The prevalence of lice on sheep and control practices in South Australia.

Abstract

OBJECTIVE: To assess the prevalence of infestations of lice in sheep flocks and to survey control practices for lice in South Australia DESIGN: A total of 201 managers of sheep flocks, 75 chosen randomly from the high rainfall zone (HR), 76 from the cereal sheep zone (CS) and 50 from the pastoral zone (PA), were surveyed by telephone interview. PROCEDURE: Interviews were conducted between May 19 and May 25, 1999, according to a set questionnaire. Information was collected on presence of lice at last shearing, control practices for lice, factors important for gaining good effect from chemical treatments, sources of information on control practices and property details. Survey results were analysed by agricultural region. RESULTS: The apparent state prevalence of flocks infested with lice was 21%, with 13% infested in the HR, 21% in the CS and 25% in the PA. Ninety one percent of managers claimed to take precautions to prevent the introduction of lice and 91% routinely checked their flocks for lice. Seventy eight percent treated their sheep for lice annually and 85% had treated within the last 12 months. Of those treating in the last year, 69% had used a backline application, 16% had used a shower dip and 17% had used plunge dipping. Only 4% of producers used a long wool treatment. Synthetic pyrethroid (SP) based products were used by 50% of producers who used backline treatments in the preceding 12 months, compared to 42% and 8% for insect growth regulator and organophosphorous (OP) based products, respectively. Only 34% of managers identified SP-based products as having potential resistance problems. Of those producers who used shower or plunge dips in the last 12 months, 75% used an OP based product. Rural newspapers and magazines were by far the most commonly noted source of information for the control of lice on sheep.