Table 1.

Prevalence of and morbidity caused by major human helminth infections. DALYs are disability-adjusted life years.

disease	main etiologic helminth	number infected (million)	DALYs (million)	morbidity
soil-transmitted helminths
ascariasis	Ascaris lumbricoides	819 [8–9]	1.3 [5]	infections (due in part to size and number of worms) and intestinal blockages (potentially requiring surgery), growth stunting and effects on cognition [10–12].
hookworm	Necator americanus; Ancylostoma duodenale	439 [8–9]	1.7 [5]	anaemia which can cause complications during pregnancy and post-birth; growth stunting and effects on cognition [13–14].
trichuriasis	Trichuris trichiura	465 [8–9]	0.3 [5]	inflammatory foci and haemorrhaging, growth stunting and effects on cognition [15–17].
filarial nematodes
lymphatic filariasis	Wuchereria bancroft; Brugia malayi	120 [18]	1.2 [5]	lymphedema (elephantiasis), hydrocele, renal pathology manifesting as chyluria, and acute dermatolymphangioadenitis causing regular fevers.
onchocerciasis	Onchocerca volvulus	20 [19]	1.0 [5]	itching, skin inflammation and visual impairment or blindness
platyhelminth trematodes
schistosomiasis	Schistosoma haematobium, Schistosoma mansoni, Schistosoma japonicum	Over 250 [20]	1.9 [5]	acute infection: myalgia, abdominal pain in the right upper quadrant, diarrhoea, fatigue, malaise, fever, chronic infection: reactions against eggs trapped in host tissues lead to inflammatory and obstructive symptoms; the tissues and organs affected depend on the Schistosoma spp. schistosomiasis is also associated with undernutrition, exercise intolerance, diarrhoea (sometimes bloody), chronic pain and anaemia [20].