The long and intimate association between humans and parasites through time

While the interaction between humans and their parasites is well studied today, taking a long view of infection throughout human evolution helps to place the current picture in context and identify trends in infection over time. After considering how early technologies may have facilitated the transmission of parasites to humans, we examine the association between humans and parasites through time using archaeological and genetic evidence. Techniques such as microscopy, immunoenzymatic assays and DNA analysis have identified a range of protozoa, helminths and ectoparasites in our ancestors. Evidence is discussed for the origins and impact upon societies through time for protozoa causing malaria, leishmaniasis, Chagas' Disease and diarrhoeal illnesses, helminths such as schistosomiasis, soil-transmitted helminths, <i>Taenia</i> tapeworms, fish tapeworms and liver flukes, and ectoparasites such as fleas, body lice and pubic lice. Prevalence studies show widespread infection for some parasites, such as 36% with falciparum malaria in ancient Egypt, and 40% with Chagas disease in prehistoric Peru and northern Chile. Humans have been responsible for the inadvertent spread of a range of parasites around the world, ranging from African heirloom parasites with early human migrations to the introduction of malaria and schistosomiasis to the Americas with the transatlantic slave trade in the 1600s-1800s. It is clear that the epidemics due to bacterial pathogens spread by ectoparasites since the Bronze Age must have had major impacts upon past societies, particularly for bubonic plague and epidemic typhus.