[1] Univ Penn, Sch Vet Med, Dept Clin Studies Philadelphia, Philadelphia, PA 19104 USA
[2] Univ Bristol, Bristol Vet Sch, Langford House, Bristol BS40 5DU, Avon, England
[3] Friendship Hosp Anim, 4105 Brandywine St NW, Washington, DC 20016 USA
[4] IDEXX Labs Inc, One IDEXX Dr, Westbrook, ME 04092 USA