Epidemiology of gastrointestinal nematode parasitism in a commercial sheep flock and its implications for control programmes

Abstract

The epidemiology of nematode infections in a UK commercial crossbred sheep flock was studied from January 2004 to January 2005. The ewes were treated orally with moxidectin when they were turned out of the lambing shed on to nematode-contaminated pasture, and the lambs were treated orally with ivermectin throughout the summer in accordance with the farm's usual practice, with the aim of near-suppressive nematode control. The lactating ewes experienced a significant increase in faecal egg count during the early summer, after the period of persistence of the moxidectin treatment had ended. The ewes' and lambs' egg outputs were dominated by Teladorsagia species, despite the persistence of the effect of moxidectin against this genus. The gimmers (primiparous two-year-old ewes) had a significantly greater faecal egg count at lambing than the three- to four-year-old ewes, but the older ewes had significantly greater post-treatment increases. The population of Trichostrongylus species appeared to follow accepted epidemiological patterns, with no evidence of summer trichostrongylosis. In late summer and autumn the faecal egg output of the ewes was primarily due to large intestinal nematodes.

Expression of sheep interleukin 23 (IL23A, alpha subunit p19) in two distinct gastrointestinal diseases

“…Higher demand for meat and diminishing pasture lands has led farmers to increase their stocking density (Taylor, 2012) Mediterranean and sub-tropical and tropical regions while T. circumcincta is found in cool, temperate areas (Craig et al, 2006;Larsen and Anderson, 2009;Taylor, 2012;Wilson et al, 2008). Adult T. colubriformis reside in the small intestine while H. contortus and T. circumcincta are both found in the abomasum.…”

“…However, morbidity is high and the associated pathology results in significant production losses in meat, milk and wool (Taylor et al, 2007;Urquhart, 1996). Continuous reinfection with ubiquitous GI nematode parasites and their high rate of establishment can reduce weight gain b up to 50% (Sargison, 2008).…”

“…T. circumcincta is a ubiquitous, persistent parasite that is responsible for seasonal outbreaks of parasitic gastroenteritis in weaned lambs (Gruner et al, 1994;Urquhart, 1996;Sargison, 2008). The pathogenesis and associated clinical effects of T. circumcincta are attributed largely to the host immunologic response to clear infection (Houdijk et al, 2003;Jackson et al, 2009;Kyriazakis and Houdijk, 2006).…”

“…These changes result in reduced or no production of digestive enzymes and leakage of macromolecules and proteins across the damaged mucosa resulting in hypoproteinemia, hypoalbuminemia and increased plasma pepsinogen (Lawton et al, 1996;Simpson et al, 2009). The disease is characterised by anorexia, intermittent diarrhoea, dehydration and weakness which may lead to emaciation and death if left untreated (Aitken, 2007;Kyriazakis et al, 1998;Stear et al, 2003;Sargison et al, 2008).…”

Use of fluorescent lectin binding to distinguish Teladorsagia circumcincta and Haemonchus contortus eggs, third-stage larvae and adult worms

“…Adult worms can be readily identified, but collecting them requires euthanasia of the host. Morphological features cannot be used to distinguish eggs of all species parasitising sheep (Wilson et al 2008;Bailey et al 2009) and cattle (Waghorn et al 2006); therefore, eggs are hatched in culture and the larvae are examined. Routine identification of third-stage infective larvae (L3) is based on either morphological features or size (Lancaster and Hong 1987;McMurtry et al 2000;van Wyk et al 2004): Haemonchus contortus can be identified by a long, whiplike tail, whereas Teladorsagia circumcincta and Trichostrongylus colubriformis are distinguished by length, the ranges of which can overlap for the two species (Lancaster and Hong 1987).…”