Robert Woodgate

Geometric means provide a biased efficacy result when conducting a faecal egg count reduction test (FECRT)

The process of conducting a faecal egg count reduction test was simulated to examine whether arithmetic or geometric means offer the best estimate of efficacy in a situation where the true efficacy is known. Two components of sample variation were simulated: selecting hosts from the general population which was modelled by the negative binomial distribution (NBD), and taking an aliquot of faeces from the selected host to estimate the worm egg count by assuming a Poisson distribution of sample counts. Geometric mean counts were determined by adding a constant (C) to each count prior to log transformation, C was set at 25, 12 or 1. Ten thousand Monte Carlo simulations were run to estimate mean efficacy, the 2.5% (lower) and the 97.5% (upper) percentile based on arithmetic or geometric means. Arithmetic means best estimated efficacy for all different levels of worm aggregation. For moderate levels of aggregation and with C=1 the geometric mean substantially overestimated efficacy. The bias was reduced if C was increased to 25 but the results were no better than those based on arithmetic means. For very high levels of aggregation (over-dispersed populations) the geometric mean underestimated efficacy regardless of the size of C. It is recommended that the guidelines on anthelmintic resistance be revised to advocate the use of arithmetic means to estimate efficacy.

Sustainable use of anthelmintics in an Integrated Parasite Management Program for sheep nematodes

Anthelmintic resistance is a major problem affecting sheep nematode control; however, chemical treatments will always be a likely routine part of any parasite control program. The present paper, with the aim of minimising the selection pressure for worsening anthelmintic resistance, outlines important practical and strategic aspects of planning the anthelmintic component of an integrated approach to sheep worm management.

Integrated parasite management: Products for adoption by the Australian sheep industry

The increasing cost of production loss caused by gastrointestinal nematodes (GIN) highlights the importance of good control programs. However, the endemic nature of anthelmintic resistance also reminds of the need for nonchemical options. Both chemical and nonchemical control options need to be integrated into regional parasite management programs (IPM) with the emphasis on component options determined by factors such as major GIN species, regional climate, property size and enterprise structure. The Integrated Parasite Management of Sheep project was established to develop and demonstrate regional parasite control programs, that integrated chemical and nonchemical options, for the main sheep-producing regions of Australia. The project included research about the ecology of the main endo and ecto-parasites of sheep and a national survey of parasite control practices by sheep producers. IPM approaches developed for two contrasting regions of Australia are discussed. Barriers for the adoption of IPM programs include perceived complexity associated with a multi-component approach, time requirements and difficulty. Facilitating the industry adoption of IPM programs is discussed with relevance to the use of small group extension and involvement of the commercial sector. Perceptions of complexity of IPM may be managed by facilitating adoption of components in a step-wise process such that learning outcomes accumulate over time. Extension efforts must address the needs of industry sectors other than sheep producers and explore user pay approaches. The success of these approaches will depend on the relation of the extra profit to producers, through adoption of IPM programs, with remuneration sufficient to attract a commercial service.

The efficacy of ivermectin, pyrantel and fenbendazole against Parascaris equorum infection in foals on farms in Australia

This study was performed to estimate the prevalence of patent Parascaris equorum infections and determine the efficacy of ivermectin, pyrantel and fenbendazole against P. equorum infection in foals on farms in southern Australia. Foals aged >3 months on five farms in the south-western slopes region of New South Wales were used. Faeces were collected from each foal and foals with a P. equorum faecal egg count (FEC) of >100 eggs per gram (EPG) were used to measure anthelmintic efficacy using the FEC reduction (FECR) test, after random allocation to a control group or an ivermectin, pyrantel embonate or fenbendazole treatment group. Treatment was administered on day 0 and faeces were collected on day 14 and a FEC was performed. For determination of anthelmintic efficacy, FECRs and lower 95% confidence intervals (LCL) were calculated using previously described methods, based on individual or group FECRs. P. equorum populations were considered susceptible when FECR was >90% and LCL >90%, suspected resistant when FECR was FECR was 80-90% and LCL <90% and resistant when FECR was <80% and LCL <90%. A Poisson distribution quality control method was applied to the data to remove suspected erroneous FECR results. Prevalence of patent P. equorum infection was 58.3% (147/252 foals) and 89 foals on 5 farms were included in the FECR study. Resistance of P. equorum to ≥ 1 anthelmintic was present on all five farms prior to and on four farms after application of the quality control method. Two farms had evidence of multiple drug resistance. Ivermectin was effective and ineffective on two and three farms, respectively. Fenbendazole was effective on two farms, equivocal on one farm and ineffective on one farm. Pyrantel embonate was effective on three farms and ineffective on one farm. These data indicate that anthelmintic-resistant P. equorum populations are present on farms in Australia and multiple drug resistance may occur on individual farms.

Comparison of molecular and McMaster microscopy techniques to confirm the presence of naturally acquired strongylid nematode infections in sheep.

Patent strongylid nematode infections were identified using McMaster worm egg counts (WEC) and PCR assays (ITS-2 nuclear ribosomal DNA) to screen genomic DNA extracted directly from lamb faecal samples. Lambs from four different farms in southern Western Australia were sampled rectally on two separate occasions, with McMaster WECs and PCRs conducted on a total of 858 samples. Negative controls (n=96) (WEC <50 eggs per gram [epg]) and positive controls (n=96) (faecal samples spiked with a 100 μL suspension of third-stage larvae (L(3)) containing approximately equal proportions of Teladorsagia circumcincta, Trichostrongylus colubriformis, Haemonchus contortus, Oesophagostomum spp. and Chabertia ovina) were generated. All control samples amplified in accordance with positive controls. High levels of agreement (Kappa values ≥ 0.93) were identified between the two diagnostic tests. PCRs detected an additional 2.0% of samples as strongylid-positive but there was no significant difference in the number of strongylid-positive samples identified using PCR or McMaster WEC.

Impacts of naturally acquired protozoa and strongylid nematode infections on growth and faecal attributes in lambs

On two separate sampling occasions, faecal samples were collected from lambs (2-5 months of age) grazing pasture on two separate sheep farms in southern Western Australia. Live weight, body condition score (BCS), faecal consistency score (FCS) and faecal dry matter percentage (DM%) were measured. Faecal samples were screened by PCR for Cryptosporidium (18S rRNA, actin and 60 kDa glycoprotein [gp60] loci), Giardia duodenalis (glutamate dehydrogenase [gdh] and β-giardin) and patent strongylid nematode infections (ITS-2 nuclear ribosomal DNA for Haemonchus contortus, Teladorsagia circumcincta, Trichostrongylus spp. Chabertia ovina and Oesophagostomum spp.). Faecal worm egg counts (WECs) were performed using a modified McMaster WEC technique. The WECs were adjusted for FCS and transformed using log(10)(adjusted WEC+25) prior to statistical analyses. Cryptosporidium, Giardia and Trichostrongylus spp. detected by PCR were associated with an increased risk of non-pelleted faeces (FCS ≥ 3.0) for both flocks. Cryptosporidium-positive lambs were 2.8-11.6 times more likely to have non-pelleted faeces and Giardia-positive lambs were 2.4-14.0 times more likely to have non-pelleted faeces compared to lambs negative for each respective parasite. Lambs positive for both Cryptosporidium and Giardia were 2.9-11.8 times more likely to have non-pelleted faeces than lambs positive for only one or neither of these parasites. Mixed internal parasite infections were found to have greater impacts on FCS and BCS than single infections. A higher number of internal parasites detected per lamb was associated with lower BCS and more loose faeces. The relationship between parasite detection and live weight or growth rate were inconsistent for both flocks. Adjusted WEC was correlated with FCS and faecal DM% for one flock only, although little or no correlation was found with live weight and growth rate for both flocks. Cryptosporidium ubiquitum and Cryptosporidium parvum were the most prevalent Cryptosporidium species isolated in the two flocks. Giardia assemblage E was the most commonly isolated genotype assemblage from both flocks, while assemblage A was isolated almost as frequently as assemblage E in the one flock. One flock was a potential source of zoonotic Cryptosporidium and the other flock was a potential source of zoonotic Giardia.

Occurrence, Measurement and Clinical Perspectives of Drug Resistance in Important Parasitic Helminths of Livestock

Livestock parasite resistance to anthelmintics remains one of the major limitations to ongoing animal health, welfare and productivity worldwide. Subsequent less-than-optimal parasite control can impose significant direct and indirect costs within all production and recreation livestock enterprises.

Influence of dag score and breech wrinkle score on the time taken to crutch unmulesed Merino sheep

This study used 393 ewe and 377 wether unmulesed Merino sheep to investigate the relationship between breech wrinkle score, dag score and the time required to crutch Merino sheep. Dag score and breech wrinkle score both significantly affected the time taken to crutch individual sheep (P < 0.001 for both). The mean crutching time of the ewe mob was significantly greater than that of the wether mob (P < 0.001), with factors other than breech wrinkle score and dag score accounting for approximately half of this difference. The potential of anthelmintic treatments to reduce overall dag formation was also highlighted.

Summer-autumn rainfall effects on wool staple strength and position of break. II. Rainfall simulations, with or without wind, on sheep on days of different ambient temperatures

Previous small-scale field work failed to show any influence on staple strength from various different rainfall simulations, other than those where sheep grazed germinating green pasture following rainfall. The present study was designed to incorporate variables such as ambient temperature and the influence of wind into rainfall simulations onto Merino sheep. Different treatments did not show any effect on staple strength despite sheep being subjected to simulated rainfall events on warm and cool days, with or without additional wind. This lack of effect on wool quality was despite significant treatment effects on sheep rectal and skin temperatures.

Understanding animal health communication networks among smallholder livestock producers in Australia using stakeholder analysis

Smallholder livestock producers are a diverse population with wide ranging motivations for keeping livestock. The biosecurity risk posed by smallholders has been the subject of much conjecture, with comparisons often made between the level of animal health and biosecurity knowledge of smallholders, versus that of commercial livestock producers. This research aimed to gain a better understanding of current knowledge of smallholder production in Australia, particularly in relation to biosecurity and emergency animal disease, and to investigate the relationships that exist between smallholders and the organisations and individuals from which they seek information, assistance and support. Engagement with stakeholders is an important component of an effective biosecurity communication strategy as the dissemination of biosecurity related information from a single source cannot be expected to satisfy the needs of such a broad ranging population. A qualitative study involving a review of literature, semi-structured interviews with government and non-government stakeholders and the development of smallholder and stakeholder influence and interest grids was undertaken. This paper forms part of a broader mixed methods research project among smallholders. Results from the stakeholder analysis showed variation in the parameters used to define smallholders and in the level of stakeholder involvement. Smallholders identified breeding consultants, other producers, private veterinarians and family, friends and colleagues as having a significant to high level of interest and potential to influence their practices. Government agencies were perceived to only have some level of interest but significant influence. Industry stakeholders and rural suppliers were positioned in the quadrant reflecting perceived low levels of interest and influence. The interest and influence grid developed from stakeholders perspectives demonstrate a clustering around the mid points for both interest and influence, with the exception of those from industry who described low levels of interest and influence. Commonwealth and State government stakeholders reported a higher level of interest than influence. Veterinarians, both government and private, reported some to significant levels of interest and influence. In contrast to the results from the smallholder grid, rural suppliers reported relatively high levels of both interest and influence. The current study demonstrates that to maximise the effectiveness of biosecurity communication, there is a need for government and industry organisations to further engage with all stakeholders involved with smallholders.