Haemonchus
contortus
Haemonchus contortus, also known as the
barber's pole worm, is a very common
parasite and one of the most pathogenic
nematodes of ruminants. Adult worms
attach to abomasal mucosa and feed on
the blood. This parasite is responsible for
anemia, oedema, and death of infected
sheep and goats, mainly during summer in
warm, humid climates.[1]
Haemonchus contortus
These 11 Haemonchus contortus adult females
were taken from one sheep infected with a
single strain of this worm species.
Haemonchus contortus egg
Scientific classification
Kingdom: Animalia
Phylum: Nematoda
Class: Secernentea
Subclass: Rhabditia
Order: Strongylida
Family: Trichostrongylidae
Genus: Haemonchus
Species: H. contortus
Binomial name
Haemonchus contortus
(Rudolphi, 1803) Cobb, 1898
Females may lay over 10,000 eggs a day,[2]
which pass from the host animal in the
faeces. After hatching from their eggs, H.
contortus larvae molt several times,
resulting in an L3 form that is infectious for
the animals. The host ingests these larvae
when grazing. The L4 larvae, formed after
another molt, and adult worms suck blood
in the abomasum of the animal, potentially
giving rise to anaemia and oedema, which
eventually can lead to death.[3]
The infection, called haemonchosis,
causes large economic losses for farmers
around the world, especially for those
living in warmer climates. Anthelminthics
are used to prevent and treat these, and
other, worm infections, but resistance of
the parasites against these chemicals is
growing. Some breeds, such as the West
African Dwarf goat and N'Dama cattle, are
more resistant than other breeds to H.
contortus (haemonchotolerance).[4]
Morphology
The ova is yellowish in color. The egg is
about 70–85 μm long by 44 μm wide, and
the early stages of cleavage contain
between 16 and 32 cells. The adult female
is 18–30 mm long and is easily recognized
by its trademark "barber pole" coloration.
The red and white appearance is because
H. contortus is a blood feeder, and the
white ovaries can be seen coiled around
the blood-filled intestine. The male adult
worm is much smaller at 10–20 mm long,
and displays the distinct feature of a well-
developed copulatory bursa, containing an
asymmetrical dorsal lobe and a Y-shaped
dorsal ray.
Life cycle
The adult female worm can release
between 5,000 and 10,000 eggs, which are
passed out in the feces. Eggs then develop
in moist conditions in the feces and
continue to develop into the L1
(rhabditiform), and L2 juvenile stages by
feeding on bacteria in the dung. The L1
stage usually occurs within four to six
days under the optimal conditions of 24–
29 °C. The L2 rhabditform sheds its cuticle
and then develops into the L3 filiariform
infective larvae. The L3 form has a
protective cuticle, but under dry, hot
conditions, survival is reduced. Sheep,
goats, and other ruminants become
infected when they graze and ingest the L3
infective larvae. The infective larvae pass
through the first three stomach chambers
to reach the abomasum. There, the L3
shed their cuticles and burrow into the
internal layer of the abomasum, where they
develop into L4, usually within 48 hours, or
preadult larvae. The L4 larvae then molt
and develop into the L5 adult form. The
male and female adults mate and live in
the abomasum, where they feed on blood.
Genetics
The H. contortus draft genome was
published in 2013.[5] Further work to
complete the reference genome is
underway at the Wellcome Trust Sanger
Institute[6] in collaboration with the
University of Calgary, the University of
Glasgow, and the Moredun Research
Institute. Developing genetic and genomic
resources for this parasite will facilitate
the identification of the genetic changes
conferring anthelmintic resistance and
may help design new drugs or vaccines to
combat disease and improve animal
health.
Pathogenicity
Clinical signs are largely due to blood loss.
Sudden death may be the only observation
in acute infection, while other common
clinical signs include pallor, anemia,
oedema, ill thrift, lethargy, and depression.
The accumulation of fluid in the
submandibular tissue, a phenomenon
commonly called "bottle jaw", may be
seen. Growth and production are
significantly reduced.
Prevention and treatment
Prophylactic anthelmintic treatment
necessary to prevent infection in endemic
regions, but wherever possible, a reduction
on reliance on chemical treatment is
warranted given the rapid rise of
anthelmintic resistance. A commercial
vaccine known as Barbervax in Australia or
Wirevax in South Africa has become
available in recent years. This works
mainly by reducing egg output and hence
pasture contamination. The vaccine
contains proteins from the lining of the
intestines of the Barber's Pole worm. The
animal produces antibodies against the
protein which circulate in the blood. When
the Barber's pole worm drinks the blood
the antibodies attach to its stomach lining,
preventing digestion and starving the
animal. Following this, the worm produces
fewer eggs and eventually dies off. [7]
Targeted selective treatment methods
such as the FAMACHA method may be
valuable in reducing the number of dosing
intervals, thus reducing the percentage of
surviving parasites that are resistant to
anthelmintics. Faecal egg counts are used
to track parasite infestation levels,
individual animals' susceptibility, and
anthelmintic effectiveness.
Other management strategies include
selective breeding for more parasite-
resistant sheep or goats (e.g. by culling
the most susceptible animals or by
introducing parasite-resistant breeds such
as Gulf Coast Native sheep); careful
pasture management, such as managed
intensive rotational grazing, especially
during peak parasite season; and
"cleaning" infested pastures by haying,
tilling, or grazing with a nonsusceptible
species (e.g. swine or poultry).[8]
Recent research has also shown that the
use of hair sheep breeds, such as
Katahdins, Dorpers, and St. Croix, can be
chosen for resistance to internal parasites
for economical standards; additionally, the
hair breeds provide resistance without
showing any significant effect growth
performance of their progeny.[9]
One of the riskiest methods that can be
used for treatments is the use copper of
oxide wire particles (COWP) to aid in the
destruction of the parasites inside the gut
without the use of chemicals. However, in
sheep, the dosing would need to be
monitored extremely closely because if
they are administered too high of a dose,
then they will slip into copper toxicity. For
the COWP, the lowest recommended dose
would need to be administered to remain
safe for sheep. The study conducted
found that treatment with the COWP
reduced faecal egg counts by >85%.
Treatment with the copper oxide wire
particles could lead to less reliance on
anthelmintics because the COWP allows
for the reduction in establishment of
parasitic infections, especially if the
producer is trying to reduce the larval
population on their pastures.[10]
Recent research shows fugal lectins are
able to inhibit larval development. These
fungal lectins are Corprinopsis cinerea
lectins - CCL2, CGL2; Aleuria aurantia lectin
- AAL; and Marasmius oreades agglutinin -
MOA. These four toxic lectins bind to
specific glycan structures found in H.
controtus. Some of these glycan structures
might represent antigens which are not
exposed to host immune system, and thus
have potential for vaccine or drug
development.[11]
References
1. Burke, Joan, Research Animal
Scientist. Management of Barber pole
Worm in Sheep and Goats in the
Southern U.S. USDA, ARS, Dale
Bumpers Small Farms Research
Center, Booneville, AR. >
2. Barber's pole worm (Haemonchus
contortus) at Australian Wool Limited.
3. "Haemonchus, Ostertagia, and
Trichostrongylus spp" . The Merck
Veterinary Manual. 2006. Retrieved
2007-07-01.
4. Chiejina, Samuel N; Behnke, Jerzy M;
Fakae, Barineme B (2015).
"Haemonchotolerance in West African
Dwarf goats: Contribution to
sustainable, anthelmintics-free
helminth control in traditionally
managed Nigerian dwarf goats" .
Parasite. 22: 7.
doi:10.1051/parasite/2015006 .
PMC 4321401 . PMID 25744655 .
5. Laing, Roz; Kikuchi, Taisei; Martinelli,
Axel; Tsai, Isheng J; Beech, Robin N;
Redman, Elizabeth; Holroyd, Nancy;
Bartley, David J; Beasley, Helen;
Britton, Collette; Curran, David;
Devaney, Eileen; Gilabert, Aude; Hunt,
Martin; Jackson, Frank; Johnston,
Stephanie L; Kryukov, Ivan; Li, Keyu;
Morrison, Alison A; Reid, Adam J;
Sargison, Neil; Saunders, Gary I;
Wasmuth, James D; Wolstenholme,
Adrian; Berriman, Matthew; Gilleard,
John S; Cotton, James A (2013). "The
genome and transcriptome of
Haemonchus contortus, a key model
parasite for drug and vaccine
discovery" . Genome Biology. 14 (8):
R88. doi:10.1186/gb-2013-14-8-r88 .
PMC 4054779 . PMID 23985316 .
6. https://www.sanger.ac.uk/resources/d
ownloads/helminths/haemonchus-
contortus.html
7. "Haemonchus contortus" . Moredun
research institute. Moredun. Retrieved
16 February 2019.
8. Anderson, Samuel. "Summary of
Results: New England Small Ruminant
Producer Survey." Northeast IPM
Center, 2013.
http://www.northeastipm.org/neipm/a
ssets/File/New-England-Small-
Ruminant-Survey-Results-2013.pdf
9. Tadesse, D; Puchala, R; Gipson, T. A;
Portugal, I; Sahlu, T; Dawson, L. J;
Goetsch, A. L (2017). "692 Effects of
high heat load conditions on rectal
temperature, panting score, and
respiration rate of hair sheep breeds
from different regions of the United
States". Journal of Animal Science. 95:
337–8.
doi:10.2527/asasann.2017.692 .
10. Soli, F; Terrill, T.H; Shaik, S.A; Getz,
W.R; Miller, J.E; Vanguru, M; Burke, J.M
(2010). "Efficacy of copper oxide wire
particles against gastrointestinal
nematodes in sheep and goats".
Veterinary Parasitology. 168 (1–2):
93–6.
doi:10.1016/j.vetpar.2009.10.004 .
PMID 19931291 .
11. Heim, Christian; Hertzberg, Hubertus;
Butschi, Alex; Bleuler-Martinez, Silvia;
Aebi, Markus; Deplazes, Peter; Künzler,
Markus; Štefanić, Saša (2015).
"Inhibition of Haemonchus contortus
larval development by fungal lectins" .
Parasites & Vectors. 8: 425.
doi:10.1186/s13071-015-1032-x .
PMC 4539729 . PMID 26283415 .
Further reading
Newton, S (1995). "Progress on
vaccination of Haemonchus contortus".
International Journal for Parasitology. 25
(11): 1281–1289. doi:10.1016/0020-
7519(95)00065-a .
Roberts, L., J. Janovy. 2000.
Foundations of Parasitology. US: The
McGraw Hill Companies, Inc..
Fetterer, R.; Rhoads, M. (1996). "The role
of the sheath in resistance of
Haemonchus contortus infective stage
larvae to proteolytic digestion" .
Veterinary Parasitology. 64 (4): 267–276.
doi:10.1016/0304-4017(95)00926-4 .
Dorny, P.; Batubara, A.; Iskander, M.;
Pandey, V. (1996). "Helminth infections
of sheep in North Sumatra, Indonesia".
Veterinary Parasitology. 61 (3–4): 353–
358. doi:10.1016/0304-4017(95)00826-
8.
Retrieved from
"https://en.wikipedia.org/w/index.php?
title=Haemonchus_contortus&oldid=924004812"
Last edited 20 days ago by Uziel302
Content is available under CC BY-SA 3.0 unless
otherwise noted.
