title: Role of carriers in the transmission of pneumonia in bighorn sheep (Ovis canadensis).
abstract: In the absence of livestock contact, recurring lamb mortality in bighorn sheep (Ovis canadensis) populations previously exposed to pneumonia indicates the likely presence of carriers of pneumonia-causing pathogens, and possibly inadequate maternally derived immunity. To investigate this problem we commingled naïve, pregnant ewes (n=3) with previously exposed rams (n=2). Post-commingling, all ewes and lambs born to them acquired pneumonia-causing pathogens (leukotoxin-producing Pasteurellaceae and Mycoplasma ovipneumoniae), with subsequent lamb mortality between 4-9 weeks of age. Infected ewes became carriers for two subsequent years and lambs born to them succumbed to pneumonia. In another experiment, we attempted to suppress the carriage of leukotoxin-producing Pasteurellaceae by administering an antibiotic to carrier ewes, and evaluated lamb survival. Lambs born to both treatment and control ewes (n=4 each) acquired pneumonia and died. Antibody titers against leukotoxin-producing Pasteurellaceae in all eight ewes were 'protective' (>1:800 and no apparent respiratory disease); however their lambs were either born with comparatively low titers, or with high (but non-protective) titers that declined rapidly within 2-8 weeks of age, rendering them susceptible to fatal disease. Thus, exposure to pneumonia-causing pathogens from carrier ewes, and inadequate titers of maternally derived protective antibodies, are likely to render bighorn lambs susceptible to fatal pneumonia.
authors.affiliation: Department of Veterinary Microbiology & Pathology, Washington State University, Pullman, WA 99163, USA.
authors.forename: Bindu
authors.initials: B
authors.lastname: Raghavan
authors.affiliation: Department of Veterinary Microbiology & Pathology, Washington State University, Pullman, WA 99163, USA.
authors.forename: Kayla
authors.initials: K
authors.lastname: Erickson
authors.affiliation: Department of Veterinary Microbiology & Pathology, Washington State University, Pullman, WA 99163, USA.
authors.forename: Abirami
authors.initials: A
authors.lastname: Kugadas
authors.affiliation: Department of Veterinary Microbiology & Pathology, Washington State University, Pullman, WA 99163, USA.
authors.forename: Sai A
authors.initials: SA
authors.lastname: Batra
authors.affiliation: Paul G. Allen School for Global Animal Health, Washington State University, Pullman, WA 99163, USA.
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Call
authors.affiliation: Paul G. Allen School for Global Animal Health, Washington State University, Pullman, WA 99163, USA.
authors.forename: Margaret A
authors.initials: MA
authors.lastname: Davis
authors.affiliation: Department of Veterinary Microbiology & Pathology, Washington State University, Pullman, WA 99163, USA.
authors.forename: William J
authors.initials: WJ
authors.lastname: Foreyt
authors.affiliation: Department of Veterinary Microbiology & Pathology, Washington State University, Pullman, WA 99163, USA ssrikumaran@vetmed.wsu.edu.
authors.forename: Subramaniam
authors.identifier: http://orcid.org/0000-0002-8824-9892
authors.initials: S
authors.lastname: Srikumaran
keywords: Antibodies; Bighorn sheep; Carrier; Mycoplasma; Pasteurellaceae; Pneumonia