Survival away from sheep and alternative methods of transmission of sheep lice (Bovicola ovis)

Transmission of sheep lice is thought to occur mainly by sheep to sheep con tact although the possibility of other sources of infestation is often sugg ested. This study investigated the period of survival of Bovicola ovis afte r removal from sheep under varying conditions and assessed the likelihood o f new infestations arising from contaminated facilities, wool caught on fen ces and shearers' footwear. In laboratory studies with lice held away from sheep at 4, 20, 25 and 36.5 degreesC, adults and nymphs survived longest at 25 degreesC (LT90 of 11.7 a nd 24.1 days for adults and large nymphs, respectively). Nymphs survived lo nger than adults and lice provided with raw wool survived longer than lice provided with wool that had been degreased. Nymphal lice survived for up to 29 days on unscoured wool at 36.5 degreesC, but the LT50 was less than 9 d ays in most experiments. In shearing sheds in winter and early spring lice survived for up to 14 and 16 days, respectively. These periods of survival are considerably longer than previously indicated for B. ovis. Most lice dropped out of wool staples attached to a fence within 1 h and on ly two of a total of 225 lice were still present after 24 h, suggesting tha t sheep are unlikely to become infested from wool caught on fences. Adult a nd nymphal lice readily transferred to shearers' moccasins and survived the re for up to 10 days, indicating that transmission of lice on the footwear of shearers or other sheep handlers may be a cause of new infestations. Mic rowaving each moccasin for 5 min killed all lice and may provide a simple m ethod of reducing the likelihood of transmission of B. ovis between propert ies. (C) 2001 Elsevier Science B.V. All rights reserved.