Severity and prevalence of small lungworm infection on three South Australian farms and associations with sheep carcass characteristics

Jenny E Hanks; Angus J D Campbell; John W A Larsen

doi:10.1016/j.vetpar.2021.109503

Severity and prevalence of small lungworm infection on three South Australian farms and associations with sheep carcass characteristics

Vet Parasitol. 2021 Aug:296:109503. doi: 10.1016/j.vetpar.2021.109503. Epub 2021 Jun 24.

Authors

Jenny E Hanks¹, Angus J D Campbell², John W A Larsen³

Affiliations

¹ Mackinnon Project, Faculty of Veterinary and Agricultural Sciences, University of Melbourne, 250 Princes Highway, Werribee, Victoria, 3030, Australia. Electronic address: jenny.hanks@unimelb.edu.au.
² Nossal Institute for Global Health, Melbourne School of Population & Global Health, University of Melbourne, Level 5, 333 Exhibition St, Melbourne, Victoria, 3010, Australia.
³ Mackinnon Project, Faculty of Veterinary and Agricultural Sciences, University of Melbourne, 250 Princes Highway, Werribee, Victoria, 3030, Australia.

PMID: 34237518
DOI: 10.1016/j.vetpar.2021.109503

Abstract

This field and abattoir study assessed the association of the severity and prevalence of small lungworm lesions with the carcass characteristics of 1332 lambs and adult sheep bred on three farms in southeast SA. Liveweight and measures of lungworm infection were measured on farm, then lung lesions and carcass characteristics assessed at slaughter. The overall prevalence of small lungworm lesions at slaughter was 79 % (928/1177; 95 % CI 76, 81), with a prevalence of 87 % (569/658; 95 % CI 84, 89) in lambs, and 69 % (359/519; 95 % CI 65, 73) in adults, respectively. Small lungworm infected lambs and adults had a similar hot standard carcass weight and dressing percentage compared to non-infected animals, both overall and within their respective cohort. Overall, the mean carcass weight for non-infected and infected lambs was 23.4 kg (95 % CI 18, 29), and 23.6 kg (95 % CI 18, 29), respectively, with a mean difference of 0.2 kg (95 % CI -0.4, 0.8; P = 0.5). Mean carcass weight for non-infected and infected adults was 21.3 kg (95 % CI 15, 28), and 21.5 kg (95 % CI 15, 28), with a mean difference of 0.2 kg (95 % CI -0.5, 0.9; P = 0.5). This study confirmed a very high prevalence of small lungworm lesions in sheep bred on farms in this region of SA, but their hot standard carcass weights were not reduced by these lesions. Additional information to compare the presence of lesions with productivity within an individual was collected at slaughter which provided more detailed information than is currently collected by routine abattoir surveillance. The limitations of the currently available diagnostic tests for small lungworm were also demonstrated. This indicated a need for the development of more sensitive tests to assess lungworm infections both on farm and at the abattoir. Currently, farmers in this region are concerned about the very high prevalence of small lungworm in their sheep, but this study provides reassurance that the presence of mild lesions does not reduce production.

Keywords: Age; Carcass characteristics; Prevalence; Sheep; Small lungworm.

MeSH terms

Animals
Body Composition
Farms / statistics & numerical data
Prevalence
Sheep
Sheep Diseases* / epidemiology
Sheep Diseases* / parasitology
Sheep Diseases* / pathology
South Australia / epidemiology
Strongylida
Strongylida Infections* / epidemiology
Strongylida Infections* / parasitology
Strongylida Infections* / pathology
Strongylida Infections* / veterinary