Ostertagia		Contents		Rev 10/18/2025
		Classification		Biology and Ecology
		Morphology and Anatomy		Life Cycle
Return to Ostertagia Menu				Ecosystem Functions and Services
		Distribution		Management
Return to Haemonchidae Menu		Feeding		References
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Classification:

Chromadorea

Chromadoria

Rhabditida

  Rhabditina

   Trichostronglyloidea

    Haemonchidae

Ostertagiinae

Ostertagia Ransom, 1907

Type species of the genus: Ostertagia ostertagi (Stiles, 1892) Ransom, 1907

Note Teladorsagia considered indistinguishable from Ostertagia

Synonyms:

Strongylus ostertagi, Stiles, 1892

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Morphology and Anatomy:

Based on molecular analyses, Ostertagia and Orloffia are considered close but independent genera (Kuznetsov, 2011).

The genera Ostertagia and Teladorsagia are morphologically indistinguishable with species differentiation based on the structure of the spicules that usually have three distinct branches (Snyder et al., 2020)

• 	Female: Male: Spicules of O. ostertagi measure 220-230 um long and end in three bluntly hooked processes;  spicules of Teladorsagia circumcincta measure 280-320 um are slender and trifurcate with the third division of the spicule difficult to see microscopically (Snyder et al., 2020). Gubernaculum present between the spicules

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Distribution:

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Economic Importance:

Ostertagia ostertagi is the causal agent of ostertagiasis, one of the most important nematode parasitic diseasaes of young cattle.

The genus Ostertagia is a major cause of parasitic gastritis in abomasum of cattle in temperate areas of the world

 Species in domestic ruminants all occur in the abomasum. Teladorsagia species parasitize the abomasum of sheep and goats.

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Hosts:

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Feeding:

Food Sources and Feeding strategies for the genus Ostertagia

Many of the species are parasites of the abomasa and small intestine of ruminants.

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Life Cycle:

Life cycle direct, no intermediate host. From studies in cattle, it appears that young calves slowly develop an incomplete  immunity to O. ostertagi (Michel, 1963)

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Damage:

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Management:

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References:

Beveridge, I., Spratt, D.M., Durette-Desset, M-C. 2013. Order Strongylida (Railliet & Henry, 1913). Handbook Of Zoology Online. De Gruyter

Drozdz, J., 1995. Polymorphism in the Ostertagiinae Lopez Neyra, 1947 and Comments on the Systematics of These Nematodes, Syst. Parasitol., 1995, 32:91-99.

Kuznetsov, D.N. 2011. Taxonomic Revision of the Genus Ostertagia (Nematoda: Ostertagiinae) Based on an ITS2 rDNA Study. Biology Bulletin, 38:608-614. Original Russian Text: Kuznetsov, D.N. 2011, in Izvestiya Akademii Nauk, Seriya Biologicheskaya, 2011, 6: 710-16.

Michel JF. 1963. The phenomena of host resistance and the course of infection of Ostertagia ostertagi in calves. Parasitology. 1963;53(1-2):63-84. doi:10.1017/S0031182000072541

Ransom. B.H. 1907. Notes of Parasitic Nematodes, Including Descriptions of New Genera and Species and Observations on Life Histories. US Govwernment Printing Office 7pp.

Snyder, D.E., Marchiondo, A.A. Cruthers, L.R. 2020. Nematoda, Trichostrongyloidea. Chapter 2 in Marchiondo, Cruthers and Fourie (eds) Parasiticide Screening Vol 2. Academic Press.

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