Low seasonal variation in greater mouse-eared bat (Myotis myotis) blood parameters

Advances in understanding bat infection dynamics across biological scales

Over the past two decades, research on bat-associated microbes such as viruses, bacteria and fungi has dramatically increased. Here, we synthesize themes from a conference symposium focused on advances in the research of bats and their microbes, including physiological, immunological, ecological and epidemiological research that has improved our understanding of bat infection dynamics at multiple biological scales. We first present metrics for measuring individual bat responses to infection and challenges associated with using these metrics. We next discuss infection dynamics within bat populations of the same species, before introducing complexities that arise in multi-species communities of bats, humans and/or livestock. Finally, we outline critical gaps and opportunities for future interdisciplinary work on topics involving bats and their microbes.

Functional Activity of the Blood System in Two Migratory Bat Species of the Urals

Functional activity of the blood system was studied in two migratory Ural species, Vespertilio murinus Linnaeus, 1758 and Pipistrellus nathusii Keyserling et Blasius, 1839. A multivariate nonparametric ANOVA of red blood parameters showed significant interspecific differences (p < 0.05) between the migrating bats and the resident species pond bat. A certain genetically determined multidirectionality in the mobilization of emergency regulation mechanisms of the lymphoid blood system was observed in bats.

Bat-derived cells use glucose as a cryoprotectant

Evolution of heterothermy in environments with variable temperatures has allowed bats to survive food scarcity during seasonal climatic extremes by using torpor as a hibernation strategy. The controlled reduction of body temperature and metabolism through complex behavioural and physiological adaptations at organismal, organ, cellular and molecular levels includes the ability of tissues and cells to adapt to temperature alterations. Based on the prediction that cells of different tissues cultured in vitro would differ in their ability to withstand freezing and thawing of the medium, we determined the survival rate of bat-derived cells following exposure to -20 °C for 24 h in media with no cryoprotective agents or medium supplemented by glucose in concentration range 0-3333 mM. Cell survival rates were determined in relation to availability of glucose in the medium, organ origin, cell concentration and bat species. In general, increased glucose helped cells survive at sub-zero temperatures, though concentrations up to 80-fold higher than those found in chiropterans were needed. However, cells in glucose-free phosphate buffered saline also survived, suggesting that other mechanisms may be contributing to cell survival at low temperatures. Highest in vitro viability was observed in nervus olfactorius-derived cell cultures, with high survival rates and rapid re-growth under optimal conditions after exposure to -20 °C. Kidney cells from different bat species showed comparable overall survival rate patterns, though smaller chiropteran species appeared to utilise lower glucose levels as a cryoprotectant than larger species. Our in vitro data provide evidence that cells of heterothermic bats can survive sub-zero temperatures and that higher glucose levels in important tissues significantly improve hibernation survival at extremely low temperatures.

Seasonal Variation of Immunohematological Parameters of the Peripheral Blood in the Pond Bat Myotis dasycneme (Boie, 1825) of the Urals

Immunohematological parameters were for the first time studied in the pond bat Myotis dasycneme (Boie, 1825), the most common chiropteran species in the Urals, during seasonal periods of the annual life cycle. Multivariate nonparametric analysis of variance showed the absence of significant gender differences in red blood cell parameters (p = 0.35). Gender differences were observed in the counts of white blood cells, band neutrophils, segments neutrophils, and lymphocytes in the blood (p < 0.05). Males showed a higher development of innate immunity in summer compared with females (p < 0.05). A high lymphocyte level (50.6-53.5%) was observed in both males and females in the autumn-winter hibernation period, providing immune surveillance and specific reactive activation of the acquired adaptive immune response.

Baseline of Physiological Body Temperature and Hematological Parameters in Captive Rousettus aegyptiacus and Eidolon helvum Fruit Bats

The discovery of bats as reservoir hosts for a number of highly pathogenic zoonotic agents has led to an increasing interest of infectious disease research in experimental studies with bats. Therefore, we established breeding colonies of Rousettus aegyptiacus and Eidolon helvum fruit bats, which both have been identified as reservoir hosts for relevant zoonotic disease agents, such as Marburg virus and Lagos bat virus. Since 2013, individuals of both species have been recruited to the Friedrich-Loeffler-Institut (FLI) from zoological gardens in Europe, to where these species had been introduced from the wild several decades ago. The aviaries have been designed according to national recommendations published by the Federal Ministry of Agriculture. Under these conditions, both species have been reproducing for years. To better understand the physiology of these animals, and to generate baseline knowledge for infection experiments, we monitored the body core temperatures of R. aegyptiacus bats in the aviaries, and found a circadian variation between 34°C and 41.5°C. We also determined the hematological parameters of both species, and detected specific differences between both bat species. For values of clinical chemistry, no correlation to age or sex was observed. However, species-specific differences were detected since ALT, BUN and CREA were found to be significantly higher in R. aegyptiacus and GLU and TP were significantly higher in E. helvum bats. A higher hematocrit, hemoglobin and red blood cell level was observed in subadult R. aegyptiacus, with hemoglobin and red blood cells also being significantly increased compared to E. helvum. Lymphocytes were found to be the dominant white blood cells in both species and are higher in female E. helvum. Neutrophil granulocytes were significantly higher in E. helvum bats. This underlines the necessity to define baseline profiles for each bat species prior to their use in experimental challenge.