Differential locomotor activity responses to day-time light intensity in juvenile and adult solitary Cape mole-rats, Georychus capensis (Rodentia: Bathyergidae).

The Cape mole-rat (Georychus capensis) is a solitary, strictly subterranean rodent that is responsive to light and entrains to photic cues despite having a reduced visual system. Circadian entrainment is maintained throughout life, but age can alter the amplitude of the response and re-entrainment time. Mole-rats are long-lived for their size which raises questions regarding the robustness of their circadian rhythms and how impacts their locomotor activity rhythms. The locomotor activity rhythms of juvenile and adult Cape mole-rats were investigated. They were exposed to pre-experimental and post-experimental control cycles under fluorescent lights, six 12 h light:12 h dark cycles of decreasing intensities and a constant dark cycle (DD). All animals exhibited more activity during the dark phases of all light regimes. Juveniles were more active than adults and displayed more variable activity during both the light and dark phases. Adults exhibited relatively stable levels of activity under all experimental conditions, whereas juvenile activity decreased as the light intensity was reduced. The amplitude of Cape mole-rat rhythms was consistently low, but similar across light regimes and between adults and juveniles. Cape mole-rats have functional circadian systems, are primarily nocturnal and respond differentially to light intensity depending on their age. Light intensity does not affect the locomotor activity responses of Cape mole-rats in a predictable manner, and could indicate more complex interactions with light wavelengths. The circadian systems of juveniles appear to be more sensitive than those of adults, although the mechanism of the light response remains unclear.

Universal DNA methylation age across mammalian tissues.

Aging, often considered a result of random cellular damage, can be accurately estimated using DNA methylation profiles, the foundation of pan-tissue epigenetic clocks. Here, we demonstrate the development of universal pan-mammalian clocks, using 11,754 methylation arrays from our Mammalian Methylation Consortium, which encompass 59 tissue types across 185 mammalian species. These predictive models estimate mammalian tissue age with high accuracy (r > 0.96). Age deviations correlate with human mortality risk, mouse somatotropic axis mutations and caloric restriction. We identified specific cytosines with methylation levels that change with age across numerous species. These sites, highly enriched in polycomb repressive complex 2-binding locations, are near genes implicated in mammalian development, cancer, obesity and longevity. Our findings offer new evidence suggesting that aging is evolutionarily conserved and intertwined with developmental processes across all mammals.

The best of both worlds: no apparent trade-off between immunity and reproduction in two group-living African mole-rat species.

Co-operatively breeding mammals often exhibit a female reproductive skew and suppression of the subordinate non-breeding group members. According to evolutionary theory and the immunity-fertility axis, an inverse relationship between reproductive investment and survival (through immunocompetence) is expected. As such, this study investigated if a trade-off between immunocompetence and reproduction arises in two co-operatively breeding African mole-rat species, namely the Damaraland mole-rat (Fukomys damarensis) and common mole-rat (Cryptomys hottentotus hottentotus), which possess female reproductive division of labour. This study also attempted to investigate the relationship between the immune and endocrine systems in Damaraland mole-rats. There was no trade-off between reproduction and immunocompetence in co-operatively breeding African mole-rat species, and in the case of the Damaraland mole-rats, breeding females (BFs) possessed increased immunocompetence compared with non-breeding females (NBFs). Furthermore, the increased levels of progesterone possessed by Damaraland mole-rat BFs compared with NBFs appear to be correlated to increased immunocompetence. In comparison, BF and NBF common mole-rats possess similar immunocompetence. The species-specific differences in the immunity-fertility axis may be due to variations in the strengths of reproductive suppression in each species. This article is part of the theme issue 'Evolutionary ecology of inequality'.

The endocrine control of reproductive suppression in an aseasonally breeding social subterranean rodent, the Mahali mole-rat (Cryptomys hottentotus mahali).

Cooperative behaviour, sociality and reproductive suppression in African mole-rats have been extensively studied. Nevertheless, endocrine correlates of some species of social mole-rats have been neglected, and these species may hold the key to understanding the behavioural and physiological complexity that allows the maintenance of social groups in African mole-rats. In this study, we investigated endocrine correlates implicated in the suppression of reproduction and cooperative behaviours, namely glucocorticoids (a stress-related indicator) through faecal glucocorticoid metabolites (fGCMs), plasma testosterone (an indicator of aggression) and plasma prolactin in the Mahali mole-rat (Cryptomys hottentotus mahali) across reproductive classes (breeding females and males, non-breeding females and males) and season (wet and dry). Breeders possessed higher levels of testosterone than non-breeders. In reproductively suppressed non-breeding females, fGCMs were significantly higher than in breeders. Furthermore, an adrenocorticotropic hormone stimulation test (ACTH challenge test) on both male and female non-breeders revealed that female non-breeders show a more significant response to the ACTH challenge than males. At the same time, plasma prolactin levels were equally elevated to similar levels in breeding and non-breeding females. Chronically high levels of prolactin and fGCM are reported to cause reproductive suppression and promote cooperative behaviours in non-breeding animals. Furthermore, there was a negative relationship between plasma prolactin and progesterone in non-breeding females. However, during the wet season, a relaxation of suppression occurs through reduced prolactin which corresponds with elevated levels of plasma progesterone in non-breeding females. Therefore, prolactin is hypothesised to be the primary hormone controlling reproductive suppression and cooperative behaviours in non-breeding females. This study provides new endocrine findings for the maintenance of social suppression in the genus Cryptomys.

Species limits and phylogeographic structure in two genera of solitary African mole-rats Georychus and Heliophobius.

African mole-rats (Bathyergidae) are an intensively studied family of subterranean rodents including three highly social and three solitary genera. Although their phylogenetic interrelations are clear, genetic diversity and the number of species within each genus is much less certain. Among the solitary genera, Heliophobius and Georychus were for a long time considered as monotypic, but molecular studies demonstrated strong phylogeographic structure within each genus and proposed that they represent complexes of cryptic species. The present study re-evaluates their internal genetic/phylogenetic structure using a combination of methodological approaches. We generated datasets of one mitochondrial and six specifically selected nuclear markers as well as of a large number of double digest restriction site associated (ddRAD) loci and then applied species delimitation analyses based on the multispecies coalescent model or clustering on co-ancestry matrices. The population structure was largely congruent across all analyses, but the methods differed in their resolution scale when determining distinct gene pools. While the multispecies coalescent model distinguished five Georychus and between eleven to thirteen Heliophobius gene pools in both Sanger sequenced and ddRAD loci, two clustering algorithms revealed significantly finer or coarser structure in ddRAD based co-ancestry matrices. Tens of clusters were distinguished by fineRADstructure and one (in Georychus) or two clusters (in Heliophobius) by Infomap. The divergence dating of the bathyergid phylogeny estimated that diversification within both genera coincided with the onset of the Pleistocene and was likely driven by repeated large-scale climatic changes. Based on this updated genetic evidence, we suggest recognizing one species of Georychus and two species of Heliophobius, corresponding to a northern and southern major lineage, separated by the Eastern Arc Mountains. Yet, the final taxonomic revision should await integrated evidence stemming from e.g. morphological, ecological, or behavioral datasets.

Flexibility in body temperature rhythms of free-living natal mole-rats (Cryptomys hottentotus natalensis).

The subterranean niche is a specialised and particularly challenging environment to obtain direct physiological and behavioural measurements from free-living animals. Rhythmicity has been examined in many mole-rat species in the laboratory, but field reports are relatively scarce. We implanted Natal mole-rats with temperature loggers in summer and winter to record core body temperature (Tb), before releasing the animals again. Animals were recaptured after two months to recover the loggers. Natal mole-rats can maintain rhythmicity of their Tb in their natural habitat and display seasonal differences in their Tb rhythms. During winter mole-rats have unimodal Tb rhythms, whereas in summer many animals have bimodal Tb patterns, which may be related to temperatures in the foraging burrows close to the soil surface. Individuals from the same colonies frequently exhibited similar rhythms, especially in the larger colonies, which may indicate social entrainment of rhythms. Males and females differ in their seasonal variation of Tb, with males having more variation in winter, while the opposite was true for females. Entire colonies may undergo sporadic torpor bouts, presumably to conserve energy, but the trigger for these events is unknown. This is the first report of torpor occurring in an African mole-rat species. The ability to respond to environmental and social cues, while rhythms remain flexible, can provide an adaptive advantage to animals living in challenging and energetically demanding habitats.

African Naked Mole-Rats Demonstrate Extreme Tolerance to Hypoxia and Hypercapnia.

Naked mole-rats are extremely tolerant to low concentrations of oxygen (hypoxia) and high concentrations of carbon dioxide (hypercapnia), which is consistent with the environment that they inhabit. Naked mole-rats combine subterranean living with living in very densely populated colonies where oxygen becomes depleted and carbon dioxide accumulates. In the laboratory, naked mole-rats fully recover from 5 h exposure to 5% O2 and 5 h exposure to 80% CO2, whereas both conditions are rapidly lethal to similarly sized laboratory mice. During anoxia (0% O2) naked mole-rats enter a suspended animation-like state and switch from aerobic metabolism of glucose to anaerobic metabolism of fructose. Additional fascinating characteristics include that naked mole-rats show intrinsic brain tolerance to anoxia; a complete lack of hypoxia-induced and CO2-induced pulmonary edema; and reduced aversion to high concentrations of CO2 and acidic fumes. Here we outline a constellation of physiological and molecular adaptations that correlate with the naked mole-rat's hypoxic/hypercapnic tolerance and which offer potential targets for ameliorating pathological conditions in humans, such as the damage caused during cerebral ischemia.

A non-invasive assessment of essential trace element utilization at different trophic levels in African wildlife.

The complex relationships that exist between terrestrial mammals and their habitats make African ecosystems highly interactive environments. Anthropogenic activities including climate change have altered geochemical cycles, which influence nutrient availability and deficiency at local, regional and global scales. As synergistic and antagonistic interactions occur between essential elements at both deficiency and excess concentrations, the differences in feeding strategy between trophically distinct groups of terrestrial vertebrates are likely to influence the degree to which overall nutrient needs are met or may be deficient. The overall aim of this study was to investigate and compare quantitative differences of nine essential elements in terrestrial vertebrates occupying different trophic levels within two protected areas; Tswalu Kalahari Reserve (TKR) and Manyeleti Nature Reserve (MNR) South Africa, using faeces as an analytical matrix. Results from linear mixed effects models highlight that concentrations varied widely between individuals. Overall, measured concentrations above their respective means were evident for B and Mn in herbivores, Fe in omnivores and Cu, Co, Fe, Se and Zn in carnivores. Measured concentrations of Mo and Ni did not differ significantly between trophic groups. Although site-specific differences were evident for specific elements, measured mean concentrations of B, Co, Cu, Fe, Mo, Ni, Se and Zn were significantly higher overall at the MNR study site compared to the TKR site. This is the first study to non-invasively assess essential element concentrations across trophic levels in free ranging African wildlife species within protected areas of the savannah biome. Combined with the assessment of environmental matrices, this approach can be used as an effective diagnostic tool for the assessment of animal welfare and the management of protected areas globally.

Oxidative stress in response to heat stress in wild caught Namaqua rock mice, Micaelamys namaquensis.

Modelling of anthropogenic induced climate suggests more frequent and severe heatwaves in the future, which are likely to result in the mass die-off of several species of organisms. Oxidative stress induced by severe heat stress has previously been associated with a reduction in animal cognitive performance, depressed reproduction and lower life expectancy. Little is known about the non-lethal consequences of species should they survive extreme heat exposure. We investigated the oxidative stress experienced by the Namaqua rock mouse, a nocturnal rodent, using two experimental heat stress protocols, a 6 hour acute heat stress protocol without access to water and a 3-day heatwave simulation with ad libitum water. Oxidative stress was determined in the liver, kidney and brain using malondialdehyde (MDA) and protein carbonyl (PC) as markers of oxidative damage, and superoxide dismutase (SOD) and total antioxidant capacity (TAC) as markers of antioxidant defence. Incubator heat stress (heat and dehydration stress) was brought about by increasing the body temperatures of animals to 39-40.8 °C for 6 hours. Following incubator heat stress, significantly higher levels of MDA were observed in the liver. Dehydration did not explain the variation in oxidative markers and is likely a combined effect of thermal and dehydration stress. Individual body mass was significantly negatively correlated to kidney SOD and lipid peroxidation. A heatwave was simulated using a temperature cycle that would naturally occur during a heatwave in the species' local habitat, with a maximal ambient temperature of 38 °C. Following the simulated heatwave, SOD activity of the kidney demonstrated significantly lowered activity suggesting oxidative stress. Current heat waves in this species have the potential of causing oxidative stress. Heat and dehydration stress following exacerbated temperatures are likely to incur significant oxidative stress in multiple tissues demonstrating the importance of water availability to allow for rehydration to prevent oxidative stress.

Locomotor activity in field captured crepuscular four-striped field mice, Rhabdomys dilectus and nocturnal Namaqua rock mice, Micaelamys namaquensis during a simulated heat wave.

Activity of animals is influenced by ambient temperature and increasing temperatures brought about by climate change may impose a heat stress risk. Previous studies investigating the effect of heat waves on activity usually measure animals at different, but constant temperatures, however, rarely are they studied under a natural temperature cycle. General activity, behavioural flexibility and frequency of water drinking counts during a normal day, hot day and a simulated heat wave temperature cycle were studied in the crepuscular four-striped field mouse, Rhabdomys dilectus, and the nocturnal Namaqua rock mouse, Micaelamys namaquensis. Both R. dilectus and M. namaquensis showed typical daily locomotor activity under control conditions. During the heat wave, peak activity times changed for R. dilectus, but both species exhibited higher bouts of activity for the heat wave during the day compared to the control, which was accompanied by an increased amount of time spent drinking water. The increased activity during the heat wave is likely due to enhanced water requirements and potentially a form of behavioural thermoregulation as animals may be uncomfortable and try to move to cooler areas. Thus, in the absence of a typical microclimate, access to water may allow rodents to overcome heat stress from extreme temperatures without having to shift their temporal active times.

Hind foot drumming: morphological adaptations of the muscles and bones of the hind limb in three African mole-rat species.

Seismic signalling in the form of hind foot drumming plays an integral role in the communication of several species of African mole-rats (Bathyergidae). To produce these vibrational signals, alternating hind limbs strike the ground repetitively at high speeds by flexion and extension of the hip and knee. This descriptive study aimed to determine whether anatomical differences in hind limb osteology and/or musculature between drumming and non-drumming species of three Bathyergidae species could be detected. Formalin-fixed left and right hind limbs of 24 animals (N = 48) consisting of three species (n = 16 each) of two drumming species, Georychus capensis and Bathyergus suillus, and one non-drumming species, Cryptomys hottentotus natalensis, were dissected to determine the origins and insertions of individual muscles. After dissection, all soft tissue was removed by maceration. Hind limb bones, including the pelvis, were photographed, and the exact muscle origin and insertion points were electronically mapped onto the images using imaging software. On lateral view, the acetabular position was parallel to the sacrum in G. capensis, while being more ventral in position in the other two species. The shape of the femur head was spherical and the neck defined in all species. The distal shaft of the femur was gracile and the epicondyles were robust and prominent in the non-drumming C. h. natalensis compared with the drumming species. Shallow and relatively wide patellar grooves were observed in all three species. In the two drumming species, m. gracilis was single, whereas it was double in C. h. natalensis. In all three species, m. tensor fasciae latae was absent. The more dorsal positioning of the acetabulum in G. capensis may be needed to increase the stability of the spine and allow for more force to be exerted on the pelvis during drumming. It is unlikely that m. gracilis plays a role in drumming, as the singularity or doubling thereof is variable among rodents. It is additionally postulated that m. gluteus superficialis has taken the hip rotator role of m. tensor fasciae latae as it partially inserted onto the lateral fascia of the thigh. The more robust ilia, femoral shafts and tibiae observed in the two drumming species studied here are possible adaptations for hind foot drumming, as robust bones are able to withstand the additional biomechanical loading during drumming.

Evidence for contrasting roles for prolactin in eusocial naked mole-rats, Heterocephalus glaber and Damaraland mole-rats, Fukomys damarensis.

Elevated prolactin (PRL) has been associated with the expression of social and cooperative behaviours in a number of vertebrate species, as well as suppression of reproduction. As social mole-rats exhibit both of these traits, PRL is a prime candidate in mediating their social phenotype. While naked and Damaraland mole-rats (NMRs and DMRs) have evolved eusociality independently within their family, both species exhibit an extreme skew in lifetime reproductive success, with breeding restricted to a single female and one or two males. Non-breeding NMRs of both sexes are physiologically inhibited from reproducing, while in DMRs only the non-breeding females are physiologically suppressed. Newly emerging work has implicated the dopamine system and PRL as a component in socially induced reproductive suppression and eusociality in NMR, but the DMR remains unstudied in this context. To investigate evolutionary convergence in the role of PRL in shaping African mole-rat eusociality, we determined plasma PRL concentrations in breeders and non-breeders of both sexes, comparing DMRs with NMRs. Among samples from non-breeding NMRs 80% had detectable plasma PRL concentrations. As a benchmark, these often (37%) exceeding those considered clinically hyperprolactinaemic (25 ng ml-1) in humans: mean ± s.e.m.: 34.81 ± 5.87 ngml-1; range 0.00-330.30 ng ml-1 Conversely, 85% of non-breeding DMR samples had undetectable values and none had concentrations above 25 ng ml-1: 0.71 ± 0.38 ng ml-1; 0.00-23.87 ngml-1 Breeders in both species had the expected variance in plasma PRL concentrations as part of normal reproductive function, with lactating queens having significantly higher values. These results suggest that while elevated PRL in non-breeders is implicated in NMR eusociality, this may not be the case in DMRs, and suggests a lack of evolutionary convergence in the proximate control of the social phenotype in these mole-rats.

Reproductive status-dependent kisspeptin and RFamide-related peptide (Rfrp) gene expression in female Damaraland mole-rats.

Damaraland mole rats (Fukomys damarensis) are cooperatively breeding, subterranean mammals that exhibit a high reproductive skew. Reproduction is monopolised by the dominant female of the group, whereas subordinates are physiologically suppressed to the extent that they are anovulatory. In these latter animals, it is assumed that normal gonadotropin-releasing hormone secretion from the hypothalamus is disrupted. The RFamide peptides kisspeptin (Kiss1) and RFamide-related peptide-3 (RFRP-3) are considered as potent regulators of gonadotropin release. To assess whether these neuropeptides are involved in the mechanism of reproductive suppression, we investigated the distribution and gene expression of Kiss1 and Rfrp by means of in situ hybridisation in wild-caught female Damaraland mole-rats with different reproductive status. In both reproductive phenotypes, substantial Kiss1 expression was found in the arcuate nucleus and only few Kiss1-expressing cells were detected in the anteroventral periventricular nucleus (AVPV), potentially as a result of low circulating oestradiol concentrations in breeding and nonbreeding females. Rfrp gene expression occurred in the dorsomedial nucleus, the paraventricular nucleus and the periventricular nucleus. While in female breeders and nonbreeders, plasma oestradiol levels were low and not significantly different, quantification of the hybridisation signal for both genes revealed significant differences in relation to reproductive status. Reproductively active females had more Kiss1-expressing cells and a higher number of silver grains per cell in the arcuate nucleus compared to nonreproductive females. This difference was most pronounced in the caudal part of the nucleus. No such differences were found in the AVPV. Furthermore, breeding status was associated with a reduced number of Rfrp-expressing cells in the anterior hypothalamus. This reproductive status-dependent expression pattern of Kiss1 and Rfrp suggests that both neuropeptides play a role in the regulation of reproduction in Damaraland mole-rats. Enhanced long-term negative feedback effects of oestradiol could be responsible for the lower Kiss1 expression in the arcuate nucleus of reproductively suppressed females.

The impact of age-class and social context on fecal glucocorticoid metabolite levels in free-ranging male giraffes.

One of the primary sources of perceived stress is the social environment of an animal and the interactions with conspecifics. An essential component of the response to a stressor is the activation of the hypothalamic-pituitary-adrenocortical axis, which results amongst others in a temporal increase in circulating glucocorticoid (GC) levels. Giraffes occur in a highly flexible fission-fusion social system and group compositions can change on a daily basis, with bulls establishing an age-related dominance hierarchy and showing a roaming strategy in the search for fertile females. The aim of this study was to non-invasively monitor the influence of different group compositions (mixed sex groups vs. all-male groups) on GC concentrations in free ranging giraffe bulls of different age classes. We collected fecal samples from free-ranging giraffe bulls for 12months in a South African Private Game Reserve to examine age- and social context-related patterns of fecal GC metabolite (fGCM) concentrations. We found that fGCM levels in giraffe bulls are age-class dependent, as well asassociated with changes in the social environment. Independently of the social setting, bulls of the youngest age class exhibited the highest fGCM levels compared to bulls of the other two older age-classes, with differences most pronounced when the bulls are associated in all-male groups. In contrast, an almost reversed picture appears when looking at the fGCM levels of sexually active individuals in mixed sex groups, where highest levels were found for the bulls in the oldest age-class, and the lowest for the bulls in the youngest age-class. The study stresses the importance to taking factors such asage-related status and social settings into account, when interpreting fGCM levels in free ranging giraffes.

Age and socially related changes in fecal androgen metabolite concentrations in free-ranging male giraffes.

In many mammal species, androgen levels in males are elevated during periods of mating activity, often to facilitate aggressive behavior between males over access to fertile females. However, this pattern might be less obvious in species with a rather low male-male aggression rate, or in those that are not strictly seasonal breeders. A complex social structure, as well as additional social and environmental factors, might add more to the complexity. Here, we applied a non-invasive method to monitor fecal androgen metabolite (fAM) levels in free-ranging giraffe bulls over a period of months to examine longitudinal patterns of androgen metabolite concentrations in relation to observed male sexual behavior in different age classes. Giraffes are non-seasonal breeders, living in a fission-fusion social system and males show a roaming strategy to search for fertile females. Our results show that season has an impact on fAM levels in free-ranging giraffes, with respective steroid concentrations being higher in summer. In the presence of females, fAM levels of bulls are significantly higher compared to when found in all-male groups, with old adult bulls showing the highest fAM levels. In contrast, young adult bulls have overall slightly higher fAM levels compared to old adult bulls when residing in all male groups. Sexual behavior increases fAM levels only in old adult bulls.

The Distribution of Gastrointestinal Parasites in Two Populations of Common Mole-Rats ( Cryptomys hottentotus hottentotus).

The spread of parasites through a host population is based on the variation in behavior and immune function between individuals and is rarely uniform. We studied the gastrointestinal parasites of common mole-rats ( Cryptomys hottentotus hottentotus, Lesson 1826) from 2 sites and assessed the levels of infection based on host sex, breeding status, and season. Only nematode species were found: Neoheligmonella sp. and Mammalakis macrospiculum (Ortlepp, 1939) and a single specimen of Trichuris sp., all of which have direct life cycles. Parasite burden and species richness was greater in the mesic habitat. The abundance of Neoheligmonella sp. differed significantly between seasons, and the season of peak abundance differed between sites, perhaps due to differences in host densities between sites. In addition, parasite burden did not differ between the sexes, but breeding animals had higher infections of Neoheligmonella sp. and M. macrospiculum than non-breeding animals. This and previous studies thus suggest that the subterranean environment is beneficial in reducing parasite diversity, although the restrictions on movement may lead to certain individuals suffering higher parasite burdens.

Living on the edge: Daily, seasonal and annual body temperature patterns of Arabian oryx in Saudi Arabia.

Heterothermy, the ability to allow body temperature (Tb) to fluctuate, has been proposed as an adaptive mechanism that enables large ungulates to cope with the high environmental temperatures and lack of free water experienced in arid environments. By storing heat during the daytime and dissipating it during the night, arid-adapted ungulates may reduce evaporative water loss and conserve water. Adaptive heterothermy in large ungulates should be particularly pronounced in hot environments with severely limited access to free water. In the current study we investigated the effects of environmental temperature (ambient, Ta and soil, Ts) and water stress on the Tb of wild, free-ranging Arabian oryx (Oryx leucoryx) in two different sites in Saudi Arabia, Mahazat as-Sayd (MS) and Uruq Bani Ma'arid (UBM). Using implanted data loggers wet took continuous Tb readings every 10 minutes for an entire calendar year and determined the Tb amplitude as well as the heterothermy index (HI). Both differed significantly between sites but contrary to our expectations they were greater in MS despite its lower environmental temperatures and higher rainfall. This may be partially attributable to a higher activity in an unfamiliar environment for translocated animals in UBM. As expected Tb amplitude and HI were greatest during summer. Only minor sex differences were apparent that may be attributable to sex-specific investment into reproduction (e.g. male-male competition) during rut. Our results suggest that the degree of heterothermy is not only driven by extrinsic factors (e.g. environmental temperatures and water availability), but may also be affected by intrinsic factors (e.g. sex and/or behaviour).

Psychological stress affects the severity of radiation-induced acute skin reactions in breast cancer patients.

Psychological stress exacerbates many pathological conditions including inflammatory skin conditions. The effect of psychological stress on acute radiation-induced skin reactions has not been documented before. Here, we aimed to explore if psychological stress could aggravate skin reaction severity in breast cancer patients. We conducted a secondary analysis of patient data obtained during a randomised, controlled clinical trial for acute radiation-induced skin reaction severity in 78 breast cancer patients. Patients were assessed three times a week during treatment. Skin reaction severity was measured using the modified Radiation-Induced Skin Reaction Assessment Scale (RISRAS) and Radiation Therapy Oncology Group grades. Stress levels were determined using a 5-point LIKERT scale to rate physical well-being, managing stress levels, house, family, work and other commitments. A total of 20 patients (26%) of the 78-patient cohort were considered stressed. Skin reaction severity in stressed patients was twice that of non-stressed patients (p < 0.001) and stressed patients were five times more likely to develop moist desquamation. Our results show that psychological stress aggravates skin reaction severity during radiation therapy. This research needs to be validated in a more rigorous manner by incorporating a validated scale such as the Distress Thermometer and Impact Thermometer in future skin trials.

Ectoparasite fauna of rodents collected from two wildlife research centres in Saudi Arabia with discussion on the implications for disease transmission.

The majority of human pathogens are zoonotic and rodents play an important role as reservoirs of many of these infectious agents. In the case of vector-borne pathogens, rodent reservoirs not only act as a source of infection for vectors but also serve as hosts for the vectors themselves, supporting their populations. Current data on rodent-ectoparasite relationships is limited in Saudi Arabia, however, this is needed to assess disease risk and the relative importance of different hosts for the maintenance of vector-borne pathogen cycles. In order to provide baseline data for the region that could be used to assess zoonotic disease risk, we collected and identified 771 ectoparasite specimens (ticks, fleas and mites) from 161 rodents at two wildlife research centres in Saudi Arabia and discuss our results in the context of possible zoonotic disease risk based on the hosts and vectors present.