page_title: Conservation biology of parasites
section_title: Deliberate extermination
hierarchical_section_title: Conservation biology of parasites / Deliberate extermination
caption_attribution_description: English: Dracunculus medinensis larvae. Parasite.
context_page_description: A large proportion of living species on Earth live a parasitic way of life. Parasites have traditionally been seen as targets of eradication efforts, and they have often been overlooked in conservation efforts. In the case of parasites living in the wild – and thus harmless to humans and domesticated animals – this view is changing.
context_section_description: Naturally, medical and veterinary sciences have attempted to exterminate parasites and pathogens living in humans and in domesticated animals. In the case of a few highly host-specific pathogens, this means the extinction of the entire pathogen species. Throughout human history, however, only two species, the smallpox virus and the rinderpest virus, have been wholly eradicated. The last reported cases of smallpox occurred 1978, while the last confirmed case of rinderpest was reported in 2001. However, secure samples of the smallpox virus are known to exist in the United States and Russia, purportedly for defensive purposes such as developing new vaccines, antiviral drugs, as well as for diagnostic tests. It is not known, but is speculated that these countries may have shared their samples with some of their allies during the Cold War. Stocks of the rinderpest virus are also maintained by some secure laboratories.
  Two other diseases are currently the subjects of global eradication programs: poliovirus and Dracunculus medinensis, the guinea worm. The 175 diagnosed wild polio virus (WPV) cases worldwide in 2019 represented the highest number of cases since 2014, but still a 76% reduction from the 719 diagnosed cases in 2000 and a 99.95% reduction from the estimated 350,000 cases when the eradication effort began in 1988. Of the three strains of polio virus, the last recorded wild case caused by type 2 (WPV2) was in 1999, and WPV2 was declared eradicated in 2015. Type 3 (WPV3) is last known to have caused polio in 2012, and was declared eradicated in 2019. All wild-virus cases since that date have been due to type 1 (WPV1). Three countries remain where the disease is still classified as endemic—Afghanistan, Pakistan and Nigeria. The guinea worm, once widespread across some 20 nations of Africa and Asia, today survives only in four of the countries of Sub-Saharan Africa, with only a few hundred known cases of infection in 2011. Prevalent civil wars in the region, such as the War in Darfur, by preventing safe access to medical aid, have resulted in the survival of this species up to the present.
caption: Larvae of the guinea worm: one of the species targeted for eradication.
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