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Notley SR, Mitchell D, Taylor NAS. A century of exercise physiology: concepts that ignited the study of human thermoregulation. Part 3: Heat and cold tolerance during exercise. Eur J Appl Physiol 2024; 124:1-145. [PMID: 37796292 DOI: 10.1007/s00421-023-05276-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Accepted: 07/04/2023] [Indexed: 10/06/2023]
Abstract
In this third installment of our four-part historical series, we evaluate contributions that shaped our understanding of heat and cold stress during occupational and athletic pursuits. Our first topic concerns how we tolerate, and sometimes fail to tolerate, exercise-heat stress. By 1900, physical activity with clothing- and climate-induced evaporative impediments led to an extraordinarily high incidence of heat stroke within the military. Fortunately, deep-body temperatures > 40 °C were not always fatal. Thirty years later, water immersion and patient treatments mimicking sweat evaporation were found to be effective, with the adage of cool first, transport later being adopted. We gradually acquired an understanding of thermoeffector function during heat storage, and learned about challenges to other regulatory mechanisms. In our second topic, we explore cold tolerance and intolerance. By the 1930s, hypothermia was known to reduce cutaneous circulation, particularly at the extremities, conserving body heat. Cold-induced vasodilatation hindered heat conservation, but it was protective. Increased metabolic heat production followed, driven by shivering and non-shivering thermogenesis, even during exercise and work. Physical endurance and shivering could both be compromised by hypoglycaemia. Later, treatments for hypothermia and cold injuries were refined, and the thermal after-drop was explained. In our final topic, we critique the numerous indices developed in attempts to numerically rate hot and cold stresses. The criteria for an effective thermal stress index were established by the 1930s. However, few indices satisfied those requirements, either then or now, and the surviving indices, including the unvalidated Wet-Bulb Globe-Thermometer index, do not fully predict thermal strain.
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Affiliation(s)
- Sean R Notley
- Defence Science and Technology Group, Department of Defence, Melbourne, Australia
- School of Human Kinetics, University of Ottawa, Ottawa, Canada
| | - Duncan Mitchell
- Brain Function Research Group, School of Physiology, University of the Witwatersrand, Johannesburg, South Africa
- School of Human Sciences, University of Western Australia, Crawley, Australia
| | - Nigel A S Taylor
- Research Institute of Human Ecology, College of Human Ecology, Seoul National University, Seoul, Republic of Korea.
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He SX, Li R, Yang HH, Wang ZQ, Peng YM, Huang JH, Ma Q. Optimization of a Rhabdomyolysis Model in Mice With Exertional Heat Stroke Mouse Model of EHS-Rhabdomyolysis. Front Physiol 2020; 11:642. [PMID: 32655408 PMCID: PMC7325941 DOI: 10.3389/fphys.2020.00642] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2019] [Accepted: 05/20/2020] [Indexed: 12/12/2022] Open
Abstract
Exertional heat stroke (EHS) is a life-threatening disease characterized by high mortality and incidence of rhabdomyolysis (RM). It would therefore be valuable to establish a stable EHS-induced RM model that accurately reflects the clinical characteristics of EHS patients and provides an objective animal model for further study of the pathogenesis of RM. In the current study, 8∼9-week-old, male, wild-type C57BL/6J mice, at the stage of sexual maturity, were randomly divided into four groups: the EHS group, the classical heat stroke (CHS) group, the sham heat exercise group, and sham heat rest group. The survival rate of mice was determined under relatively high levels of temperature and humidity (37.5°C, 65% relative humidity (RH); 37.5°C, 70% RH; 39.5°C, 65% RH; and 39.5°C, 70% RH) as well as a high core temperature (Tc; 42, 42.5, and 43°C). Results showed that the environmental condition of 39.5°C and 65% RH was most suitable for EHS modeling. The end point of EHS evaluation was exhaustion or an individual’s core temperature reaching 43°C. The survival rate of mice in the EHS group within 24 h under these conditions was 37.34%, which is consistent with the high mortality characteristics noted in EHS patients. Severe RM was observed in the EHS group by H&E staining and transmission electron microscopy. Creatine kinase levels in the EHS group mostly exceeded 10,000 U/L, which was approximately 10 times higher than that in the sham heat rest group. Renal tubules of the EHS group exhibited severe necrosis, and calcium overload in the skeletal muscles of this group was also observed using intravital 2-photon microscopy. In conclusion, we made improvements to a stable EHS-induced RM animal model to truly reflect the clinical characteristics of EHS patients. This new model should be helpful in the further study of RM pathogenesis.
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Affiliation(s)
- Si-Xiao He
- Department of Biopharmaceutics, School of Laboratory Medicine and Biotechnology, Southern Medical University, Guangzhou, China
| | - Ru Li
- Department of Biopharmaceutics, School of Laboratory Medicine and Biotechnology, Southern Medical University, Guangzhou, China
| | - Huo-Hong Yang
- Cancer Research Institute, Southern Medical University, Guangzhou, China
| | - Zi-Qing Wang
- Department of Biopharmaceutics, School of Laboratory Medicine and Biotechnology, Southern Medical University, Guangzhou, China
| | - Yan-Mei Peng
- Department of General Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Jun-Hao Huang
- Department of Biopharmaceutics, School of Laboratory Medicine and Biotechnology, Southern Medical University, Guangzhou, China
| | - Qiang Ma
- Department of Biopharmaceutics, School of Laboratory Medicine and Biotechnology, Southern Medical University, Guangzhou, China
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Chun JK, Choi S, Kim HH, Yang HW, Kim CS. Predictors of poor prognosis in patients with heat stroke. Clin Exp Emerg Med 2020; 6:345-350. [PMID: 31910506 PMCID: PMC6952628 DOI: 10.15441/ceem.18.081] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Accepted: 11/23/2018] [Indexed: 11/23/2022] Open
Abstract
Objective The predictors of poor prognosis in heat stroke (HS) remain unknown. This study investigated the predictive factors of poor prognosis in patients with HS. Methods Data were obtained and analyzed from the health records of patients diagnosed with heat illness at Ajou university hospital between January 2008 and December 2017. Univariate and multivariate analyses were performed to identify the independent predictors of poor prognosis. Results Thirty-six patients (median age, 54.5 years; 33 men) were included in the study. Poor prognosis was identified in 27.8% of the study population (10 patients). The levels of S100B protein, troponin I, creatinine, alanine aminotransferase, and serum lactate were statistically significant in the univariate analysis. Multiple regression analysis revealed that poor prognosis was significantly associated with an increased S100B protein level (odds ratio, 177.37; 95% confidence interval, 2.59 to 12,143.80; P=0.016). The S100B protein cut-off level for predicting poor prognosis was 0.610 μg/L (area under the curve, 0.906; 95% confidence interval, 0.00 to 1.00), with 86% sensitivity and 86% specificity. Conclusion An increased S100B protein level on emergency department admission is an independent prognostic factor of poor prognosis in patients with HS. Elevation of the S100B protein level represents a potential target for specific and prompt therapies in these patients.
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Affiliation(s)
- Jae-Kwon Chun
- Department of Emergency Medicine, Ajou University School of Medicine, Suwon, Korea
| | - Sangchun Choi
- Department of Emergency Medicine, Ajou University School of Medicine, Suwon, Korea
| | - Hyuk-Hoon Kim
- Department of Emergency Medicine, Ajou University School of Medicine, Suwon, Korea
| | - Hee Won Yang
- Department of Emergency Medicine, Ajou University School of Medicine, Suwon, Korea
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Figiel W, Morawski M, Grąt M, Kornasiewicz O, Niewiński G, Raszeja-Wyszomirska J, Krasnodębski M, Kowalczyk A, Hołówko W, Patkowski W, Zieniewicz K. Fulminant liver failure following a marathon: Five case reports and review of literature. World J Clin Cases 2019; 7:1467-1474. [PMID: 31363475 PMCID: PMC6656669 DOI: 10.12998/wjcc.v7.i12.1467] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2019] [Revised: 04/29/2019] [Accepted: 05/01/2019] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND The growing popularity of marathon and half-marathon runs has led to an increased number of patients presenting with exertion-induced heat stroke. Mild hepatic involvement is often observed in these patients; however, fulminant liver failure may occur in approximately 5% of all cases. Liver transplantation is a potentially curative approach for exertion-induced liver failure, although there is a lack of consensus regarding the criteria and optimal timing of this intervention.
CASE SUMMARY This paper describes 5 patients (4 men and 1 woman) who were referred to the department where this study was performed with the diagnosis of exertion-induced acute liver failure. Three patients underwent liver transplantation, 1 recovered spontaneously, and 1 patient died on day 11 following the exertion.
CONCLUSION Exertion-induced heat stroke may present as fulminant liver failure. These patients may recover with conservative treatment, may require liver transplantation, or may die. No definitive criteria are available to determine patient suitability for a conservative vs surgical approach.
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Affiliation(s)
- Wojciech Figiel
- Department of General, Transplant, and Liver Surgery, Medical University of Warsaw, Warsaw 02097, Poland
| | - Marcin Morawski
- Department of General, Transplant, and Liver Surgery, Medical University of Warsaw, Warsaw 02097, Poland
| | - Michał Grąt
- Department of General, Transplant, and Liver Surgery, Medical University of Warsaw, Warsaw 02097, Poland
| | - Oskar Kornasiewicz
- Department of General, Transplant, and Liver Surgery, Medical University of Warsaw, Warsaw 02097, Poland
| | - Grzegorz Niewiński
- Department of Anaesthesiology and Intensive Care, Medical University of Warsaw, Warsaw 02097, Poland
| | - Joanna Raszeja-Wyszomirska
- Liver and Internal Medicine Unit, Department of General, Transplant, and Liver Surgery, Medical University of Warsaw, Warsaw 02097, Poland
| | - Maciej Krasnodębski
- Department of General, Transplant, and Liver Surgery, Medical University of Warsaw, Warsaw 02097, Poland
| | - Arkadiusz Kowalczyk
- Department of General, Transplant, and Liver Surgery, Medical University of Warsaw, Warsaw 02097, Poland
| | - Wacław Hołówko
- Department of General, Transplant, and Liver Surgery, Medical University of Warsaw, Warsaw 02097, Poland
| | - Waldemar Patkowski
- Department of General, Transplant, and Liver Surgery, Medical University of Warsaw, Warsaw 02097, Poland
| | - Krzysztof Zieniewicz
- Department of General, Transplant, and Liver Surgery, Medical University of Warsaw, Warsaw 02097, Poland
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McKinley MJ, Martelli D, Pennington GL, Trevaks D, McAllen RM. Integrating Competing Demands of Osmoregulatory and Thermoregulatory Homeostasis. Physiology (Bethesda) 2019; 33:170-181. [PMID: 29616878 DOI: 10.1152/physiol.00037.2017] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Mammals are characterized by a stable core body temperature. When maintenance of core temperature is challenged by ambient or internal heat loads, mammals increase blood flow to the skin, sweat and/or pant, or salivate. These thermoregulatory responses enable evaporative cooling at moist surfaces to dissipate body heat. If water losses incurred during evaporative cooling are not replaced, body fluid homeostasis is challenged. This article reviews the way mammals balance thermoregulation and osmoregulation.
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Affiliation(s)
- Michael J McKinley
- Florey Institute of Neuroscience and Mental Health, University of Melbourne , Parkville , Australia.,Department of Physiology, University of Melbourne , Parkville , Australia
| | - Davide Martelli
- Florey Institute of Neuroscience and Mental Health, University of Melbourne , Parkville , Australia.,University of Bologna, Bologna , Italy
| | - Glenn L Pennington
- Florey Institute of Neuroscience and Mental Health, University of Melbourne , Parkville , Australia
| | - David Trevaks
- Florey Institute of Neuroscience and Mental Health, University of Melbourne , Parkville , Australia
| | - Robin M McAllen
- Florey Institute of Neuroscience and Mental Health, University of Melbourne , Parkville , Australia
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Roncal-Jimenez CA, Sato Y, Milagres T, Andres Hernando A, García G, Bjornstad P, Dawson JB, Sorensen C, Newman L, Krisher L, Madero M, Glaser J, Gárcía-Trabanino R, Romero EJ, Song Z, Jensen T, Kuwabara M, Rodriguez-Iturbe B, Sanchez-Lozada LG, Lanaspa MA, Johnson RJ. Experimental heat stress nephropathy and liver injury are improved by allopurinol. Am J Physiol Renal Physiol 2018; 315:F726-F733. [PMID: 29667911 DOI: 10.1152/ajprenal.00543.2017] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
An epidemic of chronic kidney disease (CKD) has been observed in Central America among workers in the sugarcane fields. One hypothesis is that the CKD may be caused by recurrent heat stress and dehydration, and potentially by hyperuricemia. Accordingly, we developed a murine model of kidney injury associated with recurrent heat stress. In the current experiment, we tested whether treatment with allopurinol (a xanthine oxidase inhibitor that reduces serum urate) provides renal protection against recurrent heat stress and dehydration. Eight-week-old male C57BL/6 mice were subjected to recurrent heat stress (39.5°C for 30 min, 7 times daily, for 5 wk) with or without allopurinol treatment and were compared with control animals with or without allopurinol treatment. Mice were allowed ad libitum access to normal laboratory chow (Harlan Teklad). Kidney histology, liver histology, and renal function were examined. Heat stress conferred both kidney and liver injury. Kidneys showed loss of proximal tubules, infiltration of monocyte/macrophages, and interstitial collagen deposition, while livers of heat-stressed mice displayed an increase in macrophages, collagen deposition, and myofibroblasts. Allopurinol provided significant protection and improved renal function in the heat-stressed mice. The renal protection was associated with reduction in intrarenal uric acid concentration and heat shock protein 70 expression. Heat stress-induced renal and liver injury can be protected with allopurinol treatment. We recommend a clinical trial of allopurinol for individuals developing renal injury in rural areas of Central America where the epidemic of chronic kidney disease is occurring.
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Affiliation(s)
- Carlos A Roncal-Jimenez
- Division of Renal Diseases and Hypertension, University of Colorado Anschutz Medical Campus , Aurora, Colorado
| | - Yuka Sato
- Division of Renal Diseases and Hypertension, University of Colorado Anschutz Medical Campus , Aurora, Colorado
| | - Tamara Milagres
- Division of Renal Diseases and Hypertension, University of Colorado Anschutz Medical Campus , Aurora, Colorado
| | - Ana Andres Hernando
- Division of Renal Diseases and Hypertension, University of Colorado Anschutz Medical Campus , Aurora, Colorado
| | - Gabriela García
- Division of Renal Diseases and Hypertension, University of Colorado Anschutz Medical Campus , Aurora, Colorado
| | - Petter Bjornstad
- Department of Pediatric Endocrinology, University of Colorado School of Medicine , Aurora, Colorado
| | - Jaime Butler Dawson
- Center for Health, Work and Environment, Colorado School of Public Health , Aurora, Colorado
| | - Cecilia Sorensen
- Center for Health, Work and Environment, Colorado School of Public Health , Aurora, Colorado
| | - Lee Newman
- Center for Health, Work and Environment, Colorado School of Public Health , Aurora, Colorado
| | - Lyndsay Krisher
- Center for Health, Work and Environment, Colorado School of Public Health , Aurora, Colorado
| | - Magdalena Madero
- Department of Nephrology, Institution Nacional de Cardiologia, Ignacio Chavez, Mexico City, Mexico
| | | | | | | | - Zhilin Song
- Division of Renal Diseases and Hypertension, University of Colorado Anschutz Medical Campus , Aurora, Colorado
| | - Thomas Jensen
- Division of Renal Diseases and Hypertension, University of Colorado Anschutz Medical Campus , Aurora, Colorado
| | - Masanari Kuwabara
- Division of Renal Diseases and Hypertension, University of Colorado Anschutz Medical Campus , Aurora, Colorado
| | - Bernardo Rodriguez-Iturbe
- Nephrology Service Hospital Universitario and Instituto Venezolano de Investigaciones Cientificas-Zulia , Maracaibo , Venezuela
| | | | - Miguel A Lanaspa
- Division of Renal Diseases and Hypertension, University of Colorado Anschutz Medical Campus , Aurora, Colorado
| | - Richard J Johnson
- Division of Renal Diseases and Hypertension, University of Colorado Anschutz Medical Campus , Aurora, Colorado
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Surviving physiological stress: Can insights into human adaptation to austere environments be applied to the critical care unit? TRENDS IN ANAESTHESIA AND CRITICAL CARE 2016. [DOI: 10.1016/j.tacc.2016.11.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Alzeer AH, Al Otair HA. Sweat chloride concentration in patients with heat stroke. J Taibah Univ Med Sci 2014. [DOI: 10.1016/j.jtumed.2013.06.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Abstract
BACKGROUND Human activity in wilderness areas has increased globally in recent decades, leading to increased risk of injury and illness. Wilderness medicine has developed in response to both need and interest. METHODS The field of wilderness medicine encompasses many areas of interest. Some focus on special circumstances (such as avalanches) while others have a broader scope (such as trauma care). Several core areas of key interest within wilderness medicine are discussed in this study. RESULTS Wilderness medicine is characterized by remote and improvised care of patients with routine or exotic illnesses or trauma, limited resources and manpower, and delayed evacuation to definitive care. Wilderness medicine is developing rapidly and draws from the breadth of medical and surgical subspecialties as well as the technical fields of mountaineering, climbing, and diving. Research, epidemiology, and evidence-based guidelines are evolving. A hallmark of this field is injury prevention and risk mitigation. The range of topics encompasses high-altitude cerebral edema, decompression sickness, snake envenomation, lightning injury, extremity trauma, and gastroenteritis. Several professional societies, academic fellowships, and training organizations offer education and resources for laypeople and health care professionals. CONCLUSIONS THE FUTURE OF WILDERNESS MEDICINE IS UNFOLDING ON MULTIPLE FRONTS: education, research, training, technology, communications, and environment. Although wilderness medicine research is technically difficult to perform, it is essential to deepening our understanding of the contribution of specific techniques in achieving improvements in clinical outcomes.
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Affiliation(s)
- Douglas G. Sward
- Department of Emergency Medicine, University of Maryland School of Medicine, Hyperbaric Medicine, Shock Trauma Center, Baltimore, Maryland, USA
| | - Brad L. Bennett
- Military & Emergency Medicine Department, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA
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Junglee NA, Di Felice U, Dolci A, Fortes MB, Jibani MM, Lemmey AB, Walsh NP, Macdonald JH. Exercising in a hot environment with muscle damage: effects on acute kidney injury biomarkers and kidney function. Am J Physiol Renal Physiol 2013; 305:F813-20. [DOI: 10.1152/ajprenal.00091.2013] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Unaccustomed strenuous physical exertion in hot environments can result in heat stroke and acute kidney injury (AKI). Both exercise-induced muscle damage and AKI are associated with the release of interleukin-6, but whether muscle damage causes AKI in the heat is unknown. We hypothesized that muscle-damaging exercise, before exercise in the heat, would increase kidney stress. Ten healthy euhydrated men underwent a randomized, crossover trial involving both a 60-min downhill muscle-damaging run (exercise-induced muscle damage; EIMD), and an exercise intensity-matched non-muscle-damaging flat run (CON), in random order separated by 2 wk. Both treatments were followed by heat stress elicited by a 40-min run at 33°C. Urine and blood were sampled at baseline, after treatment, and after subjects ran in the heat. By design, EIMD induced higher plasma creatine kinase and interleukin-6 than CON. EIMD elevated kidney injury biomarkers (e.g., urinary neutrophil gelatinase-associated lipocalin (NGAL) after a run in the heat: EIMD-CON, mean difference [95% CI]: 12 [5, 19] ng/ml) and reduced kidney function (e.g., plasma creatinine after a run in the heat: EIMD-CON, mean difference [95% CI]: 0.2 [0.1, 0.3] mg/dl), where CI is the confidence interval. Plasma interleukin-6 was positively correlated with plasma NGAL ( r = 0.9, P = 0.001). Moreover, following EIMD, 5 of 10 participants met AKIN criteria for AKI. Thus for the first time we demonstrate that muscle-damaging exercise before running in the heat results in a greater inflammatory state and kidney stress compared with non-muscle-damaging exercise. Muscle damage should therefore be considered a risk factor for AKI when performing exercise in hot environments.
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Affiliation(s)
- Naushad A. Junglee
- Extremes Research Group, College of Health and Behavioural Sciences, Bangor University, Bangor, Wales, United Kingdom
- Department of Nephrology, Gwynedd Hospital, Betsi Cadwaladr University Health Board, Bangor, Wales, United Kingdom; and
| | - Umberto Di Felice
- Extremes Research Group, College of Health and Behavioural Sciences, Bangor University, Bangor, Wales, United Kingdom
- Department of Biomedical Sciences and Technologies, University of L'Aquila, Coppito, Italy
| | - Alberto Dolci
- Extremes Research Group, College of Health and Behavioural Sciences, Bangor University, Bangor, Wales, United Kingdom
| | - Matthew B. Fortes
- Extremes Research Group, College of Health and Behavioural Sciences, Bangor University, Bangor, Wales, United Kingdom
| | - Mahdi M. Jibani
- Department of Nephrology, Gwynedd Hospital, Betsi Cadwaladr University Health Board, Bangor, Wales, United Kingdom; and
| | - Andrew B. Lemmey
- Extremes Research Group, College of Health and Behavioural Sciences, Bangor University, Bangor, Wales, United Kingdom
| | - Neil P. Walsh
- Extremes Research Group, College of Health and Behavioural Sciences, Bangor University, Bangor, Wales, United Kingdom
| | - Jamie H. Macdonald
- Extremes Research Group, College of Health and Behavioural Sciences, Bangor University, Bangor, Wales, United Kingdom
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Sprake PM, Hubertus C, Bissett WT, Porter BF, Russell KE, Garland T, Young BD, Washburn KE. Neurological disease in lambs associated with exposure to high environmental temperature and humidity. J Vet Intern Med 2013; 27:1242-7. [PMID: 23952523 DOI: 10.1111/jvim.12157] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Revised: 04/22/2013] [Accepted: 07/10/2013] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND We detected a pattern of lambs presenting with hyperthermia and neurological signs during the summer. OBJECTIVES The main objectives of this study were to compare clinical findings and results of diagnostic testing and to identify a potential etiology. ANIMALS Fifteen clinical cases of lambs less than 12 months of age presenting with neurological signs, tachypnea, and hyperthermia over 4 summers. METHODS Retrospective case series. Medical records were searched for lambs less than 12 months of age that presented with neurological signs including the following: kyphosis, pelvic limb hyperextension, treading of feet, muscle tremors and recumbency, and hyperthermia of greater than 104°F. A grading system was established to describe severity of presenting neurological signs. Weather data were collected from weather stations near the farm of origin for 3 days prior to presentation. RESULTS The lambs were from 7 flocks in central Texas. All cases occurred between July and September, with a median heat index of 90.5 for the 3 days before presentation. Complete blood count, serum chemistry, necropsy examination, rumen content, virology, brain MRI, liver copper, selenium, and vitamin E failed to identify a consistent etiology for the signs presented. The only common factor was high heat and humidity. Histopathological examination identified axonal degeneration and skeletal muscle necrosis in some lambs. CONCLUSIONS AND CLINICAL IMPORTANCE These clinical cases appeared similar to the Australian disease humpyback and indicate that lambs exposed to high environmental temperatures and humidity might be at risk of developing the described clinical presentation.
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Affiliation(s)
- P M Sprake
- Large Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX
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