Kicking a dying dog. DDT and the demise of malaria in the American South, 1942-1950

How long is the last mile? Evaluating successful malaria elimination trajectories

Background

Many national malaria programmes have set goals of eliminating malaria, but realistic timelines for achieving this goal remain unclear. In this investigation, historical data are collated on countries that successfully eliminated malaria to assess how long elimination has taken in the past, and thus to inform feasible timelines for achieving it in the future.

Methods

Annual malaria case series were sought for 56 successful elimination programmes through a non-systematic review. Up to 40 years of annual case counts were compiled leading up to the first year in which zero locally acquired or indigenous cases were reported. To separate the period over which effective elimination efforts occurred from prior background trends, annual case totals were log transformed, and their slopes evaluated for a breakpoint in linear trend using the segmented package in R. The number of years from the breakpoint to the first year with zero cases and the decline rate over that period were then calculated. Wilcox-Mann-Whitney tests were used to evaluate whether a set of territory characteristics were associated with the timelines and decline rates.

Results

Case series declining to the first year with zero cases were compiled for 45/56 of the candidate elimination programmes, and statistically significant breakpoints were identified for 42. The median timeline from the breakpoint to the first year with zero local cases was 12 years, over which cases declined at a median rate of 54% per year. Prior to the breakpoint, the median trend was slightly decreasing with median annual decline of < 3%. Timelines to elimination were fastest among territories that lacked land boundaries, had centroids in the Tropics, received low numbers of imported cases, and had elimination certified by the World Health Organization.

Conclusion

The historical case series assembled here may help countries with aspirations of malaria elimination to set feasible milestones towards this goal. Setting goals for malaria elimination on short timescales may be most appropriate in isolated, low importation settings, such as islands, while other regions aiming to eliminate malaria must consider how to sustainably fund and maintain vital case management and vector control services until zero cases are reached.

Conceptual Frameworks in Scientific Inquiry and the Centers for Disease Control and Prevention's Approach to Pesticide Toxicity (1948-1968)

This article examines the rise of the Centers for Disease Control and Prevention's (CDC's) small but influential program on the human toxicology of synthetic pesticides after World War II. For nearly 20 years, scientists working in the CDC's Toxicology Section conducted a range of laboratory, field, and clinical studies to assess whether pesticides, such as dichlorodiphenyltrichloroethane (DDT), caused harm to humans. Applying an industrial hygiene approach to study pesticide toxicity, the team used the symptoms of poisoning as their criteria for harm and consistently found that, when used as intended, pesticides were generally safe for humans. In the post-Silent Spring era, these findings were increasingly challenged as the field of toxicology developed and different ways of understanding pesticide toxicity gained greater acceptance. While it is easy to dismiss the CDC's findings as excessively narrow, examining how the team arrived at their conclusions provides an instructive lesson about the powerful ways conceptual frameworks shape scientific inquiry and the unexpected ways data can be reinterpreted in different problem contexts. (Am J Public Health. 2019;109:1548-1556. doi: 10.2105/AJPH.2019.305260).

The Invisible and Indeterminable Value of Ecology: From Malaria Control to Ecological Research in the American South

This essay tells the story of the Emory University Field Station, a malaria research station in southwest Georgia that operated from 1939 to 1958. Using the tools of environmental history and the history of science, it examines the station's founding, its fieldwork, and its place within the broader history of malaria control, eradication, and research. A joint effort of Emory University, the U.S. Public Health Service, and the Communicable Disease Center (CDC), this station was closely aligned with a broader movement of ideas about tropical diseases across the globe, but it also offers a case study of how science in the field can veer from mainstream thinking and official policy. As the CDC and other disease-fighting organizations were moving toward a global strategy of malaria eradication through the use of DDT, the Emory Field Station developed a postsanitarian approach to malaria. Drawing on resistance among American conservationists to environmental transformation in the name of malaria control, the station's staff embraced the science and worldview of ecology in an effort to lighten public health's hand on the land and to link human health to the environment in innovative, if sometimes opaque, ways. This essay, then, argues that the Emory Field Station represents an early confluence of ecology with the biomedical sciences, something very similar to what is now the important discipline of disease ecology.

Institutional resources for communicable disease control in Europe: diversity across time and place

This commentary discusses the causes and consequences of diversity in how European countries organize communicable disease control. Drawing on the historical record of the US Centers for Disease Control and Prevention, it first reviews the main explanations of that diversity, with a focus on the political dynamic of building institutional capacity in the field of public health. It then examines the significance of institutional diversity in the process of Europeanization, and closes with a few thoughts on factors that have shaped the development of communicable disease control capacities in the United States and the European Union.

[A method called Pinotti: medicated salt, malaria, and international health (1952-1960)]

The article analyzes the creation, acceptance, and abandonment of a means of fighting malaria known as the Pinotti method: kitchen salt mixed with chloroquine. The early 1950s brainchild of Brazilian malariologist Mario Pinotti, this method was intended to both prevent and treat malaria. Chloroquine-medicated salt was tested during the first half of that decade and used in Brazil from 1959 through 1961 as part of a malaria eradication campaign coordinated by the World Health Organization. The method won recognition on the world health stage, drew criticism, and underwent testing in other countries until the mid-1960s. We argue that Brazil's abandonment of the method was primarily due to the political decline of its creator, which began in 1960.

Costs and financial feasibility of malaria elimination

The marginal costs and benefits of converting malaria programmes from a control to an elimination goal are central to strategic decisions, but empirical evidence is scarce. We present a conceptual framework to assess the economics of elimination and analyse a central component of that framework-potential short-term to medium-term financial savings. After a review that showed a dearth of existing evidence, the net present value of elimination in five sites was calculated and compared with effective control. The probability that elimination would be cost-saving over 50 years ranged from 0% to 42%, with only one site achieving cost-savings in the base case. These findings show that financial savings should not be a primary rationale for elimination, but that elimination might still be a worthy investment if total benefits are sufficient to outweigh marginal costs. Robust research into these elimination benefits is urgently needed.

The persistent problem of malaria: addressing the fundamental causes of a global killer

Despite decades of global eradication and control efforts and explosive global economic development, malaria is the most important vector-borne disease of our day, killing more people today than 40 years ago and affecting millions worldwide, particularly poor residents of tropical regions. Global eradication efforts from the 1950s through the 1980s largely failed, leaving vector and parasite resistance in their wake. The persistence of malaria and the magnitude of its effects call for an action paradigm that links the traditional proximal arenas of intervention with malaria's fundamental causes by addressing the environmental, economic, and political dimensions of risk. We explore the more distal determinants of malaria burden that create underlying vulnerabilities, evaluating malaria risk as a function of socioeconomic context, environmental conditions, global inequality, systems of health care provision, and research. We recommend that future action to combat malaria be directed by a broad-spectrum approach that meaningfully addresses both the proximal and fundamental causes of this disease.