Haemonchus contortus

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Ecology

Haemonchus contortus is an animal endoparasite infecting ruminants worldwide also known as red stomach worm, wire worm or Barber's pole worm, is very common parasite and one the most pathogenic nematodes of ruminants. Adult worms are attached to abomasal mucosa and feed on the blood.

H. contortus is a member of the superfamily Trichostrongyloidea (Strongylida) which contains most of the economically important parasitic nematodes of grazing livestock. These parasites cost the global livestock industry billions of dollars per annum in lost production and drug costs. Resistance to all the major anthelmintic classes is now common worldwide often leading to failure of treatment and control. H. contortus is a close relative of the human hookworm species and belongs to the nearest phylogenetic group of parasites to the free-living model nematode Caenorhabditis elegans. This makes it an important model of parasitic nematode biology that is commonly used for experimental studies. They are dioecious with single females typically producing several thousand eggs per day which pass out of the host in faeces and develop to infective larvae on the pasture.

Eggs develop in moist conditions in the feces and continue to develop into the L1(rhabditiform), and L-2 juvenile stages by feeding on bacteria in the manure. The L-1 stage usually occurs within 4–6 days under the optimal conditions of 24–29 °C. The L-2 rhabditform sheds its cuticle and then develops into the L-3 filiariform infective larvae. The L-3 have a protective cuticle, however under dry hot conditions will not survive long. The L-3 then crawl up the blades of wet grass and wait to be ingested by a grazing animal. Sheep, goats and other ruminants become infected when they graze and eat grasses containing the L3 infecting larvae. The infecting larvae pass through the first three stomachs to reach the abomasum. There the L-3 sheds its cuticle and burrows into the internal layer of the abomasum where they develop into L-4, usually within 48 hours, or pre-adult larvae. The L-4 larvae then molts and develops into the L-5 adult form. The male and female adults mate and live in the abomasum, where they feed upon the blood.


Genome Details

Sex Determination: gonochoristic

Haploid No. chromosomes: 6 (5 autosomes, XO)

Genomics

The current assembly shown at WormBase is from August 2009 and provided by a collaboration of the Wellcome Trust Sanger Institute and the University of Calgary. It is a combination of capillary and 454 sequence reads assembled into a draft 59707 supercontigs of a total size of 297 975 349 bp. The experimentally determined genome size is ~60 million bp. In addition RNAseq reads were used to determine the structures of 6201 genes using the EnsEMBL pipeline. A first analysis found that for ~50% of them ortholog C.elegans genes could be determined.

WormBase Ressources

  • DNA and protein sequences
  • GFF3 annotation
    • homology
    • protein domains
    • ortholog C.elegans genes

External Ressources