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Recent studies have provided an unprecedented view of the microbial communities colonizing captive mice; yet the host and environmental factors that shape the rodent gut microbiota in their natural habitat remain largely unexplored. Here, we present results from a 2-year 16 S ribosomal RNA gene sequencing-based survey of wild wood mice (Apodemus sylvaticus) in two nearby woodlands. Similar to other mammals, wild mice were colonized by 10 bacterial phyla and dominated by the Firmicutes, Bacteroidetes and Proteobacteria. Within the Firmicutes, the Lactobacillus genus was most abundant. Putative bacterial pathogens were widespread and often abundant members of the wild mouse gut microbiota. Among a suite of extrinsic (environmental) and intrinsic (host-related) factors examined, seasonal changes dominated in driving qualitative and quantitative differences in the gut microbiota. In both years examined, we observed a strong seasonal shift in gut microbial community structure, potentially due to the transition from an insect- to a seed-based diet. This involved decreased levels of Lactobacillus, and increased levels of Alistipes (Bacteroidetes phylum) and Helicobacter. We also detected more subtle but statistically significant associations between the gut microbiota and biogeography, sex, reproductive status and co-colonization with enteric nematodes. These results suggest that environmental factors have a major role in shaping temporal variations in microbial community structure within natural populations.

Organisms have evolved diverse strategies to manage parasite infections. Broadly, hosts may avoid infection by altering behaviour, resist infection by targeting parasites or tolerate infection by repairing associated damage. The effectiveness of a strategy depends on interactions between, for example, resource availability, parasite traits (virulence, life‐history) and the host itself (nutritional status, immunopathology). To understand how these factors shape host parasite‐mitigation strategies, we developed a mathematical model of within‐host, parasite‐immune dynamics in the context of helminth infections. The model incorporated host nutrition and resource allocation to different mechanisms of immune response: larval parasite prevention; adult parasite clearance; damage repair (tolerance). We also considered a non‐immune strategy: avoidance via anorexia, reducing intake of infective stages. Resources not allocated to immune processes promoted host condition, whereas harm due to parasites and immunopathology diminished it. Maximising condition (a proxy for fitness), we determined optimal host investment for each parasite‐mitigation strategy, singly and combined, across different environmental resource levels and parasite trait values. Which strategy was optimal varied with scenario. Tolerance generally performed well, especially with high resources. Success of the different resistance strategies (larval prevention or adult clearance) tracked relative virulence of larval and adult parasites: slowly maturing, highly damaging larvae favoured prevention; rapidly maturing, less harmful larvae favoured clearance. Anorexia was viable only in the short term, due to reduced host nutrition. Combined strategies always outperformed any lone strategy: these were dominated by tolerance, with some investment in resistance. Choice of parasite mitigation strategy has profound consequences for hosts, impacting their condition, survival and reproductive success. We show that the efficacy of different strategies is highly dependent on timescale, parasite traits and resource availability. Models that integrate such factors can inform the collection and interpretation of empirical data, to understand how those drivers interact to shape host immune responses in natural systems. [ABSTRACT FROM AUTHOR]

Gastrointestinal (GI) helminths are common parasites of humans, wildlife, and livestock, causing chronic infections. In humans and wildlife, poor nutrition or limited resources can compromise an individual's immune response, predisposing them to higher helminth burdens. This relationship has been tested in laboratory models by investigating infection outcomes following reductions of specific nutrients. However, much less is known about how diet supplementation can impact susceptibility to infection, acquisition of immunity, and drug efficacy in natural host–helminth systems. We experimentally supplemented the diet of wood mice (Apodemus sylvaticus) with high-quality nutrition and measured resistance to the common GI nematode Heligmosomoides polygyrus. To test whether diet can enhance immunity to reinfection, we also administered anthelmintic treatment in both natural and captive populations. Supplemented wood mice were more resistant to H. polygyrus infection, cleared worms more efficiently after treatment, avoided a post-treatment infection rebound, produced stronger general and parasite-specific antibody responses, and maintained better body condition. In addition, when applied in conjunction with anthelmintic treatment, supplemented nutrition significantly reduced H. polygyrus transmission potential. These results show the rapid and extensive benefits of a well-balanced diet and have important implications for both disease control and wildlife health under changing environmental conditions. [ABSTRACT FROM AUTHOR]

To purchase or authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1523-1739.2007.00776.x Byline: AMY B. PEDERSEN (*[double dagger][double dagger]), KATE E. JONES (s.), CHARLES L. NUNN ([double dagger]**), SONIA ALTIZER (*) Keywords: domesticated animal; IUCN Red List; mammal conservation; parasite; pathogen; transmission mode; virus Abstract: Abstract: Parasite-driven declines in wildlife have become increasingly common and can pose significant risks to natural populations. We used the IUCN Red List of Threatened and Endangered Species and compiled data on hosts threatened by infectious disease and their parasites to better understand the role of infectious disease in contemporary host extinctions. The majority of mammal species considered threatened by parasites were either carnivores or artiodactyls, two clades that include the majority of domesticated animals. Parasites affecting host threat status were predominantly viruses and bacteria that infect a wide range of host species, including domesticated animals. Counter to our predictions, parasites transmitted by close contact were more likely to cause extinction risk than those transmitted by other routes. Mammal species threatened by parasites were not better studied for infectious diseases than other threatened mammals and did not have more parasites or differ in four key traits demonstrated to affect parasite species richness in other comparative studies. Our findings underscore the need for better information concerning the distribution and impacts of infectious diseases in populations of endangered mammals. In addition, our results suggest that evolutionary similarity to domesticated animals may be a key factor associated with parasite-mediated declines; thus, efforts to limit contact between domesticated hosts and wildlife could reduce extinction risk. Abstract (Spanish): Enfermedades Infecciosas y Riesgo de Extincion en Mamiferos Silvestres Resumen: Las declinaciones de vida silvestre debido a parasitos se han vuelto mas comunes y pueden ser riesgos significativos para las poblaciones naturales. Utilizamos la Lista Roja de IUCN de Especies Amenazadas y en Peligro y compilamos datos sobre huespedes amenazados por enfermedades infecciosas y sus parasitos para comprender el papel de enfermedades infecciosas en las extinciones contemporaneas de huespedes. La mayoria de las especies de mamiferos consideradas amenazadas por parasitos fueron carnivoros o artiodactilos, dos clados que incluyen a la mayoria de los animales domesticados. Los parasitos que afectan el estatus amenazado de huespedes son predominantemente virus y bacterias que infectan a una amplia gama de especies huesped, incluyendo animales domesticos. Contrario a nuestras predicciones, los parasitos transmitidos por contacto cercano tuvieron mayor probabilidad de causar riesgo de extincion que los transmitidos por otras rutas. Las especies de mamiferos amenazadas por parasitos no fueron mejor estudiadas para enfermedades infecciosas que otros mamiferos amenazados y no tuvieron mas parasitos ni difirieron en cuatro caracteristicas clave que afectan la riqueza de especies de parasitos en otros estudios comparativos. Nuestros hallazgos subrayan la necesidad de mayor informacion relacionada con la distribucion e impacto de enfermedades infecciosas en poblaciones de mamiferos en peligro. Adicionalmente, nuestros resultados sugieren que la similitud evolutiva con animales domesticados puede ser un factor clave asociados con las declinaciones debidas a parasitos; por lo tanto, los esfuerzos para limitar contacto entre huespedes domesticados y vida silvestre podrian reducir el riesgo de extincion. Author Affiliation: (*)Odum School of Ecology, University of Georgia, Athens, GA 30602, U.S.A., and Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield S10 2TN, United Kingdom ([double dagger])Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103 Leipzig, Germany (s.)Institute of Zoology, Zoological Society of London, Regents Park, London, NW1 4RY, United Kingdom (**)Department of Integrative Biology, University of California, Berkeley, CA, U.S.A. Article History: Paper submitted January 16, 2007; revised manuscript accepted May 1, 2007. Article note: ([double dagger][double dagger]) email a.pedersen@sheffield.ac.uk

Recent evidence suggests that most parasites can infect multiple host species and that these are primarily responsible for emerging infectious disease outbreaks in humans and wildlife. However, the ecologic and [...]