Epidemiological connectivity between humans and animals across an urban landscape.

Urbanization is predicted to be a key driver of disease emergence through human exposure to novel, animal-borne pathogens. However, while we suspect that urban landscapes are primed to expose people to novel animal-borne diseases, evidence for the mechanisms by which this occurs is lacking. To address this, we studied how bacterial genes are shared between wild animals, livestock, and humans (n = 1,428) across Nairobi, Kenya-one of the world's most rapidly developing cities. Applying a multilayer network framework, we show that low biodiversity (of both natural habitat and vertebrate wildlife communities), coupled with livestock management practices and more densely populated urban environments, promotes sharing of Escherichia coli-borne bacterial mobile genetic elements between animals and humans. These results provide empirical support for hypotheses linking resource provision, the biological simplification of urban landscapes, and human and livestock demography to urban dynamics of cross-species pathogen transmission at a landscape scale. Urban areas where high densities of people and livestock live in close association with synanthropes (species such as rodents that are more competent reservoirs for zoonotic pathogens) should be prioritized for disease surveillance and control.

Population dynamics of synanthropic rodents after a chemical and infrastructural intervention in an urban low-income community.

Synanthropic rodents are ubiquitous in low-income communities and pose risks for human health, as they are generally resistant to control programs. However, few or no studies have evaluated the long-term effect of chemical and infrastructural interventions on rodent population dynamics, especially in urban low-income communities, or evaluated the potential recovery of their population following interventions. We conducted a longitudinal study in a low-income community in the city of Salvador (BA, Brazil) to characterize the effect of interventions (chemical and infrastructural) on the dynamics of rodent population, and documented the post-intervention recovery of their population. We evaluated the degree of rodent infestation in 117 households/sampling points over three years (2014-2017), using tracking plates, a proxy for rodent abundance/activity. We reported a significant lower rodent activity/abundance after the chemical and infrastructural interventions (Z = -4.691 (p < 0.001)), with track plate positivity decreasing to 28% from 70% after and before interventions respectively. Therefore, the combination of chemical and infrastructural interventions significantly decreased the degree of rodent infestation in the study area. In addition, no rodent population rebound was recorded until almost a year post-intervention, and the post-intervention infestation level did not attain the pre-intervention level all through the study. Moreover, among pre-treatment conditions, access to sewer rather than the availability of food was the variable most closely associated with household rodent infestation. Our study indicates that Integrated Pest Management (IPM)-approaches are more effective in reducing rodent infestation than the use of a single method. Our findings will be useful in providing guidance for long-term rodent control programs, especially in urban low-income communities.

Why is leptospirosis hard to avoid for the impoverished? Deconstructing leptospirosis transmission risk and the drivers of knowledge, attitudes, and practices in a disadvantaged community in Salvador, Brazil.

Several studies have identified socioeconomic and environmental risk factors for infectious disease, but the relationship between these and knowledge, attitudes, and practices (KAP), and more importantly their web of effects on individual infection risk, have not previously been evaluated. We conducted a cross-sectional KAP survey in an urban disadvantaged community in Salvador, Brazil, leveraging on simultaneously collected fine-scale environmental and epidemiological data on leptospirosis transmission. Residents' knowledge influenced their attitudes which influenced their practices. However, different KAP variables were driven by different socioeconomic and environmental factors; and while improved KAP variables reduced risk, there were additional effects of socioeconomic and environmental factors on risk. For example, males and those of lower socioeconomic status were at greater risk, but once we controlled for KAP, male gender and lower socioeconomic status themselves were not direct drivers of seropositivity. Employment was linked to better knowledge and a less contaminated environment, and hence lower risk, but being employed was independently associated with a higher, not lower risk of leptospirosis transmission, suggesting travel to work as a high risk activity. Our results show how such complex webs of influence can be disentangled. They indicate that public health messaging and interventions should take into account this complexity and prioritize factors that limit exposure and support appropriate prevention practices.

Socio-ecological drivers of vertebrate biodiversity and human-animal interfaces across an urban landscape.

Urbanization can have profound impacts on the distributional ecology of wildlife and livestock, with implications for biodiversity conservation, ecosystem services and human health. A wealth of studies have assessed biotic responses to urbanization in North America and Europe, but there is little empirical evidence that directly links human activities to urban biodiversity in the tropics. Results from a large-scale field study conducted in Nairobi, Kenya, are used to explore the impact of human activities on the biodiversity of wildlife and livestock with which humans co-exist across the city. The structure of sympatric wildlife, livestock and human populations are characterized using unsupervised machine learning, and statistical modelling is used to relate compositional variation in these communities to socio-ecological drivers occurring across the city. By characterizing landscape-scale drivers acting on these interfaces, we demonstrate that socioeconomics, elevation and subsequent changes in habitat have measurable impacts upon the diversity, density and species assemblage of wildlife, livestock and humans. Restructuring of wildlife and livestock assemblages (both in terms of species diversity and composition) has important implications for the emergence of novel diseases at urban interfaces, and we therefore use our results to generate a set of testable hypotheses that explore the influence of urban change on microbial communities. These results provide novel insight into the impact of urbanization on biodiversity in the tropics. An understanding of associations between urban processes and the structure of human and animal populations is required to link urban development to conservation efforts and risks posed by disease emergence to human health, ultimately informing sustainable urban development policy.

The drivers of squirrelpox virus dynamics in its grey squirrel reservoir host.

Many pathogens of conservation concern circulate endemically within natural wildlife reservoir hosts and it is imperative to understand the individual and ecological drivers of natural transmission dynamics, if any threat to a related endangered species is to be assessed. Our study highlights the key drivers of infection and shedding dynamics of squirrelpox virus (SQPV) in its reservoir grey squirrel (Sciurus carolinensis) population. To clarify SQPV dynamics in this population, longitudinal data from a 16-month mark-recapture study were analysed, combining serology with real-time quantitative PCR to identify periods of acute viraemia and chronic viral shedding. At the population level, we found SQPV infection prevalence, viral load and shedding varied seasonally, peaking in autumn and early spring. Individually, SQPV was shown to be a chronic infection in >80% of grey squirrels, with viral loads persisting over time and bouts of potential recrudescence or reinfection occurring. A key recurring factor significantly associated with SQPV infection risk was the presence of co-infecting squirrel adenovirus (ADV). In dual infected squirrels, longitudinal analysis showed that prior ADV viraemia increased the subsequent SQPV load in the blood. However, there was a strong, negative association between prior ADV viraemia and subsequent SQPV shedding from the forearm, probably caused by ADV prolonging the SQPV acute viraemic phase, so delaying onset of the chronic shedding phase, and thereby altering viral shedding patterns over the time scales examined here. Hence, co-circulating ADV infection may be involved in mediating both the quantitative levels of SQPV infection and the timing and degree of subsequent infectiousness of grey squirrels.

Clinically relevant antimicrobial resistance at the wildlife-livestock-human interface in Nairobi: an epidemiological study.

BACKGROUND: Antimicrobial resistance is one of the great challenges facing global health security in the modern era. Wildlife, particularly those that use urban environments, are an important but understudied component of epidemiology of antimicrobial resistance. We investigated antimicrobial resistance overlap between sympatric wildlife, humans, livestock, and their shared environment across the developing city of Nairobi, Kenya. We use these data to examine the role of urban wildlife in the spread of clinically relevant antimicrobial resistance. METHODS: 99 households across Nairobi were randomly selected on the basis of socioeconomic stratification. A detailed survey was administered to household occupants, and samples (n=2102) were collected from the faeces of 75 wildlife species inhabiting household compounds (ie, the household and its perimeter; n=849), 13 livestock species (n=656), and humans (n=333), and from the external environment (n=288). Escherichia coli, our sentinel organism, was cultured and a single isolate from each sample tested for sensitivity to 13 antibiotics. Diversity of antimicrobial resistant phenotypes was compared between urban wildlife, humans, livestock, and the environment, to investigate whether wildlife are a net source for antimicrobial resistance in Nairobi. Generalised linear mixed models were used to determine whether the prevalence of antimicrobial resistant phenotypes and multidrug-resistant E coli carriage in urban wildlife is linked to variation in ecological traits, such as foraging behaviour, and to determine household-level risk factors for sharing of antimicrobial resistance between humans, wildlife, and livestock. FINDINGS: E coli were isolated from 485 samples collected from wildlife between Sept 6,2015, and Sept 28, 2016. Wildlife carried a low prevalence of E coli isolates susceptible to all antibiotics tested (45 [9%] of 485 samples) and a high prevalence of clinically relevant multidrug resistance (252 [52%] of 485 samples), which varied between taxa and by foraging traits. Multiple isolates were resistant to one agent from at least seven antimicrobial classes tested for, and a single isolate was resistant to all antibiotics tested for in the study. The phenotypic diversity of antimicrobial-resistant E coli in wildlife was lower than in livestock, humans, and the environment. Within household compounds, statistical models identified two interfaces for exchange of antimicrobial resistance: between both rodents, humans and their rubbish, and seed-eating birds, humans and their rubbish; and between seed-eating birds, cattle, and bovine manure. INTERPRETATION: Urban wildlife carry a high burden of clinically relevant antimicrobial-resistant E coli in Nairobi, exhibiting resistance to drugs considered crucial for human medicine by WHO. Identifiable traits of the wildlife contribute to this exposure; however, compared with humans, livestock, and the environment, low phenotypic diversity in wildlife is consistent with the hypothesis that wildlife are a net sink rather than source of clinically relevant resistance. Wildlife that interact closely with humans, livestock, and both human and livestock waste within households, are exposed to more antimicrobial resistant phenotypes, and could therefore act as conduits for the dissemination of clinically relevant antimicrobial resistance to the wider environment. These results provide novel insight into the broader epidemiology of antimicrobial resistance in complex urban environments, characteristic of lower-middle-income countries. FUNDING: UK Medical Research Council and CGIAR Research Program on Agriculture for Nutrition and Health.

A candidate tolerance gene identified in a natural population of field voles (Microtus agrestis).

The animal immune response has hitherto been viewed primarily in the context of resistance only. However, individuals can also employ a tolerance strategy to maintain good health in the face of ongoing infection. To shed light on the genetic and physiological basis of tolerance, we use a natural population of field voles, Microtus agrestis, to search for an association between the expression of the transcription factor Gata3, previously identified as a marker of tolerance in this system, and polymorphism in 84 immune and nonimmune genes. Our results show clear evidence for an association between Gata3 expression and polymorphism in the Fcer1a gene, with the explanatory power of this polymorphism being comparable to that of other nongenetic variables previously identified as important predictors of Gata3 expression. We also uncover the possible mechanism behind this association using an existing protein-protein interaction network for the mouse model rodent, Mus musculus, which we validate using our own expression network for M. agrestis. Our results suggest that the polymorphism in question may be working at the transcriptional level, leading to changes in the expression of the Th2-related genes, Tyrosine-protein kinase BTK and Tyrosine-protein kinase TXK, and hence potentially altering the strength of the Th2 response, of which Gata3 is a mediator. We believe our work has implications for both treatment and control of infectious disease.

High prevalence of epilepsy in onchocerciasis endemic regions in the Democratic Republic of the Congo.

BACKGROUND: An increased prevalence of epilepsy has been reported in many onchocerciasis endemic areas. The objective of this study was to determine the prevalence of epilepsy in onchocerciasis endemic areas in the Democratic Republic of the Congo (DRC) and investigate whether a higher annual intake of Ivermectin was associated with a lower prevalence of epilepsy. METHODOLOGY/PRINCIPLE FINDINGS: Between July 2014 and February 2016, house-to-house epilepsy prevalence surveys were carried out in areas with a high level of onchocerciasis endemicity: 3 localities in the Bas-Uele, 24 in the Tshopo and 21 in the Ituri province. Ivermectin uptake was recorded for every household member. This database allowed a matched case-control pair subset to be created that enabled putative risk factors for epilepsy to be tested using univariate logistic regression models. Risk factors relating to onchocerciasis were tested using a multivariate random effects model. To identify presence of clusters of epilepsy cases, the Kulldorff's scan statistic was used. Of 12, 408 people examined in the different health areas 407 (3.3%) were found to have a history of epilepsy. A high prevalence of epilepsy was observed in health areas in the 3 provinces: 6.8-8.5% in Bas-Uele, 0.8-7.4% in Tshopo and 3.6-6.2% in Ituri. Median age of epilepsy onset was 9 years, and the modal age 12 years. The case control analysis demonstrated that before the appearance of epilepsy, compared to the same life period in controls, persons with epilepsy were around two times less likely (OR: 0.52; 95%CI: (0.28, 0.98)) to have taken Ivermectin than controls. After the appearance of epilepsy, there was no difference of Ivermectin intake between cases and controls. Only in Ituri, a significant cluster (p-value = 0.0001) was identified located around the Draju sample site area. CONCLUSIONS: The prevalence of epilepsy in health areas in onchocerciasis endemic regions in the DRC was 2-10 times higher than in non-onchocerciasis endemic regions in Africa. Our data suggests that Ivermectin protects against epilepsy in an onchocerciasis endemic region. However, a prospective population based intervention study is needed to confirm this.

Endemic Hantavirus in Field Voles, Northern England.

We report a PCR survey of hantavirus infection in an extensive field vole (Microtus agrestis) population present in the Kielder Forest, northern England. A Tatenale virus-like lineage was frequently detected (≈17% prevalence) in liver tissue. Lineages genetically similar to Tatenale virus are likely to be endemic in northern England.

Urbanization and Disease Emergence: Dynamics at the Wildlife-Livestock-Human Interface.

Urbanization is characterized by rapid intensification of agriculture, socioeconomic change, and ecological fragmentation, which can have profound impacts on the epidemiology of infectious disease. Here, we review current scientific evidence for the drivers and epidemiology of emerging wildlife-borne zoonoses in urban landscapes, where anthropogenic pressures can create diverse wildlife-livestock-human interfaces. We argue that these interfaces represent a critical point for cross-species transmission and emergence of pathogens into new host populations, and thus understanding their form and function is necessary to identify suitable interventions to mitigate the risk of disease emergence. To achieve this, interfaces must be studied as complex, multihost communities whose structure and form are dictated by both ecological and anthropological factors.

Risk factors for epilepsy in Bas-Uélé Province, Democratic Republic of the Congo: a case-control study.

BACKGROUND: The reason for the high prevalence of epilepsy in onchocerciasis endemic areas remains unknown. The aim of this study was to detect risk factors associated with epilepsy in a region endemic for onchocerciasis. METHODS: In June 2014, a case-control study was performed in Titule, Bas-Uélé Province in the Democratic Republic of the Congo. Individuals with unprovoked convulsive epilepsy of unknown aetiology were enrolled as cases (n=59). Healthy members of families without cases of epilepsy in the same village were recruited as controls (n=61). A multivariate binomial logistic regression analysis was performed to identify potential risk factors associated with epilepsy. To evaluate the potential protective effect of ivermectin treatment on the development of epilepsy, a nested age-matched case-control study was performed including only those who were eligible for ivermectin treatment in the year before they developed epilepsy. RESULTS: Suspected onchocerciasis skin lesions were more often present in cases than in controls: 12/41 (29%) vs. 1/56 (2%), respectively (odds ratio (OR) 20.26, 95% confidence interval (CI) 2.42-170; p<0.01). Ivermectin had been taken 7 months earlier in 29/59 (49%) cases and 29/61 (48%) controls. Onchocerca volvulus (OV) DNA was detected by PCR in skin snips in 26/34 cases (76%) and 10/14 controls (71%) (p=0.7), and there was presence of OV IgG4 antibodies in 35/48 (73%) cases and 15/18 (83%) controls (p=0.5). OV DNA was not detected in the cerebrospinal fluid of cases (controls not tested). Both cases and controls reported frequent bites by blackflies (Diptera, Simuliidae). Bathing daily as opposed to less often (OR 16.7, 95% CI 2.2-125.8; p<0.01), bathing between 11 a.m. and 4 p.m. (OR 12.7, 95% CI 1.6-103.7; p=0.02), and washing clothes between 11 a.m. and 4 p.m. (OR 10.9, 95% CI 1.5-77.3; p=0.02) were all independently associated with epilepsy. Blood screening by specific PCR tests for Toxoplasma and Wuchereria bancrofti was negative in all cases and controls. A Loa loa infestation was found in only one case and one control by PCR and Giemsa smear. Antibodies to Taenia solium, Toxocara, and Trypanosoma sp were not detected in any of the participants. In an age-matched case-control analysis, 16/18 (89%) cases had not taken ivermectin the year before they developed epilepsy, compared to 7/18 (39%) controls that same year (p=0.002). CONCLUSIONS: These data suggest that frequent activities at rivers known to be blackfly breeding sites and a historical lack of ivermectin treatment were risk factors for epilepsy in this onchocerciasis endemic area.

Enhancement of wildlife disease surveillance using multiplex quantitative PCR: development of qPCR assays for major pathogens in UK squirrel populations.

Rapid development in polymerase chain reaction (PCR) technology has revolutionised the speed and accuracy of many diagnostic assays. However, comparatively few wildlife epidemiological studies use quantitative PCR (qPCR) for pathogen detection, even fewer employ an internal control, to ensure confidence in negative results, and PCR's ability to multiplex and therefore detect several targets in a single reaction is underutilised. Here, we describe the development of two multiplex qPCR assays for the red and grey squirrel that detect the pathogens squirrelpox virus (SQPV) and adenovirus in squirrels (SADV), both of which cause mortality in the red squirrel. Both assays use a section of the squirrel phosphoglycerate kinase gene as an endogenous internal control that identifies and compensates for both, inadequate sampling or PCR inhibition. Tests on infected squirrel tissue demonstrate that simple swab samples (particularly from distal antebrachial skin) are sufficient to detect and identify the relative quantity of SQPV DNA in both squirrel species, while rectal swabs and blood cell pellets can be used to reliably indicate SADV infection. These assays are sensitive and specific with an endogenous internal control providing confidence in negative results and allowing comparison across laboratories. Using such assays should prove advantageous in wildlife studies with limited resources while allowing the maximum data yield.

Estimates of coextinction risk: how anuran parasites respond to the extinction of their hosts.

Amphibians are known as the most threatened vertebrate group. One of the outcomes of a species' extinction is the coextinction of its dependents. Here, we estimate the extinction risk of helminth parasites of South America anurans. Parasite coextinction probabilities were modeled, assuming parasite specificity and host vulnerability to extinction as determinants. Parasite species associated with few hosts were the most prone to extinction, and extinction risk varied amongst helminth species of different taxonomic groups and life cycle complexity. Considering host vulnerability in the model decreased the extinction probability of most parasites species. However, parasite specificity and host vulnerability combined to increase the extinction probabilities of 44% of the helminth species reported in a single anuran species.

Genome characterisation of two Ljungan virus isolates from wild bank voles (Myodes glareolus) in Sweden.

Ljungan virus (LV) (family Picornaviridae, genus Parechovirus) is a suspected zoonotic pathogen with associations to human disease in Sweden. LV is a single-stranded RNA virus with a positive sense genome. There are five published Ljungan virus strains, three isolated from Sweden and two from America, and are classified into four genotypes. A further two strains described here were isolated from wild bank voles (Myodes glareolus) caught in Västmanlands county, Sweden in 1994. These strains were sequenced using next generation pyrosequencing technology on the GS454flx platform. Genetic and phylogenetic analysis of the obtained genomes confirms isolates LV340 and LV342 as two new putative members of genotype 2 along with LV145SL, with 92% and 99% nucleotide identities respectively. Only two codon sites throughout the entire genome were identified as undergoing positive selection, both situated within the VP3 structural region, in or near to major antigenic sites. Whilst these two strains do not constitute new genotypes they provide evidence, though weakly supported, which suggests the evolution of Ljungan viruses to be relatively slow, a characteristic unlike other picornaviruses. Additional genomic sequences are urgently required for Ljungan virus strains, particularly from different locations or hosts, to fully understand the evolutionary and epidemiological properties of this potentially zoonotic virus.

First report of Anaplasma phagocytophilum and Babesia microti in rodents in Finland.

Tick-borne diseases pose an increasingly important public health problem in Europe. Rodents are the reservoir host for many tick-transmitted pathogens, including Anaplasma phagocytophilum and Babesia microti, which can cause human granulocytic anaplasmosis and babesiosis, respectively. To estimate the presence of these pathogens in rodents in Finland, we examined blood samples from 151 bank voles (Myodes glareolus) and demonstrate, for the first time, that A. phagocytophilum and B. microti commonly infect bank voles (in 22% and 40% of animals, respectively) in Finland. Sequence analysis of a fragment of 18S rRNA showed that the B. microti strain isolated was identical to the Munich strain, which is considered to be nonzoonotic. The A. phagocytophilum strain (based on a fragment of the msp4 gene) was identical to one found earlier in rodents in the United Kingdom that is transmitted by the tick Ixodes trianguliceps, all the life stages of which feed on small mammals. The infection probability of B. microti in the bank voles was the greater the older the individual was, and males were more often infected than females. A. phagocytophilum infection probability first increased and then decreased with the age of individual without any difference between sexes. While these pathogens presumably pose a limited zoonotic risk to humans in Finland, they might have important interactions with other rodent pathogens and therefore affect infection dynamics of, for example, zoonotic pathogens.

Ljungan virus is endemic in rodents in the UK.

Ljungan virus is a recently identified member of the family Picornaviridae that was isolated from bank voles in Sweden. LjV has been associated with [corrected] type 1 diabetes-like symptoms and myocarditis in bank voles (Myodes glareolus), and it has been suggested that it has zoonotic potential. Here, we show for the first time that Ljungan virus is prevalent (20-27 % positive by PCR) in four species of UK rodent (Myodes glareolus [bank vole], Apodemus sylvaticus [wood mouse], Microtus agrestis [field vole] and Mus musculus [house mouse]). Sequence analysis showed that Ljungan virus of genotypes 1 and 2 were present, although genotype 1 was more prevalent and more frequently associated with brain tissue. This study highlights the prevalence of Ljungan virus in the UK and the need for assessment [corrected] of its zoonotic potential.

European red squirrel population dynamics driven by squirrelpox at a gray squirrel invasion interface.

Infectious disease introduced by non-native species is increasingly cited as a facilitator of native population declines, but direct evidence may be lacking due to inadequate population and disease prevalence data surrounding an outbreak. Previous indirect evidence and theoretical models support squirrelpox virus (SQPV) as being potentially involved in the decline of red squirrels (Sciurus vulgaris) following the introduction of the non-native gray squirrel (Sciurus carolinensis) to the United Kingdom. The red squirrel is a major UK conservation concern and understanding its continuing decline is important for any attempt to mitigate the decline. The red squirrel-gray squirrel system is also exemplary of the interplay between infectious disease (apparent competition) and direct competition in driving the replacement of a native by an invasive species. Time series data from Merseyside are presented on squirrel abundance and squirrelpox disease (SQPx) incidence, to determine the effect of the pathogen and the non-native species on the native red squirrel populations. Analysis indicates that SQPx in red squirrels has a significant negative impact on squirrel densities and their population growth rate (PGR). There is little evidence for a direct gray squirrel impact; only gray squirrel presence (but not density) proved to influence red squirrel density, but not red squirrel PGR. The dynamics of red SQPx cases are largely determined by previous red SQPx cases, although previous infection of local gray squirrels also feature, and thus, SQPV-infected gray squirrels are identified as potentially initiating outbreaks of SQPx in red squirrels. Retrospective serology indicates that approximately 8% of red squirrels exposed to SQPV may survive infection during an epidemic. This study further highlights the UK red squirrel - gray squirrel system as a classic example of a native species population decline strongly facilitated by infectious disease introduced by a non-native species. It is therefore paramount that disease prevention and control measures are integral in attempts to conserve red squirrels in the United Kingdom.

How do childhood diagnoses of type 1 diabetes cluster in time?

BACKGROUND: Previous studies have indicated that type 1 diabetes may have an infectious origin. The presence of temporal clustering-an irregular temporal distribution of cases--would provide additional evidence that occurrence may be linked with an agent that displays epidemicity. We tested for the presence and form of temporal clustering using population- based data from northeast England. MATERIALS AND METHODS: The study analysed data on children aged 0-14 years diagnosed with type 1 diabetes during the period 1990-2007 and resident in a defined geographical region of northeast England (Northumberland, Newcastle upon Tyne, and North Tyneside). Tests for temporal clustering by time of diagnosis were applied using a modified version of the Potthoff-Whittinghill method. RESULTS: The study analysed 468 cases of children diagnosed with type 1 diabetes. There was highly statistically significant evidence of temporal clustering over periods of a few months and over longer time intervals (p<0.001). The clustering within years did not show a consistent seasonal pattern. CONCLUSIONS: The study adds to the growing body of literature that supports the involvement of infectious agents in the aetiology of type 1 diabetes in children. Specifically it suggests that the precipitating agent or agents involved might be an infection that occurs in "mini-epidemics".

The analysis of immunological profiles in wild animals: a case study on immunodynamics in the field vole, Microtus agrestis.

A revolutionary advance in ecological immunology is that postgenomic technologies now allow molecular mediators defined in laboratory models to be measured at the mRNA level in field studies of many naturally occurring species. Here, we demonstrate the application of such an approach to generate meaningful immunological profiles for wild mammals. We sampled a natural field vole population across the year (n = 307) and developed a battery of cellular assays in which functionally different pro- and anti-inflammatory signalling responses (transcription factors and cytokines) were activated and quantified by Q-PCR. Temporal trends were the strongest feature in the expression data, although some life history stages (mating vs. nonmating males and pregnant females) were also associated with significant variation. There was a striking set of significant negative associations between inflammatory mediators and condition indices reflecting packed erythrocyte volume and relative liver size, spleen size and splenocyte count. Grouped (principal component) measures of inflammatory and anti-inflammatory expression were high in winter, with minima in the breeding season that occurred earlier for grouped anti-inflammatory responses than for grouped inflammatory responses. Some individual immunological mediators also showed patterns unrelated to the breeding season or annual periodic cues. For example, interferon regulatory factor 5 (IRF5) expression declined throughout the study period, indicating a systematic trend in antimicrobial defences. Pinpointing the causes and consequences of such variation may help identify underlying environmental drivers of individual fitness and demographic fluctuation.