The adaptive value of fever

Antimicrobial prophylaxis is not indicated for horses undergoing general anaesthesia for elective orthopaedic MRI

BACKGROUND

Post-anaesthetic fever is a known complication of general anaesthesia, however, its incidence in horses undergoing elective magnetic resonance imaging (MRI) is unknown.

OBJECTIVE

To determine the incidence of post-anaesthetic fever in horses undergoing elective orthopaedic MRI and determine whether prophylactic antimicrobial therapy would be associated with a reduction in the incidence of post-anaesthetic fever. We hypothesised that prophylactic antimicrobials would be associated with a reduction in the incidence of post-anaesthetic fever.

STUDY DESIGN

Retrospective cross-sectional study.

METHODS

This retrospective study included 791 elective orthopaedic MRIs in systemically healthy horses between June 2006 and March 2020 that recovered from general anaesthesia and did not undergo surgery or intensive medical therapy soon after recovery. Potential factors associated with post-anaesthetic fever were evaluated using multivariable logistic regression. Case signalment, travel time, preanaesthetic haematology and fibrinogen abnormalities, use of prophylactic antimicrobials, peri-anaesthetic nonsteroidal anti-inflammatories, anaesthesia time and recovery time were all evaluated for association with post-anaesthetic fever.

RESULTS

Of 791 MRI cases, 44 (5.6%) developed a post-anaesthetic fever. Horses that received prophylactic antimicrobials were [odds ratio (OR) 3.8, 95% confidence interval (CI) 1.98-7.46; p ≤ 0.001] more likely to develop a post-anaesthetic fever than those that did not receive antimicrobials. Young horses (1-4 years of age) were (OR 2.8, 95% CI 1.26-6.17; p = 0.01) more likely to develop fever compared with adult horses (≥5 years of age).

MAIN LIMITATIONS

Limitations of this study pertain to retrospective analysis including nonrandomised case selection and incomplete data records.

CONCLUSIONS

While fever may indicate infection, the majority of early post-anaesthetic fevers resolved before discharge from the hospital with no identified cause. The use of prophylactic antimicrobials to reduce the risk of post-anaesthetic fever for elective MRI is not supported by this study.

Antipyretic Use in Noncritically Ill Patients With Fever: A Review

Antipyretics are one of the most frequently used agents in medicine. Numerous pharmacological agents, such as acetaminophen, non-steroidal anti-inflammatory agents (NSAIDs), salicylates, and selective cyclooxygenase 2 (COX-2) inhibitors, and nonpharmacological treatment modalities, such as tepid sponging and cooling blankets, are available for temperature reduction. There is a scarcity of definitive clinical guidelines on the choice of various agents in noncritically ill febrile patients. Our review examined the various modalities available for antipyresis and compared their safety and efficacy. The rationale for the choice of a particular pharmacological agent and route of administration were scrutinized. Our review also envisaged the perceived beneficial effects of antipyretics against the harmful side effects, including the evaluation of morbidity or mortality advantage conferred by antipyretics. The various toxicities associated with these agents were also highlighted.

Diketopyrrolopyrrole-based fluorescent probe for visualizing over-expressed carboxylesterase in fever via ratiometric imaging

Fever is the result of inflammation and the innate self-defense response of organisms, can cause abnormal changes in the activity of many enzymes in organisms, including the important carboxylesterase (CE). Monitoring the activity changes of CE in vivo during a fever will help to understand heat-related pathological mechanisms. In this paper, we designed diketopyrrolopyrrole-based ratiometric fluorescent probes DPP-FBC-P and DPP-FBO-P containing alkyl chain and diethylene glycol monomethyl ether chain respective for detection of CE. Both probes could realized fast response to CE and displayed good selectivity and high sensitivity. Compared with DPP-FBO-P, DPP-FBC-P had better biocompatibility, larger signal to noise ratio (225-fold vs 125-fold) and lower detection limit (1.6 × 10-5 U/mL vs 4.2 × 10-5 U/mL). Moreover, the probe DPP-FBC-P had been successfully applied to image the endogenous CE in HepG2 cells and solid tumors, and also visualized the over expressed CE in fever cells. Most importantly, the changes of CE level in the liver of fever mice model induced by LPS were monitored with the assistance of DPP-FBC-Pvia dual channel ratio imaging for the first time. In addition, fluorescence color signal in solution was captured by smart phone, and the linear relationship between RGB ratio (G/R) and CE concentration was established. This work will provide a potential approach for investigating the physiological and pathological processes of heat related diseases.

Host-pathogen interactions under pressure: A review and meta-analysis of stress-mediated effects on disease dynamics

Human activities have increased the intensity and frequency of natural stressors and created novel stressors, altering host-pathogen interactions and changing the risk of emerging infectious diseases. Despite the ubiquity of such anthropogenic impacts, predicting the directionality of outcomes has proven challenging. Here, we conduct a review and meta-analysis to determine the primary mechanisms through which stressors affect host-pathogen interactions and to evaluate the impacts stress has on host fitness (survival and fecundity) and pathogen infectivity (prevalence and intensity). We assessed 891 effect sizes from 71 host species (representing seven taxonomic groups) and 78 parasite taxa from 98 studies. We found that infected and uninfected hosts had similar sensitivity to stressors and that responses varied according to stressor type. Specifically, limited resources compromised host fecundity and decreased pathogen intensity, while abiotic environmental stressors (e.g., temperature and salinity) decreased host survivorship and increased pathogen intensity, and pollution increased mortality but decreased pathogen prevalence. We then used our meta-analysis results to develop susceptible-infected theoretical models to illustrate scenarios where infection rates are expected to increase or decrease in response to resource limitations or environmental stress gradients. Our results carry implications for conservation and disease emergence and reveal areas for future work.

Evolutionary Aspects of Infections: Inflammation and Sickness Behaviors

Sickness behavior was conceptualized initially as the behavioral counterpart of the fever response to infectious pathogens. It helps to raise body temperature to its higher setpoint and to maintain it at this new level and it has the additional benefit of enabling a weakened organism to protect itself from other dangers. The discovery of the behavioral effects of proinflammatory cytokines produced by activated immune cells provided a cellular and molecular basis to this phenomenon. The administration of cytokines or cytokine inducers like lipopolysaccharide to healthy rodents allowed to reveal the similarities and differences between inflammation-induced sickness behavior and the fever response. It also led to the understanding of how the inflammatory response that is triggered at the periphery can propagate into the brain and induce the behavioral manifestations of sickness. At the behavioral level, the demonstration that sickness behavior is the expression of a motivational state that reorganizes perception and action in face of a microbial pathogen just like fear in face of a predator appeared at first glance to strengthen the adaptive value of this behavior. However, all aspects of sickness behavior are not always favorable for the organism. This is the case for anorexia that is beneficial in the context of bacterial infection but detrimental in the context of viral infection. In addition, studies of sickness behavior in natural conditions revealed that like any other defensive behavior, sickness behavior requires trade-offs between its survival benefits for the sick individual and the costs incurred especially in the context of gregarious groups. Thanks to these studies, evidence is emerging that sickness behavior is much more variable in its expression than initially thought, and that part of this variability depends not only on the pathogen and the social context in which the infection develops but also on individual factors including species, sex, age, nutrition, and physiological status.

Measurements of body temperature and oxidative stress reveal differential costs associated with humoral immune function in a passerine bird

Eco-immunology considers resistance to antigens a costly trait for an organism, but actual quantification of such costs is not straightforward. Costs of the immune response are visible in impaired coloration and reduced growth or reproductive success. Activation of the humoral immune response is a slow, complex and long-lasting process, which makes the quantification of its energetic cost a potential losing game. We implemented near-continuous measurements of body temperature in zebra finches (Taeniopygia guttata) as a proxy for the energetic cost, with a particular focus during activation of the humoral immune response until the peak of antibody release several days later. At the peak of the antibody release we additionally measured oxygen consumption (open-flow respirometry) and markers of oxidative stress (dROMs, OXY). Birds with an activated immune response maintained a higher night-time body temperature during the first 4 nights after an immune challenge in comparison to controls, implying increased night-time energy use. At peak antibody production, we did not find differences in night-time body temperature and oxygen consumption but observed differentiated results for oxygen consumption during the day. Immune-challenged females had significantly higher oxygen consumption compared with other groups. Moreover, we found that activation of the humoral immune response increases oxidative damage, a potential cost of maintaining the higher night-time body temperature that is crucial at the early stage of the immune response. The costs generated by the immune system appear to consist of two components - energetic and non-energetic - and these appear to be separated in time.

Factors Associated with Mortality in Patients with COVID-19 Receiving Prolonged Ventilatory Support

Background: Since its emergence in early 2020, coronavirus disease 2019 (COVID-19)-associated pneumonia has caused a global strain on intensive care unit (ICU) resources with many intubated patients requiring prolonged ventilatory support. Outcomes for patients with COVID-19 who receive prolonged intubation (>21 days) and possible predictors of mortality in this group are not well established. Patients and Methods: Data were prospectively collected from adult patients with COVID-19 requiring mechanical ventilation from March 2020 through December 2021 across a system of 11 hospitals. The primary end point was in-hospital mortality. Factors associated with mortality were evaluated using univariable and multivariable logistic regression analyses. Results: Six hundred six patients were placed on mechanical ventilation for COVID-19 pneumonia during the study period, with in-hospital mortality of 40.3% (n = 244). Increased age (odds ratio [OR], 1.06; 95% confidence interval [CI], 1.03-1.09), increased creatinine (OR, 1.40; 95% CI, 1.08-1.82), and receiving corticosteroids (OR, 2.68; 95% CI, 1.20-5.98) were associated with mortality. Intubations lasting longer than 21 days (n = 140) had a lower in-hospital mortality of 25.7% (n = 36; p < 0.001). Increasing Elixhauser comorbidity index (OR, 1.12; 95% CI, 1.04-1.19) and receiving corticosteroids (OR, 1.92; 95% CI, 1.06-3.47) were associated with need for prolonged ventilation. In this group, increased age (OR, 1.06; 95% CI, 1.01-1.08) and non-English speaking (OR, 3.74; 95% CI, 1.13-12.3) were associated with mortality. Conclusions: In-hospital mortality in mechanically ventilated patients with COVID-19 pneumonia occurs primarily in the first 21 days after intubation, possibly related to the early active inflammatory process. In patients on prolonged mechanical ventilation, increased age and being non-English speaking were associated with mortality.

Cutaneous TRPV4 Channels Activate Warmth-Defense Responses in Young and Adult Birds

Transient receptor potential vanilloid 4 (TRPV4) channels are sensitive to warm ambient temperatures (Tas), triggering heat loss responses in adult rats in a Tas range of ∼26–30°C. In birds, however, the thermoregulatory role of TRPV4 has never been shown. Here, we hypothesized that stimulation of TRPV4 induces thermolytic responses for body temperature (Tb) maintenance in birds, and that this function is already present in early life, when the Ta range for TRPV4 activation does not represent a warm condition for these animals. We first demonstrated the presence of TRPV4 in the dorsal and ventral skin of chickens (Gallus gallus domesticus) by immunohistochemistry. Then, we evaluated the effects of the TRPV4 agonist, RN1747, and the TRPV4 antagonists, HC067047 and GSK2193874, on Tb and thermoeffectors at different Tas in 5-day-old chicks and 60-day-old adult chickens. For the chicks, RN1747 transiently reduced Tb both in thermoneutrality (31°C) and in a cold Ta for this phase (26°C), which relied on huddling behavior inhibition. The TRPV4 antagonists alone did not affect Tb or thermoeffectors but blocked the Tb decrease and huddling inhibition promoted by RN1747. For the adults, TRPV4 antagonism increased Tb when animals were exposed to 28°C (suprathermoneutral condition for adults), but not to 19°C. In contrast, RN1747 decreased Tb by reducing metabolic rate and activating thermal tachypnea at 19°C, a Ta below the activation range of TRPV4. Our results indicate that peripheral TRPV4 receptors are functional in early life, but may be inhibited at that time when the range of activation (∼26–30°C) represents cold Ta for chicks, and become physiologically relevant for Tb maintenance when the activation Ta range for TRPV4 becomes suprathermoneutral for adult chickens.

Fever therapy in febrile adults: systematic review with meta-analyses and trial sequential analyses

OBJECTIVE

To investigate the effects of fever therapy compared with no fever therapy in a wide population of febrile adults.

DESIGN

Systematic review with meta-analyses and trial sequential analyses of randomised clinical trials.

DATA SOURCES

CENTRAL, BIOSIS, CINAHL, MEDLINE, Embase, LILACS, Scopus, and Web of Science Core Collection, searched from their inception to 2 July 2021.

ELIGIBILITY CRITERIA

Randomised clinical trials in adults diagnosed as having fever of any origin. Included experimental interventions were any fever therapy, and the control intervention had to be no fever therapy (with or without placebo/sham).

DATA EXTRACTION AND SYNTHESIS

Two authors independently selected studies, extracted data, and assessed the risk of bias. Primary outcomes were all cause mortality and serious adverse events. Secondary outcomes were quality of life and non-serious adverse events. Aggregate data were synthesised with meta-analyses, subgroup analyses, and trial sequential analyses, and the evidence was assessed using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach.

RESULTS

Forty two trials assessing 5140 participants were included. Twenty three trials assessed 11 different antipyretic drugs, 11 trials assessed physical cooling, and eight trials assessed a combination of antipyretic drugs and physical cooling. Of the participants, 3007 were critically ill, 1892 were non-critically ill, 3277 had infectious fever, and 1139 had non-infectious fever. All trials were assessed as being at high risk of bias. Meta-analysis and trial sequential analysis showed that the hypothesis that fever therapy reduces the risk of death (risk ratio 1.04, 95% confidence interval 0.90 to 1.19; I²=0%; P=0.62; 16 trials; high certainty evidence) and the risk of serious adverse events (risk ratio 1.02, 0.89 to 1.17; I²=0%; P=0.78; 16 trials; high certainty evidence) could be rejected. One trial assessing quality of life was included, showing no difference between fever therapy and control. Meta-analysis and trial sequential analysis showed that the hypothesis that fever therapy reduces the risk of non-serious adverse events could be neither confirmed nor rejected (risk ratio 0.92, 0.67 to 1.25; I²=66.5%; P=0.58; four trials; very low certainty evidence).

CONCLUSIONS

Fever therapy does not seem to affect the risk of death and serious adverse events.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42019134006.

Distinct Cellular Tools of Mild Hyperthermia-Induced Acquired Stress Tolerance in Chinese Hamster Ovary Cells

Mild stress could help cells to survive more severe environmental or pathophysiological conditions. In the current study, we investigated the cellular mechanisms which contribute to the development of stress tolerance upon a prolonged (0-12 h) fever-like (40 °C) or a moderate (42.5 °C) hyperthermia in mammalian Chinese Hamster Ovary (CHO) cells. Our results indicate that mild heat triggers a distinct, dose-dependent remodeling of the cellular lipidome followed by the expression of heat shock proteins only at higher heat dosages. A significant elevation in the relative concentration of saturated membrane lipid species and specific lysophosphatidylinositol and sphingolipid species suggests prompt membrane microdomain reorganization and an overall membrane rigidification in response to the fluidizing heat in a time-dependent manner. RNAseq experiments reveal that mild heat initiates endoplasmic reticulum stress-related signaling cascades resulting in lipid rearrangement and ultimately in an elevated resistance against membrane fluidization by benzyl alcohol. To protect cells against lethal, protein-denaturing high temperatures, the classical heat shock protein response was required. The different layers of stress response elicited by different heat dosages highlight the capability of cells to utilize multiple tools to gain resistance against or to survive lethal stress conditions.

Temperature Management in the ICU

OBJECTIVE

Temperature abnormalities are recognized as a marker of human disease, and the therapeutic value of temperature is an attractive treatment target. The objective of this synthetic review is to summarize and critically appraise evidence for active temperature management in critically ill patients.

DATA SOURCES

We searched MEDLINE for publications relevant to body temperature management (including targeted temperature management and antipyretic therapy) in cardiac arrest, acute ischemic and hemorrhagic stroke, traumatic brain injury, and sepsis. Bibliographies of included articles were also searched to identify additional relevant studies.

STUDY SELECTION

English-language systematic reviews, meta-analyses, randomized trials, observational studies, and nonhuman data were reviewed, with a focus on the most recent randomized control trial evidence.

DATA EXTRACTION

Data regarding study methodology, patient population, temperature management strategy, and clinical outcomes were qualitatively assessed.

DATA SYNTHESIS

Temperature management is common in critically ill patients, and multiple large trials have been conducted to elucidate temperature targets, management strategies, and timing. The strongest data concerning the use of therapeutic hypothermia exist in comatose survivors of cardiac arrest, and recent trials suggest that appropriate postarrest temperature targets between 33°C and 37.5°C are reasonable. Targeted temperature management in other critical illnesses, including acute stroke, traumatic brain injury, and sepsis, has not shown benefit in large clinical trials. Likewise, trials of pharmacologic antipyretic therapy have not demonstrated improved outcomes, although national guidelines do recommend treatment of fever in patients with stroke and traumatic brain injury based on observational evidence associating fever with worse outcomes.

CONCLUSIONS

Body temperature management in critically ill patients remains an appealing therapy for several illnesses, and additional studies are needed to clarify management strategies and therapeutic pathways.

Potential for Further Mismanagement of Fever During COVID-19 Pandemic: Possible Causes and Impacts

Fever remains an integral part of acute infectious diseases management, especially for those without effective therapeutics, but the widespread myths about "fevers" and the presence of confusing guidelines from different agencies, which have heightened during the coronavirus disease 2019 (COVID-19) pandemic and are open to alternate interpretation, could deny whole populations the benefits of fever. Guidelines suggesting antipyresis for 37.8-39°C fever are concerning as 39°C boosts the protective heat-shock and immune response (humoral, cell-mediated, and nutritional) whereas ≥40°C initiates/enhances the antiviral responses and restricts high-temperature adapted pathogens, e.g., severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), strains of influenza, and measles. Urgent attention is accordingly needed to address the situation because of the potential public health consequences of the existence of conflicting guidelines in the public domain. We have in this article attempted to restate the benefits of fever in disease resolution, dispel myths, and underline the need for alignment of national treatment guidelines with that of the WHO, to promote appropriate practices and reduce the morbidity and mortality from infectious diseases, such as COVID-19.

Acute-Phase Immune Response Involves Fever, Sickness Behavior, and an Elevated Metabolic Rate in the Subterranean Rodent Ctenomys talarum

AbstractThe acute-phase response (APR) is an induced innate response and may involve pronounced physiological and behavioral changes. One of the most common assays to study the APR involves the use of a lypopolysaccharide (LPS) from the cell wall of gram-negative bacteria. In this study, we determined the energetic costs of the APR in the subterranean rodent Ctenomys talarum, as well as the effects of the exposure to LPS on body temperature, body mass loss, and behavior in this species. Furthermore, we monitored levels of circulating endotoxin after LPS exposure. Our results suggest that in C. talarum, the APR is energetically costly, resulting in a 14% increase in metabolic rate. Animals exposed to LPS experienced a short-term thermal response, weight loss, and changes in their behavior that included more time spent resting and with their eyes totally or partially closed. However, the magnitude of the effects of LPS exposure varied between sexes and among animals. Also, there was a clear peak in circulating endotoxin levels in plasma 3 h postinjection (hpi) and a significant decrease of these levels 24 hpi, but peak endotoxin concentration values recorded were highly variable among animals. In light of these results, ecological determinants of immune function variation in tuco-tucos are discussed considering the roles of pace of life, habitat, and degree of pathogen exposure in these subterranean rodents.

Metabolic trade-offs favor regulated hypothermia and inhibit fever in immune-challenged chicks

The febrile response to resist a pathogen is energetically expensive while regulated hypothermia seems to preserve energy for vital functions. We hypothesized here that immune challenged birds under metabolic trade-offs (reduced energy supply / increased energy demand) favor a regulated hypothermic response at the expense of fever. To test this hypothesis, we compared 5-days old broiler chicks exposed to fasting, cold (25oC), and fasting combined with cold to a control group fed at thermoneutral condition (30oC). The chicks were injected with saline or with a high dose of endotoxin known to induce a biphasic thermal response composed of body temperature (Tb) drop followed by fever. Then Tb, oxygen consumption (metabolic rate), peripheral vasomotion (cutaneous heat exchange), breathing frequency (respiratory heat exchange), and huddling behavior (heat conservation indicator) were analyzed. Irrespective of metabolic trade-offs, chicks presented a transient regulated hypothermia in the first hour, which relied on a suppressed metabolic rate for all groups, increased breathing frequency for chicks fed/fasted at 30oC, and peripheral vasodilation in fed/fasted chicks at 25oC. Fever was observed only in chicks kept at thermoneutrality and was supported by peripheral vasoconstriction and huddling behavior. Fed and fasted chicks at 25oC completely eliminated fever despite the ability to increase metabolic rate for thermogenesis in the phase correspondent to fever when it was pharmacologically induced by 2.4-Dinitrophenol. Our data suggest that increased competing demands affect chicks’ response to an immune challenge favoring regulated hypothermia to preserve energy while the high costs of fever to resist a pathogen are avoided.

Evolutionary physiology at 30+: Has the promise been fulfilled?: Advances in Evolutionary Physiology: Advances in Evolutionary Physiology

Three decades ago, interactions between evolutionary biology and physiology gave rise to evolutionary physiology. This caused comparative physiologists to improve their research methods by incorporating evolutionary thinking. Simultaneously, evolutionary biologists began focusing more on physiological mechanisms that may help to explain constraints on and trade-offs during microevolutionary processes, as well as macroevolutionary patterns in physiological diversity. Here we argue that evolutionary physiology has yet to reach its full potential, and propose new avenues that may lead to unexpected advances. Viewing physiological adaptations in wild animals as potential solutions to human diseases offers enormous possibilities for biomedicine. New evidence of epigenetic modifications as mechanisms of phenotypic plasticity that regulate physiological traits may also arise in coming years, which may also represent an overlooked enhancer of adaptation via natural selection to explain physiological evolution. Synergistic interactions at these intersections and other areas will lead to a novel understanding of organismal biology.

Preventive Administration of the Heat Shock Protein Hsp70 Relieves Endotoxemia-Induced Febrile Reaction in Pigeons ( ) and Rats

The stress-inducible 70 kDa heat shock protein (Hsp70) can exert a protective effect on endotoxemia and sepsis due to its ability to interact with immune cells and modulate the immune response. However, it remains unknown whether Hsp70 is able to relieve endotoxemia-induced fever. We carried out a comparative study of the effects of preventive administration of the human recombinant Hsp70 (HSPA1A) on lipopolysaccharide (LPS)-induced endotoxemia in pigeons and rats with preimplanted electrodes and thermistors for recording the thermoregulation parameters (brain temperature, peripheral vasomotor reaction, muscular contractile activity). Additionally, we analyzed the dynamics of the white blood cell (WBC) count in rats under the same conditions. It was found that preventive administration of Hsp70 relieves the LPS-induced febrile reaction in pigeons and rats and accelerates the restoration of the WBC count in rats. The data obtained suggest that these warm-blooded animals share a common physiological mechanism that underlies the protective effect of Hsp70.

The effects of aging on host resistance and disease tolerance to SARS-CoV-2 infection

The ongoing coronavirus disease 2019 (COVID-19) crisis caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has triggered a large-scale pandemic that is afflicting millions of individuals in over 200 countries. The clinical spectrum caused by SARS-CoV-2 infections can range from asymptomatic infection to mild undifferentiated febrile illness to severe respiratory disease with multiple complications. Elderly patients (aged 60 and above) with comorbidities such as cardiovascular diseases and diabetes mellitus appear to be at highest risk of a severe disease outcome. To protect against pulmonary immunopathology caused by SARS-CoV-2 infection, the host primarily depends on two distinct defense strategies: resistance and disease tolerance. Resistance is the ability of the host to suppress and eliminate incoming viruses. By contrast, disease tolerance refers to host responses that promote host health regardless of their impact on viral replication. Disruption of either resistance or disease tolerance mechanisms or both could underpin predisposition to elevated risk of severe disease during viral infection. Aging can disrupt host resistance and disease tolerance by compromising immune functions, weakening of the unfolded protein response, progressive mitochondrial dysfunction, and altering metabolic processes. A comprehensive understanding of the molecular mechanisms underlying declining host defense in elderly individuals could thus pave the way to provide new opportunities and approaches for the treatment of severe COVID-19.

Behavioural Fever Promotes an Inflammatory Reflex Circuit in Ectotherms

Background: The communication between the brain and the immune system is a cornerstone in animal physiology. This interaction is mediated by immune factors acting in both health and pathogenesis, but it is unclear how these systems molecularly and mechanistically communicate under changing environmental conditions. Behavioural fever is a well-conserved immune response that promotes dramatic changes in gene expression patterns during ectotherms’ thermoregulatory adaptation, including those orchestrating inflammation. However, the molecular regulators activating the inflammatory reflex in ectotherms remain unidentified. Methods: We revisited behavioural fever by providing groups of fish a thermal gradient environment during infection. Our novel experimental setup created temperature ranges in which fish freely moved between different thermal gradients: (1) wide thermoregulatory range; T° = 6.4 °C; and (2) restricted thermoregulatory range; T° = 1.4 °C. The fish behaviour was investigated during 5-days post-viral infection. Blood, spleen, and brain samples were collected to determine plasmatic pro- and anti-inflammatory cytokine levels. To characterize genes’ functioning during behavioural fever, we performed a transcriptomic profiling of the fish spleen. We also measured the activity of neurotransmitters such as norepinephrine and acetylcholine in brain and peripheral tissues. Results: We describe the first set of the neural components that control inflammatory modulation during behavioural fever. We identified a neuro-immune crosstalk as a potential mechanism promoting the fine regulation of inflammation. The development of behavioural fever upon viral infection triggers a robust inflammatory response in vivo, establishing an activation threshold after infection in several organs, including the brain. Thus, temperature shifts strongly impact on neural tissue, specifically on the inflammatory reflex network activation. At the molecular level, behavioural fever causes a significant increase in cholinergic neurotransmitters and their receptors’ activity and key anti-inflammatory factors such as cytokine Il10 and Tgfβ in target tissues. Conclusion: These results reveal a cholinergic neuronal-based mechanism underlying anti-inflammatory responses under induced fever. We performed the first molecular characterization of the behavioural fever response and inflammatory reflex activation in mobile ectotherms, identifying the role of key regulators of these processes. These findings provide genetic entry points for functional studies of the neural–immune adaptation to infection and its protective relevance in ectotherm organisms.

Pathophysiology of Fever and Application of Infrared Thermography (IRT) in the Detection of Sick Domestic Animals: Recent Advances

Body-temperature elevations are multifactorial in origin and classified as hyperthermia as a rise in temperature due to alterations in the thermoregulation mechanism; the body loses the ability to control or regulate body temperature. In contrast, fever is a controlled state, since the body adjusts its stable temperature range to increase body temperature without losing the thermoregulation capacity. Fever refers to an acute phase response that confers a survival benefit on the body, raising core body temperature during infection or systemic inflammation processes to reduce the survival and proliferation of infectious pathogens by altering temperature, restriction of essential nutrients, and the activation of an immune reaction. However, once the infection resolves, the febrile response must be tightly regulated to avoid excessive tissue damage. During fever, neurological, endocrine, immunological, and metabolic changes occur that cause an increase in the stable temperature range, which allows the core body temperature to be considerably increased to stop the invasion of the offending agent and restrict the damage to the organism. There are different metabolic mechanisms of thermoregulation in the febrile response at the central and peripheral levels and cellular events. In response to cold or heat, the brain triggers thermoregulatory responses to coping with changes in body temperature, including autonomic effectors, such as thermogenesis, vasodilation, sweating, and behavioral mechanisms, that trigger flexible, goal-oriented actions, such as seeking heat or cold, nest building, and postural extension. Infrared thermography (IRT) has proven to be a reliable method for the early detection of pathologies affecting animal health and welfare that represent economic losses for farmers. However, the standardization of protocols for IRT use is still needed. Together with the complete understanding of the physiological and behavioral responses involved in the febrile process, it is possible to have timely solutions to serious problem situations. For this reason, the present review aims to analyze the new findings in pathophysiological mechanisms of the febrile process, the heat-loss mechanisms in an animal with fever, thermoregulation, the adverse effects of fever, and recent scientific findings related to different pathologies in farm animals through the use of IRT.

How Does the Social Grouping of Animals in Nature Protect Against Sickness? A Perspective

Sickness behavior is broadly represented in vertebrates, usually in association with the fever response in response to acute infections. The reactions to sickness behavior in a group member or potential group member in humans is quite variable, depending upon circumstances. In animals, the reactions to sickness behavior in a group member or potential group member evoke a specific response that reflects the species-specific lifestyle. Groups of animals can employ varied strategies to reduce or address exposure to sickness. Most of these have scarcely been studied in nature from a disease perspective: (1) adjusting exposure to sick conspecifics or contaminated areas; (2) caring for a sick group member; (3) peripheralization and agonistic behaviors to strange non-group conspecifics; and (4) using special strategies at parturition when newborn are healthy but vulnerable. Unexplored in this regard is infanticide, where newborn that are born with very little immunity until they receive antibody-rich colostrum, could be a target of maternal infanticide if they manifest signs of sickness and could be infectious to littermates. The strategies used by different species are highly specific and dependent upon the particular circumstances. What is needed is a more general awareness and consideration of the possibilities that avoiding or adapting to sickness behavior may be driving some social behaviors of animals in nature.

Recognition in Emergency Department of Septic Patients at Higher Risk of Death: Beware of Patients without Fever

Background and Objectives: Chances of surviving sepsis increase markedly upon prompt diagnosis and treatment. As most sepsis cases initially show-up in the Emergency Department (ED), early recognition of a septic patient has a pivotal role in sepsis management, despite the lack of precise guidelines. The aim of this study was to identify the most accurate predictors of in-hospital mortality outcome in septic patients admitted to the ED. Materials and Methods: We compared 651 patients admitted to ED for sepsis (cases) with 363 controls (non-septic patients). A Bayesian mean multivariate logistic regression model was performed in order to identify the most accurate predictors of in-hospital mortality outcomes in septic patients. Results: Septic shock and positive qSOFA were identified as risk factors for in-hospital mortality among septic patients admitted to the ED. Hyperthermia was a protective factor for in-hospital mortality. Conclusions: Physicians should bear in mind that fever is not a criterium for defining sepsis; according to our results, absence of fever upon presentation might be indicative of greater severity and diagnosis of sepsis should not be delayed.

Sickness behaviors across vertebrate taxa: proximate and ultimate mechanisms

There is nothing like a pandemic to get the world thinking about how infectious diseases affect individual behavior. In this respect, sick animals can behave in ways that are dramatically different from healthy animals: altered social interactions and changes to patterns of eating and drinking are all hallmarks of sickness. As a result, behavioral changes associated with inflammatory responses (i.e. sickness behaviors) have important implications for disease spread by affecting contacts with others and with common resources, including water and/or sleeping sites. In this Review, we summarize the behavioral modifications, including changes to thermoregulatory behaviors, known to occur in vertebrates during infection, with an emphasis on non-mammalian taxa, which have historically received less attention. We then outline and discuss our current understanding of the changes in physiology associated with the production of these behaviors and highlight areas where more research is needed, including an exploration of individual and sex differences in the acute phase response and a greater understanding of the ecophysiological implications of sickness behaviors for disease at the population level.

Regulated hypothermia in response to endotoxin in birds

KEY POINTS

The costs associated with immune and thermal responses may exceed the benefits to the host during severe inflammation. In this case, regulated hypothermia instead of fever can occur in rodents as a beneficial strategy to conserve energy for vital functions with consequent tissue protection and hypoxia prevention. We tested the hypothesis that this phenomenon is not exclusive to mammals, but extends to the other endothermic group, birds. A decrease in metabolic rate without any failure in mitochondrial respiration, nor oxygen delivery, is the main evidence supporting the regulated nature of endotoxin-induced hypothermia in chicks. Thermolytic mechanisms such as tachypnea and cutaneous vasodilatation can also be recruited to facilitate body temperature decrease under lipopolysaccharide treatment, especially in the cold. Our findings bring a new perspective for evolutionary medicine studies on energy trade-off in host defence because regulated hypothermia may be a phenomenon spread among vertebrates facing a severe immune challenge.

ABSTRACT

A switch from fever to regulated hypothermia can occur in mammals under circumstances of reduced physiological fitness (e.g. sepsis) to direct energy to defend vital systems. Birds in which the cost to resist a pathogen is additive to the highest metabolic rate and body temperature (T_b ) among vertebrates may also benefit from regulated hypothermia during systemic inflammation. Here, we show that the decrease in T_b observed during an immune challenge in birds is a regulated hypothermia, and not a result of metabolic failure. We investigated O₂ consumption (thermogenesis index), ventilation (respiratory heat loss), skin temperature (sensible heat loss) and muscle mitochondrial respiration (thermogenic tissue) during T_b fall in chicken chicks challenged with endotoxin [lipopolysaccharide (LPS)]. Chicks injected with LPS were also tested regarding the capacity to raise O₂ consumption to meet an increased demand driven by 2,4-dinitrophenol. LPS decreased T_b and the metabolic rate of chicks without affecting muscle uncoupled, coupled and non-coupled mitochondrial respiration. LPS-challenged chicks were indeed capable of increasing metabolic rate in response to 2,4-dinitrophenol, indicating no O₂ delivery limitation. Additionally, chicks did not attempt to prevent T_b from falling during hypothermia but, instead, activated cutaneous and respiratory thermolytic mechanisms, providing an additional cooling force. These data provide the first evidence of the regulated nature of the hypothermic response to endotoxin in birds. Therefore, it changes the current understanding of bird's thermoregulation during severe inflammation, indicating that regulated hypothermia is either a convergent trait for endotherms or a conserved response among vertebrates, which adds a new perspective for evolutionary medicine research.

Influence of EPs 7630 on Antipyretic Comedication and Recovery from Acute Tonsillopharyngitis in Children: A Meta-analysis of Randomized, Placebo-Controlled, Clinical Trials

Objective Acute tonsillopharyngitis (ATP) is a common, seasonal infection of predominantly viral origin. Management is aimed at shortening the course of the disease and restoring the comfort of the patient. We performed a meta-analysis to investigate whether treatment with the Pelargonium sidoides extract EPs 7630 reduces the use of antipyretic comedication (i.e., acetaminophen) in children suffering from ATP.

Methods Studies were identified from clinical trial registries and medical literature. Randomized, placebo-controlled, clinical trials investigating EPs 7630 in children with ATP and reporting the coadministration of paracetamol were eligible. Based on the raw data of eligible trials, we analyzed cumulative paracetamol use, as well as the ability to attend school at the end of treatment. Three trials including a total of 345 children aged 6 to 10 years and suffering from non-β-hemolytic streptococcal ATP were identified and eligible. Children were administered EPs 7630 or placebo for 6 days.

Results Compared with placebo, EPs 7630 reduced the cumulative paracetamol dose by an average of 449 mg (95% confidence interval [CI]: 252–646 mg; p < 0.001). A total of 19.1% (EPs 7630) and 71.5% (placebo) of children were still unable to attend school at the end of the treatment (risk ratio = 0.28; 95% CI: 0.16–0.48; p < 0.001).

Conclusion Our meta-analysis demonstrates that EPs 7630 reduced the use of antipyretic comedication and accelerated recovery.

Let fever do its job: The meaning of fever in the pandemic era

Although fever is one of the main presenting symptoms of COVID-19 infection, little public attention has been given to fever as an evolved defense. Fever, the regulated increase in the body temperature, is part of the evolved systemic reaction to infection known as the acute phase response. The heat of fever augments the performance of immune cells, induces stress on pathogens and infected cells directly, and combines with other stressors to provide a nonspecific immune defense. Observational trials in humans suggest a survival benefit from fever, and randomized trials published before COVID-19 do not support fever reduction in patients with infection. Like public health measures that seem burdensome and excessive, fevers involve costly trade-offs but they can prevent infection from getting out of control. For infections with novel SARS-CoV-2, the precautionary principle applies: unless evidence suggests otherwise, we advise that fever should be allowed to run its course. Lay summary: For COVID-19, many public health organizations have advised treating fever with medicines such as acetaminophen or ibuprofen. Even though this is a common practice, lowering body temperature has not improved survival in laboratory animals or in patients with infections. Blocking fever can be harmful because fever, along with other sickness symptoms, evolved as a defense against infection. Fever works by causing more damage to pathogens and infected cells than it does to healthy cells in the body. During pandemic COVID-19, the benefits of allowing fever to occur probably outweigh its harms, for individuals and for the public at large.

New Insights into the Role of Glutathione in the Mechanism of Fever

Glutathione is one of the most important and potent antioxidants. The development of pharmacological compounds that can either increase or decrease glutathione concentrations has allowed investigation into the role of glutathione in various biological processes, including immune responses. Recent findings have shown that glutathione not only affects certain factors involved in immunological processes but also modifies complex immune reactions such as fever. Until recently, it was not known why some patients do not develop fever during infection. Data suggest that fever induction is associated with oxidative stress; therefore, antioxidants such as glutathione can reduce pyrexia. Surprisingly, new studies have shown that low glutathione levels can also inhibit fever. In this review, we focus on recent advances in this area, with an emphasis on the role of glutathione in immune responses accompanied by fever. We describe evidence showing that disturbed glutathione homeostasis may be responsible for the lack of fever during infections. We also discuss the biological significance of the antipyretic effects produced by pharmacological glutathione modulators.

Fever control interventions versus placebo, sham or no intervention in adults: a protocol for a systematic review with meta-analysis and Trial Sequential Analysis

INTRODUCTION

Fever is an integral part of the inflammatory response and has therefore likely a physiological role in fighting infections. Nevertheless, whether fever in itself is beneficial or harmful in adults is unknown. This protocol for a systematic review aims at identifying the beneficial and harmful effects of fever control interventions in adults.

METHODS AND ANALYSIS

This protocol for a systematic review was conducted following the recommendations of Cochrane, GRADE and the eight-step assessment suggested by Jakobsen and colleagues for better validation of meta-analytical results in systematic reviews. We plan to include all relevant randomised clinical trials comparing any fever control intervention with placebo, sham or no intervention in adults. We plan to search CENTRAL, MEDLINE, Embase, LILACS, BIOSIS, CINAHL, Scopus and Web of Science Core Collection to identify relevant trials. Any eligible trial will be assessed and classified as either at high risk of bias or low risk of bias, and our primary conclusions will be based on trials at low risk of bias. We will perform our meta-analyses of the extracted data using Review Manager 5.3 and Trial Sequential Analysis. For all our outcomes, we will create a 'Summary of Findings' table based on GRADE assessments of the certainty of the evidence.

ETHICS AND DISSEMINATION

No formal approval or review of ethics is required for this systematic review as individual patient data will not be included. This systematic review has the potential to highlight (1) whether one should believe fever to be beneficial, harmful or neither in adults; (2) the existing knowledge gaps on this topic; and (3) whether the recommendations from guidelines and daily clinical practice are correct. These results will be disseminated through publication in a leading peer-reviewed journal.

PROSPERO REGISTRATION NUMBER

CRD42019134006.

The impact of ectoparasitism on thermoregulation in Yarrow’s Spiny Lizards (Sceloporus jarrovii)

Parasites are ubiquitous and can have large impacts on the fitness of their hosts. The effects of ectoparasites on physiology, behaviour, and immune function suggest that they could be part of the factors which impact thermoregulation. We tested the hypothesis that ectoparasites impact thermoregulation in Yarrow’s Spiny Lizards (Sceloporus jarrovii Cope in Yarrow, 1875) living along an elevational gradient. We predicted a positive association between ectoparasite load and body temperature (Tb), and a negative association between ectoparasite load and effectiveness of thermoregulation (de – db index). We also predicted that the impacts of ectoparasites would be greatest at high elevation where thermal quality of the environment is low because the costs of thermoregulation increase with elevation and these costs can impact thermal immune responses. We found a significant association between the number of chiggers (Trombiculoidea) harboured by lizards and Tb that depended on elevation, but no association between ectoparasite load and de – db index. The mean chigger infection rate was associated with a ΔTb of +0.18 °C at low elevation (consistent with fever) and of –1.07 °C at high elevation (consistent with hypothermia). These findings suggest that parasitism by chiggers impacts lizard Tb in a way that depends on environmental thermal quality.

Febrile and sleep responses to an immune challenge are affected by trait aggressiveness in rats

Sleep is altered in response to an immune challenge: non-rapid eye movement (NREM) sleep is increased and fragmented, REM sleep is inhibited. Sleep and immune response are affected by stress: several stressors inhibit sleep and increase waking time; stress-induced cortisol secretion affects the immune response, with immunosuppressive effects. Different levels of trait aggressiveness are associated with specific patterns of neuroendocrine and autonomic stress responsiveness. Aim of this study was to test the hypothesis that trait aggressiveness, by affecting response to stressors, modifies sleep alterations induced by the activation of the immune response. To this aim, rats were selected on the basis of their latency time to attack a male intruder in the resident-intruder test. Animals were instrumented for chronic recordings of sleep-wake activity and injected, intraperitoneally, with an immune challenge (250 μg/kg lipopolysaccharide - LPS, a component of gram-negative bacterial cell wall). Here we report that high aggressive (HA) rats responded to an immune challenge with a 24-h long increase in cortical brain temperature. During the first 12 post-injection hours, HA rats also responded with a prolonged increase in NREM sleep amount, and a 5-h long and continuous inhibition of REM sleep. In HA rats, the LPS-induced increase in the amount of time spent in NREM sleep was due to an increase in the number of episodes of this sleep phase, without any change in the bout duration. The LPS-induced REM sleep inhibition observed in HA rats was due to a decrease in both the number and duration of REM sleep bouts. In HA rats, during REM sleep, LPS administration significantly reduced the power of the EEG theta band. In non-aggressive (NA) rats, in response to LPS administration, cortical brain temperature was increased only for two hours, NREM sleep was unaffected, and REM sleep inhibition was scattered along the first 8 post-injection hours. The LPS-induced changes in the number of NREM sleep bouts of NA rats were limited to few and scattered hours, with a change in bout duration only in a single hour. A combination of decreases, in few hours, in both REM sleep bouts and their duration contributed to the REM sleep inhibition observed in NA rats. In NA rats, the power of EEG theta band was not modified, during REM sleep, by LPS administration. Gross motor activity was inhibited in both HA and NA rats. Results of this study show that trait aggressiveness affects febrile and sleep responses to an immune challenge.

High mobility group box 1 protein released in the course of aseptic necrosis of tissues sensitizes rats to pyrogenic effects of lipopolysaccharide

It is still an open question as to whether or not aseptic injuries affect the generation of fever due to exogenous pyrogens including bacterial products. Therefore, in the present paper we have investigated the course of endotoxin fever in rats induced with lipopolysaccharide (LPS; given intraperitoneally in a dose of 50 μg/kg) 48 h after subcutaneous administration of turpentine oil (TRP; 0.1 mL per rat) that causes aseptic necrosis of tissues. We found that febrile response was significantly augmented in the animals pre-treated with turpentine compared to control rats (pre-treated with saline), and that observed excessive elevation of body temperature (Tb) was accompanied by enhanced release of fever mediators: interleukin-6 (IL-6) and prostaglandin E₂ (PGE₂) into plasma. Moreover, we found that sensitization to pyrogenic effects of lipopolysaccharide was associated with the increase in plasma level of high mobility group box 1 protein (HMGB1), one of the best-known damage-associated molecular patterns (DAMP), which was recently discovered as inflammatory mediator. Since the injection of anti-HMGB1 antibodies weakened observed hyperpyrexia in the animals pre-treated with turpentine, we conclude that HMGB1 is a plasma-derived factor released in the course of aseptic injury that enhances pyrogenic effects of LPS.

Extract from Coriolus versicolor fungus partially prevents endotoxin tolerance development by maintaining febrile response and increasing IL-6 generation

Endotoxin tolerance is defined as a reduced endotoxin-induced fever following repeated injections of lipopolysaccharide (LPS). Clinical examples of endotoxin tolerance include sepsis or cystic fibrosis. This state is characterized by inhibition of pro-inflammatory cytokines production and decrease in nuclear factor-kappa B (NF-κB) activation. Extract from Coriolus versicolor (CV) fungus is classified as a biological response modifier, which exhibits various biological activities, including immunopotentiating properties. The aim of study was to examine the effect of CV extract injection on body core temperature of Wistar rats during LPS-induced endotoxin tolerance. Body temperature was measured using biotelemetry. CV extract was injected intraperitoneally (100 mg kg^-1) 2 h prior to the first LPS peritoneal administration (50 μg/kg). Endotoxin tolerance was induced by three consecutive daily injections of LPS at the same dose. We also investigated the influence of CV extract pre-injection on the properties of peripheral blood mononuclear cells (PBMCs) isolated from LPS-treated rats in response to LPS stimulation ex vivo. PBMCs were isolated 2 h after the first LPS injection. After 24 h pre-incubation, the cells were stimulated with LPS (1 μg ml^-1) for 4 h. Our results revealed that CV extract partially prevents endotoxin tolerance through maintaining febrile response in rats following consecutive exposure to LPS. This state was accompanied by the ability of PBMCs isolated from rats injected with CV extract and LPS to release larger amounts of interleukin 6 and greater NF-κB activation in response to LPS stimulation ex vivo compared with the cells derived from rats injected only with LPS. Data also showed that CV extract augmented mitogenic effect of LPS on PBMCs and caused increase in reactive oxygen species generation. We concluded that CV extract, by a modifying effect on body temperature during endotoxin tolerance, can be consider as the immunostimulating agent, which prevents the non-specific refractoriness described in patients with sepsis or ischemia.

Faster recovery and reduced paracetamol use - a meta-analysis of EPs 7630 in children with acute respiratory tract infections

OBJECTIVE

Fever is a very common adaptive immune response in acute respiratory tract disorders during infancy. Antipyretic / analgesic drugs such as paracetamol (acetaminophen) are widely used to improve the comfort of the child but may cause medically unneeded antipyresis and rare but potentially serious side effects. We assess whether treatment with Pelargonium sidoides extract EPs 7630 reduces the administration of paracetamol in children with acute tonsillopharyngitis (ATP) or acute bronchitis (AB).

DESIGN

Meta-analysis of randomised, placebo-controlled clinical trials.

METHODS

We searched clinical trial registries (ISRCTN, ClinicalTrials.gov ) and medical literature (MEDLINE, EMBASE), for randomised, placebo-controlled trials investigating the administration of EPs 7630 to children with ATP or AB and reporting the co-administration of paracetamol. Based on the individual participant data of the eligible trials, study populations were characterized according to sex and age, and meta-analyses were performed for cumulative paracetamol use and ability to attend school at treatment end.

RESULTS

Six trials including a total of 523 children aged 6-10 years (EPs 7630: 265; placebo: 258) and suffering from non-β-hemolytic streptococcal ATP (3 trials) or from AB (3 trials) were identified and eligible. Children received EPs 7630 or placebo for 6 (ATP) or 7 days (AB). Compared to placebo, EPs 7630 reduced the cumulative dose of paracetamol in 5 out of the 6 trials, by an average of 244 mg (Hedges' g; - 0.28; 95% confidence interval: [- 0.53; - 0.02]; p < 0.03). At treatment end, 30.2% (EPs 7630) and 74.4% (placebo) of the children were still unable to attend school (risk ratio: 0.43; 95% confidence interval: [0.29; 0.65]; p < 0.001).

CONCLUSIONS

In children aged 6-10 years with AB or ATP, EPs 7630 alleviated the symptom burden and accelerated recovery. Although EPs 7630 has no known antipyretic effect, concomitant use of paracetamol was reduced.

Pyrexia in juvenile dogs: a review of 140 referred cases

Objectives

To describe the presentation, influence of previous treatment and diagnosis in juvenile dogs presenting with pyrexia to a UK referral centre.

Materials and Methods

Clinical records of dogs aged 1 to 18 months presenting with a problem list including pyrexia (≥⃒39∙2°C) that was reproducible during referral hospitalisation were retrospectively reviewed. Signalment, history ‐ including previous treatment, clinical examination findings and diagnosis were recorded. Diagnoses were categorised as non‐infectious inflammatory, infectious, congenital, neoplastic and miscellaneous. The influence of previous treatment on the ability to reach a final diagnosis was analysed.

Results

A total of 140 cases was identified. Diagnosis was reached in 115 cases. Non‐infectious inflammatory disease was identified in 91 cases (79%), infectious disease in 19 cases (17%), a congenital disorder in four dogs (3%) and neoplasia in one dog (1%). Breeds most commonly identified were Border collies (17/140; 12%), beagles (16/140; 11%), Labrador retrievers (11/140; 8%), springer spaniels (9/140; 6%) and cocker spaniels (8/140; 6%). Before presentation, most dogs had received antibiotics (83/140; 59%), non‐steroidal anti‐inflammatory drugs (84/140; 60%) or steroids (9/140; 6%), either alone or in combination. Neither antibiotics nor non‐steroidal anti‐inflammatory drugs influenced the ability to reach a diagnosis. Steroid‐responsive meningitis‐arteritis comprised 55 of 91 (60%) individuals of the non‐infectious inflammatory cohort. All four dogs diagnosed with congenital disorders were Border collies.

Clinical significance

Non‐infectious inflammatory disease, particularly steroid‐responsive meningitis‐arteritis, immune‐mediated polyarthritis and metaphyseal osteopathy, was commonly diagnosed in this population of pyrexic juvenile dogs.

Dose-dependent behavioural fever responses in desert locusts challenged with the entomopathogenic fungus Metarhizium acridum

Behavioural fever is a common response to immune challenge in ectotherms and confers survival benefits. However, costs accrue rapidly as body temperature rises. Thus, the magnitude of adaptive fever responses might reflect the balance of costs and benefits. We investigated behavioural fever in desert locusts, Schistocerca gregaria, infected with the entomopathogenic fungus Metarhizium acridum. We first tracked the time course of behavioural fever in infected locusts, demonstrating that body temperatures rose on the day following inoculation (day 1), and reached peak intensity on the day after that (day 2). Subsequently, the magnitude of fever responses varied during a day, and locusts tended to exhibit high-intensity fever responses in the mornings when basking was first possible. We speculate that this may have resulted from increased fungal load caused by unimpeded growth overnight when locusts could not fever. We next inoculated locusts with different M. acridum doses ranging from 0 to ca. 75,000 conidia. The magnitude of their behavioural fever responses on day 2 post-inoculation was positively related to fungal dose. Thus, we demonstrate dose-dependency in the behavioural fever responses of desert locusts and suggest that this may reflect the adaptive deployment of behavioural fever to minimize costs relative to benefits.

Behavioral Fever Drives Epigenetic Modulation of the Immune Response in Fish

Ectotherms choose the best thermal conditions to mount a successful immune response, a phenomenon known as behavioral fever. The cumulative evidence suggests that behavioral fever impacts positively upon lymphocyte proliferation, inflammatory cytokine expression, and other immune functions. In this study, we have explored how thermal choice during infection impacts upon underpinning molecular processes and how temperature increase is coupled to the immune response. Our results show that behavioral fever results in a widespread, plastic imprint on gene regulation, and lymphocyte proliferation. We further explored the possible contribution of histone modification and identified global associations between temperature and histone changes that suggest epigenetic remodeling as a result of behavioral fever. Together, these results highlight the critical importance of thermal choice in mobile ectotherms, particularly in response to an infection, and demonstrate the key role of epigenetic modification to orchestrate the thermocoupling of the immune response during behavioral fever.

Influence of Aging and Environment on Presentation of Infection in Older Adults

In older adults, pathophysiologic, clinical, and environmental factors all affect the presentation of infections. We explore how age-related changes influence the manifestation and evaluation of infections in this population. Specific topics include immunosenescence, age-related organ-specific physiologic changes, and frailty. We also describe clinical factors influencing infection risk and presentation in older adults, including temperature regulation, cognitive decline, and malnutrition. Finally, we discuss the influence of the setting in which older adults reside on the clinical evaluation of infection. Understanding the influence of all these changes may facilitate the prevention, early recognition, and treatment of infections in older adults.

Host Energy Source Is Important for Disease Tolerance to Malaria

Pathologic infections are accompanied by a collection of short-term behavioral perturbations collectively termed sickness behaviors [1, 2]. These include changes in body temperature, reduced eating and drinking, and lethargy and mimic behaviors of animals in torpor and hibernation [1, 3-6]. Sickness behaviors are important, pathogen-specific components of the host response to infection [1, 3, 7-9]. In particular, host anorexia has been shown to be beneficial or detrimental depending on the infection [7, 8]. While these studies have illuminated the effects of anorexia on infection, they consider this behavior in isolation from other behaviors and from its effects on host metabolism and energy. Here, we explored the temporal dynamics of multiple sickness behaviors and their effect on host energy and metabolism throughout infection. We used the Plasmodium chabaudi AJ murine model of malaria as it causes severe pathology from which most animals recover. We found that infected animals did become anorexic, skewing their metabolism toward fatty acid oxidation and ketosis. Metabolism of fats requires oxygen for the production of ATP. In this model, animals also suffer severe anemia, limiting their ability to carry oxygen concurrent with their switch toward fatty acid metabolism. We reasoned that the combination of anorexia and anemia would increase pressure on glycolysis as a critical energy pathway because it does not require oxygen. Treating infected mice when anorexic with the glycolytic inhibitor 2-deoxyglucose (2DG) reduced survival; treating animals with glucose improved survival. Peak parasite loads were unchanged, demonstrating changes in disease tolerance. Parasite clearance was reduced with 2DG treatment, suggesting altered resistance.

Reverse Engineering the Febrile System

Fever, the elevation of core body temperature by behavioral or physiological means, is one of the most salient aspects of human sickness, yet there is debate regarding its functional role. In this paper, we demonstrate that the febrile system is an evolved adaptation shaped by natural selection to coordinate the immune system to fight pathogens. First, we show that previous arguments in favor of fever being an adaptation are epistemologically inadequate, and we describe how an adaptationist strategy addresses this issue more effectively. Second, we argue that the mechanisms producing fever provide clear indications of adaptation. Third, we demonstrate that there are many beneficial immune system responses activated during fever and that these responses are not mere byproducts of heat on chemical reactions. Rather, we show that natural selection appears to have modified several immune system effects to be coordinated by fever. Fourth, we argue that there are some adaptations that coordinate the febrile system with other important fitness components, particularly growth and reproduction. Finally, we discuss evidence that the febrile system may also have evolved an antitumor function, providing suggestions for future research into this area. This research informs the debate on the functional value of fever and antipyretic use.

Predicting 30-day mortality in patients with sepsis: An exploratory analysis of process of care and patient characteristics

Background

Sepsis represents a significant public health burden, costing the NHS £2.5 billion annually, with 35% mortality in 2006. The aim of this exploratory study was to investigate risk factors predictive of 30-day mortality amongst patients with sepsis in Nottingham.

Methods

Data were collected prospectively from adult patients with sepsis in Nottingham University Hospitals NHS Trust as part of an on-going quality improvement project between November 2011 and March 2014. Patients admitted to critical care with the diagnosis of sepsis were included in the study. In all, 97 separate variables were investigated for their association with 30-day mortality. Variables included patient demographics, symptoms of systemic inflammatory response syndrome, organ dysfunction or tissue hypoperfusion, locations of early care, source of sepsis and time to interventions.

Results

A total of 455 patients were included in the study. Increased age (adjOR = 1.05 95%CI = 1.03-1.07 p < 0.001), thrombocytopenia (adjOR = 3.10 95%CI = 1.23-7.82 p = 0.016), hospital-acquired sepsis (adjOR = 3.34 95%CI = 1.78-6.27 p < 0.001), increased lactate concentration (adjOR = 1.16 95%CI = 1.06-1.27 p = 0.001), remaining hypotensive after vasopressors (adjOR = 3.89 95%CI = 1.26-11.95 p = 0.02) and mottling (adjOR = 3.80 95%CI = 1.06-13.55 p = 0.04) increased 30-day mortality odds. Conversely, fever (adjOR = 0.46 95%CI = 0.28-0.75 p = 0.002), fluid refractory hypotension (adjOR = 0.29 95%CI = 0.10-0.87 p = 0.027) and being diagnosed in surgical wards (adjOR = 0.35 95%CI = 0.15-0.81 p = 0.015) were protective. Treatment timeliness were not significant factors.

Conclusion

Several important predictors of 30-day mortality were found by this research. Retrospective analysis of our sepsis data has revealed mortality predictors that appear to be more patient-related than intervention-specific. With this information, care can be improved for those identified most at risk of death.

Mass mortality of eastern box turtles with upper respiratory disease following atypical cold weather

Emerging infectious diseases cause population declines in many ectotherms, with outbreaks frequently punctuated by periods of mass mortality. It remains unclear, however, whether thermoregulation by ectotherms and variation in environmental temperature is associated with mortality risk and disease progression, especially in wild populations. Here, we examined environmental and body temperatures of free-ranging eastern box turtles Terrapene carolina during a mass die-off coincident with upper respiratory disease. We recorded deaths of 17 turtles that showed clinical signs of upper respiratory disease among 76 adult turtles encountered in Berea, Kentucky (USA), in 2014. Of the 17 mortalities, 11 occurred approximately 14 d after mean environmental temperature dropped 2.5 SD below the 3 mo mean. Partial genomic sequencing of the major capsid protein from 1 sick turtle identified a ranavirus isolate similar to frog virus 3. Turtles that lacked clinical signs of disease had significantly higher body temperatures (23°C) than sick turtles (21°C) during the mass mortality, but sick turtles that survived and recovered eventually warmed (measured by temperature loggers). Finally, there was a significant negative effect of daily environmental temperature deviation from the 3 mo mean on survival, suggesting that rapid decreases in environmental temperature were correlated with mortality. Our results point to a potential role for environmental temperature variation and body temperature in disease progression and mortality risk of eastern box turtles affected by upper respiratory disease. Given our findings, it is possible that colder or more variable environmental temperatures and an inability to effectively thermoregulate are associated with poorer disease outcomes in eastern box turtles.

Fever Phobia as a Reason for Pediatric Emergency Department Visits: Does the Primary Care Physician Make a Difference?

BACKGROUND

Fever is a source of considerable parental anxiety. Numerous studies have also confirmed similar anxiety among health care workers. This study analyzed caregiver knowledge of fever, and beliefs concerning children with a febrile illness, with an emphasis on the referring physician.

METHODS

This was a cross-sectional study of 100 caregivers of children 3 months to 12 years old, treated at an urban tertiary care pediatric emergency department for fever. Caregiver knowledge was assessed with a questionnaire.

RESULTS

Most caregivers correctly defined the threshold for fever as >38.0-38.3°C. Caregivers commonly believed that fever can cause brain damage and epilepsy; the frequency of this belief was not affected by whether they were referred to the emergency department by their pediatrician/family physician or by another physician or arrived without a referral. For a comfortable-appearing child with a temperature not above 38.0°C, both groups reported that they would give antipyretics in similar proportions (mean 31%). The majority of parents in both groups believed that teething could cause fever (mean 74%).

CONCLUSION

Caregivers in this study had limited knowledge of fever and its management in children, even if referred by their primary care physician. We suggest that there is a need for aggressive educational interventions to reduce parents' fever phobia, in clinics as well as in pediatric emergency departments, and that this need may extend to the education of medical personnel as well.

The Association of Fever with Total Mechanical Ventilation Time in Critically Ill Patients

This research aims to investigate the impact of fever on total mechanical ventilation time (TVT) in critically ill patients. Subgroup analysis was conducted using a previous prospective, multicenter observational study. We included mechanically ventilated patients for more than 24 hours from 10 Korean and 15 Japanese intensive care units (ICU), and recorded maximal body temperature under the support of mechanical ventilation (MAX(MV)). To assess the independent association of MAX(MV) with TVT, we used propensity-matched analysis in a total of 769 survived patients with medical or surgical admission, separately. Together with multiple linear regression analysis to evaluate the association between the severity of fever and TVT, the effect of MAX(MV) on ventilator-free days was also observed by quantile regression analysis in all subjects including non-survivors. After propensity score matching, a MAX(MV) ≥ 37.5°C was significantly associated with longer mean TVT by 5.4 days in medical admission, and by 1.2 days in surgical admission, compared to those with MAX(MV) of 36.5°C to 37.4°C. In multivariate linear regression analysis, patients with three categories of fever (MAX(MV) of 37.5°C to 38.4°C, 38.5°C to 39.4°C, and ≥ 39.5°C) sustained a significantly longer duration of TVT than those with normal range of MAX(MV) in both categories of ICU admission. A significant association between MAX(MV) and mechanical ventilator-free days was also observed in all enrolled subjects. Fever may be a detrimental factor to prolong TVT in mechanically ventilated patients. These findings suggest that fever in mechanically ventilated patients might be associated with worse mechanical ventilation outcome.

Fever-range hyperthermia inhibits cells immune response to protein-bound polysaccharides derived from Coriolus versicolor extract

The aim of the study was to explore whether fever-range hyperthermia (FRH) might enhance the anticancer and immunoregulatory activities of protein-bound polysaccharides (PBP), a class of fungus derived immunomodifiers used in the cancer adjuvant therapy. Blood lymphocytes and breast cancer cells (MCF-7) were cultured at 39.5°C in humidified atmosphere containing 5% CO₂ for 2h. After rested at 37°C for 6h, the cells were treated with PBP extract at 100- and 300μg/ml concentration. After indicated time, the proliferative response was analyzed and cytokine mRNA expression assessment was performed by qRT-PCR. In animal model, the FRH was induced by placing rats in the Homeothermic Controller with heating blanket. Animals were heated until Tb reached 39.5°C (±0.2°C) and were maintained at this temperature for 30min. The protein-bound polysaccharides solution was injected i.p. at a dose of 100 mg/kg 6h post FRH. Twenty four hours after treatment, the blood was collected and cytokines expression analysis were performed. The results have shown that fever-range hyperthermia has an inhibitory effect on PBP extract-induced proliferative response of blood lymphocytes, as well as IL-1β and IL-6 mRNA expression. Moreover, the temperature of 39.5°C blocks PBP-induced cytotoxicity against MCF-7 cells, which correlates with significant reduction in TNF-α level. Combined treatment of rats (FRH+PBP) results in decrease of IL-1β, IL-6 and TNF-α mRNA expression in peripheral blood mononuclear cells compared to cells derived from rats treated with protein-bound polysaccharides extract alone. This study demonstrates that fever-range temperature inhibits immunostimulatory as well as anticancer effects mediated by protein-bound polysaccharides.

Fish can show emotional fever: stress-induced hyperthermia in zebrafish

Whether fishes are sentient beings remains an unresolved and controversial question. Among characteristics thought to reflect a low level of sentience in fishes is an inability to show stress-induced hyperthermia (SIH), a transient rise in body temperature shown in response to a variety of stressors. This is a real fever response, so is often referred to as ‘emotional fever’. It has been suggested that the capacity for emotional fever evolved only in amniotes (mammals, birds and reptiles), in association with the evolution of consciousness in these groups. According to this view, lack of emotional fever in fishes reflects a lack of consciousness. We report here on a study in which six zebrafish groups with access to a temperature gradient were either left as undisturbed controls or subjected to a short period of confinement. The results were striking: compared to controls, stressed zebrafish spent significantly more time at higher temperatures, achieving an estimated rise in body temperature of about 2–4°C. Thus, zebrafish clearly have the capacity to show emotional fever. While the link between emotion and consciousness is still debated, this finding removes a key argument for lack of consciousness in fishes.

Sleep and Microbes

Sleep is profoundly altered during the course of infectious diseases. The typical response to infection includes an initial increase in nonrapid eye movement sleep (NREMS) followed by an inhibition in NREMS. REMS is inhibited during infections. Bacterial cell wall components, such as peptidoglycan and lipopolysaccharide, macrophage digests of these components, such as muramyl peptides, and viral products, such as viral double-stranded RNA, trigger sleep responses. They do so via pathogen-associated molecular pattern recognition receptors that, in turn, enhance cytokine production. Altered sleep and associated sleep-facilitated fever responses are likely adaptive responses to infection. Normal sleep in physiological conditions may also be influenced by gut microbes because the microbiota is affected by circadian rhythms, stressors, diet, and exercise. Furthermore, sleep loss enhances translocation of viable bacteria from the intestine, which provides another means by which sleep-microbe interactions impact neurobiology.

LPS alters pattern of sickness behavior but does not affect glutathione level in aged male rats

Behavioral symptoms of sickness, such as fever and motor activity are a coordinated set of changes that develop during infection. The aim of study was to compare the sickness behaviour (SB) in healthy old and young rats treated with pyrogenic dose of endotoxin and to check their glutathione level. Before experimentation male Wistar rats were selected according to standard body mass, motor activity, and white blood cells count. Intraperitoneal injection of lipopolysaccharide (LPS) from E. coli was used to provoke SB. The level of liver glutathione, interleukin (IL) -6, deep body temperature (Tb) and motor activity were measured. Glutathione level in old and young rats did not differ significantly. In both young and old rats LPS administration provoked fever (the mean value of Tb was 38.06 ± 0.01 °C in old rats, and 38.19 ± 0.06 °C in young rats). LPS injection affected night-time activity in both groups (12 h averages were 1.56 ± 0.40 counts in old LPS-treated rats vs 2.74 ± 0.53 counts in not-treated old rats and 3.44 ± 0.60 counts for young LPS-treated vs 4.28 ± 0.57 counts for young not-treated rats). The injection of LPS provoked an elevation of plasma IL-6 concentration (from values below the lowest detectable standard in not-treated groups of animals to 6322.82 ± 537.00 pg/mL in old LPS-treated rats and 7415.62 ± 451.88 pg/mL in young LPS-treated rats). Based on these data, we conclude that good health of aged rats prevents decrease in the glutathione level. Old rats are still able to develop SB in response to pyrogenic dose of LPS, although its components have changed pattern compared to young animals.