2. Gnathostoma spinigerum – This unfortunate little creature is an amalgamation of problems. At best, a person who becomes its host can look forward to swelling under the skin. But if it gets into your eye, brain, spinal cord, nerves, or liver, you could find yourself dealing with much worse problems, including paralysis, coma, and even death. Thankfully, as long as you avoid consuming certain raw meats, you should be fine.
1. Plasmodium falciparum – Now this one is quite the doozy. Plasmodium falciparum is noted for putting its hosts at risk of contracting malaria, which is the deadliest parasitic disease known to humankind, infecting more than 200 million people and killing 1 million of those infected every single year. There's not much witty or funny to say here – it is just a scary parasite!
Sources:
https://blogs.discovermagazine.com/bodyhorrors/2013/07/22/screwworm-myiasis/#.VmzfreIbClY – for New World screwworm
https://emedicine.medscape.com/article/229312-overview – for Strongyloide
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3752803/ – for Halicephalobus gingivalis
https://blogs.discovermagazine.com/bodyhorrors/2013/07/22/screwworm-myiasis/ – Cochliomyia hominivorax
https://www.cdc.gov/parasites/onchocerciasis/ – for Onchocerca volvulus
https://theconversation.com/five-deadly-parasites-that-have-crossed-the-globe-35944 – for Spirometra erinaceieuropae
https://www.cdc.gov/parasites/toxoplasmosis/gen_info/faqs.html – for Toxoplasma gondii
https://www.cartercenter.org/health/guinea_worm/index.html – for Guinea worm
https://www.parasitesinhumans.org/plasmodium-falciparum-malaria.html – for Plasmodium Falciparum
https://alltoptens.com/top-ten-incredibly-dangerous-parasites/ – Loa loa
https://www.cdc.gov/parasites/naegleria/ – Naegleria fowleri
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3194829/ – Trypanosoma cruzi
https://www.cdc.gov/parasites/taeniasis/ – Taenis solium
https://www.cdc.gov/parasites/clonorchis/faqs.html – Clonorchis sinensis
https://www.cdc.gov/parasites/gnathostoma/ – Gnathostoma spinigerum
https://www.who.int/mediacentre/factsheets/fs102/en/ – Filarial parasites
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2683991/ – Opisthorchis viverrini
https://www.cdc.gov/parasites/schistosomiasis/ – Schistosoma mansoni
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3063928/ – Fasciola gigantica
https://www.businessinsider.com/scariest-parasites-in-the-world-2012-6?op=1 – Candiru