Australian livestock are challenged by liver fluke (Fasciola hepatica) in grazing regions endemic to the intermediate snail host. Liver fluke infests a wide range of herbivores including free-roaming wildlife such as kangaroos (Macropods). The role played by Macropods in cross-species transmission and as vectors for anthelmintic resistance is largely unknown. In Phase 1 of this study, liver fluke of Eastern grey kangaroo (Macropus giganteus Shaw, 1790) origin (Kangaroo isolate) were artificially infected in sheep to confirm establishment and crossspecies transmission. In Phase 2, the efficacy of triclabendazole (TCBZ) was assessed in vivo against the Kangaroo isolate to identify any drug resistance. Forty (40) merino sheep were housed in pens and allocated to one of 4 groups (Groups 1–4). Groups 1 and 2 were artificially infected with a TCBZ resistant liver fluke isolate (Oberon) originating from sheep whilst Groups 3 and 4 were infected with the Kangaroo isolate (Phase 1). At 9 weeks post infection (wpi), sheep in Groups 2 and 4 were treated with 10 mg/kg TCBZ (Phase 2). Sheep were subsequently euthanased at 11 wpi to conduct total fluke counts (TFC) in the liver. Faecal samples were collected fortnightly to measure fluke egg counts and coproantigens. Individual blood samples were collected, concurrently with faecal sampling, to monitor haematocrit and plasma proteins levels. Liver fluke of kangaroo origin established to patent infections in sheep with similar establishment and pathogenicity to the Oberon isolate. TCBZ achieved an 86 % reduction in TFC (99.8 % - adult fluke, 0 % - immature fluke) in sheep with the Kangaroo isolate and a 28 % reduction in the Oberon isolate (37 % - adult, 0 % - immature fluke). An 89 % reduction in faecal coproantigens was observed in sheep with the Kangaroo isolate and no reduction in sheep with Oberon. This study confirmed cross-species transmission of liver fluke from a kangaroo to sheep. When cohabiting the livestock grazing environment, kangaroos may act as reservoirs for liver fluke and vectors for drug resistance within liver fluke endemic areas.

Liver fluke (Fasciola hepatica) is a parasite of herbivores including wildlife. Macropods, such as Eastern grey kangaroo (Macropus giganteus) and Common wallaroo (Osphranter robustus), are frequently observed sharing grazing sites with domestic livestock. The impact of Macropods, as reservoirs of infection, on livestock production and risks to cross-species transmission are largely unknown. In Phase 1 of this study, liver and faecal samples were collected from 245 Macropods (181 Eastern grey kangaroos, 64 Common wallaroos) cohabiting livestock farms (n = 7) in the Northern Tablelands regions of New South Wales. Total fluke (TFC) and fluke eggs (FEC) were counted in the liver and faeces, respectively, to assess prevalence. Faecal antigens were also measured using the commercial Bio-X Diagnostic Monoscreen AgELISA Fasciola hepatica kit (cELISA) to assess suitability as a diagnostic tool. In Phase 2, Macropod faecal samples were collected from 60 livestock farms to conduct FEC and assess prevalence by region. Liver fluke was prevalent in 22% of Eastern grey kangaroo and 20% of Common wallaroos with prevalence as high as 45% in the Eastern grey kangaroo. Fluke burdens ranged from 1 to 122 flukes (mean = 9 flukes) with a FEC range of 0–195 eggs per gram (epg) of faeces (mean = 18 epg). Evidence of dead and live flukes trapped within fibrotic capsules confirms the ability of Macropods to resolve infections. cELISA proved highly specific (100%) and sensitive (98%) in liver fluke detection however fibrotic capsules observed in the liver may reduce the correlation of coproantigens with fluke burden. Phase 2 revealed that 27% of livestock farms had Macropods infected with liver fluke. Overall, this study confirmed Eastern grey kangaroo and Common wallaroo are susceptible hosts and potential reservoirs for liver fluke and, monitoring infections in Macropods would assist in livestock disease management.

A survey of livestock producers (graziers) located in north eastern NSW Australia, collected information on perceptions and management practices for liver fluke control in livestock. The total area farmed by the 161 respondents was 195,600 ha (ranging in size from 4 to 10,522 ha) with cattle and sheep being the dominant livestock enterprises. Overall, 80% of graziers relied exclusively on anthelmintics for liver fluke control and few of these graziers (9%) integrated parasite management (IPM) strategies to reduce disease prevalence. Of those relying on anthelmintic control, triclabendazole (TCBZ) was preferentially chosen by 75% of graziers. Fifty five percent of these graziers used TCBZ in combination with oxfendazole (46%), ivermectin (5%) or abamectin (4%) whilst 45% used TCBZ as a single active ingredient. Thirty eight percent of graziers drenched livestock one or more times per year for liver fluke despite claiming they had no liver fluke or confirmed knowledge of infection. Fifty one percent of graziers based anthelmintic dose on the known weight of the heaviest animal in the herd whilst 43% visually guessed livestock bodyweight to calculate anthelmintic dose. Choice of anthelmintic was predominately based on perceived efficacy (45%) despite very few graziers (2%) having conducted post-treatment fluke egg counts. The majority of graziers (76%) were unsure if they had anthelmintic resistance, 21% claimed they had no resistance whilst 3% of graziers had confirmed resistance. Most graziers (97%) also reported farms were cohabited by kangaroos highlighting additional grazing pressures on-farm. This current survey has revealed that graziers rely on anthelmintics as their primary choice for liver fluke control. Reluctance to adopt IPM strategies and a continued heavy reliance on TCBZ, whilst basing anthelmintic decisions on perception rather than measurement and testing, pose threats for the future control of liver fluke in livestock within this endemic area.

Domestic livestock are highly susceptible to liver fluke (Fasciola hepatica) and suffer from the effects of fasciolosis in regions endemic to the intermediate snail host. Other definitive hosts include herbivorous wildlife such as macropods and cervids. These wildlife species are often observed grazing alongside livestock yet their potential impact on livestock production, as reservoirs of liver fluke infection, is largely unknown; including their role as vectors for anthelmintic resistance. The Northern Tablelands of NSW, Australia is a productive livestock region but is also a region where the liver fluke snail is endemic. For these reasons, this region was a suitable environment in which to investigate three main aspects of this thesis; (i) grazier perceptions and management practices for liver fluke control, (ii) liver fluke prevalence in macropods and Cervids, and (iii) cross-species transmission and vectors for anthelmintic resistance.

A survey of graziers was used to identify management practices for liver fluke in livestock, and for identifying farm sites for testing of macropod faeces for the presence of liver fluke. Graziers relied exclusively on anthelmintics for liver fluke control with few having adopted integrated parasite management (IPM) strategies to reduce disease prevalence. Macropods (eastern grey kangaroo and common wallaroo) and cervids (fallow deer; from routine pest or herd management programs) examined on graziers’ farms were identified with active or resolved infections, with prevalence of up to 45 % in both species across “high” risk farm sites. Gross pathology of the liver, attributed to liver flukes, correlated strongly with fluke burden and revealed the inherent ability of wildlife to resolve infections. Examination of macropods also provided the opportunity to assess the commercial BIOK201-2 Monoscreen AgELISA Fasciola hepatica (Bio-X Diagnostic, Belgium) as a diagnostic tool for use in macropods. This assay was a suitable test for the detection of liver fluke in macropods however gross pathology of the liver may influence sensitivity. Sheep subsequently infected with liver flukes originating from macropods confirmed cross-species transmission. The role they played as vectors for anthelmintic resistance remains inconclusive and warrants further investigation.

Overall, the research reported in this thesis has revealed that the low adoption of IPM practices by graziers for liver fluke in livestock could ultimately threaten future control within the region. Free-roaming wildlife cohabiting farms pose further challenges as macropods and cervids are able to harbour liver fluke and have the potential for cross-species transmission. Better adoption of IPM strategies including monitoring of wildlife for liver fluke and/or actively managing their ingress onto livestock grazing land will assist both the efficacy and sustainability of liver fluke control within this region.