Do sheep regulate the size of their mallophagan louse populations?

Alternatives to chemicals for controlling parasites are required to minimis e problems from resistance, residues in animal products and occupational ex posure. Utilisation of host response to parasites through selection of resi stant types or vaccination is an appealing option. To date most studies hav e been with haematophagous or invasive parasites which directly contact ele ments of the host immune system. Sheep lice (Bovicola ovis) feed superficia lly on the skin of sheep ingesting lipid, scurf, bacteria and loose stratum corneum squames. Evidence is presented that despite their surface feeding habit Bovicola ovis stimulate an immune response in sheep and that this res ponse may play a part in regulating the size of louse populations. (C) 1999 Australian Society for Parasitology Inc. Published by Elsevier Science Ltd . All rights reserved.