Effects of control of the sheep body louse (Damalinia ovis) on wool production and quality

Abstract

Groups of 35 Merino wethers under natural challenge by sheep body lice, Damalinia ovis, in south-western Queensland were subjected to four different chemical lice control treatments (arsenic, diazinon, cypermethrin and deltamethrin) over a 12-month period. Shearing took place in June. Louse populations were reduced by repeated treatments with cypermethrin. Despite high temperatures and some rainfall, populations in controls peaked at the end of summer, indicating that wool length influenced population growth. Greasy and clean fleece weights of treated sheep were higher (P<0.05) than those of controls by 0.4-1.1 kg/sheep and 0.3-0.9 kg/sheep, respectively, depending on treatment. Wool base yield was 2-45.5% higher. Sheep that were repeatedly treated with cypermethrin produced more (P<0.05) sound fleece wool (3.0 vs 1.7 kg/head greasy) and less cast fleece wool (0.1 vs 0.4 kg/head greasy) than controls. The differences in wool value between treated groups and controls ranged from $A0.45 to $A3.19 per sheep. No effect on liveweight could be attributed to treatment.

On-farm factors affecting physical quality of Merino wool. 1. Nutrition, reproduction, health and management

“…Cleland et al (1989) and James et al (2011) found no significant effect of lice on SS, but other studies have demonstrated some small negative effect. Niven and Pritchard (1985) reported sheep with moderate to heavy infestations produced less sound wool (1.7 vs 3.0 kg/head) and more cast wool (0.4 vs 0.1 kg/head) than sheep with few lice present. Several reports indicate lice have no effect on FD (Wilkinson et al, 1982;Niven and Pritchard, 1985;Cleland et al, 1989;James et al, 2011).…”

Effects of the Sheep-Chewing Louse (Damalinia ovis) on the Epidermis of the Australian Merino

“…The data suggest that a positive correlation exists between the thickness of each region of the epidermis and the level of louse infestation (Table 1). Thus, although Britt et al (1985) established that epidermal thickness in louse-free adult Merino sheep does not vary significantly over a 12-month period, it is probable that any seasonal fluctuation in louse numbers [for example following shearing when the louse population is dramatically reduced (Niven and Pritchard 1985), or following treatment with insecticidal formulations] could result in an apparent seasonal variation to epidermal thickness.…”

Serum and skin surface antibodies and their associations with sheep biting lice, Bovicola ovis, on experimentally infested sheep

“…The sheep biting louse, Bovicola ovis (Schrank) (Phthiraptera: Trichodectidae), is an ectoparasite of sheep in most parts of the world. Infestations cause economic losses by decreasing wool cut per head, reducing wool quality and causing cockle in sheep leather (Kettle & Lukies, 1982;Wilkinson et al, 1982;Niven & Pritchard, 1985;Heath et al, 1995). Historically, control of sheep lice has been mainly by insecticides.…”