Mosquitoes, the Military, and Why the CDC is in Atlanta
To most of us in the US, malaria is a health problem restricted to distant parts of the globe. Even in the international media, the disease receives little attention. However, it has only been since 1949 that Malaria was declared “eliminated” in the US.
As a public health issue, malaria presents some unique challenges. For instance, there are four species of the Plasmodium parasite that cause malaria in humans (P. falciparum, P. vivax, P. malariae and P. ovale), that are spread by about 30 different species of Anopheles mosquitoes. Another challenge is the parasite’s life cycle. Plasmodium species undergo more than 10 stages of cellular differentiation and invade four different types of cells in two different hosts.
The World Health Organization estimates that 214 million people worldwide have malaria, which causes 438,000 deaths every year. We know how to fight malaria (prevention, treatment, and vector control) and the parasite is gradually losing ground. Between 2000 and 2015, the number of new cases fell by 37 percent globally, and overall death rates among those at risk fell by 60 percent (65 percent among children under age five). However, many challenges remain, and to grasp these challenges—and the role of biobanking—we need to review the past.
Malaria has afflicted humanity for hundreds of years and was thought to be caused by “bad air” (mal aire), especially near wet lowlands. The disease was described in the ancient Chinese Nei ChIng (Canon of Medicine) around 2,700 BCE, by numerous physicians of the Roman empire, as well as in the Sanskrit medical text, the Susruta Samhita, written perhaps about 500 CE.
Unlike most infectious diseases, a treatment was known and available before the cause was identified. The Chinese have used en extract from the Quinhao plant (Artemisia annua) for hundreds of years to treat malaria. The plant is the source of the compound Artesunate; when administered intravenously, the agent kills the malaria parasite soon after it invades red blood cells. The compound also reduces cytoadherance. The other remedy for Malaria, known from the 1700s, is quinine, originally extracted from the bark of a cinchona tree, a member of the Rubiaceae family—which also includes coffee.
From a public health perspective, our successes against malaria to date are largely due to the military. The parasite has been a major problem of military campaigns around the world, and it was a French military doctor, Alphonse Laveran, who first saw the parasite in the blood of a patient in 1880.
Laveran examined many blood samples from many patients and then proceeded to look for the parasite in air, water, and soil samples from swamps and marshy areas. He could not find the parasite in the environmental samples, and like others, he began to suspect mosquitoes.
Laveran published his discovery of the parasite in patient’s blood, and possible transmission via mosquito. Ironically, the scientific community now held strictly to Pasteur’s model of a bacterial cause of disease, and Laveran’s theory of a parasitic origin for malaria was not well received. Eventually, Laveran invited Pasteur to visit and see the parasites for himself. Pasteur did, and immediately agreed with Laveran, although it was not until about 1890 (after methylene blue stain was in use) that a parasitic cause of malaria was fully accepted. Soon after, Sir Ronald Ross, a physician in India, positively identified Anopheles mosquitoes as the vector for both human and bird malaria.
When construction of a canal across the Isthmus of Panama resumed in 1904, the US turned to the military and appointed Colonel William C. Gorgas as chief sanitation officer. The French began the canal in 1881, but engineering problems combined with a death rate of more than 200 workers per month led them to abandon the project. Now armed with the knowledge that mosquitoes were a primary factor, the colonel implemented a number of measures against yellow fever, malaria, and the other tropical diseases plaguing the workers, including clean water systems, fumigation of the buildings, window screens, mosquito netting, and draining areas of standing water. Insecticides were not commercially available at the time, so where standing water could not be drained, oiling and a mixture of carbolic acid, resin, and caustic soda was applied. Quinine dispensers were placed on mess hall tables. Malaria was not eliminated, but the percent of employees hospitalized for malaria dropped to 1.6 percent, and mortality to 2.5 per 1,000 workers by 1909.
It was also the army that instigated the elimination of malaria in the US. The parasite was a significant problem for the military bases in the south, and the army established an “Office of Malaria Control in War Areas” in 1942, and placed it in Atlanta, Georgia, rather than Washington, DC. The Office made use of an extraordinary new chemical, dichloro-diphenyl-trichloroethane, or DDT, which was very successful in eliminating the parasite by killing off its mosquito host.
As a result of its success, the Office was made part of the Public Health Service and charged with eliminating malaria and other infectious diseases throughout the US. Now known as the Centers for Disease Control and Prevention (CDC), the organization is still deeply involved with the control of malaria, but that is for Part 2 of this Evolution of Public Health Research blog post. In the meantime, download our latest case study Supporting our Troops - Transporting the AFMES DNA Repository to Dover Air Force Base.
- http://www.cdc.gov/malaria/about/history/index.html. Centers for Disease Control and Prevention, Center for Global Health, Division of Parasitic Diseases and Malaria.
- World Health Organization. (2015) Control and elimination of plasmodium vivax malaria: a technical brief. WHO.
- World Health Organization. (2015) World Malaria Report. WHO. http://www.who.int/malaria/visual-refresh/en/