Caroline Jacobson

Over the past 25 years, significant progress has been made in understanding and managing equine gastrointestinal parasites in the Asia-Pacific region, particularly in Australia and New Zealand. This review synthesises current knowledge of the epidemiology, diagnostic methods, anthelmintic resistance (AR), and control strategies for major equine intestinal parasites, including cyathostomins, Parascaris spp., Anoplocephala perfoliata, and Strongyloides westeri. Recent studies highlight substantial regional variation in parasite prevalence, egg shedding and cyathostomin population composition, shaped by diverse climatic conditions. Of increasing concern is the emergence of resistance to commonly used anthelmintics which is now evident in both Parascaris and cyathostomins, although data for S. westeri and A. perfoliata remain limited. High-throughput molecular diagnostics, such as next-generation sequencing, have advanced species-level characterisation in Australia and Thailand. ELISA-based tests for A. perfoliata and encysted cyathostomins are promising but remain unvalidated and underutilised regionally. The routine use of combination anthelmintics, including benzimidazoles, praziquantel, pyrimidines, and macrocyclic lactones, may accelerate resistance across nematode and cestode populations, emphasising the need for regular efficacy monitoring and improved antiparasitic stewardship. Findings from recent research on horse parasites in Australia have informed the development of country's first national equine parasite control guidelines which recommend targeted or selective treatment strategies. However, the effectiveness of these strategies requires ongoing evaluation, particularly in year-round grazing systems in tropical and subtropical regions. Sustainable parasite control will depend on the integration of non-chemical strategies along with the use of anthelmintics and the establishment of a national parasite surveillance database. This review highlights the need for climate-specific treatment protocols, strengthened collaborative research infrastructure, and continued investment in innovative diagnostic and control methods to preserve equine health and anthelmintic efficacy across the region.

Managing breeding ewe mortality is a priority for the Australian sheep industry. The periparturient period carries the highest risk of mortality, but the incidence and causes in Merino ewes are not well characterised. Here, we outline the reported incidence of annual and periparturient mortality for Australian Merino ewes, causes and risk factors for ewe mortality and current recommendations for managing periparturient ewes and gaps in the literature. The mean incidence of periparturient mortality reported in Merino ewes ranges from 0.3% to 11.4%. However, there are challenges with reporting mortality figures in extensive production systems due to the nature of record keeping and farm characteristics. Studies reporting causes of periparturient mortality indicate that these are typically multifactorial, with metabolic disease and dystocia likely to be important. Identifying potential mitigation strategies has the potential to improve productivity, profitability and welfare on Australian farms.

Over the past few decades, the emergence of resistance amongst intestinal parasites of horses to all available anthelmintic classes has emphasised the need for a paradigm shift in parasite control approaches within the Australian equine industry. Findings of a recent Australia-wide research project have provided new insights into intestinal parasites (i.e. strongyles and ascarids) and parasite control from the perspectives of Australian horse breeders and equine veterinarians. The published data have revealed recent trends in parasite prevalence and distribution, breeders' and veterinarians' attitudes and perspectives on controlling horse internal parasites, the efficacy of commonly used anthelmintic products and post-treatment egg reappearance periods. These studies have formed the basis of newly developed guidelines managing and treating gastrointestinal nematodes in horses. Tailored for equine veterinarians, these guidelines contain information on target parasites and risk factors for their transmission, as well as practical advice for surveillance, anthelmintic choice, timing of treatment, testing for anthelmintic resistance and managing refugia. The Australian Guidelines for Equine Internal Parasite Management (AGEIPM) will serve as a pocket companion for equine veterinarians, providing best-practice recommendations grounded in locally conducted scientific research. Dissemination and extension of the AGEIPM to industry will strengthen the client-practitioner relationship. The aim is to reduce reliance on blanket deworming in equine parasite management programs and help curb the progression of resistance to the limited anthelmintic classes available for treating horses.

Over the past 20 years, a lower percentage of veterinary and animal science students entering Australian and New Zealand schools have a background or ongoing contact with livestock production systems. The increasing use of digital technologies over the same time provides a practical option to introduce students to the seasonal operations on livestock farms. This article describes the development of the 4D Virtual Farm, established to showcase 11 representative livestock farms across Australasia allowing students to virtually travel through seasons and place over each farming enterprise. Students can virtually visit different beef cattle, prime lamb, wool-sheep and dairy cattle farms, and a piggery. Any electronic device connected to the web including mobile phones, tablets, computers, and virtual reality headsets can be used to view the enterprises. For educators, the virtual farm can be used for a range of teaching and learning scenarios, such as demonstration of a particular production system via weblink for lectures or embedding within learning management systems. It also allows students to start at a particular point in time and space and guide themselves to other areas for self-learning or for a range of assessment tasks. This site provides an example that could be used in other teaching areas including abattoirs, exotic diseases, surgery, communication, and many other veterinary examples.

Background
The level and cause of ewe mortality over the peri-parturient period is poorly understood in Australia. The purpose of this study was to determine the frequency of peri-parturient ewe mortality and investigate the causes of death in commercial, non-Merino ewes over the peri-parturient period.

Methods
An observational study involving 50 commercial, non-Merino farms across southern Australia during two lambing seasons was conducted. The study population was the breeding flock of ewes on each farm. Ewes were monitored by farmers from the time they were first placed in their lambing paddocks before lambing, up until lamb marking (the lambing period). The project required no change to normal practice. Veterinarians conducted postmortem (PM) examinations at three time points on each farm over the lambing period. A standard PM protocol was followed by all participating veterinarians.

Results
The mean peri-parturient mortality over the lambing period was 2.5% in Year 1 and 2.0% in Year 2, with no significant difference between years. Factors that increased the risk of peri-parturient ewe mortality included ewe age (>5 years old) and litter size (triplet-bearing ewes). The most common causes of ewe death according to farmers was dystocia and unknown causes. The three most common diagnoses on veterinary PM examination were dystocia, septicaemia and trauma.

Conclusions
This study reveals the relative importance of each cause of ewe mortality over the peri-parturient period. Risk reduction could include identification and management of older ewes (aged above 5 years or older) and ewes carrying twins or triplets.

This study assessed worm control practices used by Australian Thoroughbred farm managers with an online questionnaire survey. The questionnaire comprised 52 questions (close-ended: 44; open-ended: 8) about farm demography and general husbandry practices, farm managers’ knowledge of gastrointestinal nematodes (GIN) and their importance, diagnosis, worm control strategies and anthelmintics, anthelmintic resistance (AR) and grazing management. Following the pilot survey, the link for the questionnaire survey was sent to all (n = 657) registered members of the Thoroughbred Breeders Australia on 12th April 2020. The response rate for the questionnaire was 18.5% (122 of 675). The farm managers reported a good understanding of GIN and their importance in different age groups of horses as most respondents (70% of 122) perceived worm-related illness to be more important in young (i.e., foals, weanlings and yearlings) than adult (> 3 years old) horses. Although most respondents (93%, 113 of 122) used anthelmintics prophylactically to control GIN, only 15% (18 of 122) observed worm-related illness in their horses. Just under 40% of respondents were performing faecal egg counts, with less than 20% using the results of faecal egg counts to guide deworming decisions. The interval-based deworming strategy was the most common method (≥55% of 122 respondents) to control GIN in all age groups of horses. Macrocyclic lactones were the first choice of anthelmintics for all age groups of horses. Although the majority of respondents (88%, 107 of 122) perceived resistance in GIN against commonly used anthelmintics as an important issue in managing worms in horses, only 29% assessed the efficacy of anthelmintics and 91% (111 of 122) were unaware of AR on their properties. Grazing management practices, such as manure removal, were more frequently performed on smaller paddocks (<0.20 ha: 58%) than on larger paddocks (>0.20 ha: 18%). Multiple correspondence analyses showed that the likelihood of suboptimal worm control practices on small farms (n = ≤50 horses) was greater than that of medium (n = 51–100) and large (n = >100) farms. This study provides insights into the demography of Thoroughbred farms in Australia, husbandry practices used by stud managers and their knowledge about worms, control options and AR concerns, thereby paving the way for taking any initiatives to address the problem of AR in GIN of Australian Thoroughbred horses.

This chapter addresses the nutritional, husbandry and disease processes which affect ewes and their foetuses in the time from early pregnancy to parturition and through early lactation. Nutrition of the ewe through pregnancy has a major effect on her health, her ability to deliver robust and healthy lambs and her ability to bond with, protect and nourish her lambs in the neonatal period. It also has major effects on the survival rate of the lambs in the neonatal period. Some of the most common clinical diseases which affect ewes during pregnancy are pregnancy toxaemia and hypocalcaemia, and these conditions are most effectively prevented by flock management strategies. There are numerous infectious agents which can cause abortion in ewes. Many of these agents can also cause stillbirths and the birth of lambs of low birthweight and poor viability. The normal behaviours of ewes and lambs at parturition are described. Factors which interfere with the development of a strong bond between ewes and lambs, and factors which reduce the intake of sufficient nutrients by lambs soon after birth, have a major effect on the probability of lamb survival in the first few days of life. Perinatal mortality in lambs is one of the most important causes of economic loss to the Australian sheep industry. Veterinary investigations of perinatal mortality can identify the steps that need to be taken to reduce perinatal mortality on sheep farms. Adequate nutrition of the lactating ewe is essential to achieve satisfactory health and growth in their lambs. The most important disease condition of the lactating ewe is mastitis.

The study presents the results of a cross-sectional survey to describe the epidemiology of ascarid and strongylid nematodes in horses, the impact of diverse climatic conditions on parasite diversity and the levels of faecal egg shedding in different age groups of managed Thoroughbred horses. Individual faecal samples (n = 1377) collected from 62 Thoroughbred farms across four climatic zones in Australia were analysed using the modified McMaster technique for faecal egg counts (FECs) and strongylid nematodes were identified utilising PCR-directed next-generation sequencing (NGS) of the second internal transcribed spacer of the nuclear ribosomal DNA (ITS-2). Across all age groups, the prevalence of ascarid and strongylid nematodes was 12% (95% confidence interval 10–14%) and 72% (70–74%), respectively. Based on strongylid FECs, yearlings had the highest prevalence (89%) followed by weanlings (83%), foals (79%), wet mares (61%), dry mares (59%) and stallions (54%). However, for Parascaris spp., foals had the highest prevalence (46%) followed by weanlings (32%) and yearlings (13%). The highest mean FECs for Parascaris spp. were observed in foals (418 eggs per gram [EPG] of faeces) while those for strongylids were in yearlings (1002 EPG). Of the adult horses (mares and stallions), 67% (489 of 729) and 11% (77 of 729) were low (i.e., ≤250 EPG) and moderate (i.e., 251–500 EPG) strongylid egg-shedders, respectively. Strongylid egg shedding varied across climatic zones, with the highest mean FECs in the summer rainfall (723 EPG) followed by non-seasonal rainfall (629 EPG), winter rainfall (613 EPG), and Mediterranean (606 EPG) rainfall zones. Twenty-three nematode species were detected using NGS, with Cylicostephanus longibursatus (28%), Cylicocyclus nassatus (23%) and Coronocyclus coronatus (23%), being the most abundant species. Three species of Strongylus (i.e., S. vulgaris, S. equinus and S. edentatus) were also detected. The nemabiome composition, species richness and relative abundance varied within horse age and between climatic zones. These empirical findings provide a comprehensive understanding of the prevalence of parasites within horse populations and the multifaceted factors that influence their occurrence, thereby allowing for the formulation of tailored strategies aimed at parasite control in domestic horses.

This study aimed to assess Australian veterinarians’ knowledge, perceptions and treatment strategies for worm control in horses with an online questionnaire. The questionnaire comprised 64 questions covering various aspects of: (i) veterinary practice; (ii) the veterinarian’s knowledge of gastrointestinal nematodes (GINs) and the importance of parasites in different age groups of horses; (iii) the diagnosis and control of worms; (iv) anthelmintics and anthelmintic resistance (AR); (v) grazing management; and (vi) the means of communication and the discussion between veterinarians and their clients regarding worm control. Following a pilot survey, a link for the questionnaire survey was sent to all ( n = 1,148) registered members of Equine Veterinarians Australia in April 2020. The response rate for the questionnaire was 10% (118 of 1,148). The findings of this study illustrate veterinarians’ good understanding of aspects of equine parasites, including control. However, respondents mainly recommended frequent, interval-based prophylactic deworming in young horses, and only 40% (96 of 239) diagnosed GIN infections based on faecal egg count (FEC) results in all age groups of horses. Furthermore, only 27% (88 of 330) of the respondents made deworming decisions based on FECs. Most of the respondents recommended macrocyclic lactones (MLs) for all age groups of horses (71%, 481 of 677), and the most frequently used method to calculate the dose of anthelmintics was by estimating the weight of animals visually (53%, 63 of 118). Although the majority of respondents (97%, 115 of 118) perceived AR to be a critical issue in managing worms in horses, 58% (67 of 118) of them were unaware of the status of AR on their clients’ properties. Forty-two percent (50 of 118) of the respondents perceived the presence of AR in worms, including pinworms (16%), strongylins (15%), species of Draschia and Habronema (6%), Strongyloides westeri (2%) and tapeworms (1%). Twenty-seven percent (32 of 118) of the respondents rarely discussed equine worm control practices with their clients. This study provides insights into the perception and worm control practices recommended by Australian veterinarians to manage equine parasites. The findings highlight the importance of continued education and awareness of AR, and the use of non-chemical methods as well as consideration of the legislation of prescription-only use of anthelmintics based on FECs to achieve sustainable control of GINs in Australian horses.

This study reports the spatial and temporal distribution of ascarid and strongylid nematodes in Thoroughbred horses by age category across different climatic zones in Australia over an 18-month period. Faecal samples ( = 2046) from individual horses were analysed using the modified McMaster technique for faecal egg counts (FECs). Strongylids were identified using PCR-directed next-generation sequencing of the second internal transcribed spacer (ITS-2) of the nuclear ribosomal DNA. Yearlings had the highest prevalence (82%) of strongyle eggs followed by weanlings (79%), foals (58%), wet mares (49%) and dry mares (46%). For Parascaris spp., foals had the highest prevalence (35%) followed by weanlings (21%) and yearlings (10%). The highest mean FECs for Parascaris spp. were observed in foals (525 eggs per gram [EPG] of faeces) while those for strongyles were in yearlings (962 EPG). Among horses that were classified as adults at the time of sampling, 77% (860 of 1119) of mares were low (i.e., <250 EPG) strongyle egg-shedders. Mean strongyle FEC counts were highest in the Mediterranean (818 EPG) followed by summer (599 EPG), winter (442 EPG), and non-seasonal (413 EPG) rainfall zones. Twenty-six nematode species were detected, with Cylicostephanus longibursatus (26.5%), Cylicocyclus nassatus (23.7%) and Coronocyclus coronatus (20.5%) being the most frequently detected species. Their richness and relative abundance varied with horse age, season and climatic zone. In addition, Strongylus equinus and Triodontophorus spp. (T. brevicauda and T. serratus) were also detected. This comprehensive study elucidates spatial (climatic zone) and temporal (i.e., seasonal) trends in prevalence and burdens of intestinal nematodes in Australian horses using non-invasive conventional and molecular methods. The information presented in this study is crucial for developing integrated management strategies to control horse parasites in farmed horses.