[1] Univ Zambia, Sch Vet Med, Lusaka, Zambia
[2] Univ Zambia, Dept Econ, Lusaka, Zambia
[3] Univ Edinburgh, Sch Biomed Sci, Div Infect & Pathway Med, Coll Med & Vet Med, Chancellors Bldg,49 Little France Crescent, Edinburgh EH16 4SB, Midlothian, Scotland
[4] Univ Edinburgh, Sch Biomed Sci, Ctr Infect Dis, Coll Med & Vet Med, Chancellors Bldg,49 Little France Crescent, Edinburgh EH16 4SB, Midlothian, Scotland
[5] Univ Edinburgh, Royal Dick Sch Vet Studies, Roslin EH25 9RG, Midlothian, Scotland
[6] Univ Edinburgh, Roslin Inst, Roslin EH25 9RG, Midlothian, Scotland
[7] AP Consultants, Walworth Enterprise Ctr, Andover SP10 5AP, England
[8] Univ Zambia, Sch Vet Med, Dept Dis Control, POB 32379, Lusaka, Zambia