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Title: No loss of production due to larval challenge in sheep given continuous anthelmintic treatment via a controlled release capsule
Contributor(s): Kelly, Gareth A  (author); Walkden-Brown, Steve W  (author)orcid ; Kahn, Lewis  (author)orcid 
Publication Date: 2012
DOI: 10.1016/j.vetpar.2011.07.033
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Abstract: This study aimed to quantify production loss due to larval challenge in sheep administered a controlled release albendazole capsule (CRC) and thus determine the suitability of CRC treated sheep as a proxy for worm-free sheep in grazing experiments. The experiment used an incomplete 2 x 3 latin square design with 81 Merino wethers. Sheep were either infected (INF) with mixed oral infection of albendazole-susceptible 'Haemonchus contortus', 'Trichostrongylus colubriformis', and 'Teladorsagia circumcincta' (initial bolus then thrice weekly maintenance) or remained uninfected (UINF). Worm control treatments were with a CRC (CRCT), threshold treatment with a short-acting anthelmintic when worm egg count (WEC) exceeded 1500 epg (TT) or untreated (UT). The experiment was conducted in two 63-day periods (separated by a 14 day washout period) with infection treatments swapped between periods. A subset of animals was killed at the end of each period for worm counts and tissue sampling. Faecal worm egg count in UINF-UT reached 10,204 and 6078 epg at day 63 in periods 1 and 2, respectively, and remained 0 throughout in the CRT treatments. There was no difference in live weight gain or wool growth of INF-CRCT sheep (67 and 70 g/d) relative to UINF-CRCT (67 and 76 g/d). Live weight gain was significantly lower in INF-UT (27 g/d) and INF-TT (55 g/d) than UINF-UT (88 g/d) or UINF-TT (81 g/d) treatments. During the first infection period, greasy fleece weight growth was significantly lower in INF-UT (6.33 g/d) and INF-TT (6.37 g/d) than UINF-UT (7.80 g/d) or UINF-TT (7.32 g/d) treatments. The effects of infection on production persisted in INF-UT, but not INF-TT sheep for several weeks after termination of infection. Eosinophil counts were elevated in all infected groups and the antibody response to 'T. colubriformis' was greater in INF-CRCT and INF-TT groups compared to uninfected sheep. Together, these results indicate that larval challenge in sheep with a CRC is mildly immunogenic but is not associated with production loss. The results also showed that the CRC itself reduced live weight gain and that anthelmintic treatment at a WEC threshold of 1500 epg reduces production loss during infections and prevents persistence of adverse effects following infection.
Publication Type: Journal Article
Source of Publication: Veterinary Parasitology, 183(3-4), p. 274-283
Publisher: Elsevier BV
Place of Publication: Netherlands
ISSN: 1873-2550
Fields of Research (FoR) 2008: 070708 Veterinary Parasitology
070205 Animal Protection (Pests and Pathogens)
Fields of Research (FoR) 2020: 300909 Veterinary parasitology
300304 Animal protection (incl. pests and pathogens)
Socio-Economic Objective (SEO) 2008: 830311 Sheep - Wool
830310 Sheep - Meat
Socio-Economic Objective (SEO) 2020: 100413 Sheep for wool
100412 Sheep for meat
Peer Reviewed: Yes
HERDC Category Description: C1 Refereed Article in a Scholarly Journal
Appears in Collections:Journal Article
School of Environmental and Rural Science

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