Effects of Mycoplasma ovipneumoniae, abundance, and climate conditions on bighorn sheep lamb:ewe ratios in New Mexico

Abstract Mycoplasma ovipneumoniae is a primary causative agent responsible for initiating polymicrobial pneumonia in bighorn sheep (Ovis canadensis). Infections of bighorn sheep populations are typically characterized by initial all‐age epizootics followed by long‐term periods of repressed juvenile...

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Main Authors: Colton J. Padilla, Caitlin Q. Ruhl, James W. Cain III, Matthew E. Gompper
Format: Article
Language:English
Published: Wiley 2024-12-01
Series:Ecosphere
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Online Access:https://doi.org/10.1002/ecs2.70095
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author Colton J. Padilla
Caitlin Q. Ruhl
James W. Cain III
Matthew E. Gompper
author_facet Colton J. Padilla
Caitlin Q. Ruhl
James W. Cain III
Matthew E. Gompper
author_sort Colton J. Padilla
collection DOAJ
description Abstract Mycoplasma ovipneumoniae is a primary causative agent responsible for initiating polymicrobial pneumonia in bighorn sheep (Ovis canadensis). Infections of bighorn sheep populations are typically characterized by initial all‐age epizootics followed by long‐term periods of repressed juvenile (lamb) survival. Populations of bighorn sheep in New Mexico, USA, were thought to be free of this pathogen prior to 2017 but recent infection of multiple herds raised concerns regarding impacts on population size and juvenile:female ratios. Using aerial survey, survival, and disease sampling data in an exploratory framework, we (1) characterize age‐related differences in M. ovipneumoniae prevalence and seroprevalence, (2) quantify differences in lamb:ewe ratios pre‐ and post‐M. ovipneumoniae detection, and (3) investigate differences in survival between previously exposed and naïve individuals. From 2007 to 2022, we sampled 466 bighorn sheep across 19 populations in New Mexico for M. ovipneumoniae exposure. While the timing of initial herd infections varied across populations, one population sustained active infections for over 15 years. We found reduced juvenile:female ratios post M. ovipneumoniae exposure for both desert (O. c. mexicana) and Rocky Mountain (O. c. canadensis) bighorn sheep populations. Post‐exposure ratio declines ranged from 20% to 69%. Evaluation of population size and environmental condition effects on juvenile:female ratios indicated varying impacts for each subspecies. Notably, population size was negatively related to Rocky Mountain juvenile:female ratios only after populations were exposed to M. ovipneumoniae. Additionally, climatic conditions in the previous lambing season and pre‐parturition time frame were associated with juvenile:female ratios for Rocky Mountain populations, while juvenile:female ratios of desert bighorn appeared to only be affected by pre‐parturition climatic conditions. Kaplan–Meier survival estimation of previously exposed, but putatively recovered, individuals (n = 31) and naïve individuals (n = 70) revealed lower (75%; 95% CI: 62%–93%) but not statistically significant (p = 0.2) 1‐year survival rates for individuals that were seropositive but not actively infected, when compared to seronegative individuals (88%; 95% CI: 81%–97%). These results collectively suggest that following M. ovipneumoniae introduction, bighorn sheep populations in New Mexico could be limited by lamb survival.
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spelling doaj-art-d10c062e106e4e84851a9164b9680afc2025-01-27T14:51:33ZengWileyEcosphere2150-89252024-12-011512n/an/a10.1002/ecs2.70095Effects of Mycoplasma ovipneumoniae, abundance, and climate conditions on bighorn sheep lamb:ewe ratios in New MexicoColton J. Padilla0Caitlin Q. Ruhl1James W. Cain III2Matthew E. Gompper3Department of Fish, Wildlife and Conservation Ecology New Mexico State University Las Cruces New Mexico USANew Mexico Department of Game and Fish Santa Fe New Mexico USAU.S. Geological Survey, New Mexico Cooperative Fish and Wildlife Research Unit Las Cruces New Mexico USADepartment of Fish, Wildlife and Conservation Ecology New Mexico State University Las Cruces New Mexico USAAbstract Mycoplasma ovipneumoniae is a primary causative agent responsible for initiating polymicrobial pneumonia in bighorn sheep (Ovis canadensis). Infections of bighorn sheep populations are typically characterized by initial all‐age epizootics followed by long‐term periods of repressed juvenile (lamb) survival. Populations of bighorn sheep in New Mexico, USA, were thought to be free of this pathogen prior to 2017 but recent infection of multiple herds raised concerns regarding impacts on population size and juvenile:female ratios. Using aerial survey, survival, and disease sampling data in an exploratory framework, we (1) characterize age‐related differences in M. ovipneumoniae prevalence and seroprevalence, (2) quantify differences in lamb:ewe ratios pre‐ and post‐M. ovipneumoniae detection, and (3) investigate differences in survival between previously exposed and naïve individuals. From 2007 to 2022, we sampled 466 bighorn sheep across 19 populations in New Mexico for M. ovipneumoniae exposure. While the timing of initial herd infections varied across populations, one population sustained active infections for over 15 years. We found reduced juvenile:female ratios post M. ovipneumoniae exposure for both desert (O. c. mexicana) and Rocky Mountain (O. c. canadensis) bighorn sheep populations. Post‐exposure ratio declines ranged from 20% to 69%. Evaluation of population size and environmental condition effects on juvenile:female ratios indicated varying impacts for each subspecies. Notably, population size was negatively related to Rocky Mountain juvenile:female ratios only after populations were exposed to M. ovipneumoniae. Additionally, climatic conditions in the previous lambing season and pre‐parturition time frame were associated with juvenile:female ratios for Rocky Mountain populations, while juvenile:female ratios of desert bighorn appeared to only be affected by pre‐parturition climatic conditions. Kaplan–Meier survival estimation of previously exposed, but putatively recovered, individuals (n = 31) and naïve individuals (n = 70) revealed lower (75%; 95% CI: 62%–93%) but not statistically significant (p = 0.2) 1‐year survival rates for individuals that were seropositive but not actively infected, when compared to seronegative individuals (88%; 95% CI: 81%–97%). These results collectively suggest that following M. ovipneumoniae introduction, bighorn sheep populations in New Mexico could be limited by lamb survival.https://doi.org/10.1002/ecs2.70095density dependencemanagementpneumoniarecruitment
spellingShingle Colton J. Padilla
Caitlin Q. Ruhl
James W. Cain III
Matthew E. Gompper
Effects of Mycoplasma ovipneumoniae, abundance, and climate conditions on bighorn sheep lamb:ewe ratios in New Mexico
Ecosphere
density dependence
management
pneumonia
recruitment
title Effects of Mycoplasma ovipneumoniae, abundance, and climate conditions on bighorn sheep lamb:ewe ratios in New Mexico
title_full Effects of Mycoplasma ovipneumoniae, abundance, and climate conditions on bighorn sheep lamb:ewe ratios in New Mexico
title_fullStr Effects of Mycoplasma ovipneumoniae, abundance, and climate conditions on bighorn sheep lamb:ewe ratios in New Mexico
title_full_unstemmed Effects of Mycoplasma ovipneumoniae, abundance, and climate conditions on bighorn sheep lamb:ewe ratios in New Mexico
title_short Effects of Mycoplasma ovipneumoniae, abundance, and climate conditions on bighorn sheep lamb:ewe ratios in New Mexico
title_sort effects of mycoplasma ovipneumoniae abundance and climate conditions on bighorn sheep lamb ewe ratios in new mexico
topic density dependence
management
pneumonia
recruitment
url https://doi.org/10.1002/ecs2.70095
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