Obviously, the ‘unholy trinity’ mentioned in the title of this essay is a play on words. However, when I make the connection between the so-called ‘unholy trinity’ and the geohelminths, any parasitologist would know the three parasites to which I refer. These would include Ascaris lumbricoides, Trichuris trichiura, and the hookworms. Generally, the two species of human hookworms, Ancylostoma duodenale and Necator americanus, are lumped together and considered as one, mainly because their biology is so similar, and because the disease they cause is so nearly the same. While their geographic distributions are essentially sympatric in today's world, A. duodenale probably had an Asian origin. Charles Wardell Stiles of the U.S. Bureau of Animal Industry in Beltsville, Maryland, first described Necator americanus in 1906, but its origins are not of the New World. It most likely evolved in Africa and was imported into the western hemisphere, along with malaria, yellow fever, schistosomiasis, and several other diseases, during the slave trade.

Estimates regarding the numbers of people infected with the ‘unholy trinity’ vary, but all would agree that these parasites, collectively, have perhaps the greatest impact on DALYs (Disability-Adjusted Life Years) on a worldwide basis when it comes to the helminth parasites.