Effects of adult and larval Haemonchus contortus on abomasal secretion

Simpson, H.V.; Lawton, D.E.B.; Simcock, David C.; Reynolds, Gordon; Pomroy, W.E.

doi:10.1016/s0020-7519(97)00037-4

Cited by 42 publications

(24 citation statements)

References 31 publications

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“…The pits are expanded and there are fewer parietal cells and chief cells, however, more mucous neck cells (MNCs) and undifferentiated cells [172]. Similar generalized histological changes are observed after adult T. circumcincta [168; 173] or H. contortus transfer [174] even though there are no damaged glands where larvae have grown. There may be an association between the pathology, histopathology and inflammatory responses to the nematode presence, especially through the parietal cell loss and inhibition.…”

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confidence: 75%

“…The magnitude of the increased plasma pepsinogen levels in ovine gastrointestinal trichostrongyles, including Ostertagia leptospicularis and O. circumcincta varies between animals, from approximately zero [166; 174; 182; 187; 189] to remarkable increase in immune animals, even with small worm burdens [190]. After transfer of adult H. contortus [174], Ostertagia ostertagi [165], or T. circumcincta [164; 166; 168; 188], abomasal pH, serum gastrin and pepsinogen concentrations increase within the first day. These effects on abomasal secretion are proposed to be initiated by abomasal parasite chemicals [164; 166; 167; 168], but later also to include the host response.…”

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confidence: 99%

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Haemonchus Contortus and Ovine Host: A Retrospective Review.

Ashram¹,

Nasr²,

Mehmood³

et al. 2017

IJAR

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Gastrointestinal (GI) parasitic infections are a world-wide problem for both small-and large-scale farmers. Infection by GI parasites in ruminants, including sheep and goat can result in harsh economic losses in a variety of ways: reproductive inefficiency, decreased work capacity, involuntary culling, diminished food intake, poor animal growth rates and lower weight gains, treatment and management costs, and mortality in heavily parasitized animals. Among the GI parasites that cause losses to the farming industry, the barber"s pole worm Haemonchus contortus is the predominant, blood-sucking, highly pathogenic, and economically important nematode that infects small ruminants. Here, we review the historical and recent literature on the ovine-parasite-environment interaction for H. contortus to bring avenues where advances in the understanding of these interactions is an indispensible to develop a cost effective control strategies as potential options for the haemonchosis control in sheep and the proper management of sheep in various production systems.

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confidence: 75%

mentioning

confidence: 99%

Haemonchus Contortus and Ovine Host: A Retrospective Review.

Ashram¹,

Nasr²,

Mehmood³

et al. 2017

IJAR

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“…The presence of T. circumcincta in the abomasum causes the pH to increase with an associated reduction in establishment of H. contortus, while removal of infection restores normal establishment. 7 Barger 15 observed this phenomenon in the field and Simpson et al 16 demonstrated that H. contortus was also capable of causing an elevation in abomasum pH. These findings suggest that two processes cause reduction in establishment of H. contortus larvae: one due to physiological changes in the abomasum and the other due to acquired immunity.…”

Section: Introductionmentioning

confidence: 94%

A multi‐species model to assess the effect of refugia on worm control and anthelmintic resistance in sheep grazing systems

et al. 2011

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1A multi-species model to assess the impact of refugia on worm control and anthelmintic resistance in sheep grazing systems. RJ ObjectiveDevelop a computer simulation model that uses daily meteorological data and farm management practices to predict populations of Trichostrongylus colubriformis, Haemonchus contortus and Teladorsagia (Ostertagia) circumcincta and the evolution of anthelmintic resistance within a sheep flock. Use the model to explore if increased refugia, provided by leaving some adult sheep untreated, would delay development of anthelmintic resistance without compromising nematode control. ProceduresCompare model predictions with field observations from a breeding flock in Armidale, NSW. Simulate the impact of leaving 1-10% of adult sheep untreated in diverse sheep grazing systems. ResultsPredicted populations of T. colubriformis and T. circumcincta were less than those observed in the field. Attributed to nutritional stress experienced by sheep during drought, and not accounted for by the model. Observed variation in faecal egg count explained by the model (R 2 ) for these species was 40-50%. H. contortus populations and R 2 were both low.Leaving some sheep untreated worked best in situations where animals were already grazing or were moved on to pastures with low populations of infective larvae. In these cases anthelmintic resistance was delayed and nematode control was maintained when 1-4% of adult stock remained untreated. ConclusionsIn general, the model predicted that leaving more than 4% of adults untreated did not sufficiently delay the development of anthelmintic resistance to justify the increased 2 production risk from such a strategy. The choice of a drug rotation strategy had an equal or larger impact on nematode control, and selection for resistance, than leaving 1-10% of adults untreated. The multi-species model described here allows for these phenomena and estimates host mortalities and inappetence based on the total worm populations. To determine the utility of the model, worm populations were monitored in flocks of breeding ewes and weaners that were managed under typical grazing systems in north-eastern Australia. Daily meteorological and management records were kept so that worm populations could be predicted using the multispecies model. Keywords 3In this simulation study, the model was used to: a) estimate the consequences of leaving a proportion of adult stock untreated (as a source of refugia) on the development of anthelmintic resistance and effectiveness of parasite control; b) determine how best to use a new anthelmintic class (amino-acetonitrile derivatives (AAD), represented by monepantel; Zolvix ® , Novartis Animal Health Inc., Switzerland) to control gastro-intestinal nematodes while minimising selection for drug resistance; and c) examine these issues in four environments to determine if there are common principles that can be applied and/or how they need to be modified to suit local environments. The aim was to fully explore the interaction between the fundamen...

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“…H. contortus is known to produce calcium and a clotting factor binding substance known as calreticulin (Suchitra & Joshi, 2005), enabling the parasite to feed easily on host blood and in so doing, cause haemorrhagic lesions. Studies of field parasitism and experimental larval infestations have also identified the morphological and physiological effects of abomasal nematodes: nodule development, mucous cell hyperplasia, superficial epithelial damage, reduced acid secretion and increased serum gastrin and pepsinogen concentrations (Simpson, 1997;Scott et al, 1999). When both internal and external conditions are favourable, the pre-patent period for H. contortus in sheep is between two and three weeks.…”

Section: Factors Affecting H Contortus Populations Intrinsic Factorsmentioning

confidence: 99%

Trends and challenges in the effective and sustainable control ofHaemonchus contortusinfection in sheep. Review

2007

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Summary :Haemonchosis, with its very wide distribution, has become a very important production constraint in sheep farms in tropical, subtropical and temperate regions worldwide. Various intrinsic and extrinsic factors determine the survival of Haemonchus contortus and hence the development of the disease in the animal. In general, control of gastrointestinal nematode infestation in sheep relies heavily on anthelmintic treatments. However, the indiscriminate use of these drugs has led to the widespread emergence of drug resistant strains of parasites, that has necessitated the development and use of various parasite control methods such as grazing management, biological agents and vaccines and the selection of resistant breeds of animals, with or without moderate use of anthelmintics. The ultimate goal of such control programs is to enhance productivity, while minimising risks regarding drug resistance and consumer and environmental concerns. This review attempts to highlight the different methods employed in the control of haemonchosis in sheep and the practical limitations associated with both control programs and the internal and external factors associated with the parasite and its microenvironment. Résumé : MOYENS DE LUTTE CONTRE HAEMONCHUS CONTORTUS

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Effects of adult and larval Haemonchus contortus on abomasal secretion

Cited by 42 publications

References 31 publications

Haemonchus Contortus and Ovine Host: A Retrospective Review.

Haemonchus Contortus and Ovine Host: A Retrospective Review.

A multi‐species model to assess the effect of refugia on worm control and anthelmintic resistance in sheep grazing systems

Trends and challenges in the effective and sustainable control ofHaemonchus contortusinfection in sheep. Review

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