Haemonchus contortus females look like a barber’s pole because their white ovaries spiral around their intestine and they consume so much host blood that their intestine appears red. Males are shorter and also feed on blood. Since heavy infections with H. contortus can involve thousands of worms in a single host (1), the amount of blood the worms consume can cause the host to become anaemic and in some cases die of blood loss (1). Furthermore, each adult female can spew thousands of eggs per day (2), leading to heavy pasture contamination and rapid spread through herds of susceptible hosts (1). Possible hosts include sheep, goats, cows, and other small ruminants (1,2).
H. contortus is globally distributed in tropical and temperate areas and can even survive winter conditions by suspending development within its host until spring (1). The worms have a one-host lifecycle, where eggs on pasture develop through two larval stages to become infective third stage larvae. When eaten by a host, the larvae continue developing in the abomasum (the fourth and final stomach compartment in grazing animals) to adulthood, where they mate and lay their eggs, which get passed with the feces (3).
Parasite Comics Team:
Dr. Chenhua Li (Lead, Ideas), Dr. Þórey Jónsdóttir (Illustrator, Ideas), Stephen Pollo (Writer, Researcher), Yuanzhe Wang (Digital Consultant).