John William Alexander Larsen

John William Alexander Larsen
University of Melbourne | MSD · Faculty of Veterinary and Agricultural Sciences

BVSc, PhD

About

39
Publications
1,663
Reads
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598
Citations
Citations since 2017
4 Research Items
171 Citations
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2017201820192020202120222023010203040
2017201820192020202120222023010203040
2017201820192020202120222023010203040
Education
May 1993 - September 1998
University of Melbourne
Field of study
  • Veterinary parsitology and immunology
March 1987 - October 1989
Federation University Australia
Field of study
  • Business management
January 1974 - December 1978

Publications

Publications (39)
Article
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....
Article
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 wi...
Article
A prospective longitudinal study was conducted to investigate potential risk factors for faecal shedding of Yersinia enterocolitica and Y. pseudotuberculosis by Merino lambs in four flocks in south-eastern Australia. The primary aims of the study were to determine the seasonal patterns of shedding of pathogenic Y. enterocolitica and Y. pseudotuberc...
Article
Detecting the genera and species of gastrointestinal (GI) nematode infections in faecal samples obtained from cattle requires the incubation of faeces (‘larval culture’) followed by identification of the third-stage larvae that are harvested after 10–14 days. Substantial research in the development of PCR-based methods for the rapid and specific id...
Article
The movement of animals between farms contributes to infectious disease spread in production animal populations, and is increasingly investigated with social network analysis methods. Tangible outcomes of this work include the identification of high-risk premises for targeting surveillance or control programs. However, knowledge of the effect of sa...
Article
Full-text available
Objective: Compare breech-strike on Merino ewes and hoggets that were mulesed, had breech and tail clips applied ('clipped') or left unmulesed and treated strategically with long-acting insecticide. Design: A cohort study on two farms in southern Victoria. Methods: Three treatment groups were established at lamb marking in 2008 and 2009 on eac...
Article
Within Australia, sheep are managed under diverse conditions. Because of considerable differences between these areas it is difficult to make universal recommendations about what constitutes a ‘sustainable’ worm control program, although some broad principles apply. However, to be effective and profitable in the longer term programs should cost-eff...
Article
Full-text available
The accurate diagnosis of parasitic nematode infections in livestock (including sheep and goats) is central to their effective control and the detection of the anthelmintic resistance. Traditionally, the faecal egg count reduction test (FECRT), combined with the technique of larval culture (LC), has been used widely to assess drug-susceptibility/re...
Article
To compare the prevalence of breech flystrike ('breech-strike') on 12-20-month-old Merino hoggets that were mulesed, had breech and tail clips applied ('clipped') or were left unmulesed but treated strategically with long-acting insecticide. A cohort study on three farms in southern Victoria. Three treatment groups were established at lamb marking...
Article
To assess the financial effect of programs for controlling bovine Johne's disease (BJD) in beef herds. A spreadsheet simulation model of a self-replacing beef herd in south-eastern Australia selling 400-kg steers at 15 months old. The model calculated the monthly cash flow, and net present value (NPV) of cumulative cash flow, over 10 years. Four ma...
Article
Overwintering of larvae of the Australian sheep blowfly, Lucilia cuprina (Wiedemann), was studied over 2 years in south‐eastern Australia. There was a biphasic pattern of emergence of flies from larvae entering the ground during April. Some larvae deposited in April developed immediately and emerged in late autumn, whereas others entered a state of...
Article
To describe the epidemiology of bovine Johne's disease (BJD) in beef herds in Australia. Retrospective survey of beef herds detected with BJD between 1991 and 2006. Information about the management and physical characteristics of affected herds, index and clinical cases, testing and control programs, and attitudes to BJD were collated from existing...
Article
Time of shearing affects many aspects of wool production and sheep health but no study has examined these factors concurrently in a spring-lambing, self-replacing Merino flock in southern Australia. A 5-year field experiment compared wool production in spring-lambing Merino ewes and their progeny shorn at different times and managed under commercia...
Article
Develop a computer simulation model that uses daily meteorological data and farm management practices to predict populations of Trichostrongylus colubriformis, Haemonchus contortus and Teladorsagia (Ostertagia) circumcincta and the evolution of anthelmintic resistance within a sheep flock. Use the model to explore if increased refugia, provided by...
Article
To compare the risk of different treatment scenarios on selecting for anthelmintic resistance on Australian sheep farms. A computer simulation model predicted populations of Trichostrongylus colubriformis, Haemonchus contortus or Teladorsagia (Ostertagia) circumcincta, and the frequency of anthelmintic resistance genes. Nematode populations and the...
Article
To measure associations between body weight, growth rate, sex, time of shearing and post-weaning mortality of Merino sheep. Uni- and multivariable survival analyses of sheep mortality during the first year after weaning, using records (n = 3657) from two field experiments conducted in Western Victoria from 1996 to 2003. Overall mortality was 14.3%...
Article
To compare the effectiveness of a single long-acting injection of moxidectin, given in either summer or winter, with a two-summer ('standard') treatment strategy for controlling gastrointestinal nematodes in spring-lambing Merino ewes. A replicated study over 2 years in the high winter rainfall environment of western Victoria. Measures of worm infe...
Article
To compare infections of gastrointestinal nematodes in 2-year-old ('maiden') spring-lambing Merino ewes in the upper and lower 25% of body weights (BW) at joining. An observational study over two consecutive years on two farms in western Victoria. On each farm, ewes were weighed at the end of mating. Ewes within the upper and lower quartile of BW f...
Article
Nematodes resistant to the benzimidazoles and levamisole anthelminitics have been present in many sheep flocks in South-Eastern (SE) Australia for over 20 years. We examined the productivity and profitability of six self-replacing Merino flocks, in which resistance to these anthelmintics had been confirmed for over 10 years. The profitability of th...
Conference Paper
Nematodes resistant to the benzimidazoles and levamisole anthelminitics have been present in many sheep flocks in South-Eastern (SE) Australia for over 20 years. We examined the productivity and profitability of six self-replacing Merino flocks, in which resistance to these anthelmintics had been confirmed for over 10 years. The profitability of th...
Article
The South Roxby Project is a research, demonstration and educational project for wool production systems in the high-rainfall zone of south-eastern Australia. The need for the project was identified by the failure of many Australian woolgrowers to adopt simple yet cost-effective strategies generated by over 40 years of agricultural research. A mode...
Article
Background and objective: A hypersensitive inflammatory response, associated with the ingestion of trichostrongylid larvae, is a major cause of diarrhoea and soiling of the breech with faeces in adult Merino sheep ('hypersensitivity scours'). This response is characterised by an infiltration of eosinophils and altered lymphocyte populations in the...
Article
Diarrhoea and soiling of the breech with faeces ('winter scours') is a serious problem in adult Merino sheep grazing improved pastures in south-eastern Australia during winter and spring. This occurs even on farms where gastro-intestinal nematodes are effectively controlled. It was shown that winter scours was associated with the ingestion of trich...
Article
To determine sheep farmers' attitudes to and beliefs about ovine footrot, and to improve their knowledge about the diagnosis, control and eradication of this disease. Eighteen workshops, involving 291 farmers, were conducted across Victoria in the spring of 1996. The workshops were designed as small-group discussions with a maximum attendance of 20...
Article
The productivity of Merino ewes treated with ivermectin and a controlled-release capsule containing albendazole was compared with untreated ewes grazing the same pastures on each of 3 farms. Treated breeding ewes had significantly increased greasy fleece weights (GFW, 6.5% and 7.1%) compared with untreated breeding ewes, on 2 of 3 farms but treatme...
Article
A study on 3 farms, each having a preventive strategy for the control of nematode infections, determined the risk factors associated with diarrhoea among Merino ewes in winter. Comparisons were made among groups of mated and unmated ewes with and without treatment with controlled-release capsules containing albendazole. Diarrhoea was assessed from...
Article
Full-text available
Sheep in winter-rainfall regions typically show a rise in faecal worm egg count (WEC) over the summer-autumn period, when pasture larval challenge is low or near zero. This rise is important epidemiologically for worm control. Our study found that the peak WEC of sheep bred for worm-resistance was reduced by 43% compared to unselected control sheep...

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