1. Veterinary Parasitology & Ecology Group; University of Bristol, Bristol Life Sciences Building; Bristol BS8 1TQ UK
2. APHA, Carmarthen Veterinary Investigation Centre; Job's Well Rd Johnstown Carmarthen SA31 3EZ UK
3. University of Edinburgh, Royal (Dick) School of Veterinary Studies, Easter Bush Veterinary Centre; Roslin Midlothian Edinburgh EH25 9RG UK