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

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.

The effect of pasture molluscicide on small lungworm infections and the productivity of grazing lambs.

The aim of this study was to assess the effect of pasture molluscicide treatment on the prevalence and severity of small lungworm infections, and the productivity of lambs grazing improved pastures in southeastern Australia. A randomised control field trial of 260 Merino-cross lambs was conducted on a commercially managed farm in South Australia with a history of high small lungworm prevalence. Separate groups of lambs rotationally grazed irrigated lucerne paddocks treated with iron chelate molluscicide or untreated control paddocks. Lambs were monitored every 2-6 weeks from weaning until slaughter with liveweight, lungworm and gastrointestinal nematode infection status measured. At slaughter indicators of small lungworm infection via inspection and carcass characteristics were assessed. The density of the intermediate host snail and lucerne pasture availability were also measured. There was a higher population of adult Prietocella barbara molluscs in the Control paddocks compared to the Treatment paddocks after molluscicide had been applied and prior to grazing commencing (206 vs. 14 snails/m2, respectively; P = 0.03; 95 % CI 8, 528). However, the overall mollusc density was similar between Control and Treatment. The prevalence of small lungworm infections was quite low during the trial (0-13 %), in both Control and Treatment lambs, except at day 94 when 48 % of 28 Control lambs were positive compared to none of 27 Treatment lambs (P < 0.001; 95 % CI 30, 66). A similar proportion of Treatment and Control lambs had evidence of small lungworm infection lesions at slaughter (both 67.8 %). Control lambs grew slightly faster than Treatment lambs, with an average daily gain of 202 (± 3 SEM) g/head/day for Control and 190 (± 4 SEM) for Treatment (P < 0.001) during the 112-day trial. Despite historic evidence of very high prevalence of lungworm infection in this region of southeastern Australia, iron chelate molluscicide treatment prior to lambs grazing the pasture had no demonstrable effect on the prevalence and severity of small lungworm infections, nor the productivity of lambs grazing these pastures. This study indicates that for a commercial sheep farm, additional molluscicide treatments of pastures after they are established, for the prevention of small lungworm infection, may not be warranted. Furthermore, requirements for more precisely monitoring snails are discussed.

Using longitudinal syndromic surveillance to describe small ruminant health in village production systems in Myanmar.

A novel syndromic surveillance approach was used to describe small ruminant health in Myanmar, to help overcome limitations in disease diagnosis common in many parts of the world, especially in low and middle income countries (LMICs). Observations were made from July 2015 to June 2016 of ten clinical syndromes in 12 goat herds and sheep flocks owned by smallholders in the Central Dry Zone. Strengths and weaknesses to using syndromic surveillance in a village setting were identified using a formal surveillance evaluation framework, 'SERVAL'. Larger reporting teams made disproportionately more reports than smaller ones (86% compared to 14% of all reports, with a reporting rate ratio of 4.3 95% CI 3.5-5.4), which may have affected surveillance sensitivity. The benefits of the syndromic surveillance included its relatively low cost and ability to produce quantitative disease estimates that could be used to prioritise further disease investigation and extension activities. In particular, significant mortality was observed, with monthly mortality of 3.0% (95% CI 2.5-3.7%) and 0.28% (0.15-0.53%) in young and adult animals, respectively, and a population attributable fraction of mortality for young animals of 82% (68-91%). Mortality was associated with ill-thrift in young animals but had not previously been considered an important production-limiting condition in Myanmar. This information contributes to an understanding of the prevalence of excessive mortality in smallholder goat and sheep production systems. It is a practical example of the use of syndromic surveillance in a LMIC livestock production system, the results of which can direct future disease research, treatment and prevention to improve the health and productivity of small ruminants in Myanmar.