A Review: Haemonchus contortus Infection in Pasture-Based Sheep Production Systems, with a Focus on the Pathogenesis of Anaemia and Changes in Haematological Parameters
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Department of Veterinary Clinical Sciences, Jockey Club College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Kowloon Tong, Hong Kong, China
2
CityU Veterinary Diagnostic Laboratory Co., Ltd., City University of Hong Kong, Kowloon Tong, Hong Kong, China
*
Author to whom correspondence should be addressed.
Animals 2022, 12(10), 1238; https://doi.org/10.3390/ani12101238
Submission received: 16 February 2022
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Revised: 21 March 2022
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Accepted: 9 May 2022
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Published: 11 May 2022
(This article belongs to the Special Issue Anaemia Associated Disorders in Sheep)
Simple Summary
Infection with Haemonchus contortus parasites (haemonchosis) is an important cause of anaemia in sheep. Haemonchosis is a global problem, although sheep that are kept in warm, high rainfall environments are at the greatest risk of infection due to the favourable conditions for H. contortus survival. Following ingestion, the parasites develop in the abomasum of sheep. Various factors such as age, breed, health, nutritional status, and larval challenge influence the severity of clinical disease. Hyperacute, acute, and chronic haemonchosis are reviewed, focusing on the pathophysiology of haemonchosis, associated clinical signs, and haematological and biochemical findings.
Abstract
Haemonchosis is an important cause of anaemia in sheep worldwide, particularly those that are kept in pasture-based systems in warm, high rainfall environments. Potential outcomes vary based on the severity of infection and the sheep’s immune response, however, in some sheep infection can lead to death. The consequences of Haemonchus contortus infection mean that it has been well-studied in a range of different farming systems. However, to our knowledge, there has not been a recent review focused on the pathophysiology of anaemia caused by haemonchosis. Thus, this review provides an in-depth discussion of the literature related to the pathophysiology of haemonchosis and associated clinical signs for hyperacute, acute, and chronic haemonchosis. Additionally, haematological and biochemical findings are presented, and various diagnostic methods are assessed.
Keywords:
parasite; barbers pole; small ruminant; nematode; gastrointestinal parasite; worm
