UT Arlington assistant professor Daniel Sledge’s new study about elimination of malaria in the 1930s American South could have significant implications for solving modern-day malaria epidemics in parts of Africa, Central and Latin America and Asia.
Dr. Sledge’s research team challenged a leading argument that movement of Southern tenant farmers away from mosquito breeding grounds was the dominant factor in the decline of malaria in U.S. during the 1930s. Instead, they point to targeted public health interventions and development of local-level public health infrastructure as major factors that helped eradicate the disease
Dr. Daniel Sledge PhD is an assistant professor of political science at UT Arlington and lead author of a “Eliminating Malaria in the American South: An Analysis of the Decline of Malaria in 1930s Alabama,” (August 2013, Vol. 103, No. 8, pp. 1381-1392. doi: 10.2105/AJPH.2012.301065 — a paper recently published by the American Journal of Public Health, co-authored with George Mohler, PhD, an assistant professor of mathematics and computer science in the Department of Mathematics and Computer Science at Santa Clara University, Santa Clara, California.
Dr. Sledge developed the article’s argument, did research into the development of health infrastructure, conceived the idea of using quantitative data to examine the decline of malaria, and identified and collected data, while Dr. Mohler identified and implemented an appropriate model for analyzing the data and suggested and found potential variables.
Malaria is an infectious disease caused by a parasite called plasmodium and transmitted through the bites of infected mosquitoes. The disease causes fever, headache and vomiting. Untreated, it can become life threatening.
In the article abstract, Sledge and Mohler note that until the 1930s, malaria was endemic throughout large swaths of the American South. They used a Poisson mixture model to analyze the decline of malaria at the county level in Alabama (as an archetypical Deep South cotton state) during the 1930s. Employing a novel data set, the co-authors argue that, contrary to a leading theory, the decline of malaria in the American South was not caused by population movement away from malarial areas or the decline of Southern tenant farming, elaborating and providing evidence for an alternate explanation that emphasizes the role of targeted New Deal-era public health interventions and the development of local-level public health infrastructure. They show that, rather than disappearing as a consequence of social change or economic improvements, malaria was eliminated in the Southern United States in the face of economic dislocation and widespread and deep-seated poverty.
They further observe that over the past decade, aid agencies such as the World Health Organization, the Gates Foundation, and the United States Agency for International Development (USAID) have grappled with the problem of malaria in the Global South, the WHO estimating that there were around 216 million cases and 655 000 deaths in 2010, while another recent study found that there were approximately 1.24 million malaria deaths in 2010. They cite development economists such as Jeffrey Sachs who have argued that malaria is a central factor inhibiting the Global South’s economic development.
“We found that targeted public health interventions, supported by the federally backed development of state and local public health infrastructure, led to the decline of malaria despite widespread and deep-seated poverty,” says Dr. Sledge in a UTA release which also cites Beth Wright, dean of the College of Liberal Arts at UT Arlington, commenting that Dr. Sledge’s research benefits the public, health professionals and policy makers globally.
“Dr. Sledge’s work has far-reaching implications for those who work to eradicate malaria and similar diseases,” Dr. Wright says. “Huge challenges remain, but such research brings about better understanding of potential solutions and could ultimately help save lives.”
Historian Margaret Humphreys argued in her landmark 2001 book, “Malaria: Race, Poverty, and Public Health in the United States,” that it was removal of the malaria carrier and victim from the vicinity of the anopheles mosquito that likely had the largest effect on the decline of the disease in this country.
But Dr. Sledge and Dr. Mohler found otherwise. “We assessed this argument using Census data on the number of farms operated by tenants during the 1930s. We found that highly malarial areas actually gained population during the period that malaria declined,” says Dr. Sledge. “Changes in the type of farms, meanwhile, didn’t lead to a decline in malaria.”
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He continues: “Put another way, population movement didn’t lead to the end of malaria in the United States – public health work did,” noting that during the 1930s, the federal Works Progress Administration put unemployed Southerners to work draining millions of acres of wetlands. Along with the federally sponsored creation of local health departments, these drainage projects led to the decline of malaria, the co-authors say.
The federal government further ramped up its efforts during World War II, creating the agency that became the Centers for Disease Control and Prevention specifically to fight southern malaria. After the war, the CDC used the insecticide DDT to eradicate the few remaining pockets of the disease.
For their study, Drs. Sledge and Mohler used a mathematical model to analyze the decline of malaria in each of the 67 counties in Alabama, an archetypical Deep South cotton state that experienced high levels of malaria incidence well into the 1930s.
“In the model, we categorized counties into three risk levels and then estimated the dependence of mortality rates on variables related to weather, WPA projects and population movement,” Dr. Mohler explains. “After drought, the most important variable for predicting a decline in mortality rates was the amount of drainage in a county, rather than movement out of high risk counties or a reduction in tenant farms.”
In addition to drainage work, the researchers point to the importance of measures such as screening and public health infrastructure as well as the training of public health workers in the elimination of the disease. While the team concedes that there are considerable distinctions between the current Global South and the American South of the 1930s, they argue that malaria can be controlled in the face of poverty and economic dislocation without major social change.
“Today, disease surveillance, drainage measures and screening work to ensure that, on those occasions when malaria is reintroduced from outside of the U.S., the chain of transmission does not begin again,” Dr. Sledge observes.
Dr. Daniel Sledge’s work is exemplary of world-class research under way at The University of Texas at Arlington. UTA is comprehensive research institution of more than 33,000 students and more than 2,200 faculty members situated in the heart of North Texas. To learn more visit:
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