Disease Control, Elimination, and Eradication
Smallpox and rinderpest are two infectious diseases that have been successfully eradicated. Smallpox was eradicated in 1980 and rinderpest in 2011 [1,2]. Will Guinea Worm be the next disease to be eradicated? To fully understand disease eradication, it is important to comprehend the concepts of disease control, elimination, and eradication.
Disease control is defined as the “reduction of incidence, prevalence, morbidity or mortality to a locally acceptable level as a result of deliberate efforts” [3]. This requires the continuous use of interventions to maintain disease incidence. Disease elimination has been defined as the “reduction to zero incidence in a defined geographical area” [3]. Disease elimination also requires the continued implementation of control measures to prevent the re-establishment of the disease. Finally, disease eradication is defined as the “permanent reduction to zero of worldwide incidence [of disease]” [3]. The key difference between elimination and eradication is that elimination is limited to a specific geographic location, such as a country, while eradication means the disease has been eliminated throughout the entire world. Therefore elimination is required before a disease can be eradicated.
Guinea Worm
Guinea Worm Disease, also known as Dracunculiasis, is a highly debilitating, waterborne disease caused by the parasitic worm, Dracunculus medinensis [4]. Infection occurs when an individual drinks water contaminated with Dracunculus medinensis larvae (housed within minute crustacean copepods). Following ingestion, the larvae migrate through the intestinal wall and mature. After full maturation has been reached (approximately 1 year after ingestion), the female worm migrates to the subcutaneous tissue and is slowly expelled through a blister, usually located on the lower leg [4]. This blister is very painful, therefore infected individuals often immerse their foot in a local body of water to alleviate the burning sensation. Once immersed in water the blister ruptures and releases larvae, thus continuing the transmission cycle [4].
Control efforts include mapping endemic villages, establishing surveillance and case containment (to prevent individuals from contaminating local drinking water sources), implementing interventions aimed at increasing access to safe drinking water, waterborne (?) vector control through larvicides, as well as health education and community-involvement [7,8].
So how close are we to eradication? The answer is, very close. The incidence of Guinea Worm Disease has been reduced by 99.9% [8].
Since the launch of global eradication campaigns, lead by The Carter Center, the World Health Organization and UNICEF, the number of Guinea Worm cases and endemic villages has been decreasing steadily [4,8]. When The Carter Center began their Guinea Worm Eradication Program in 1986 there were approximately 3.5 million cases annually and 20 endemic countries, primarily in Africa and Asia [5, 6,8]. Ghana became the most recent country to have eliminated Guinea Worm, the WHO declared it Guinea Worm-free in May 2010 [7]. Since 2012, the disease has been limited to 4 countries in Africa – South Sudan, Mali, Chad, and Ethiopia [6]. In 2014 there were only 30 endemic villages and 126 cases, with 70 cases in South Sudan, 40 in Mali, 13 in Chad, and only 3 in Ethiopia [5]. This means Guinea Worm has been eliminated in Asia, is being controlled in Africa, and is rapidly moving towards the universal goal of eradication. If successful, Guinea Worm would become the first human infectious disease to be eradicated without the use of a vaccine or medication [8].
Sources:
[1] http://www.who.int/csr/disease/smallpox/en/
[2] http://www.oie.int/for-the-media/rinderpest/
[3] http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2305684/pdf/bullwho00391-0020.pdf
[4] http://www.who.int/dracunculiasis/disease/en/
[5] http://outbreaknewstoday.com/guinea-worm-disease-126-cases-reported-in-2014/
[6] http://www.who.int/dracunculiasis/epidemiology/en/
[7] http://www.who.int/dracunculiasis/eradication/en/
[8] http://www.cartercenter.org/health/guinea_worm/index.html
