hcghr

We Eradicated Smallpox, So Why Not Malaria?

In Uncategorized on January 13, 2010 at 10:48 pm

Annemarie Ryu, Contributing Writer

Two infectious disease pandemics, two global eradication campaigns. The results? For one, complete eradication by 1970, within thirteen years of the campaign’s inauguration—there are no deaths today resulting from smallpox. And the other? The global malaria eradication campaign, begun in 1955, was abandoned in 1965, when goals shrank to “malaria control.”[1] Today, malaria, though preventable and curable, causes between one and three million deaths per year and is among the top ten causes of death in developing countries.[2]

Why haven’t we eradicated malaria when we did eradicate smallpox? Comparing the two campaigns teaches us about past successes and failures and informs today’s eradication efforts. The drastic divergence in health outcomes is partly a result of differences in disease characteristics. One key difference between smallpox and malaria is that a smallpox survivor is immune to the disease for life while a malaria survivor may reacquire the infection. Whereas the smallpox vaccine could ensure lifelong protection from smallpox, malaria interventions and preventative measures required continuous management in all at-risk areas to actually eliminate malaria. Such management required restructuring fundamental health services, whereas smallpox programs could simply be administered temporarily by external groups.[3]

Another crucial distinction between smallpox and malaria is in ease of diagnosis and containment. Smallpox spreads through saliva droplets from coughing, sneezing, and speaking, as well as fluids contained in pustules of the infected individual. Fortunately, anyone with smallpox was easily recognizable due to smallpox’s main symptom: innumerable skin lesions. This easy recognition facilitated disease containment, as vaccinators and community members could readily identify individuals requiring treatment. In addition, vaccinators could administer preventative treatment to community members deemed at-risk due to contact with diseased individuals. The efficient containment and treatment of infected individuals was sufficient to control the spread of disease.[3]

Malaria, on the other hand, is far more difficult to recognize and contain because it is transmitted by mosquitoes carrying one of four types of malaria parasites. Thus, for malaria to be eradicated, not only did infected individuals need to be identified and treated, but infected mosquitoes also needed to be eliminated. Malaria-infected individuals were difficult to identify because common first symptoms of malaria include  headache, chills, fever, and vomiting—symptoms similar to those of many other infections—and can appear seven days to several months after exposure, depending on the incubation period of the parasite. Furthermore, due to the life cycle of malaria parasites, malaria-infected individuals often exhibit symptoms in cyclic patterns, with symptoms of different intensities appearing and disappearing.[5]

A major complication for malaria eradication was the need to prevent infected mosquitoes from transmitting the parasite to humans. The main strategy was mass spraying of the insecticide DDT inside homes. This strategy, coupled with administration of chloroquine, a drug that kills malarial parasites, led to significant decreases in mortality rates during the first decade of the eradication campaign. However, DDT and chloroquine as applied were insufficient to halt infection by mosquitoes, which flourished in the fields and swamps often located near villages. It became clear that difficult environmental reconstruction would be necessary to eradicate malaria.[3]

Support for the malaria eradication campaign waned for several reasons. First, increasing mosquito resistance to DDT and parasite resistance to chloroquine meant higher costs and slower progress. The initial popularity of the campaign was tied to the post-WWII faith of Americans in easy solutions provided by new science and technology. Western enthusiasm dwindled as DDT failed to efficiently solve the malaria problem.[3]

Second, economic considerations played a significant role in the decline of the campaign. Initial support for the campaign was partly founded on the belief that the eradication of malaria would lead to great economic benefits for developing countries, where a significant expansion in the healthy labor force would heighten productivity, and developed countries, which could utilize the new foreign markets. In addition, campaign proponents promoted malaria eradication as a way to increase agricultural production and address the world food shortage. However, the increasing costs associated with the campaign, as well as the poor agricultural conditions induced by extensive application of insecticides, diminished hopes for economic gains. Other economic problems included pressure from pharmaceutical firms and chemical companies for continued use of DDT and drugs that were losing effectiveness. The practice of pesticide-intensive cash cropping in developing countries also encouraged mosquito growth and conflicted with much needed environmental transformation.[1]

Third, the political atmosphere ceased to favor the campaign. The United States had strongly supported the campaign at its inception as a straightforward way to win over nonaligned developing countries during the Cold War.[3] However, when over a decade of exhaustive campaign efforts met with decreasing rates of improvement rather than complete success, the campaign faced international criticism. Changes in foreign relations and public health caused WHO to broaden its focus to development of primary health services rather than simply malaria eradication, and this change led to a weakening in traditional malaria control programs.[4] With such decreases in global support of malaria eradication, malaria prevalence began to climb again by the 1970s.[3]

Today, malaria has nonetheless has been eradicated from many regions of the world. In developed countries, fundamental changes in living conditions and agricultural practices have led to environmental transformation. Socialist countries, such as Romania and Poland, eradicated malaria by means of strong health delivery systems that upheld intervention programs. Islands such as Jamaica and Taiwan have benefited from geographical barriers hindering re-introduction of the disease.[1] Still, malaria continues to thrive in developing countries. Fortunately, there is much hope for its future eradication. The latter decades of the twentieth century contributed new developments and advances in disease vector control, vaccines and drugs, and insecticide-treated mosquito nets. In addition, today we have a much better understanding of the cultural, economic, and social dimensions of malaria, as well as renewed financial support and enthusiasm for malaria eradication.[6] With the Roll Back Malaria campaign targeting 50% decreases in malaria mortality by 2010 and 2015, and the Millennium Development Goal of zero malaria incidence by 2015, the goal of global malaria eradication has returned to our vision for the future.

_________________________________________________________________________________________

1 Turshen, Meredith. The Politics of Public Health. New Brunswick: Rutgers University Press, 1989.

2 Millennium Project. “Global Burden of Malaria.” 2006. 28 Sept. 2009 <http://www.unmillenniumproject.org/documents/ GlobalBurdenofMalaria.pdf>.
3 Farmer, Paul. “A Social Analysis of Past Global Medicine.” Northwest Biolabs B103, Cambridge. 17 Sept. 2009. Lecture.
4 Cueto, Marcos. The origins of primary health care and selective primary health care. American Journal of Public Health. 2004;94(11)
5 “Malaria.” Drugs.com. 2009. 28 Sept. 2009 <http://www.drugs.com/cg/malaria.html&gt;.

6 World Health Organization. “Malaria Eradication Back on the Table.” Bulletin of the World Health Organization. 2008;86(2)

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: