This week in research.

Canine distemper virus (CDV; family Paramyxoviridae , taxon species Morbillivirus canis ) causes systemic disease in a broad range of mammalian hosts. CDV commonly targets epithelial, lymphoid, and nervous tissues. Reproductive disease is reported less frequently. Here, we describe CDV-associated placentitis and abortion in a 4-y-old, female Linnaeus’s two-toed sloth ( Choloepus didactylus ) from a private collection. The animal developed respiratory and gastrointestinal illness, aborted a midgestational fetus, and subsequently died. Gross examination revealed necrotizing placentitis. Histologically, the uterus and placenta had vasculitis with thrombosis, endothelial syncytia, and intracytoplasmic and intranuclear viral inclusions within endothelial cells. Additional maternal lesions included bronchointerstitial pneumonia, lymphoid depletion, hepatic necrosis, multisystemic intracytoplasmic and intranuclear viral inclusions, and secondary fungal infection. CDV antigen was abundant within endothelial cells, vessel walls, and perivascular stroma in the uterus and placenta by immunohistochemistry. Real-time PCR detected CDV in the maternal uterus, lung, and placenta. The hemagglutinin gene shared 98.3% nucleotide sequence identity with a CDV previously detected in a raccoon in the United States. Our case documents CDV-associated reproductive failure and endothelial tropism in a sloth, highlighting the potential for severe disease in captive nontraditional hosts.

Qualitative Behavioral Assessment is a tool to measure emotional expression, an important component of animal welfare, that was implemented in this study to capture emotions of non-replacement dairy calves at calf raisers across the Midwestern United States. This supplemental file contains the average score for each behavioral descriptor by farm from Qualitative Behavioral Assessment performed on 19 calf-raising farms in the Midwestern United States.

Qualitative Behavioral Assessment is a tool to measure emotional expression, an important component of animal welfare, that was implemented in this study to capture emotions of non-replacement dairy calves at calf raisers across the Midwestern United States. This supplemental file contains the average score for each behavioral descriptor by farm from Qualitative Behavioral Assessment performed on 19 calf-raising farms in the Midwestern United States.

Qualitative Behavioral Assessment is a tool to measure emotional expression, an important component of animal welfare, that was implemented in this study to capture emotions of non-replacement dairy calves at calf raisers across the Midwestern United States. This supplemental file contains the average score for each behavioral descriptor by farm from Qualitative Behavioral Assessment performed on 19 calf-raising farms in the Midwestern United States.

Cattle production based on monoculture pastures can increase greenhouse gas emissions, degrade soils, reduce biodiversity, and compromise animal welfare, limiting sustainability and resilience to climate change. Silvopastoral systems integrate livestock with trees, shrubs, and grasses and have been proposed as a more sustainable alternative. Here we show that silvopastoral systems in the Yucatán Peninsula improve multiple indicators of ecosystem health compared with monoculture pastures. Cattle in silvopastoral systems emit less methane per unit of dry matter intake and exhibit lower skin temperatures. These systems also increase soil nitrogen and phosphorus concentrations, enhance soil organic matter stabilization, and are associated with lower abundance of rodents susceptible to West Nile virus. Our findings indicate that silvopastoral systems improve ecosystem services, soil fertility, and animal welfare while potentially reducing proxies associated with zoonotic risk. These results support the development of more sustainable livestock systems in tropical regions. Silvopastoral systems enhance livestock sustainability by reducing methane emissions, improving soil fertility and animal welfare, and lowering indicators associated with zoonotic risk compared with monocultures, based on evaluation of 23 sustainability indicators in cattle systems.

Long COVID is a condition in which individuals experience persistent symptoms following COVID-19 infection (Crook et al., 2021). Fatigue is one of the most common and debilitating symptoms reported in long COVID (Townsend et al., 2020). Despite the prevalence of fatigue across a number of chronic conditions, there remains a lack of understanding of the underlying mechanisms which drive it. Interoception is the process by which the nervous system senses, interprets, and integrates sensory signals from within the body, at both conscious and unconscious levels (Mehling et al., 2018). Alterations in interoception have been proposed as a potential mechanism relevant to fatigue. Interoception can be conceptualised across three dimensions: sensibility (how much attention a person believes they are paying to internal bodily sensations e.g., noticing their heartbeat), accuracy (how accurately a person can detect internal bodily signals e.g., correctly detecting their own heartbeats), and awareness (how aware a person is of their accuracy in detecting signals) Garfinkel et al. (2015). We have previously explored interoceptive sensibility in long COVID (Thomas, Pattinson, Bundy, et al., 2025), but little is known about interoceptive accuracy and awareness in this population. This will be addressed by Research Question 1 in the present study: Research Question 1a: Do individuals with long COVID differ from healthy controls in baseline (pre-task) interoceptive accuracy? Research Question 1b: Do individuals with long COVID differ from healthy controls in baseline (pre-task) interoceptive awareness? Emerging evidence suggests that interoception is associated with fatigue across both healthy and clinical populations. For example, greater interoceptive awareness has been associated with lower fatigue during an endurance task in health individuals (Greenhouse-Tucknott et al., 2022), and altered interoception has been associated with symptom severity in clinical groups (Duschek et al., 2017; Rouault et al., 2023; Thomas, Pattinson, Bundy, et al., 2025; Todd et al., 2024). However, the exact nature of the relation between interoception and fatigue remains unclear. Fatigue is a multidimensional construct that can affect both cognitive and physical functioning (Dailey et al., 2015). In long COVID, it encompasses domains including physical, cognitive, emotional, psychosocial, and general fatigue, as well as post-exertional symptom exacerbation (Thomas et al., 2024). Cognitive and physical fatigue may have distinct underlying mechanisms and associations with symptoms such as depression and autonomic dysfunction (Thomas, Pattinson, Bundy, et al., 2025).It is important to examine fatigue within specific contexts. Here, we will focus on state fatigue (the amount of fatigue experienced at a given moment) induced through both cognitive and physical tasks. In addition to assessing whether interoception predicts fatigue, we will consider whether fatigue influences interoceptive processes, reflecting a potentially bidirectional relationship. This will be addressed by Research Question 3 in the present study: 3a. Among individuals with long COVID, to what extent are changes in interoceptive accuracy (pre–post task) predicted by changes in state fatigue during exertion, autonomic function, performance fatigability, and task type (cognitive/physical)? 3b. Among individuals with long COVID, to what extent are changes in interoceptive awareness (pre–post task) predicted by changes in state fatigue during exertion, autonomic function, performance fatigability, and task type? The autonomic nervous system controls involuntary physiological processes such as heart rate, blood pressure, and respiration. Alterations in autonomic nervous system function may disrupt or impact the integration of internal bodily signals, and are therefore likely to be closely linked to interoceptive processing. Around 72% of individuals with long COVID report moderate-severe symptoms consistent with autonomic dysfunction (e.g. dizziness and light sensitivity) (Eastin et al., 2025), and physiological markers such as heart rate variability provide further evidence of autonomic dysfunction (da Silva et al., 2023). These changes may reflect disruption to the balance between the sympathetic and parasympathetic activity (Jammoul et al., 2023). Autonomic dysfunction is increasingly recognised as a key factor associated with fatigue in long COVID (Costa et al., 2023; Thomas, Pattinson, Bundy, et al., 2025). Understanding the relationship between autonomic function and interoception may provide important insight into how the body can adapt to internal and external demands, and into potentials drivers of fatigue (Ueno et al., 2022). This will be addressed by Research Question 2 in the present study: Research Question 2: Among individuals with long COVID, to what extent do interoceptive sensibility, interoceptive accuracy, interoceptive awareness, task type (cognitive vs physical), and autonomic function predict post-task state fatigue, after controlling for baseline state fatigue? A comprehensive understanding of fatigue requires consideration of psychological factors. Anxiety and depression are prevalent in long COVID, and greater depressive symptoms are consistently associated with greater severity of fatigue (Bierbauer et al., 2022; Furlanis et al., 2024). Psychological distress has been linked to altered interoceptive processing, and interventions targeting interoception have been shown to reduce distress (Khoury et al., 2018; Verdonk et al., 2025). Theoretical frameworks such as that proposed by Seth and Critchley (2013), which conceptualises emotions as arising from interoceptive inference, offer a potential mechanism that may account for these associations. Our recent findings suggest that interoceptive sensibility and depressive symptoms are jointly associated with heightened fatigue in people with long COVID (Thomas, Pattinson, Bundy, et al., 2025). However, it is not yet known whether similar relationships exist for interoceptive accuracy or awareness. This will be addressed by Research Question 4 in the present study: Research Question 4: Among individuals with long COVID, do illness perceptions, depression, and anxiety moderate the relationship between interoceptive (4a) accuracy, (4b) awareness, and (4c) sensibility and baseline state fatigue? Illness perceptions may also influence fatigue experiences. In long COVID, more threatening perceptions about illness severity or consequences were associated with greater fatigue (Bierbauer et al., 2022; Furlanis et al., 2024), consistent with findings in other clinical conditions such as ME/CFS, where a strong illness identity and perceptions about severe consequences are similarly associated with fatigue (Edwards et al., 2001). Socioeconomic factors such as income, education, employment status, and deprivation may further shape these relationships and will be considered as potential moderating variables in the present study. Incorporating this contextual information supports a more holistic understanding of fatigue across individuals and conditions, and helps to inform interventions that consider lived experiences. Importantly, the experience of fatigue does not always correspond to measurable declines in performance (Bailey et al., 2007; Krupp & Elkins, 2000; Lou et al., 2003). For example, we (Thomas, Pattinson, Cunningham et al., 2025) and others (Fietsam et al., 2023) have shown that individuals with long COVID report greater fatigue than healthy controls despite demonstrating similar declines in performance. Understanding the relationship between fatigue and performance has been identified as a key research priority (Kluger et al., 2013). Accordingly, this study will incorporate both measures of state and trait fatigue alongside task performance to understand how these different constructs uniquely interact with different symptoms and mechanisms. This will be addressed by Research Question 3 in the present study: Research Question 3: (3a) Among individuals with long COVID, to what extent are changes in interoceptive accuracy (pre–post task) predicted by changes in state fatigue during exertion, autonomic function, performance fatigability, and task type (cognitive vs physical)? (3b) Among individuals with long COVID, to what extent are changes in interoceptive awareness (pre–post task) predicted by changes in state fatigue during exertion, autonomic function, performance fatigability, and task type (cognitive vs physical)? Long COVID symptoms fluctuate over time and are often exacerbated by exertion, a pattern described as post exertional symptom exacerbation (PESE). Evidence from ecological momentary assessment suggests that both physical and cognitive activity are associated short-term (30-min) increases in symptom severity, but only mild delayed fatigue at 24 hours later (Greenwood et al., 2024). To date, no study has experimentally induced both cognitive and physical fatigue in people with long COVID to assess their impact on symptoms in the days that follow. To address this gap, the present study will induce cognitive and physical fatigue in a controlled setting and assesses changes in symptom severity and impairment (fatigue, dizziness, breathlessness) 24–48 hours later. This will be addressed by Research Question 5 in the present study: Research Question 5: Among individuals with long COVID, does the change in symptom severity from baseline to 24–48 hours post-session differ between cognitive and physical tasks?