For the past few months, I've been on one of the most exciting adventures of my life - learning about malaria. Everything I'm about to say...you have to remember that I am not an expert. I am a lay person who's managing a team of brilliant researchers and statisticians in a project to answer some basic scientific questions about the biology of malaria.
What's the goal? Well in a word, eradication. But it's not that simple and I'll explain why in my very non-scientific kind of way. I'm oversimplifying for the sake of brevity, and so I don't get accused of having some studied opinion or position simply because of where I work or who funds this project. Understood? That's my CYA statement.
Now, onto the good stuff.
Malaria is a big problem across the world, and eradicating it is an even bigger goal shared by a lot of global health organizations and non-profits alike. Malaria is a nasty little disease.
The World Health Organization estimates that in 2012, there were 207 million cases of malaria. That year, the disease is estimated to have killed between 473,000 and 789,000 people, many of whom were children in Africa. (from Wikipedia)
Before we can talk about malaria eradication, we need to talk about elimination and eradication in general.
In the last century, we (that's the collective we, as in humanity) managed to eradicate smallpox, and we're on the verge of eradicating guinea worm disease. Disease eradication programs are underway for many other diseases like polio, leprosy, lymphatic filariasis, and onchocerciasis. Malaria eradication has long been a goal in the scientific community, but it is elusive.
Fundamentally, disease eradication is a protocol a country elects to undertake, and it is achieved through a combination of programs like mass treatment, vaccines, vector control, surveillance, and antibiotics, all designed with the specific country's unique disease circumstances guiding the protocol. It's not as romantic as it sounds. Elimination and eradication are concepts based on statistical analysis, and it's not as black and white as those terms might suggest.
According to Dowdle, these are the recognized definitions related to disease elimination and eradication:
- Control: The reduction of disease incidence, prevalence, morbidity or mortality to a locally acceptable level [JR: emphasis added] as a result of deliberate efforts; continued intervention measures are required to maintain the reduction. Example: diarrhoeal diseases.
- Elimination of disease: Reduction to zero of the incidence of a specified disease in a defined geographical area [JR: emphasis added] as a result of deliberate efforts; continued intervention measures are required. Example: neonatal tetanus.
- Elimination of infections: Reduction to zero of the incidence of infection caused by a specific agent in a defined geographical area [JR: emphasis added] as a result of deliberate efforts; continued measures to prevent re-establishment of transmission are required. Example: measles, poliomyelitis.
- Eradication: Permanent reduction to zero of the worldwide incidence [JR: emphasis added] of infection caused by a specific agent as a result of deliberate efforts; intervention measures are no longer needed. Example: smallpox.
- Extinction: The specific infectious agent no longer exists in nature or in the laboratory. Example: none.
So you see, in order to eradicate, you must systematically eliminate, each locale managed differently - and keep the disease from coming back while you expand geographies. This isn't easy work, but with some diseases like guinea worm, the approach is fairly straightforward.
Guinea worm disease is considered a neglected tropical disease. It occurs when a human ingests larvae from the guinea worm, usually from contaminated water. After a year, the worm begins to emerge from the human's body, usually from the lower limbs. To combat the burning sensation of worm emergence, the person will usually immerse their limbs in water. The emerging worm releases larvae directly into the water, restarting the cycle for the next person.
The guinea worm is good candidate for eradication because of a few conditions that humans can control, and one piece of biology that just happens to work in our favor. Biologically, the guinea worm has one host, the human. It can't grow or mature in any other species. That means if we can stop ingesting the guinea worm (and giving them the perfect environment in which to mature), they stop reproducing altogether. They can't turn to a dog or an ape to continue. Lose the human host, they're done.
Secondly, through focused development and education programs, you teach people how the guinea worm uses the contaminated water, and you encourage them to seek treatment for worm extraction, rather than the alternative larvae-spreading method. That's it. I mean, I'm certain that's not really it, but that's a summary of the complexity of eliminating guinea worm disease.
So why wouldn't this work for malaria? It's as if malaria learned from guinea worm and did everything the opposite times a hundred.
More on this in part 2.
Want to read more from my sources?
- The Principles of Disease Elimination and Eradication
Walter R. Dowdle
- Carter Center Guinea Worm Eradication Program
- American Museum of Natural History presents Countdown to Zero, an exhibit in collaboration with the Carter Center
- Neil deGrasse Tyson interviews Jimmy Carter on StarTalk Radio, also seen on the History Channel