Changes in physiological stress and behaviour in semi-free-ranging red-capped mangabeys (Cercocebus torquatus) following antiparasitic treatment

VESPA: an optimized protocol for accurate metabarcoding-based characterization of vertebrate eukaryotic endosymbiont and parasite assemblages

Protocols for characterizing taxonomic assemblages by deep sequencing of short DNA barcode regions (metabarcoding) have revolutionized our understanding of microbial communities and are standardized for bacteria, archaea, and fungi. Unfortunately, comparable methods for host-associated eukaryotes have lagged due to technical challenges. Despite 54 published studies, issues remain with primer complementarity, off-target amplification, and lack of external validation. Here, we present VESPA (Vertebrate Eukaryotic endoSymbiont and Parasite Analysis) primers and optimized metabarcoding protocol for host-associated eukaryotic community analysis. Using in silico prediction, panel PCR, engineered mock community standards, and clinical samples, we demonstrate VESPA to be more effective at resolving host-associated eukaryotic assemblages than previously published methods and to minimize off-target amplification. When applied to human and non-human primate samples, VESPA enables reconstruction of host-associated eukaryotic endosymbiont communities more accurately and at finer taxonomic resolution than microscopy. VESPA has the potential to advance basic and translational science on vertebrate eukaryotic endosymbiont communities, similar to achievements made for bacterial, archaeal, and fungal microbiomes.

Experimental evidence of parasite-induced behavioural alterations modulated by food availability in wild capuchin monkeys

In disease dynamics, host behaviour can both determine the quantity of parasites a host is exposed to, and be a consequence of infection. Observational and experimental studies in non-human primates have consistently found that parasitic infections result in less movement and reduced foraging, which was interpreted as an adaptive response of the host to counter infection. Variation in host nutritional condition may add complexity to the infection-behaviour relationship, and its influence may shed light on its significance. To experimentally evaluate how host activity and social relationships are affected by the interaction of parasitism and nutrition, during two years we manipulated food availability by provisioning bananas, and helminth infections by applying antiparasitic drugs, in two groups of wild black capuchin monkeys (Sapajus nigritus) in Iguazú National Park, Argentina. We collected faecal samples to determine the intensity of helminthic infections, as well as data on behaviour and social proximity. Individuals with unmanipulated helminth burdens foraged less than dewormed individuals only when food provisioning was low. Resting time was increased when capuchins were highly provisioned, but it did not vary according to the antiparasitic treatment. Proximity associations to other group members were not affected by the antiparasitic treatment. This is the first experimental evidence of a modulating effect of food availability on the influence of helminth infection on activity in wild primates. The findings are more consistent with an impact on host behaviour due to the debilitating effect caused by parasites than with an adaptive response to help fight infections.

Fecal glucocorticoids and gastrointestinal parasite infections in wild western lowland gorillas (Gorilla gorilla gorilla) involved in ecotourism

Wildlife ecotourism can offer a source of revenue which benefits local development and conservation simultaneously. However, habituation of wildlife for ecotourism can cause long-term elevation of glucocorticoid hormones, which may suppress immune function and increase an animal's vulnerability to disease. We have previously shown that western lowland gorillas (Gorilla gorilla gorilla) undergoing habituation in Dzanga-Sangha Protected Areas, Central African Republic, have higher fecal glucocorticoid metabolite (FGCM) levels than both habituated and unhabituated gorillas. Here, we tested the relationship between FGCM levels and strongylid infections in the same gorillas. If high FGCM levels suppress the immune system, we predicted that FGCM levels will be positively associated with strongylid egg counts and that gorillas undergoing habituation will have the highest strongylid egg counts, relative to both habituated and unhabituated gorillas. We collected fecal samples over 12 months in two habituated gorilla groups, one group undergoing habituation and completely unhabituated gorillas. We established FGCM levels and fecal egg counts of Necator/Oesophagostomum spp. and Mammomonogamus sp. Controlling for seasonal variation and age-sex category in strongylid infections we found no significant relationship between FGCMs and Nectator/Oesophagostomum spp. or Mammomonogamus sp. egg counts in a within group comparison in either a habituated group or a group undergoing habituation. However, across groups, egg counts of Nectator/Oesophagostomum spp. were lowest in unhabituated animals and highest in the group undergoing habituation, matching the differences in FGCM levels among these gorilla groups. Our findings partially support the hypothesis that elevated glucocorticoids reduce a host's ability to control the extent of parasitic infections, and show the importance of non-invasive monitoring of endocrine function and parasite infection in individuals exposed to human pressure including habituation process and ecotourism.

Predictors of helminth parasite infection in female chacma baboons (Papio ursinus)

Helminth parasite infection can impose major consequences on host fitness. Several factors, including individual characteristics of hosts, environmental conditions, and patterns of coinfection, are thought to drive variation in parasite risk. Here, we report on four key drivers of parasite infection-phase of reproduction, steroid hormone profiles, rainfall, and patterns of coinfection-in a population of wild female chacma baboons (Papio ursinus) in South Africa. We collected data on reproductive state and hormone profiles over a 3-year span, and quantified helminth parasite burdens in 2955 fecal samples from 24 female baboons. On a host level, we found that baboons are sensitive to parasite infection during the costliest phases of the reproductive cycle: pregnant females harbored higher intensities of Protospirura eggs than cycling and lactating females; lactating and cycling females had a higher probability of Oesophagostomum infection than pregnant females; and cycling females exhibited lower Trichuris egg counts than pregnant and lactating females. Steroid hormones were associated with both immunoenhancing and immunosuppressive properties: females with high glucocorticoid concentrations exhibited high intensities of Trichuris eggs but were at low risk of Oesophagostomum infection; females with high estrogen and progestagen concentrations exhibited high helminth parasite richness; and females with high progestagen concentrations were at high risk of Oesophagostomum infection but exhibited low Protospirura egg counts. We observed an interaction between host reproductive state and progestagen concentrations in infection intensity of Protospirura: pregnant females exhibited higher intensities and non-pregnant females exhibited lower intensities of Protospirura eggs with increasing progestagen concentrations. At a population level, rainfall patterns were dominant drivers of parasite risk. Lastly, helminth parasites exhibited positive covariance, suggesting that infection probability increases if a host already harbors one or more parasite taxa. Together, our results provide a holistic perspective of factors that shape variation in parasite risk in a wild population of animals.

Hair cortisol in captive corral-housed baboons

Hair cortisol concentrations (HCCs) are measures of long-term hypothalamic-pituitary-adrenocortical (HPA) activity and can be used as indicators of chronic stress. However, intrinsic factors such as an animal's age and sex can also have an impact on resulting HCCs. Although baboons are commonly studied in captivity, little is known about baseline HCC in this population. Here we measured HCC in two same-sex groups of captive olive (Papio hamadryas anubis) baboons and olive/yellow baboon (Papio hamadryas cynocephalus) crosses housed in large outdoor corrals, and we assessed the impact of age and sex on HCC as major variables of interest. Hair was gently shaved from the back of the neck when the animals were sedated for routine physicals. Subjects were divided into three age categories: juvenile (2-4 years), adult (9-12 years), and senior (13-19 years). The "senior" category contained only males. Results confirm an effect of sex and age on HCCs. Females had higher levels of hair cortisol than males, and juveniles had higher levels than adults. There was also a significant sex × age interaction. There were no sex differences in HCCs in juveniles, but there was a greater decline in HCCs in adult males than in adult females. Within males, there was a significant difference in levels of hair cortisol across the three age categories. Juveniles had higher levels than did adults and seniors, but adults and seniors were not significantly different from one another. These results provide baseline measures of hair cortisol in captive baboons and demonstrate effects of sex and age on HCCs.

Evaluating the Reliability of Non-Specialist Observers in the Behavioural Assessment of Semi-Captive Asian Elephant Welfare

Simple Summary

It is essential that elephant workers monitor the stress levels of their animals to uphold high standards of welfare. This can be done quickly and efficiently by observing elephant behaviour, however, the consistency of this approach is likely to vary between workers. While this variation has been tested in zoo elephants when observations were carried out by experienced observers, the consistency of observations made by non-experienced observers on the much larger population of Asian elephants working in Southeast Asia has yet to be explored. By constructing a list of elephant working behaviours, we employed three volunteer observers with no experience of elephant research to record the behaviour of Asian elephants working in Myanmar. We then tested the similarity between observations collected by the three observers, as well as the consistency that individual observers could repeatedly recognise the same behaviour. Overall, observers recognised the same behaviour from the videos and were highly consistent across repeated observations. These results suggest that the behaviours tested may represent useful indicators for welfare assessment, and that non-experienced observers can meaningfully contribute to the monitoring of elephant welfare.

Abstract

Recognising stress is an important component in maintaining the welfare of captive animal populations, and behavioural observation provides a rapid and non-invasive method to do this. Despite substantial testing in zoo elephants, there has been relatively little interest in the application of behavioural assessments to the much larger working populations of Asian elephants across Southeast Asia, which are managed by workers possessing a broad range of behavioural knowledge. Here, we developed a new ethogram of potential stress- and work-related behaviour for a semi-captive population of Asian elephants. We then used this to collect observations from video footage of over 100 elephants and evaluated the reliability of behavioural welfare assessments carried out by non-specialist observers. From observations carried out by different raters with no prior experience of elephant research or management, we tested the reliability of observations between-observers, to assess the general inter-observer agreement, and within-observers, to assess the consistency in behaviour identification. The majority of ethogram behaviours were highly reliable both between- and within-observers, suggesting that overall, behaviour was highly objective and could represent easily recognisable markers for behavioural assessments. Finally, we analysed the repeatability of individual elephant behaviour across behavioural contexts, demonstrating the importance of incorporating a personality element in welfare assessments. Our findings highlight the potential of non-expert observers to contribute to the reliable monitoring of Asian elephant welfare across large captive working populations, which may help to both improve elephant wellbeing and safeguard human workers.

Costs and drivers of helminth parasite infection in wild female baboons

Helminth parasites can have wide-ranging, detrimental effects on host reproduction and survival. These effects are best documented in humans and domestic animals, while only a few studies in wild mammals have identified both the forces that drive helminth infection risk and their costs to individual fitness. Working in a well-studied population of wild baboons (Papio cynocephalus) in the Amboseli ecosystem in Kenya, we pursued two goals, to (a) examine the costs of helminth infections in terms of female fertility and glucocorticoid hormone levels and (b) test how processes operating at multiple scales-from individual hosts to social groups and the population at large-work together to predict variation in female infection risk. To accomplish these goals, we measured helminth parasite burdens in 745 faecal samples collected over 5 years from 122 female baboons. We combine these data with detailed observations of host environments, social behaviours, hormone levels and interbirth intervals (IBIs). We found that helminths are costly to female fertility: females infected with more diverse parasite communities (i.e., higher parasite richness) exhibited longer IBIs than females infected by fewer parasite taxa. We also found that females exhibiting high Trichuris trichiura egg counts also had high glucocorticoid levels. Female infection risk was best predicted by factors at the host, social group and population level: females facing the highest risk were old, socially isolated, living in dry conditions and infected with other helminths. Our results provide an unusually holistic understanding of the factors that contribute to inter-individual differences in parasite infection, and they contribute to just a handful of studies linking helminths to host fitness in wild mammals.

Risk factors for respiratory illness in a community of wild chimpanzees (Pan troglodytes schweinfurthii)

Respiratory illnesses have caused significant mortality in African great ape populations. While much effort has been given to identifying the responsible pathogens, little is known about the factors that influence disease transmission or individual susceptibility. In the Kanyawara community of wild chimpanzees, respiratory illness has been the leading cause of mortality over 31 years, contributing to 27% of deaths. Deaths were common in all age groups except juveniles. Over 22 years of health observations, respiratory signs were rare among infants and most common among older adults of both sexes. Respiratory signs were also common among males during the transition to adulthood (ages 10-20 years), particularly among those of low rank. Respiratory signs peaked conspicuously in March, a pattern that we could not explain after modelling climatic factors, group sizes, diet or exposure to humans. Furthermore, rates of respiratory illness in the chimpanzees did not track seasonal rates of illness in the nearby village. Our data indicate that the epidemiology of chimpanzee respiratory illness warrants more investigation but clearly differs in important ways from humans. Findings on individual susceptibility patterns suggest that respiratory signs are a robust indicator for investigating immunocompetence in wild chimpanzees.

Social networks: a tool for assessing the impact of perturbations on wildlife behaviour and implications for pathogen transmission

Wildlife are increasingly subject to perturbations, which can impact pathogen transmission and lead to disease emergence. While a myriad of factors influence disease dynamics in wildlife, behaviour is emerging as a major influence. In this review, we examine how perturbations alter the behaviour of individuals and how, in turn, disease transmission may be impacted, with a focus on the use of network models as a powerful tool. There are emerging hypotheses as to how networks respond to different types of perturbations. The broad effects of perturbations make predicting potential outcomes and identifying mitigation opportunities for disease emergence critical; yet, the current paucity of data makes identification of underlying trends difficult. Social network analysis facilitates a mechanistic approach to how perturbation-induced behavioural changes result in shifts in pathogen transmission. However, the field is still developing, and future work should strive to address current deficits. There is particular need for empirical data to support modelling predictions and increased inclusion of pathogen monitoring in network studies.

Making New Connections: Insights from Primate-Parasite Networks

Social interactions are important in everyday life for primates and many other group-living animals; however, these essential exchanges also provide opportunities for parasites to spread through social groups. Network analysis is a unique toolkit for studying pathogen transmission in a social context, and recent primate-parasite network studies shed light on linkages between behavior and infectious disease dynamics, providing insights for conservation and public health. We review existing literature on primate-parasite networks, examining determinants of infection risk, issues of network scale and temporal dynamics, and applications for disease control. We also discuss analytical and conceptual gaps that should be addressed to improve our understanding of how individual and group-level factors affect infection risk, while highlighting interesting areas for future research.