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Monitoring and early detection of emerging infectious diseases in wild animals is of crucial global importance, yet reliable ways to measure immune status and responses are lacking for animals in the wild. Here we assess the usefulness of bio-loggers for detecting disease outbreaks in free-living birds and confirm detailed responses using leukocyte composition and large-scale transcriptomics. We simulated natural infections by viral and bacterial pathogens in captive mallards (Anas platyrhynchos), an important natural vector for avian influenza virus. We show that body temperature, heart rate and leukocyte composition change reliably during an acute phase immune response. Using genome-wide gene expression profiling of whole blood across time points we confirm that immunostimulants activate pathogen-specific gene regulatory networks. By reporting immune response related changes in physiological and behavioural traits that can be studied in free-ranging populations, we provide baseline information with importance to the global monitoring of zoonotic diseases.

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The immune system is important for host defense against antigens, but little is known about Steller's eider (Polysticta stelleri) immunology. This study compared hematological parameters, serum protein levels, lymphocyte proliferation, heat shock protein levels and oxidative damage in four different age classes of captive male Steller's eiders. The hatch year cohort had significantly higher total white blood cell and lymphocyte counts. The second year cohort had significantly higher albumin, alpha globulins and lymphocyte proliferation, and significantly lower beta globulin levels. The 9 year old males had a significantly higher IgY:IgY(ΔFc) ratio. The oldest eiders in the study, 14 + year old males, had significantly higher serum IgY, pre-albumin and glutathione reductase activity, and the lowest lymphocyte proliferation. This study provided a baseline of immune parameters in captive male Steller's eiders, and the results suggested the parameters were influenced by age-related changes.

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Highly pathogenic avian influenza viruses (HPAIVs) of H5 subtype have persistently caused outbreaks in domestic poultry and wild birds worldwide and sporadically infected humans. Rapid and accurate diagnosis is one of the key strategies for the control of H5 HPAIVs. However, the sensitivity of the diagnosis of H5 HPAIVs has gradually reduced due to extensive antigenic variation during their evolution. Particularly, the previously developed immunochromatographic diagnosis kit for H5 viruses, Linjudge Flu A/H5, exhibits reduced detection of H5 HPAIVs isolated in recent years. In the present study, we established a new advanced H5 rapid immunochromatographic detection kit (New Linjudge Flu A/H5) by a combination of two anti-H5 hemagglutinin monoclonal antibodies, A64/1 previously applied in the Linjudge Flu A/H5 and A32/2, a novel monoclonal antibody generated from a clade 2.3.4.4 H5 HPAIV. The new kit broadly detected all classical and recent H5 influenza viruses and showed a higher specificity and sensitivity than the original Linjudge Flu A/H5 with recently circulating H5 HPAIVs. Furthermore, the applicability of the New Linjudge Flu A/H5 was demonstrated by detecting antigens from the swabs and tissue homogenates of naturally infected birds and experimentally infected chickens with H5N6 HPAIVs belonging to the genetic clade 2.3.4.4. Our study, therefore, can provide an effective point-of-care rapid antigen detection kit for the surveillance of H5 avian influenza viruses and as a prompt countermeasure against the current widespread of the clade 2.3.4.4 H5 HPAIVs in domestic and wild birds.

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For viruses such as avian influenza, immunity within a host population can drive the emergence of new strains by selecting for viruses with novel antigens that avoid immune recognition. The accumulation of acquired immunity with age is hypothesized to affect how influenza viruses emerge and spread in species of different lifespans. Despite its importance for understanding the behaviour of avian influenza viruses, little is known about age-related accumulation of immunity in the virus's primary reservoir, wild birds. To address this, we studied the age structure of immune responses to avian influenza virus in a wild swan population (Cygnus olor), before and after the population experienced an outbreak of highly pathogenic H5N1 avian influenza in 2008. We performed haemagglutination inhibition assays on sampled sera for five avian influenza strains and show that breadth of response accumulates with age. The observed age-related distribution of antibody responses to avian influenza strains may explain the age-dependent mortality observed during the highly pathogenic H5N1 outbreak. Age structures and species lifespan are probably important determinants of viral epidemiology and virulence in birds.

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In disease dynamics, high immune gene diversity can confer a selective advantage to hosts in the face of a rapidly evolving and diverse pathogen fauna. This is supported empirically for genes involved in pathogen recognition and signalling. In contrast, effector genes involved in pathogen clearance may be more constrained. ß-Defensins are innate immune effector genes; their main mode of action is via disruption of microbial membranes. Here, five ß-defensin genes were characterized in mallards (Anas platyrhynchos) and other waterfowl; key reservoir species for many zoonotic diseases. All five genes showed remarkably low diversity at the individual-, population-, and species-level. Furthermore, there was widespread sharing of identical alleles across species divides. Thus, specific ß-defensin alleles were maintained not only spatially but also over long temporal scales, with many amino acid residues being fixed across all species investigated. Purifying selection to maintain individual, highly efficacious alleles was the primary evolutionary driver of these genes in waterfowl. However, we also found evidence for balancing selection acting on the most recently duplicated ß-defensin gene (AvBD3b). For this gene, we found that amino acid replacements were more likely to be radical changes, suggesting that duplication of ß-defensin genes allows exploration of wider functional space. Structural conservation to maintain function appears to be crucial for avian ß-defensin effector molecules, resulting in low tolerance for new allelic variants. This contrasts with other types of innate immune genes, such as receptor and signalling molecules, where balancing selection to maintain allelic diversity has been shown to be a strong evolutionary force.

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Maternal antibodies protect chicks from infection with pathogens early in life and may impact pathogen dynamics due to the alteration of the proportion of susceptible individuals in a population. We investigated the transfer of maternal antibodies against avian influenza virus (AIV) in a key AIV host species, the mallard (Anas platyrhynchos). Combining observations in both the field and in mallards kept in captivity, we connected maternal AIV antibody concentrations in eggs to (i) female body condition, (ii) female AIV antibody concentration, (iii) egg laying order, (iv) egg size and (v) embryo sex. We applied maternity analysis to the eggs collected in the field to account for intraspecific nest parasitism, which is reportedly high in Anseriformes, detecting parasitic eggs in one out of eight clutches. AIV antibody prevalence in free-living and captive females was respectively 48% and 56%, with 43% and 24% of the eggs receiving these antibodies maternally. In both field and captive study, maternal AIV antibody concentrations in egg yolk correlated positively with circulating AIV antibody concentrations in females. In the captive study, yolk AIV antibody concentrations correlated positively with egg laying order. Female body mass and egg size from the field and captive study, and embryos sex from the field study were not associated with maternal AIV antibody concentrations in eggs. Our study indicates that maternal AIV antibody transfer may potentially play an important role in shaping AIV infection dynamics in mallards.

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OBJECTIVE: To prepare polyclonal antibody against invariant chain of Muscovy duck (Cairina moschata) (MDIi) and identify its reaction with MDIi extracted from tissues of Muscovy duck. METHODS: MDIi was amplified by PCR and used to construct the prokaryotic expression vector of pET-32a/MDIi by linking with the plasmid of pET-32a. Then pET-32a/MDIi was transformed into E.coli Rosetta to induce the prokaryotic expression. After identified by SDS-PAGE, prokaryotic expression products were further purified from running gel of SDS-PAGE and injected into mice to prepare polyclonal antibody against MDIi. The titer and specificity of the polyclonal antibody against MDIi were analyzed by indirect ELISA and Western blotting, respectively. The intensity of reaction between the polyclonal antibody and MDIi extracted from tissues of Muscovy duck was also identified by indirect ELISA. RESULTS: The prokaryotic expression vector pET-32a/MDIi was successfully constructed. About 40 kD recombinant proteins of MDIi were confirmed to be expressed in the form of inclusion body in Rosetta. Polyclonal antibody against MDIi with a titer of 1:128 000 was obtained from the immunized mice and its high specificity was demonstrated by Western blotting. The titer of reaction between the polyclonal antibody and MDIi was 1:32 000. CONCLUSION: The polyclonal antibody against MDIi was successfully prepared with a high titer and specificity. It has a strong immune reaction with MDIi extracted from tissues of Muscovy duck.

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Inactivated influenza virus vaccine prepared from a non-pathogenic influenza virus strain A/duck/Hokkaido/Vac-1/2004 (H5N1) from the virus library conferred protective immunity to chickens against the challenge of antigenically drifted highly pathogenic avian influenza virus (HPAIV), A/whooper swan/Hokkaido/1/2008 (H5N1). The efficacy of the vaccine was comparable to that prepared from genetically modified HPAIV strain deltaRRRRK rg-A/ whooper swan/Mongolia/3/2005 (H5N1), which is more antigenically related to the challenge virus strain, in chickens.

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In April and May 2008, whooper swans (Cygnus cygnus) were found dead in Hokkaido in Japan. In this study, an adult whooper swan found dead beside Lake Saroma was pathologically examined and the identified H5N1 influenza virus isolates were genetically and antigenically analyzed. Pathological findings indicate that the swan died of severe congestive edema in the lungs. Phylogenetic analysis of the HA genes of the isolates revealed that they are the progeny viruses of isolates from poultry and wild birds in China, Russia, Korea, and Hong Kong. Antigenic analyses indicated that the viruses are distinguished from the H5N1 viruses isolated from wild birds and poultry before 2007. The chickens vaccinated with A/duck/Hokkaido/Vac-1/2004 (H5N1) survived for 14 days after challenge with A/whooper swan/Hokkaido/1/2008 (H5N1), although a small amount of the challenge virus was recovered from the tissues of the birds. These findings indicate that H5N1 highly pathogenic avian influenza viruses are circulating in wild birds in addition to domestic poultry in Asia and exhibit antigenic variation that may be due to vaccination.

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A serosurvey for neutralizing antibodies against West Nile virus (WNV) in common coots (Fulica atra) was conducted in Doñana, Spain. Antibody prevalence was highest in 2003, intermediate in 2004, and lowest in 2005. Some birds seroreverted <1 year after first capture. Seroconversion of birds suggests local circulation of the virus.

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Life-history theory predicts that increased current reproductive effort should lead to a fitness cost. This cost of reproduction may be observed as reduced survival or future reproduction, and may be caused by temporal suppression of immune function in stressed or hard-working individuals. In birds, consideration of the costs of incubating eggs has largely been neglected in favour of the costs of brood rearing. We manipulated incubation demand in two breeding seasons (2000 and 2001) in female common eiders (Somateria mollissima) by creating clutches of three and six eggs (natural range 3-6 eggs). The common eider is a long-lived sea-duck where females do not eat during the incubation period. Mass loss increased and immune function (lymphocyte levels and specific antibody response to the non-pathogenic antigens diphtheria and tetanus toxoid) was reduced in females incubating large clutches. The increased incubation effort among females assigned to large incubation demand did not lead to adverse effects on current reproduction or return rate in the next breeding season. However, large incubation demand resulted in long-term fitness costs through reduced fecundity the year after manipulation. Our data show that in eiders, a long-lived species, the cost of high incubation demand is paid in the currency of reduced future fecundity, possibly mediated by reduced immune function.

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