Differential immune gene expression associated with contemporary range expansion in two invasive rodents in Senegal.

Biological invasions are major anthropogenic changes associated with threats to biodiversity and health. However, what determines the successful establishment and spread of introduced populations remains unclear. Here, we explore several hypotheses linking invasion success and immune phenotype traits, including those based on the evolution of increased competitive ability concept. We compared gene expression profiles between anciently and recently established populations of two major invading species, the house mouse Mus musculus domesticus and the black rat Rattus rattus, in Senegal (West Africa). Transcriptome analyses identified differential expression between anciently and recently established populations for 364 mouse genes and 83 rat genes. All immune-related genes displaying differential expression along the mouse invasion route were overexpressed at three of the four recently invaded sites studied. Complement activation pathway genes were overrepresented among these genes. By contrast, no particular immunological process was found to be overrepresented among the differentially expressed genes of black rat. Changes in transcriptome profiles were thus observed along invasion routes, but with different specific patterns between the two invasive species. These changes may be driven by increases in infection risks at sites recently invaded by the house mouse, and by stochastic events associated with colonization history for the black rat. These results constitute a first step toward the identification of immune eco-evolutionary processes potentially involved in the invasion success of these two rodent species.

Pathogen-associated selection on innate immunity genes (TLR4, TLR7) in a neotropical rodent in landscapes differing in anthropogenic disturbance.

Toll-like receptors (TLRs) form part of the innate immune system and can recognize structurally conserved pathogen-associated molecular pattern (PAMP) molecules. Their functional importance in the resistance to pathogens has been documented in laboratory experimental settings and in humans. TLR diversity, however, has been rarely investigated in wildlife species. How the genetic diversity of TLRs is associated with various pathogens and how it is shaped by habitat disturbance are understudied. Therefore, we investigated the role of genetic diversity in the functionally important parts of TLR4 and TLR7 genes in resistance towards gastrointestinal nematodes and Hepacivirus infection. We chose a generalist study species, the rodent Proechimys semispinosus, because it is highly abundant in three Panamanian landscapes that differ in their degree of anthropogenic modification. We detected only two TLR7 haplotypes that differed by one synonymous single-nucleotide polymorphism (SNP) position. The TLR4 variability was higher, and we detected four TLR4 haplotypes that differed at one synonymous SNP and at three amino acid positions within the leucine-rich repeat region. Only TLR4 haplotypes had different frequencies in each landscape. Using generalized linear models, we found evidence that nematode loads and virus prevalence were influenced by both specific TLR4 haplotypes and landscape. Here, the variable "landscape" served as a surrogate for the important influential ecological factors distinguishing landscapes in our study, i.e. species diversity and host population density. Individuals carrying the common TLR4_Ht1 haplotype were less intensely infected by the most abundant strongyle nematode. Individuals carrying the rare TLR4_Ht3 haplotype were all Hepacivirus-positive, where those carrying the rare haplotype TLR4_Ht4 were less often infected by Hepacivirus than individuals with other haplotypes. Our study highlights the role of TLR diversity in pathogen resistance and the importance of considering immune genetic as well as ecological factors in order to understand the effects of anthropogenic changes on wildlife health.

Clinical and serological evaluation of capybaras (Hydrochoerus hydrochaeris) successively exposed to an Amblyomma sculptum-derived strain of Rickettsia rickettsii.

Brazilian spotted fever (BSF), caused by Rickettsia rickettsii, is the most lethal tick-borne disease in the western hemisphere. In Brazil, Amblyomma sculptum ticks are the main vector. Capybaras (Hydrochoerus hydrochaeris), the largest living rodents of the world (adults weighing up to 100 Kg), have been recognized as amplifying hosts of R. rickettsii for A. sculptum in BSF-endemic areas; i.e., once primarily infected, capybaras develop bacteremia for a few days, when feeding ticks acquire rickettsial infection. We conducted experimental infections of five capybaras with an A. sculptum-derived strain of R. rickettsii and performed clinical and bacteremia evaluation during primary and subsequent infections. Bacteremia was detected in all capybaras during primary infection, but not in subsequent infections. All animals seroconverted to R. rickettsii (titres range: 64-32,768), and remained seropositive throughout the study. Primary infection resulted in clinical spotted fever illness in four capybaras, of which two had a fatal outcome. Subsequent infections in seropositive capybaras resulted in no clinical signs. Capybaras developed a sustained immune response that prevented a second bacteremia. This condition may imply a high reproduction rate of capybaras in BSF-endemic areas, in order to continuously generate capybaras susceptible to bacteremia during primary infection.

A serological and molecular study on Francisella tularensis in rodents from Hamadan province, Western Iran.

INTRODUCTION AND PURPOSE: Tularemia is a zoonotic disease, the most important hosts of which are rodents. Endemic regions and reservoirs of F. tularensis are not well-researched areas in Iran. The present study aimed to study F. tularensis infection in the rodent populations of western Iran. MATERIALS AND METHODS: Samples were collected in different areas of Kabudar Ahang County in Hamadan province (west of Iran) from 2014 to 2017. Tularemia serological and molecular tests were conducted using the tube agglutination test and Real-time PCR method tracking the ISFtu2 gene. Positive serum samples were evaluated for cross-reactivity with brucellosis. RESULTS: A total of 433 rodents, collected from 33 localities, were included in the study. The most abundant species belonged to the Persian jird (Meriones persicus; 75.5%), and Libyan jird (Meriones libycus; 10.1%). Among the studied samples, three (0.74 %) were seropositive and five (1.15%) were PCR positive. Seropositive samples were two M. persicus and one M. libycus, and PCR positive rodents were four M. persicus and one M. vinogradovi. Tularemia seropositive samples showed no cross-reactivity with brucellosis. CONCLUSION: Given the presence of infection in rodents with tularemia agent in the studied area, it is crucial to elucidate the risks of rodent exposure to tularemia for physicians, health personnel and the general population.

Field-testing a single-dose immunocontraceptive in free-ranging male capybara (Hydrochoerus hydrochaeris): Evaluation of effects on reproductive physiology, secondary sexual characteristics, and agonistic behavior.

Controlling wildlife populations to mitigate human-wildlife conflicts and the spread of zoonotic diseases is an ever-growing necessity. The objective of this study was to evaluate a single-dose anti-gonadotropin-releasing hormone vaccine (GonaCon, USDA/NWRC, Fort Collins, CO, USA) as a non-lethal alternative for population control in free-ranging, synanthropic male capybara. In addition to infertility efficacy of this treatment, potential effects on the alpha male's secondary sexual characteristics and agonist behavior need to be assessed because any alterations in these factors could lead to population management failure. The treatment group (n = 3) received 1 mL of the anti-GnRH vaccine, intramuscularly, and the control group (n = 2) a 1 mL sham vaccine. Reproductive behavior and social group dynamics were monitored for 30 days prior to inoculation (June 2017) with continuous observations occurring during the study period. Antifertility effects were assessed by conducting exams of testicular morphology, semen characteristics, and histological analysis (after 270 days via hemi-gonadectomy). Compared to the control group, the testicles of the treated males had severe atrophy (P <  0.05), oligozoospermia and greater numbers of sperm cells in a static developmental phase. Courtship and agonistic alpha male behavior were not altered, and the group's social integrity was maintained. Results indicate there was 100% infertility in capybara males, observed throughout the study period of 18 months, and equally important, the male's alpha characteristics were not affected by the treatment, which is imperative for successful capybara population control efforts.

Dynamic profiles, biodistribution and integration evaluation after intramuscular/intravenous delivery of a novel therapeutic DNA vaccine encoding chicken type II collagen for rheumatoid arthritis in vaccinated normal rodent.

BACKGROUND: The persistence, biodistribution, and risk of integration into the host genome of any new therapeutic DNA vaccine must be established in preclinical studies. We previously developed the DNA vaccine pcDNA-CCOL2A1 encoding chicken type II collagen (CCII) for the treatment of rheumatoid arthritis (RA). In the present study, we characterized its dynamic profile, biodistribution, and potential for genomic DNA integration in normal vaccinated rodent. RESULTS: A real-time quantitative PCR analysis (RT-qPCR) of animals administered a single dose of pcDNA-CCOL2A1 (300 µg/kg by intramuscular injection) showed that CCOL2A1 mRNA level in the blood peaked between 2 and 6 h post-immunization and then rapidly declined, and was undetectable between day 1-42. CCOL2A1 transcript was detected at the muscle injection site on days 3-14 post-immunization. Starting from day 14, the transcript was detected in the heart, liver, lung, and kidney but not in the spleen or thymus, and was expressed only in the lung on day 28. There was no CCOL2A1 mRNA present in the testes or ovaries at any time point. Non-invasive in vivo fluorescence imaging revealed CCII protein expression from 2 h up to day 10 and from 2 h up to day 35 after administration of pcDNA-CCOL2A1 via the intravenous and intramuscular routes, respectively; the protein had disappeared by day 42. Importantly, CCOL2A1 was not integrated into the host genome. CONCLUSIONS: These results indicate that pcDNA-CCOL2A1 vaccine is rapidly cleared within a short period of time and is therefore safe, and merits further development as a therapeutic vaccine for RA treatment.

Leptospirosis in sugarcane plantation and fishing communities in Kagera northwestern Tanzania.

BACKGROUND: Leptospirosis is a bacterial zoonotic disease of worldwide importance, though relatively neglected in many African countries including sub Saharan Africa that is among areas with high burden of this disease. The disease is often mistaken for other febrile illnesses such as dengue, malaria, rickettsioses and enteric fever. Leptospirosis is an occupational disease likely to affect people working in environments prone to infestation with rodents which are the primary reservoir hosts of this disease. Some of the populations at risk include: sugarcane plantation workers, wetland farmers, fishermen and abattoir workers. In this study we investigated the prevalence of antibodies against Leptospira among sugarcane plantation and factory workers, fishing communities as well as among rodents and shrews in domestic and peridomestic environments within the study areas. METHODS: The study was conducted in Kagera region, northwestern Tanzania and it involved sugarcane plantation workers (cutters and weeders), sugar factory workers and the fishing community at Kagera Sugar Company in Missenyi district and Musira island in Lake Victoria, Kagera, respectively. Blood was collected from consenting human adults, and from rodents and shrews (insectivores) captured live using Sherman traps. Serological detection of leptospiral antibodies in blood serum was carried out by the microscopic agglutination test (MAT). RESULTS: A total of 455 participants were recruited from the sugarcane plantation (n = 401) and fishing community (n = 54) while 31 rodents and shrews were captured. The overall prevalence of antibodies against Leptospira in human was 15.8%. Sugarcane cutters had higher seroprevalence than other sugar factory workers. Prevalent antibodies against Leptospira serovars in humans were against serovars Lora (6.8%), Sokoine (5.3%), Pomona (2.4%), Hebdomadis (1.1%) and Kenya (0.2%). Detected leptospiral serovars in reservoir hosts were Sokoine (12.5%) and Grippotyphosa (4.2%). Serovar Sokoine was detected both in humans and small mammals. CONCLUSION: Leptospirosis is a public health threat affecting populations at risk, such as sugarcane plantation workers and fishing communities. Public awareness targeting risk occupational groups is much needed for mitigation of leptospirosis in the study areas and other vulnerable populations in Tanzania and elsewhere.

Detection of antibodies to Borrelia burgdorferi s.l. in wild small mammals and sensitivity of PCR and cultivation.

The aim of this study was to determine the seroprevalence of antibodies to B. burgdorferi s.l. in wild small mammals in the Czech Republic and compare sensitivity of PCR and cultivaton. Wild small mammals (n = 691) were trapped in years 2010-2014 in three localities of the Czech Republic. Heart rinses (n = 340) and sera (n = 351) were examined by modified indirect ELISA. Seventy animals were randomly selected for comparison of results of cultivation and PCR. Mean annual antiborelian positivity was 12% with statistical difference (p < 0.05) between Bank Vole (Clethrionomys glareolus) and other six animal species, while there was no statistical difference (p > 0.05) between rodentia and insectivora, gender and localities. The cultivation revealed one positive sample (1.4%), negative in both PCR and ELISA. Method PCR revealed seven positive samples (10%); two of them were simultaneously dubious in ELISA. Eleven animals, negative in cultivation and PCR, had antibodies in ELISA. Method of PCR compared to cultivation seems to be more sensitive for detection of Borrelia.

Assessment of Trade-Offs between Simultaneous Immune Challenges in a Slow-Living Subterranean Rodent.

The coexistence of two or more infectious agents in the same host is common in nature. Given this, the study of trade-offs within the immune system itself is key to understanding how immune defenses act in wild species in their natural environment. Here we assessed the possible trade-off between an inflammatory response (induced by phytohemagglutinin [PHA]; involving innate and adaptive responses in the study species) and an antibody response (induced by sheep red blood cells [SRBC]; adaptive response) in a slow-living subterranean rodent, the Talas tuco-tuco (Ctenomys talarum Thomas, 1898). According to life-history theory, slow-living species should rely more heavily on adaptive immunity, which develops more slowly than an innate response but is beneficial against repeated infections. Individual physiological condition (estimated by measuring levels of infection and immune, nutritional, and stress parameters) was analyzed during immune challenges. Contrary to what was expected, we found that the magnitude and energetic costs of both immune responses were similar when stimulated alone or simultaneously. Variation in natural antibodies, neutrophils, basophils, total leukocytes, and the ratio of neutrophils to lymphocytes in relation to the different treatments was also detected. In particular, natural antibodies were negatively affected by the induction of both immune challenges simultaneously and an increase of neutrophil counts was detected in all animals with the exception of those challenged with SRBC, while the pattern of variation of basophils, total leukocytes, and ratio of neutrophils to lymphocytes was not clearly associated with any triggered immune response. In general, our results suggest the absence of an energetic or resource-based trade-off between the immune responses triggered by PHA and SRBC in C. talarum.

Epizootological study on Toxoplasma gondii in zoo animals in the Czech Republic.

Toxoplasma gondii is protozoan parasite with ability of causing disease in wide-spectrum of animals; many species of animals in captivity died of clinical toxoplasmosis. The monitoring of T. gondii antibodies in zoo animals can be an important indicator of T. gondii circulation in zoo. The aim of this study was to examine sera of animals from eight Czech zoos by latex agglutination test with statistical evaluation and detect T. gondii DNA in stray cats and rodents captured in the zoos. T. gondii antibodies were detected in 33% of 1043 zoo animals without statistical difference between birds (27%, n = 74) and mammals (33%, n = 969). In birds, the chance to be infected with T. gondii was higher in Accipitriformes (71%) compared to Pelecaniformes (6%) (p < 0.0001). In mammals, the chance to be infected with T. gondii was higher in Carnivora (63%) compared to Cetarodactyla (30%), Perissodactyla (26%), Primates (28%) and Rodentia (13%) (p < 0.0001) and higher in Felidae (70%) compared to Bovidae (28%) and Equidae (28%) (p < 0.0001). Mammals with carnivore/scavenger way of feeding were in a higher risk of T. gondii infection compared to herbivores and omnivores (p < 0.0001). T. gondii DNA was detected in tissue of one stray cat while in none of 77 rodents caught in zoo. This study is the first report on toxoplasmosis in zoos from the Czech Republic including seroepidemiology and molecular detection.

Translational Rodent Models for Research on Parasitic Protozoa-A Review of Confounders and Possibilities.

Rodents, in particular Mus musculus, have a long and invaluable history as models for human diseases in biomedical research, although their translational value has been challenged in a number of cases. We provide some examples in which rodents have been suboptimal as models for human biology and discuss confounders which influence experiments and may explain some of the misleading results. Infections of rodents with protozoan parasites are no exception in requiring close consideration upon model choice. We focus on the significant differences between inbred, outbred and wild animals, and the importance of factors such as microbiota, which are gaining attention as crucial variables in infection experiments. Frequently, mouse or rat models are chosen for convenience, e.g., availability in the institution rather than on an unbiased evaluation of whether they provide the answer to a given question. Apart from a general discussion on translational success or failure, we provide examples where infections with single-celled parasites in a chosen lab rodent gave contradictory or misleading results, and when possible discuss the reason for this. We present emerging alternatives to traditional rodent models, such as humanized mice and organoid primary cell cultures. So-called recombinant inbred strains such as the Collaborative Cross collection are also a potential solution for certain challenges. In addition, we emphasize the advantages of using wild rodents for certain immunological, ecological, and/or behavioral questions. The experimental challenges (e.g., availability of species-specific reagents) that come with the use of such non-model systems are also discussed. Our intention is to foster critical judgment of both traditional and newly available translational rodent models for research on parasitic protozoa that can complement the existing mouse and rat models.

Immunisation - Choice of host, adjuvants and boosting schedules with emphasis on polyclonal antibody production.

Polyclonal antibodies are frequently used as immunodiagnostic tools in fundamental research. They are also used for routine diagnostic purposes in human and veterinary medicine and for quality control procedures in the food-processing industry. The antibody is a major component of the detection system. It binds with the molecule to be identified. This conjugate is subsequently revealed by means of binding the antibody with a radio-isotope, a fluorescent substance, an enzyme inducing a color change, or a biosensor based analytical system. Polyclonal antibodies are also used for treatment purposes in various pathologies. They might have immunomodulating or anti-inflammatory properties. Snake venom, rabies and tetanus antisera are examples of a therapeutic application; immunosuppressive antithymocyte serum used in order to avoid rejection in organ transplantation is another example from human medicine. These therapeutic aids need hyperimmunisation of animals. Since these are subject to a certain number of interventions such as injections and blood samplings, animal welfare prescriptions have to be taken into account. The optimisation of the immunisation protocol allows for reducing the numbers of animals used as well as reducing stress and pain while obtaining high quality antibodies. This article describes the critical steps in polyclonal antibody production with a particular focus on the choice of the animal species, the age of the subjects, the injection protocol and the sampling times.

Innate recognition of Toxoplasma gondii in humans involves a mechanism distinct from that utilized by rodents.

Toxoplasma gondii is an intracellular protozoan parasite that infects rodents as part of its natural transmission cycle and induces disease in humans, an end-stage host. As one of the natural hosts of T. gondii, the mouse has been used extensively for elucidating the cellular and molecular basis of immunity to this pathogen while relatively few studies have focused on the response of humans. In our recent work, we identified CD16+ monocytes and DC1 dendritic cells as the major myeloid cell populations that respond to T. gondii in human peripheral blood. Interestingly, these myeloid subsets represent the opposite counterparts from those triggered by the parasite in mice. Moreover, whereas the innate cytokine response to T. gondii in the mouse involves stimulation of Toll-like receptors by a soluble parasite ligand, the response of human cells instead requires phagocytosis of the live pathogen. We speculate that these marked distinctions in the pathways utilized for innate recognition of toxoplasma in mouse and man reflect the differing roles of the two hosts in the biology of this parasite.

Anti-Toxoplasma gondii and anti-Neospora caninum antibodies in capybaras (Hydrochoerus hydrochaeris) from Itu Municipality, São Paulo.

Capybaras (Hydrochoerus hydrochaeris) are the largest rodents found in South America. The aim of the present study was to investigate the occurrence of anti-Toxoplasma gondii and anti-Neospora caninum antibodies in 170 free-living capybaras in a residential park area in Itu Municipality, São Paulo State, Brazil. Serum samples were tested by indirect fluorescent antibody test (IFAT) for T. gondii (IFAT ≥ 1:16) and N. caninum (IFAT ≥ 1:50). Among the 170 samples analyzed, 10% (17/170) and 0% (0/170) were seropositive for T. gondii and N. caninum, respectively. This study confirms the widespread presence of T. gondii and reinforces the role of capybaras in the life cycle of this parasite. Capybaras may not be important as intermediate hosts of N. caninum in the studied environment.

Anti-Toxoplasma gondii and anti-Neospora caninum antibodies in capybaras (Hydrochoerus hydrochaeris) from Itu Municipality, São Paulo / Anticorpos anti-Toxoplasma gondii e anti-Neospora caninum em capivaras (Hydrochoerus hydrochaeris) do Município de Itu, São Paulo

Abstract Capybaras (Hydrochoerus hydrochaeris) are the largest rodents found in South America. The aim of the present study was to investigate the occurrence of anti-Toxoplasma gondii and anti-Neospora caninum antibodies in 170 free-living capybaras in a residential park area in Itu Municipality, São Paulo State, Brazil. Serum samples were tested by indirect fluorescent antibody test (IFAT) for T. gondii (IFAT ≥ 1:16) and N. caninum (IFAT ≥ 1:50). Among the 170 samples analyzed, 10% (17/170) and 0% (0/170) were seropositive for T. gondii and N. caninum, respectively. This study confirms the widespread presence of T. gondii and reinforces the role of capybaras in the life cycle of this parasite. Capybaras may not be important as intermediate hosts of N. caninum in the studied environment.

Resumo As capivaras (Hydrochoerus hydrochaeris) são os maiores roedores encontrados na América do Sul. O objetivo do presente estudo foi investigar a ocorrência de anticorpos anti-Toxoplasma gondii e anti-Neospora caninum em 170 capivaras de vida livre, habitando em um condomínio fechado no Município de Itu, Estado de São Paulo, Brasil. Amostras de soro foram testadas por meio da Reação de Imunofluorescência Indireta (RIFI) para T. gondii (RIFI ≥ 1:16) e N. caninum (RIFI ≥ 1:50). Entre as 170 amostras analisadas, 10% (17/170) e 0% (0/170) foram positivas para T. gondii eN. caninum, respectivamente. O presente estudo confirma a ampla distribuição de T. gondii e reforça o papel das capivaras no ciclo biológico desse parasita. Provavelmente, as capivaras não têm um papel importante como hospedeiros intermediários de N. caninum no ambiente estudado.

Strain-Related Differences in the Immune Response: Relevance to Human Stroke.

There are significant differences in the immune response and in the susceptibility to autoimmune diseases among rodent strains. It would thus be expected that the contribution of the immune response to cerebral ischemic injury would also differ among rodent strains. More importantly, there are significant differences between the immune responses of rodents and humans. All of these factors are likely to impact the successful translation of immunomodulatory therapies from experimental rodent models to patients with stroke.

Parasite infection negatively affects PHA-triggered inflammation in the subterranean rodent Ctenomys talarum.

Magnitude and effectiveness of immune responses vary greatly between and within species. Among factors reported to determine this variation, parasitism is a critical one, although controversial effects of parasites over immunological indices have been reported. Information regarding immune strategies in species with different life histories is crucial to better understand the role of immune defenses in an ecological and evolutionary context. Here, we examine the influence of the parasite community on immune responsiveness of a solitary subterranean rodent, Ctenomys talarum. To do this, we assessed the impact of the natural parasite community and the experimental infection with Eimeria sp. on the phytohemagglutinin (PHA)-response, as well as other immune, condition, nutrition, and stress parameters. PHA-triggered inflammation was similarly impaired by Eimeria sp. infection alone or co-occurring with a number of gastrointestinal nematodes. None of the other physiological parameters studied were affected by parasitism. This indicates that parasitism is a general key factor modulating immune responsiveness of the host, and in particular for C. talarum, it could explain the great inter-individual variation previously observed in the PHA-response. Thus, our results highlight the importance of taking the parasite community into account in ecoimmunological studies, particularly when using immunological indices.

The evolution of natural killer cell receptors.

Natural killer (NK) cells are immune cells that play a crucial role against viral infections and tumors. To be tolerant against healthy tissue and simultaneously attack infected cells, the activity of NK cells is tightly regulated by a sophisticated array of germline-encoded activating and inhibiting receptors. The best characterized mechanism of NK cell activation is "missing self" detection, i.e., the recognition of virally infected or transformed cells that reduce their MHC expression to evade cytotoxic T cells. To monitor the expression of MHC-I on target cells, NK cells have monomorphic inhibitory receptors which interact with conserved MHC molecules. However, there are other NK cell receptors (NKRs) encoded by gene families showing a remarkable genetic diversity. Thus, NKR haplotypes contain several genes encoding for receptors with activating and inhibiting signaling, and that vary in gene content and allelic polymorphism. But if missing-self detection can be achieved by a monomorphic NKR system why have these polygenic and polymorphic receptors evolved? Here, we review the expansion of NKR receptor families in different mammal species, and we discuss several hypotheses that possibly underlie the diversification of the NK cell receptor complex, including the evolution of viral decoys, peptide sensitivity, and selective MHC-downregulation.

Immunology in wild nonmodel rodents: an ecological context for studies of health and disease.

Transcriptomic methods are set to revolutionize the study of the immune system in naturally occurring nonmodel organisms. With this in mind, the present article focuses on ways in which the use of 'nonmodel' rodents (not the familiar laboratory species) can advance studies into the classical, but ever relevant, epidemiologic triad of immune defence, infectious disease and environment. For example, naturally occurring rodents are an interesting system in which to study the environmental stimuli that drive the development and homeostasis of the immune system and, by extension, to identify where these stimuli are altered in anthropogenic environments leading to the formation of immunopathological phenotypes. Measurement of immune expression may help define individual heterogeneity in infectious disease susceptibility and transmission and facilitate our understanding of infection dynamics and risk in the natural environment; furthermore, it may provide a means of surveillance that can filter individuals carrying previously unknown acute infections of potential ecological or zoonotic importance. Finally, the study of immunology in wild animals may reveal interactions within the immune system and between immunity and other organismal traits that are not observable under restricted laboratory conditions. Potentiating much of this is the possibility of combining gene expression profiles with analytical tools derived from ecology and systems biology to reverse engineer interaction networks between immune responses, other organismal traits and the environment (including symbiont exposures), revealing regulatory architecture. Such holistic studies promise to link ecology, epidemiology and immunology in natural systems in a unified approach that can illuminate important problems relevant to human health and animal welfare and production.