Distribution
Paleartic, Neartic, Oriental, Ethiopian, Neotropical, Australian.
Sheep are the primary host of H.
contortus while cattle are the primary
hosts of H. placei..
Economic Importance:
Parasitic gastroenteritis caused by
Haemonchus spp.
is a major cause of economic losses in the livestock industry.
It impairs weight gain and increases mortality in cattle and small ruminants,
especially in tropical and subtropical areas.
Many reports of
H. contortus, particularly in cattle might
actually represent misidentification of H.
placei because of difficulties in species
identification.
Hosts:
Haemonchus contortus is primarily considered a parasite of domestic
sheep, Ovis aries, but also infects other domestic and wild
ruminants.
Feeding
Haemonchus contortus cuts into host stomach tissues with a single
dorsal tooth. It feeds on the released blood, fluids and cell contents. The nematode secretes an anti-coagulant
to promote accesswibility of host blood..
Life Cycle:
The eggs hatch after being expelled in the feces of the host.
The first larvae hatch 14-17 hours after being passed through the feces and then go through a lethargic state for 8-10 hours. This is the first
molting period.
The first three juvenile stages of the organism are "free-living". The second
larval stage is reached 40 hours later and in 3-5 days the organism becomes
infective.
When the infective stage is reached, the nematode moves onto the foliage of
plants where it is ingested by grazing vertebrates.
Females are larger than males and have a higher metabolic rate.
Damage:
Haemonchus
contortus cuts into host stomach tissues with a single
dorsal tooth. It feeds on the released blood, fluids and cell contents.
The nematode secretes an anti-coagulant.
Parasitic gastroenteritis
caused by Haemonchus spp.
is a major cause of economic losses in the livestock industry.
Management:
De-worming lambs.
The prophylaxis of parasitic gastroenteritis relies
heavily on anthelmintic treatments. However, their frequent use has led to the
appearance of resistant parasite populations, which have been jeopardizing the
livestock industry worldwide.
Proper identification of the various species, as well as
knowledge regarding the epidemiology of parasitic gastroenteritis, is essential
for the establishment of sustainable strategies of parasite control. Until
recently, it was difficult to distinguish between H. placei and
H. contortus, because of their similar morphology.
References:
Chopra, A.K. 1982.Observations on non-specific phosphomonoesterases in relation to glycogen content in three nematodes in sheep.
pp.191-193.Springar-Garwhal, eds. Journal of Comparative Physiology and Ecology.8:3.
Croll, N.A. 1976.The organization of Nematodes. Academic Press, London, New York, San Francisco.
Gibbons, L. 1986. SEM Guide to the morphology of Nematode parasites of
vertebrates. CAB International, United Kingdom.P.191.
Lee, D.L. 1976.Physiology of Nematodes. MaCMillan Press. Columbia University.
Talamini do Amaranti, A.F. 2011. Why is it important to
correctly identify Haemonchus species? Rev. Bras. Parasit. Vet. 20:263-268
Wertjuk, M. 1964. On the infective larvae of the gastointestinal nematodes of sheep, and their identification.pp.361-404. Journal of Parasitology.2:19.
Plus material from Rebecca E. Line, 1995.
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