Mycobacterium microti at the Environment and Wildlife Interface

An unexpected high presence of Mycobacterium microti in wild boar in Northern Italy (Garda Lake) has been reported since 2003, but the factors contributing to the maintenance of this pathogen are still unclear. In this study, we investigated the presence of M. microti in wild rodents and in water and soil samples collected at wild boar aggregation areas, such as watering holes, with the aim of clarifying their role in M. microti transmission. In total, 8 out of 120 captured animals tested positive for the Mycobacterium tuberculosis complex (MTBC) as assessed by real-time PCR, and six samples were confirmed to be M. microti. A strain with a genetic profile similar to those previously isolated in wild boars in the same area was isolated from one sample. Of the 20 water and 19 mud samples, 3 and 1, respectively, tested positive for the presence of MTBC, and spacer oligotype SB0118 (vole type) was detected in one sample. Our study suggests that wild rodents, in particular Apodemus sylvaticus, Microtus sp. and Apodemus flavicollis, play roles in the maintenance of M. microti infections in wild boar through ingestion or by contact with either infected excreta or a contaminated environment, such as at animal aggregation sites.

Sulfation modification of dopamine in brain regulates aggregative behavior of animals

Behavioral plasticity and the underlying neuronal plasticity represent a fundamental capacity of animals to cope with environmental stimuli. Behavioral plasticity is controlled by complex molecular networks that act under different layers of regulation. While various molecules have been found to be involved in the regulation of plastic behaviors across species, less is known about how organisms orchestrate the activity of these molecules as part of a coherent behavioral response to varying environments. Here we discover a mechanism for the regulation of animal behavioral plasticity involving molecular sulfation in brain, a modification of substrate molecules by sulfotransferase (ST)-catalyzed addition of a sulfonate group (SO3) from an obligate donor, 3’-phosphoadenosine 5’-phosphosulfate (PAPS) to the substrates. We investigated aggregation behaviors of the migratory locusts, which are well-known for extreme phase change plasticity triggered by population density. The processes of PAPS biosynthesis acted efficiently on induction of locust behavioral transition: Inhibition of PAPS synthesis solicited a behavioral shift from gregarious to solitarious states; external PAPS dosage, by contrast, promoted aggregation in solitarious locusts. Genetic or pharmacological intervention in the sulfation catalyzation resulted into pronounced solitarizing effects. Analysis of substrate-specific STs suggests a widespread involvement of sulfated neurotransmitters in the behavioral response. Dopamine in brain was finally identified to be actively sulfate conjugated, and the sulfate conjugation enhanced the free DA-mediated behavioral aggregation. Similar results in Caenorhabditis elegans and mouse indicate that sulfation may be involved more broadly in the modulation of animal aggregation. These findings revealed a general mechanism that effectively regulates animal social-like behavioral plasticity possibly through sulfation-mediated modification of neural networks.

Food for contagion: synthesis and future directions for studying host–parasite responses to resource shifts in anthropogenic environments

Human-provided resource subsidies for wildlife are diverse, common and have profound consequences for wildlife–pathogen interactions, as demonstrated by papers in this themed issue spanning empirical, theoretical and management perspectives from a range of study systems. Contributions cut across scales of organization, from the within-host dynamics of immune function, to population-level impacts on parasite transmission, to landscape- and regional-scale patterns of infection. In this concluding paper, we identify common threads and key findings from author contributions, including the consequences of resource subsidies for (i) host immunity; (ii) animal aggregation and contact rates; (iii) host movement and landscape-level infection patterns; and (iv) interspecific contacts and cross-species transmission. Exciting avenues for future work include studies that integrate mechanistic modelling and empirical approaches to better explore cross-scale processes, and experimental manipulations of food resources to quantify host and pathogen responses. Work is also needed to examine evolutionary responses to provisioning, and ask how diet-altered changes to the host microbiome influence infection processes. Given the massive public health and conservation implications of anthropogenic resource shifts, we end by underscoring the need for practical recommendations to manage supplemental feeding practices, limit human–wildlife conflicts over shared food resources and reduce cross-species transmission risks, including to humans. This article is part of the theme issue ‘Anthropogenic resource subsidies and host–parasite dynamics in wildlife’.

The temporal selfish herd: predation risk while aggregations form

The hypothesis of the selfish herd has been highly influential to our understanding of animal aggregation. Various movement strategies have been proposed by which individuals might aggregate to form a selfish herd as a defence against predation, but although the spatial benefits of these strategies have been extensively studied, little attention has been paid to the importance of predator attacks that occur while the aggregation is forming . We investigate the success of mutant aggregation strategies invading populations of individuals using alternative strategies and find that the invasion dynamics depend critically on the time scale of movement. If predation occurs early in the movement sequence, simpler strategies are likely to prevail. If predators attack later, more complex strategies invade. If there is variation in the timing of predator attacks (through variation within or between individual predators), we hypothesize that groups will consist of a mixture of strategies, dependent upon the distribution of predator attack times. Thus, behavioural diversity can evolve and be maintained in populations of animals experiencing a diverse range of predators differing solely in their attack behaviour. This has implications for our understanding of predator–prey dynamics, as the timing of predator attacks will exert selection pressure on prey behavioural responses, to which predators must respond.