Biology subjects

Czirjak, G. A.

Publications and source records attributed to Czirjak, G. A..

8 recordsLinked to original sources

bioRxiv2025

Compromised futures: gastrointestinal parasites reduce survival and recruitment but not reproductive performance in wild female spotted hyenas (Crocuta crocuta)

BackgroundGastrointestinal parasitic (GIP) infections can decrease the survival and reproductive performance of humans and livestock. Even so, the immediate and delayed fitness consequences of GIP in unmanaged wild mammal populations, particularly during the sensitive and energetically demanding early life stage, remain largely unknown. MethodsWe investigate non-invasively the effects of GIP during early life on the survival to adulthood, age at first reproduction and longevity of 68 individually known female spotted hyenas in the Serengeti National Park, Tanzania. We also test whether a high investment in gastrointestinal local immunity (i.e. faecal mucin and immunoglobulin A) and an elevated allostatic load (i.e. faecal glucocorticoid metabolites) decrease these measures of performance, when controlling for resource availability and maternal effects (i.e. maternal social rank) using logistic regression and Cox proportional hazards models. ResultsAncylostoma sp. infections and the level of immunoglobulin A both negatively associate with survival to adulthood, probably because of the damage caused by the parasite and resource allocation trade-off between immunity and maintenance. Conversely, maternal social rank has a positive influence on survival to adulthood and longevity. Immune responses, allostatic load and GIP do not affect the age at first reproduction, suggesting either no effect, a complex interaction between different life stages, or a more immediate time-dependent effect. ConclusionOur study highlights the critical role of GIP infections and maternal effects on early-life fitness and long-term outcomes in females of a wild carnivore, thereby contributing to our understanding of ecological dynamics in unmanaged ecosystems.

ecology↗

bioRxiv2024

The gut microbiota-immune-brain axis in a wild vertebrate: dynamic interactions and health impacts

The gut microbiota-immune-brain axis is a feedback network which influences diverse physiological processes and plays a pivotal role in overall health and well-being. Although research in humans and laboratory mice has shed light into the associations and mechanisms governing this communication network, evidence of such interactions in wild, especially in young animals, is lacking. We therefore investigated these interactions during early development in a population of common buzzards (Buteo buteo) and their effects on individual condition. In a longitudinal study, we used a multi-marker approach to establish potential links between the bacterial and eukaryotic gut microbiota, a panel of immune assays and feather corticosterone measurements as a proxy for long-term stress. Using Bayesian structural equation modelling, we found no support for feedback between gut microbial diversity and immune or stress parameters. However, we did find strong relationships in the feedback network. Immunity was negatively correlated with corticosterone levels, and microbial diversity was positively associated with nestling body condition. Furthermore, corticosterone levels and eukaryotic microbiota diversity decreased with age while immune activity increased. The absence of conclusive support for the microbiota-immune-brain axis in common buzzard nestlings, coupled with the evidence for stress mediated immunosuppression, suggests a dominating role of stress-dominated maturation of the immune system during early development. Confounding factors inherent to wild systems and developing animals might override associations known from adult laboratory model subjects. The positive association between microbial diversity and body condition indicates the potential health benefits of possessing a diverse and stable microbiota.

microbiology↗

bioRxiv2024

Spotted hyena gut cross-talks:Symbionts modulate mucosal immunity

The intestinal mucosa is at the front line of host-microbiome interactions, but little is known about these interactions within natural populations. Here, we non-invasively investigated associations between the gut microbiome and mucosal immune measures while controlling for host, social, and ecological factors in 199 samples of 158 wild spotted hyenas (Crocuta crocuta) in the Serengeti National Park, Tanzania. We profiled the microbiome composition, including bacteria, fungi and parasites, using a multi-amplicon approach, and measured faecal immunoglobulin A and mucin. Probabilistic models indicated that both immune measures predict microbiome similarity among individuals in an age-dependent manner. The strength of the association effect varied, being strongest within bacteria, intermediate within parasites, and weakest within fungi communities. Machine learning regression accurately predicted both measures and identified the taxa driving these associations: symbiotic bacteria reported in humans and laboratory mice, unclassified bacteria, a hookworm, host DNA likely reflecting inflammation, and diet. Our findings indicate a complex interplay between the host, its environment and symbionts. These findings increase our knowledge of the gut microbiome in natural populations, which harbour highly dynamic and diverse eukaryotes under the influence of unpredictable environmental factors and where selection is not artificially biased.

ecology↗

bioRxiv2024

Lower baseline immunity in invasive Egyptian goose compared to sympatric native waterfowls

Successful invasive species increase their spreading success by trading-off nutritional and metabolic resources allocated to reproduction and range expansion with other costly body functions. One proposed mechanism for the reallocation of resources is a trade-off with the immune function and the regulation of oxidative status. Relying on a panel of blood-based markers of immune function and oxidative status quantified in an invasive species (Egyptian goose) and two native competing species (mallard and mute swan) in Germany, we tested the hypothesis that the invasive species would have (i) lower investment in immune function, (ii) lower levels of oxidative damage, and (iii) no higher antioxidant defences compared to the native species. We found lower levels of adaptive immune markers (lymphocytes and immunoglobulin Y), in the invasive species compared to the two native species. Reactive oxygen metabolites, a marker of oxidative damage, were also lower in Egyptian geese compared to the other species, while levels of antioxidants were generally similar. Mute swans showed the highest levels of heterophils, lysozymes and haemolysis among the three species, possibly due to its larger body mass. Our results point to a reduced investment in adaptive immune function in the invasive species as a possible resources-saving immunological strategy due to the loss of co-evolved parasites in the new colonised habitats, as observed in a previous study. A lower investment in immune function may benefit other energy-demanding activities, such as reproduction, dispersal, and territoriality. Research highlightsOur results point to a reduced investment in adaptive immune function in invasive Egyptian geese compared to native and sympatric waterfowl species, as a possible resources-saving immunological strategy due to the loss of co-evolved parasites in the new colonised habitats.

ecology↗

bioRxiv2022

SARS-CoV-2 has not emerged in roe, red or fallow deer in Germany or Austria during the COVID 19 pandemic

Spillover of SARS-CoV-2 to North American white tailed deer (Odocoileus virginianus) has been documented. We evaluated pre and pandemic exposure of German and Austrian deer species using a SARS-CoV-2 pseudoneutralization assay. In stark contrast to North American white tailed deer, we found no evidence of SARS-CoV-2 exposure. Article Summary LineUsing a sensitive serological assay, 433 pre and pandemic deer samples from Germany and Austria tested negative for SARS-CoV-2-specific antibodies highlighting a major difference between central European and North American deer exposure and in their epidemiologic roles.

microbiology↗

bioRxiv2022

Seasonal challenges of tropical bats (Rousettus aegyptiacus) in temperate zones

Egyptian fruit bats (Rousettus aegyptiacus) manage to survive and flourish in a large geographic range despite the variability of natural and anthropogenic conditions in this range. To examine the challenges faced by free-ranging R.aegyptiacus living at the northern edge of their distribution, we performed a retrospective analysis of [~]1500 clinical cases reported by a bat rescue NGO over 25 months, from all over Israel. All cases of injured or stranded bats were evaluated and categorized according to date, place, sex, age, and etiology of the morbidity. The analysis of the data showed an increase in all types of morbidity during the wintertime, with more than twice the number of cases in comparison with the summertime, over two consecutive years. Moreover, we found that the number of abandoned pups peaks during spring till autumn when adult morbidity is minimal. We characterize two prominent types of previously undescribed morbidity in R.aegyptiacus, one in the form of bacterial illness, and the other associated with feet deformation which affects bats in addition to major anthropogenic-related threats related to synanthropic predators. We analyze the reasons driving winter morbidity and conclude that winter weather and specifically low temperature best explains this morbidity. We hypothesize that R.aegyptiacus, a fruit-bat of tropical origin is facing major seasonal difficulties near the northern edge of its distribution, probably limiting its further spread northward.

ecology↗

bioRxiv2020

Sick Bats Stay Home Alone: Social distancing during the acute phase response in Egyptian fruit bats (Rousettus aegyptiacus)

Along with its many advantages, social roosting imposes a major risk of pathogen transmission. How social animals, and especially free-ranging mammals, reduce this risk is poorly documented. We used lipopolysaccharide injection to imitate bacterial sickness in both a captive and a free-ranging colony of an extremely social, long lived mammal - the Egyptian fruit bat. We monitored behavioral and physiological responses using an arsenal of methods, including on-board GPS and acceleration, video, temperature and weight measurements, and blood samples. Sick-like bats exhibited an increased immune response, as well as classical illness symptoms including fever, weight loss, anorexia, and lethargy. Notably, they also isolated themselves from the group by leaving the social cluster and avoiding contact. Free-ranging individuals ceased foraging outdoors for at least two nights. Together, these sickness behaviors demonstrate a strong, integrative immune response which promotes recovery of infected individuals while protecting their group members from transmission of pathogens, and at the same time, reducing spillover events outside the roost.

zoology↗

bioRxiv2018

Bearing the brunt: Mongolian khulan (Equus hemionus hemionus) are exposed to multiple influenza A strains

The majority of influenza A virus strains are hosted in nature by several Anseriformes and Charadriformes birds. A minority of strains have been able to cross species boundaries and establish themselves in novel non-avian hosts. Influenza viruses of horses, donkeys, and mules represent successful cases of avian to mammal influenza virus adaptation. Mongolia has over 3 million domestic horses and is home to two wild equids, the Asiatic wild ass (Equus hemionus hemionus), and Przewalski horse (Equus ferus przewalskii). Domestic and wild equids are sympatric across most of their range in Mongolia. Epizootic influenza A virus outbreaks among Mongolian domestic horses have been frequently recorded. However, the exposure, circulation and relation to domestic horse influenza A virus outbreaks among wild equids is unknown. We evaluated serum samples of Asiatic wild asses in Mongolia for antibodies against influenza A viruses, using a serological assay. We detected antibodies against hemagglutinin (H) H1, H3, H5, H7, H8 and H10 influenza A viruses. Asiatic wild asses may represent a previously unidentified influenza A virus reservoir in an ecosystem shared with populations of domestic horses in which influenza strains circulate.

epidemiology↗