<P> Helminths may cause iron - deficiency anemia . This is most severe in heavy hookworm infections , as Necator americanus and Ancylostoma duodenale feed directly on the blood of their hosts . Although the daily consumption of an individual worm ( 0.02 -- 0.07 ml and 0.14 -- 0.26 ml respectively ) is small , the collective consumption under heavy infection can be clinically significantly . Intestinal whipworm may also cause anemia . Anemia has also been associated with reduced stamina for physical labor , a decline in the ability to learn new information , and apathy , irritability , and fatigue . A study of the effect of deworming and iron supplementation in 47 students from the Democratic Republic of the Congo found that the intervention improved cognitive function . Another study found that in 159 Jamaican schoolchildren , deworming led to better auditory short - term memory and scanning and retrieval of long - term memory over a period of nine - weeks . </P>
which of the following helmiths feeds on blood
Necator americanus Ancylostoma duodenale