johns Hopkins University Press, 2001.

Morison, Samuel Eliot. The Oxford History of the American People. New York: Oxford University Press, 1965.

Nicholls, Mark. “George Percy's ‘Trewe Relacyon’: A Primary Source for the Jamestown Settlement.” Virginia Magazine of History & Biography 113, no. 3 (2005), 212-275.

Percy, George. “Observations gathered out of a Discourse of the Plantation of the Southerne Colonie in Virginia by the English, 1606.” In Purchas his Pilgrimes, vol. 4 (1625), 1685-1690.

Schweikart, Larry. “Why It’s Time for A Patriot’s History of the United States.” History News Network. http://hnn.us/articles/9536.html. 31 January 2005.

Schweikart, Larry, and Michael Allen. A Patriot’s History of the United States: From Columbus’s Great Discovery to the War on Terror, updated ed. New York: Sentinal, 2007.

Sheler, Jeffrey L. “Rethinking Jamestown.” Smithsonian 35 (October 2005), 48-54.

Stacy, Ann Hooper. “Jamestowne 1607 in Celebration of its 400th Anniversary.” The Pilgrim Newsletter 91, no. 2 (2007), 16-19.

Stripes, James. “Larry Schweikart’s Claim.” Patriots and Peoples. http://historynotebook.blogspot.com/2008/01/larry-schweikarts-claim.html. 30 January 2008.

Smith, John. “The Description of Virginia by Captaine John Smith.” In Purchas his Pilgrimes, vol. 4 (1625), 1691-1704.

Weinstein, Allen, and R. Jackson Wilson, Freedom and Crisis: An American History 2nd ed. New York, Random House, 1978.

Gone Fishing: Mosquitoes, Malaria

In the summer I eat fewer bananas and catch more fish. I cut down on fruit that seems to make me more attractive to the mosquitoes that inhabit wetlands near my favorite trout streams. It’s folk wisdom, and it may be proven false by science, but as with the flies I tie on the end of my tippet, my belief is the critical factor. I think that fewer bananas (and more garlic) renders me relatively unattractive to blood sucking insects, and so the evidence of my experience bears me out.

In the winter I do more angling in the library than along streams. There I recently netted an article of interest on the introduction of malaria in the New World: Corinne Shear Wood, “New Evidence for a Late Introduction of Malaria into the New World,” Current Anthropology 16 (March 1975), 93-104. Wood’s abstract at the end of the article sums the argument.

The unique, overwhelming group-O frequency present among indigenous American populations is seen as a result of mother-child ABO incompatibility effects operating in the absence of the positive selection pressures by malaria vectors favoring enhanced survival for genes A and B that the investigation findings suggest. It is proposed that had malaria been present to act upon the original gene pool, a balanced ABO polymorphism would be found in the New World Indians today.
Wood, “New Evidence,” 5.

Comment by sixteen scholars follow Wood’s article, taking up more pages than her report. There are several criticisms that urge caution in reasoning from her preliminary results, and most suggest the need for further studies. None of them fault her assessment of the historical literature up to the time of her study. It had been inconclusive, but was leaning toward Old World origins.

There should be no doubt from the responses, and her reply, that her study does more to raise questions than offer answers. As the article was published more than thirty years ago, we might expect to find corroborating or refuting evidence by now.

A much more recent study brought to my attention by John Hawks offers a conclusion supporting at least one aspect of Wood’s contentions, that malaria could have impacted selective pressure regarding blood groups:

This work provides insights into malaria pathogenesis and suggests that the selective pressure imposed by malaria may contribute to the variable global distribution of ABO blood groups in the human population.
J. Alexandra Rowe, et al, “Blood group O protects against severe Plasmodium falciparum malaria through the mechanism of reduced rosetting,” Proceedings of the National Academy of Sciences 104 (October 2007), 17471-17476.

In addition, some genetic analysis published a few years ago, also inconclusive, leans towards origins of malaria in Africa. See Jennifer C. C. Hume, Emily J. Lyons, and Karen P. Day, “Archaeology of Epidemic and Infectious Disease,” World Archaeology, 35 (October 2003), 180-192.

This kettle of fish increases skepticism regarding Larry Schweikart’s claim, that “considerable new research in the hard sciences and medicine shows that some diseases thought to be ‘transmitted’ from Europe likely were already here,” if this claim applies to malaria.

I’ve addressed this question from another angle near the end of “America was not a disease-free paradise.” Schweikart and Allen name malaria once, as a New World disease that struck down English colonists that “had no resistance” (A Patriot’s History, 17).