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Haemonchus contortus

By Janelin Sendow

Geographic Range

Haemonchus contortus has been found in Asia (Indonesia, India), Netherlands, Europe (Russia, Italy), South America (Brazil), Africa, as well as in the United States. This parasite has adapted to conditions ranging from tropical areas to cold, mountainous regions. (Dorny, et al., 1996; Eckert and Hertzberg, 1994; Newton, 1995)

Habitat

Although this parasitic nematode has a great range, it is more prevalent in warm, moist regions rather than cold, dry ones. Haemonchus contortus inhabit the abomasum ("fourth stomach") of ruminent animals. H. contortus has been found in humans in Brazil and Australia. (Roberts and Janovy, 2000)

Physical Description

As a nematode, Haemunchus contortus is cylindrical, has a cuticle with three main outer layers made of collagen and other compounds. The outer layers are non-cellular and are secreted by the epidermis. The cuticle layer protects the nematodes so they can invade the digestive tracts of animals. The worms molt four times, the first two before hatching, and then before their adult stage.

Since it is a blood-sucker, Haemunchus contortus generally has a reddish appearance. The white ovaries that wind around the blood filled intestine, gives the nickname "barber pole", when referring to the females. While the females have a length ranging from 18-30 mm, the males are shorter, ranging from 10-20 mm. The male's distinct feature is its well-developed copulatory bursa, containing an asymmetrical dorsal lobe and y-shaped dorsal ray.

Nematodes have longitudinal muscles along the body wall. The muscles are obliquely arranged in bands. Dorsal, ventral and longitudinal nerve cords are connected to the main body of the muscle.

As a Secernentea, Haemonchus contortus has a specialized tubular excretory system with three canals. The canals are arranged to form an “H”. (Barnes, 1987; Mieczyslaw, 1955; Roberts and Janovy, 2000)

  • Sexual Dimorphism
  • female larger
  • sexes shaped differently
  • Range length
    10 to 30 mm
    0.39 to 1.18 in

Development

The female deposits 5000-10,000 eggs in the abomasum per day, which eventually will pass out with feces of the host. In the first stage, the juveniles hatch from the eggs. During the first and second juvenile stages, they will feed on bacteria in the manure. In the third juvenile stage, that the ruminant becomes infected when eating the parasite. Physical changes to the environment that are specific to a determinate host signals the worms to develop into the next stage. Prior to further development, exsheathment, which is sheddding of the cuticle, must take place in the host's gut. Haemonchus contortus exsheath when they are stimulated by high pCO2 and elevated temperatures in the host. After exsheathment, the worm will pass into the abomasum where it will burrow into the mucosa. Here, it will molt and in the fourth stage finds its way back to the lumen of the abomasum, feeds and undergoes a final molt before reaching adulthood. (Chappell, 1979; Fetterer and Rhoads, 1996; Roberts and Janovy, 2000; White and Newton, 2001)

Reproduction

Females may produce a phermomone to attract males. The male coils around a female with his curved area over the female genital pore. The gubernaculum, made of cuticle tissue, guides spicules which extend through the cloaca and anus. Males use spicules to hold the female during copulation. Nematode sperm are amoeboid-like and lack flagella. (Barnes, 1987; Roberts and Janovy, 2000)

  • Parental Investment
  • pre-fertilization
    • provisioning

Behavior

The behavior of parasitic nematodes has evolved to have certain adaptations. For instance, during its infective stage, the third juvenile stage, Haemonchus contortus will migrate onto grass blades to make it more optimal for host ingestion. While adapting to extreme temperatures and conditions, the juvenile parasite will prefer to lay eggs in the "adapted" conditions even when given less harsh conditions. Further, although moist environments are optimal for laying eggs, the juvenile will prefer to reproduce in dry conditions when given the option between the two. (Li, et al., 1999)

Communication and Perception

Nematodes within the Secernentea have phasmids, which are unicellular glands. Phasmids likely function as chemoreceptors. Females may produce pheromones to attract males.

Nematodes in general have papillae, setae and amphids as the main sense organs. Setae detect motion (mechanoreceptors), while amphids detect chemicals (chemoreceptors). (Roberts and Janovy, 2000)

Food Habits

During the first and second juvenile stages, Haemonchus contortus feeds on bacteria in manure. In the later stages, H. contortus parasitizes the abomasum, the "true stomach", in cattle, goats, other wild ruminants, but mainly sheep. In the abomasum, it will feed on blood using a single, dorsal tooth to cut into the host tissue.

Pharyngeal glands and intestinal epithelium produce digestive enzymes to feed on the hosts’ body fluids. Extracellular digestion begins within the lumen and is finished intracellularly. (Barnes, 1987; Fetterer and Rhoads, 1996; Newton and Munn, 1999; Roberts and Janovy, 2000)

  • Animal Foods
  • blood
  • body fluids
  • Other Foods
  • dung
  • microbes

Predation

These parasites are probably not preyed on directly, but are ingested from host to host. Larval mortality is high as most of the parasites do not reach appropriate hosts. (Barnes, 1987; Roberts and Janovy, 2000)

Ecosystem Roles

Haemonchus contortus inhabit the abomasum ("fourth stomach") of ruminent animals. H. contortus has been found in humans in Brazil and Australia.

Species Used as Host

Economic Importance for Humans: Negative

The major problem lies within the agricultural industry. These parasites cause great economic losses in domestic animals, specifically sheep, cattle and goat. Because Haemonchus contortus is a blood sucker, it can induce anemia and edema. Also, the hemolytic proteins that the parasite releases can lead to other intestinal disturbances. The host will often die with major infections.

Haemonchus contortus is known to adapt well to even harsh conditions, which makes it more difficult to eliminate this parasite. (Jacquiet, et al., 1998; White and Newton, 2001)

Conservation Status

Contributors

Renee Sherman Mulcrone (editor).

Janelin Sendow (author), University of Michigan-Ann Arbor, Teresa Friedrich (editor), University of Michigan-Ann Arbor.

Glossary

Australian

Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

World Map

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

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Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Neotropical

living in the southern part of the New World. In other words, Central and South America.

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Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

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agricultural

living in landscapes dominated by human agriculture.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

causes or carries domestic animal disease

either directly causes, or indirectly transmits, a disease to a domestic animal

chaparral

Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

chemical

uses smells or other chemicals to communicate

coprophage

an animal that mainly eats the dung of other animals

cosmopolitan

having a worldwide distribution. Found on all continents (except maybe Antarctica) and in all biogeographic provinces; or in all the major oceans (Atlantic, Indian, and Pacific.

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

internal fertilization

fertilization takes place within the female's body

marsh

marshes are wetland areas often dominated by grasses and reeds.

motile

having the capacity to move from one place to another.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

World Map

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

parasite

an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

sanguivore

an animal that mainly eats blood

scrub forest

scrub forests develop in areas that experience dry seasons.

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

suburban

living in residential areas on the outskirts of large cities or towns.

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

urban

living in cities and large towns, landscapes dominated by human structures and activity.

References

Barnes, R. 1987. Invertebrate Zoology. Orlando, Florida: Dryden Press.

Chappell, L. 1979. Physiology of Parasites. NY: John Wiley and Sons, Inc..

Dorny, P., A. Batubara, M. Iskander, V. Pandey. 1996. Helminth infections of sheep in North Sumatra, Indonesia. Veterinary Parasitology, 61: 353-358.

Eckert, J., H. Hertzberg. 1994. Parasite control in transhumant situations. Veterinary Parasitology, 54: 103-125.

Fetterer, R., M. Rhoads. 1996. The role of the sheath in resistance of Haemonchus contortus infective stage larvae to proteolytic digestion. Veterinary Parasitology, 64: 267-276.

Jacquiet, P., J. Cabaret, E. Thiam, D. Cheikh. 1998. Host range and the maintenance of Haemonchus spp. in an adverse, arid climate. International Journal for Parasitology, 28: 253-261.

Li, J., X. Zhu, R. Boston, F. Ashton, H. Gamble. 1999. "The neurobiology of host-finding behavior in animal parasitic nematodes: thermotaxis and thermosensory neurons in infective larvae of Haemonchus contortus, a passively ingested species" (On-line). Accessed 09/23/04 at http://www.nal.usda.gov/ttic/tektran/data/000010/82/0000108208.html.

Mieczyslaw, 1955. On the Infective Larvae of the 61 Nematodes of Sheep and their Identification. Warsaw:

Newton, S. 1995. Progress on vaccination of Haemonchus contortus . International Journal of Parasitology, 25: 1281-1289.

Newton, S., E. Munn. 1999. The development of vaccines against gastrointestinal nematode parasites, particularly Haemonchus contortus . Parasitology Today, 15: 116-123.

Roberts, L., J. Janovy. 2000. Foundations of Parasitology. US: The McGraw Hill Companies, Inc..

White, G., S. Newton. 2001. A single chain variable reason immunoglobin library from the abomasal lymph node of sheep infected with the gastrointestinal nematode parasite Haemonchus contortus . Veterinary Immunology and Immunopathology, 78: 117-129.

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