A comparison of deterministic and stochastic models for predicting the impacts of different sheep body lice (Bovicola ovis) management practices
Brian J. Horton A B and Anna L. Carew AA Tasmanian Institute of Agriculture, University of Tasmania, PO Box 46, Kings Meadows, Tas. 7249, Australia.
B Corresponding author. Email: brian.horton@utas.edu.au
Animal Production Science 55(1) 122-132 https://doi.org/10.1071/AN13412
Submitted: 7 October 2013 Accepted: 27 November 2013 Published: 14 January 2014
Abstract
A deterministic model for predicting the prevalence of lice in sheep flocks was compared with a stochastic model. The stochastic model was based on data from 100 000 simulated farms and encompassed: a range of lice detection levels at shearing, whether or not treatment was applied where no lice were detected, the efficacy of treatments used, and the adequacy of quarantine measures against entering sheep. The deterministic model generated more extreme estimates of the effects of lice management changes, and was judged unsatisfactory for long-term decision making. Predictions based on the stochastic model were consistent with reported survey values, suggesting the stochastic model could be used to predict benefits and costs associated with changes in louse-control methods.
According to the stochastic model, the two factors that could provide the greatest reduction in dollar costs were improvement of quarantine by limiting the incidence of lice entering the flock, and improvement of eradication methods. The deterministic model suggested that there would be large benefits from improvement in detection, but the stochastic model only found small dollar benefits with improved detection in the absence of changes such as more effective treatments. Changing the proportion of flocks that were treated when no lice were detected had little effect on the predicted incidence of lousy flocks.
References
Armstrong B, Knights G, McLeish W (2001) ‘Blowflies and lice information manual. A practical approach to producing low residue wool.’ (Department of Primary Industries, Queensland: Brisbane)Brightling A (1989) Evaluation of strategies for control of sheep lice (Damalina ovis) with an epidemiological model. Australian Veterinary Journal 66, 55–58.
| Evaluation of strategies for control of sheep lice (Damalina ovis) with an epidemiological model.Crossref | GoogleScholarGoogle Scholar | 1:STN:280:DyaL1M3islyksA%3D%3D&md5=79cd3404002ae23196b31dfc96d17ddeCAS | 2712769PubMed |
Horton JD, Champion SC (2001) Some current management strategies for low residue fly and lice control. In ‘FLICS conference. Launceston, Tasmania’. (Ed. S Champion) pp. 443–453. (Tasmanian Institute of Agricultural Research, University of Tasmania: Launceston)
Horton BJ, Evans DL, James PJ, Campbell NJ (2009) Development of a model based on Bayesian networks to estimate the probability of sheep lice presence at shearing. Animal Production Science 49, 48–55.
| Development of a model based on Bayesian networks to estimate the probability of sheep lice presence at shearing.Crossref | GoogleScholarGoogle Scholar |
James PJ (2002) Sheep lice: changing control practices and wool industry implications. Wool Technology and Sheep Breeding 50, 567–573.
James P (2011) Sheep lice: industry situations and changing control practices. Available at http://flockandherd.net.au/sheep/reader/sheep%20lice%20situation.html [Verified13 November 2013]
James P, Riley M (2001) Sheep lice and the economic production of low residue wool. In ‘FLICS: flystrike and lice IPM control strategies. Launceston, Tasmania’. (Ed. S Champion) pp. 135–143. (Tasmanian Institute of Agricultural Research, University of Tasmania: Launceston)
James PJ, Moon RD, Karlsson LJE (2001) Optimising the sensitivity of sheep inspection for detecting lice. In ‘FLICS: flystrike and lice IPM control strategies. Launceston, Tasmania’. (Ed. S Champion) pp. 331–340. (Tasmanian Institute of Agricultural Research, University of Tasmania: Launceston)
James PJ, Garrett JA, Moon RD (2002) Sensitivity of two-stage sampling to detect sheep biting lice (Bovicola ovis) in infested flocks. Veterinary Parasitology 103, 157–166.
| Sensitivity of two-stage sampling to detect sheep biting lice (Bovicola ovis) in infested flocks.Crossref | GoogleScholarGoogle Scholar | 1:STN:280:DC%2BD38%2FgtFWjsA%3D%3D&md5=df114f0f1ee2394ab0067e2b10f0ff57CAS | 11751010PubMed |
Levot G (2012) Unstable pyrethroid resistance in sheep body lice Bovicola ovis (Shrank), (Phthiraptera: Trichodectidae) and its implication for lice control on sheep. Veterinary Parasitology 185, 274–278.
| Unstable pyrethroid resistance in sheep body lice Bovicola ovis (Shrank), (Phthiraptera: Trichodectidae) and its implication for lice control on sheep.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC38XjvVemsLk%3D&md5=dc5d8d34119102f67d66c002c5b548b1CAS | 22004914PubMed |
Lucas PG, Horton BJ (2014) Economic guidelines for treatment of lice in long wool based on a model of the development of sheep wool damage. Australian Veterinary Journal,
| Economic guidelines for treatment of lice in long wool based on a model of the development of sheep wool damage.Crossref | GoogleScholarGoogle Scholar | in press.
Morcombe PW, Young GE (1993) Persistence of the sheep and body louse, Bovicola ovis, after treatment. Australian Veterinary Journal 70, 147–150.
| Persistence of the sheep and body louse, Bovicola ovis, after treatment.Crossref | GoogleScholarGoogle Scholar | 1:STN:280:DyaK3s3mtlylsA%3D%3D&md5=df73bd0f12f0bb41ffcdb5068a2d95cdCAS | 8494525PubMed |
Morcombe PW, Young GE, Ball MD, Dunlop RH (1996) The detection of lice (Bovicola ovis) in mobs of sheep: a comparison of fleece parting, the lamp test and the table locks test. Australian Veterinary Journal 73, 170–173.
| The detection of lice (Bovicola ovis) in mobs of sheep: a comparison of fleece parting, the lamp test and the table locks test.Crossref | GoogleScholarGoogle Scholar | 1:STN:280:DyaK283mtFaqtw%3D%3D&md5=9b763fd8c58a56869dcc97634b307f53CAS | 8660238PubMed |
Niven DR, Pritchard DA (1985) Effects of control of the sheep body louse (Damalinia ovis) on wool production and quaility. Australian Journal of Experimental Agriculture 25, 27–31.
| Effects of control of the sheep body louse (Damalinia ovis) on wool production and quaility.Crossref | GoogleScholarGoogle Scholar |
Popp S, Eppleston J, Watt BR, Mansfield S, Bush RD (2012) The prevalence of lice (Bovicola ovis) in sheep flocks on the central and southern Tablelands of New South Wales. Animal Production Science 52, 659–664.
Reeve I, Thompson L-J (2005) Integrated parasite management in sheep project: Benchmark survey. Report to Australian Wool Innovation, Sydney.
Sackett D, Holmes P, Abbott K, Jephcott S, Barber M (2006) Assessing the economic cost of endemic disease on the profitability of Australian beef cattle and sheep producers. MLA Report AHW.087. Meat & Livestock Australia, Sydney.
Walkden-Brown SW, Reeve I, Thompson L, Kahn LP, Crampton A, Larsen JW, Woodgate RG, James PJ, de Fegely CR, Williams SH (2006) IPM’s project benchmarking survey: a national survey of parasite control practices. In ‘Proceedings of the Australian sheep veterinarians annual conference’. (Ed. C Trengrove) pp. 38–47. (Australian Sheep Veterinarians: Wagga Wagga, NSW)
Wilkinson FC (1986) Sheep lice eradication – fact or fiction. In ‘Proceedings of the sheep and wool refresher course – Adelaide, February 1986. Adelaide, South Australia’. (South Australian Department of Agriculture and The Australian Wool Corporation: Adelaide)
Wilkinson FC, de Chaneet GC, Beetson BR (1982) Growth of populations of lice, Damalinia ovis, on sheep and their effects on production and processing performance of wool. Veterinary Parasitology 9, 171–177.
| Growth of populations of lice, Damalinia ovis, on sheep and their effects on production and processing performance of wool.Crossref | GoogleScholarGoogle Scholar |
