Smallpox and Dracunculiasis: The Scientific Value of Infectious Diseases That Have Been Eradicated or Targeted for Eradication. Is Schistosomiasis Next?

Scientists and clinicians studying a particular disease have an ideal goal that, if achieved, would be paradoxical: finding the disease cure and thereby putting themselves out of work. 2015 marks the 35th year since the cure for smallpox eradicated this human scourge. Before a vaccine was developed, infection with smallpox virus occurred in over 10 million people per year around the world, with a death rate greater than 30% [1]. The World Health Organization’s (WHO’s) intensive eradication program against smallpox began in 1967 and was maintained for over ten years. The last known case of smallpox was recorded in Somalia in 1977, and WHO declared the global eradication of smallpox a success in 1980. Vaccinia virus (VACV), like smallpox a member of the Poxviridae family, was used to produce the vaccine that led to smallpox eradication. Today, VACV remains a critical research tool and serves as the laboratory model for poxvirus. VACV is currently used for the production of 2ndand 3rd-generation smallpox vaccines as well as for the exploration of immuno-oncolytic therapies against melanoma and other cancers [2,3]. VACV and its derivatives, including modified vaccinia virus (MVA) and New York attenuated vaccinia virus (NYVAC), are used as vectors by which to induce immunity to pathogens including HIV, Plasmodium falciparum, andMycobacterium tuberculosis [4,5]. VACV also continues to be an important tool for examining fundamental viral mechanisms of immune evasion, including viral immunomodulation and inhibition of cell apoptosis, and has aided investigators in characterizing the innate and adaptive host immune response to viral infection [6]. Therefore, despite the eradication of human disease caused by smallpox virus, basic and applied research using the model vaccinia virus continues to guide our understanding of host immune responses, antigen immunogenicity, viral manipulation of host defenses, and vaccine efficacy. A second infectious pathogen that is targeted for eradication is Dracunculus medinensis, or guinea worm, the nematode parasite that causes drancunculiasis. D.medinensis is contracted by drinking larvae-contaminated water. The parasite matures to an adult worm in the host gut and emerges painfully months later through the skin of the lower extremities. Through efforts of the World Health Assembly (as part of WHO), the Carter Center, and other organizations, dracunculiasis is nearing worldwide eradication. In the 1980s, 20 endemic countries accounted for 3.5 million cases of dracunculiasis; by 2014, only 126 cases were reported in four countires: