Logistic regression models to evaluate inspection of wool lots for lice

Abstract

The body louse (Bovicola ovis) is associated with reduced wool production and economic loss in sheep flocks. Although it can be controlled by pesticides (organophosphorous, OP, synthetic pyrethroid, SP and insect growth regulator, IGR), pesticide use has several disadvantages (residues on wool and market restrictions, occupational health and safety, environmental affects, development of resistance).
Most pesticide applied to Queensland sheep flocks is for louse control. Although most woolgrowers consider their flocks uninfested, >90% still use pesticides, presumably as an ‘insurance policy’ against reinfestation.2,3 To develop and measure the success of louse-control and pesticide-reduction extension programs, tests to estimate the prevalence of louse infestation are required. To interpret results, test characteristics must be known and the study population used for test evaluation and its characteristics must be considered. We describe a study to evaluate visual inspection of wool lots at sale for lice as a test, and to investigate flock and management characteristics that influence test performance.