Wild Mallards Research Articles

Longevity and migration distance differ between wild and hand-reared mallards Anas platyrhynchos in Northern Europe

The mallard Anas platyrhynchos is the world’s most widespread and numerous dabbling duck. It is also farmed and released to the wild by the millions each year, but the effects of this on wild populations remain little studied. By using historical national ringing–recovery data from Sweden and Finland, we here address three predictions based on previous studies: (1) longevity is higher in wild than in hand-reared mallards, (2) wild mallards migrate longer than hand-reared, and (3) migration distance in wild ducks surviving long enough to start fall migration has decreased over the last 50 years. Indeed, wild mallards lived longer than hand-reared (19 versus 9 months in Swedish birds and 13 versus 4 months in Finnish birds). Compared to wild mallards, a smaller proportion of hand-reared birds survived long enough to have the chance to enter the wild breeding population; less than 25 % of the Swedish birds and less than 10 % of the Finnish birds lived a year or longer. Wild birds migrated farther than hand-reared (mean distance in Swedish birds, 676 versus 523 km; in Finnish birds, 1,213 versus 157 km), a pattern caused by both shorter life span and lower migration speed in hand-reared birds. Mean migration distance in wild Swedish mallards was 787 km in 1947–1972 but 591 km in 1977–1993. This difference was not statistically significant, though, possibly due to the limited sample size and lack of data from the last two decades. In general, our study provides a conservative test of the predictions addressed, calling for more research about the consequences of restocking duck populations.

Duck’s not dead: Does restocking with captive bred individuals affect the genetic integrity of wild mallard (Anas platyrhynchos) population?

The genetic integrity of natural populations can be threatened through large-scale introduction of farmed stocks with different genetic or geographic origin. Huge numbers of farm-reared mallard (Anas platyrhynchos, Anatidae) have been introduced into the wild in many European countries since 1970. Czech breeding facilities currently produce around 200–300,000 ducks annually, exceeding wild numbers by around 10 times. Such facilities, however, were founded with hybrid ducks from outside the Czech Republic.Three types of DNA markers, two neutral (14 microsatellite DNA loci and the mitochondrial DNA control region) and one under selection (MHC class I locus), were used to genotype mallards from six Czech breeding facilities (n=131) and seven wild nesting localities (n=139). We found marked genetic divergence between wild and captive-bred populations, the latter having significantly lower genetic diversity. Released captive-bred mallards were integrated into breeding wild population through hybridization mediated by high frequency nesting. Overall, our data suggest that release of captive-bred individuals threatens the genetic integrity of wild population. Massive restocking may also be undesirable as regards public health. Waterfowl are known reservoirs of transmittable pathogens and large-scale restocking could alter immune defence gene frequencies in wild population. We propose the establishment of a national genetic monitoring programme for breeding facilities.

Human and animal integrated influenza surveillance: a novel sampling approach for an additional transmission way in the aquatic bird reservoir

Background: infectious low pathogenic avian influenza viruses (LPaIVs) have been recently detected on feathers of wild ducks. Laboratory trial results suggested that the preen oil gland secretion, covering waterbirds’ feathers, may attract and concentrate virus particles from aIV-contaminated waters to birds’ bodies. We evaluated whether ducks can become infected by the ingestion of preen oil-associated viral particles, experimentally smeared on their plumage. In addition, we compared virologic and serologic results obtained from mallards whose feathers were experimentally infected, with those from wild mallards naturally carrying aIVs on feathers. Methods: we experimentally coated 7 mallards (anas plathyrynchos) using preen oil mixed with a LPaIV (h10n7 subtype), and housed them for 45 days with a control, uncoated duck. cloacal, oropharyngeal and feather swabs were collected from all birds and examined for aIV molecular detection and isolation. Blood samples were also taken to detect influenza specific antibodies. In addition, sera from 10 wild mallards, carrying on feathers infectious LPaIV h10n7, were examined. Results: virologic and serologic results indicated that through self- and allopreening all the birds experimentally coated with the preen oil/aIV mix and the control duck ingested viruses covering feathers and became infected. Virus isolation from feathers was up to 32 days post-coating treatment. one out of 8 wild mallards showing antibodies against type a influenza virus was seropositive for h10 subtype too. Conclusions: our experimental and field results show evidences suggesting that uninfected birds carrying viruses on their feathers, including immune ones, might play an active role in spreading aIV infection in nature. For this reason, routine aIV surveillance programs, aimed at detecting intestinal and/or respiratory viruses, should include the collection of samples, such as feather swabs, enabling the detection of viruses sticky to preened birds’ bodies....

Marbofloxacin Disposition After Intravenous Administration of a Single Dose in Wild Mallard Ducks (Anas platyrhynchos)

Marbofloxacin, a fluoroquinolone developed specifically for veterinary use, has demonstrated considerable pharmokinetic variation among avian species. The goal of this study was to determine the disposition kinetics of marbofloxacin in mallard ducks (Anas platyrhynchos) after a single intravenous injection. Six wild mallard ducks were used in the study. Marbofloxacin was injected at a dose of 2 mg/kg into the basilic vein, and blood was subsequently collected at regular intervals from each bird. Plasma marbofloxacin concentrations were determined by using high-performance liquid chromatography. The volume of distribution at steady state was 1.78 +/- 0.37 L/kg, and the total plasma clearance was 0.59 +/- 0.08 L/kg per hour. Marbofloxacin had a relatively short permanence, with a elimination half-life of 2.81 +/- 1.20 hours, a terminal half-life of 2.43 +/- 0.61 hours, and a mean residence time of 2.99 +/- 0.52 hour. The maximum observed concentration (Cmax) and area under the curve (AUC) were 1.34 +/- 0.27 microg/mL and 3.75 +/- 0.56 microg x h/mL, respectively. Values of minimum inhibitory concentration (MIC), Cmax, and AUC have been used to predict the clinical efficacy of a drug in treating bacterial infections, with a Cmax: MIC value of 10 and an AUC: MIC ratio of 125-250 associated with optimal bactericidal effects. By using the study data and MIC breakpoints of 0.125 microg/mL or 0.2 microg/mL, values derived for Cmax: MIC were 9.37 +/- 0.99 and 5.85 +/- 0.62, respectively, and for AUC: MIC were 29.99 +/- 4.51 and 18.74 +/- 2.82, respectively. By using MIC values of 0.125 and 0.2 microg/mL and a target AUC: MIC = 125, the calculated optimal daily marbofloxacin dosages for mallard ducks were 9.24 and 14.78 mg/kg, respectively. These results suggest that, primarily because of the high total plasma clearance observed, the marbofloxacin dose for treatment of bacterial diseases in mallard ducks should be increased after intravenous administration. Intravenous doses of 10-15 mg/kg should be assessed by studying their potential toxicity and efficacy in sick birds.

Genetic characterization of low pathogenic H5N1 and co-circulating avian influenza viruses in wild mallards (Anas platyrhynchos) in Belgium, 2008

As part of a long-term wild bird monitoring programme, five different low pathogenic (LP) avian influenza viruses (AIVs) were isolated from wild mallards (subtypes H1N1, H4N6, H5N1, H5N3, and H10N7). A LP H5N1 and two co-circulating (same location, same time period) viruses were selected for full genome sequencing. An H1N1 (A/Anas platyrhynchos/Belgium/09-762/2008) and an H5N1 virus (A/Anas platyrhynchos/Belgium/09-762-P1/2008) were isolated on the same day in November 2008, then an H5N3 virus (A/Anas platyrhynchos/09-884/2008) 5 days later in December 2008. All genes of these co-circulating viruses shared common ancestors with recent (2001 to 2007) European wild waterfowl influenza viruses. The H5N1 virus shares genome segments with both the H1N1 (PB1, NA, M) and the H5N3 (PB2, HA) viruses, and all three viruses share the same NS sequence. A double infection with two different PA segments from H5N1 and from H5N3 could be observed for the H1N1 sample. The observed gene constellations resulted from multiple reassortment events between viruses circulating in wild birds in Eurasia. Several internal gene segments from these 2008 viruses and the N3 sequence from the H5N3 show homology with sequences from 2003 H7 outbreaks in Italy (LP) and the Netherlands (highly pathogenic). These data contribute to the growing sequence evidence of the dynamic nature of the avian influenza natural reservoir in Eurasia, and underline the importance of monitoring AIV in wild birds. Genetic information of potential hazard to commercial poultry continues to circulate in this reservoir, including H5 and H7 subtype viruses and genes related to previous AIV outbreaks.

Phenotypic and genetic diversity among intestinal spirochaetes (genus Brachyspira) in free-living wild mallards ( Anas platyrhynchos) sampled in southern Sweden

Brachyspira spp. are anaerobic intestinal spirochaetes that colonize vertebrates. Some species cause enteric diseases in pigs, chickens and possibly in humans, whereas others display a commensual relationship with their hosts. The aims were to investigate the prevalence among colonized free-living wild mallards ( Anas platyrhynchos) of three enteropathogenic Brachyspira spp., and to describe the biodiversity of Brachyspira spp. isolates. Isolates from 150 birds were screened by PCR for 3 pathogenic Brachyspira spp., and 35 isolates from 20 mallards, 4 pigs and 1 chicken were subjected to phenotypic tests, 9 diagnostic PCRs, sequencing of the 16S rRNA and NADH oxidase ( nox) genes, phylogenetic analysis and nox gene restriction enzyme analysis in silico. Of the 150 birds, 47%, 33% and 11% were positive by PCR for Brachyspira pilosicoli, Brachyspira intermedia and Brachyspira hyodysenteriae, respectively. Thirty-one characterized isolates were provisionally identified as B. intermedia, Brachyspira alvinipulli, “ Brachyspira pulli”, or B. pilosicoli, whereas 4 were of indeterminate species affiliation. Many isolates were phylogenetically related to isolates from livestock. Isolates identified by PCR as B. pilosicoli displayed particularly high biodiversity. Up to five different Brachyspira genotypes were found from the same bird. Sequencing of amplicons from isolates that displayed ambiguous results as judged from PCR and phenotyping showed that several diagnostic PCRs were non-specific. Nox gene restriction enzyme analysis in silico correctly identified 2 of 34 characterized isolates. A culture technique based on filtration that produced uncontaminated spirochaete isolates was described. The results show that mallard intestines support a high degree of biodiversity among Brachyspira spp.

Effects of Infection-Induced Migration Delays on the Epidemiology of Avian Influenza in Wild Mallard Populations

Wild waterfowl populations form a natural reservoir of Avian Influenza (AI) virus, and fears exist that these birds may contribute to an AI pandemic by spreading the virus along their migratory flyways. Observational studies suggest that individuals infected with AI virus may delay departure from migratory staging sites. Here, we explore the epidemiological dynamics of avian influenza virus in a migrating mallard (Anas platyrhynchos) population with a specific view to understanding the role of infection-induced migration delays on the spread of virus strains of differing transmissibility. We develop a host-pathogen model that combines the transmission dynamics of influenza with the migration, reproduction and mortality of the host bird species. Our modeling predicts that delayed migration of individuals influences both the timing and size of outbreaks of AI virus. We find that (1) delayed migration leads to a lower total number of cases of infection each year than in the absence of migration delay, (2) when the transmission rate of a strain is high, the outbreak starts at the staging sites at which birds arrive in the early part of the fall migration, (3) when the transmission rate is low, infection predominantly occurs later in the season, which is further delayed when there is a migration delay. As such, the rise of more virulent AI strains in waterfowl could lead to a higher prevalence of infection later in the year, which could change the exposure risk for farmed poultry. A sensitivity analysis shows the importance of generation time and loss of immunity for the effect of migration delays. Thus, we demonstrate, in contrast to many current transmission risk models solely using empirical information on bird movements to assess the potential for transmission, that a consideration of infection-induced delays is critical to understanding the dynamics of AI infection along the entire flyway.

Identification and complete genome sequencing of paramyxoviruses in mallard ducks (Anas platyrhynchos) using random access amplification and next generation sequencing technologies

BackgroundDuring a wildlife screening program for avian influenza A viruses (AIV) and avian paramyxoviruses (APMV) in Belgium, we isolated two hemagglutinating agents from pools of cloacal swabs of wild mallards (Anas platyrhynchos) caught in a single sampling site at two different times. AIV and APMV1 were excluded using hemagglutination inhibition (HI) testing and specific real-time RT-PCR tests.MethodsTo refine the virological identification of APMV2-10 realized by HI subtyping tests and in lack of validated molecular tests for APMV2-10, random access amplification was used in combination with next generation sequencing for the sequence independent identification of the viruses and the determination of their genomes.ResultsThree different APMVs were identified. From one pooled sample, the complete genome sequence (15054 nucleotides) of an APMV4 was assembled from the random sequences. From the second pooled sample, the nearly complete genome sequence of an APMV6 (genome size of 16236 nucleotides) was determined, as well as a partial sequence for an APMV4. This APMV4 was closely related but not identical to the APMV4 isolated from the first sample. Although a cross-reactivity with other APMV subtypes did not allow formal identification, the HI subtyping revealed APMV4 and APMV6 in the respective pooled samples but failed to identify the co-infecting APMV4 in the APMV6 infected pool.ConclusionsThese data further contribute to the knowledge about the genetic diversity within the serotypes APMV4 and 6, and confirm the limited sensitivity of the HI subtyping test. Moreover, this study demonstrates the value of a random access nucleic acid amplification method in combination with massive parallel sequencing. Using only a moderate and economical sequencing effort, the characterization and full genome sequencing of APMVs can be obtained, including the identification of viruses in mixed infections.

Low survival after release into the wild: assessing “the burden of captivity” on Mallard physiology and behaviour

Captive-reared animals used in reinforcement programs are generally less likely to survive than wild conspecifics. Digestion efficiency and naive behaviour are two likely reasons for this pattern. The Mallard is a species with high adaptability to its environment and in which massive reinforcement programs are carried out. We studied physiological and behavioural factors potentially affecting body condition and survival of captive-reared Mallards after being released. Digestive system morphology and an index of body condition were compared among three groups: captive-reared birds remaining in a farm (control), captive-reared birds released into the wild as juveniles (released) and wild-born birds (wild). We also compared behaviour and diet of released vs. wild Mallards. Finally, we conducted a 1-year survival analysis of captive-reared birds after release in a hunting-free area. Gizzard weight was lower in control Mallards, but the size of other organs did not differ between controls and wild birds. The difference in gizzard weight between released and wild birds disappeared after some time in the wild. Diet analyses suggest that released Mallards show a greater preference than wild for anthropogenic food (waste grain, bait). Despite similar time-budgets, released Mallards never attained the body condition of wild birds. As a consequence, survival probability in released Mallards was low, especially when food provisioning was stopped and during harsh winter periods. We argue that the low survival of released Mallards likely has a physiological rather than a behavioural (foraging) origin. In any case, extremely few released birds live long enough to potentially enter the breeding population, even without hunting. In the context of massive releases presently carried out for hunting purposes, our study indicates a low likelihood for genetic introgression by captive-reared birds into the wild population.

Influence of Body Condition on Influenza A Virus Infection in Mallard Ducks: Experimental Infection Data

Migrating waterfowl are implicated in the global spread of influenza A viruses (IAVs), and mallards (Anas platyrhynchos) are considered a particularly important IAV reservoir. Prevalence of IAV infection in waterfowl peaks during autumn pre-migration staging and then declines as birds reach wintering areas. Migration is energetically costly and birds often experience declines in body condition that may suppress immune function. We assessed how body condition affects susceptibility to infection, viral shedding and antibody production in wild-caught and captive-bred juvenile mallards challenged with low pathogenic avian influenza virus (LPAIV) H5N9. Wild mallards (n = 30) were separated into three experimental groups; each manipulated through food availability to a different condition level (−20%, −10%, and normal ±5% original body condition), and captive-bred mallards (n = 10) were maintained at normal condition. We found that wild mallards in normal condition were more susceptible to LPAIV infection, shed higher peak viral loads and shed viral RNA more frequently compared to birds in poor condition. Antibody production did not differ according to condition. We found that wild mallards did not differ from captive-bred mallards in viral intensity and duration of infection, but they did exhibit lower antibody titers and greater variation in viral load. Our findings suggest that reduced body condition negatively influences waterfowl host competence to LPAIV infection. This observation is contradictory to the recently proposed condition-dependent hypothesis, according to which birds in reduced condition would be more susceptible to IAV infection. The mechanisms responsible for reducing host competency among birds in poor condition remain unknown. Our research indicates body condition may influence the maintenance and spread of LPAIV by migrating waterfowl.

Antimicrobial susceptibility of Brachyspira spp. isolated from commercial laying hens and free-living wild mallards (Anas platyrhynchos)

In vitro antimicrobial susceptibility to tylosin, valnemulin, tiamulin, doxycycline, lincomycin and ampicillin was investigated by broth dilution in 48 Brachyspira spp. isolates from commercial laying hens (n=30) and free-living wild mallards (Anas platyrhynchos) (n=18). Presumed pathogens (Brachyspira alvinipulli, Brachyspira intermedia, Brachyspira pilosicoli), commensals (Brachyspira murdochii, Brachyspira innocens, “Brachyspira pulli”), and isolates of undetermined species affiliation were included. The laying hens had not been exposed to therapeutic levels of antimicrobials for at least 50 weeks before sampling, and low levels of environmental antimicrobial exposure were presumed in mallards. No isolates with decreased susceptibility to tylosin, valnemulin, tiamulin or doxycycline were found. Decreased susceptibility to lincomycin (minimum inhibitory concentration 16 µg/ml) was detected in two isolates (Brachyspira sp.) from laying hens. Five isolates showed decreased susceptibility to ampicillin (minimum inhibitory concentration 16 to >32 µg/ml), including two “B. pulli” and one B. alvinipulli from laying hens, and isolates of B. pilosicoli and “B. pulli” from mallards. Decreased susceptibility to ampicillin was associated with β-lactamase activity in four isolates. A new variant of a class D β-lactamase gene designated bla oxa-192 was identified in a B. pilosicoli isolate of mallard origin. This is the first time the genetic basis for antimicrobial resistance is described in Brachyspira spp. from a free-living wild bird. Isolates displaying decreased susceptibility to ampicillin were accompanied by fully susceptible isolates of the same species or other genotypes within three laying hen flocks. This underlines the need for performing antimicrobial susceptibility tests on single clones/genotypes, and to analyse multiple isolates from the same flock.

Phylogenetic analysis of low pathogenicity H5N1 and H7N3 influenza A virus isolates recovered from sentinel, free flying, wild mallards at one study site during 2006

From August 2 to October 11, 2006, clusters of low pathogenicity (LP) North American lineage H5N1 and H7N3 avian influenza A viruses (AIV), and other subtypes, were recovered from free-flying, resident, wild mallards used as sentinels at one site. The antigenic subtypes, pathogenicity potential, and Sanger sequencing of the isolates determined the H5N1 and H7N3 isolates were only recovered from samples collected on 8/2/2006 and 9/8/2006, respectively. However, subsequent efforts using next-generation sequencing (NGS) and additional Sanger sequencing found partial H7 segments in other HA–NA virus combinations on 8/2/2006, 9/8/2006 and 10/11/2006. It is well established that over larger geographic areas and years AIVs form transient genomic constellations; this sequential sampling data revealed that over a short period of time the dynamics of AIVs can be active and newer sequencing platforms increase recognition of mixed infections. Both findings provide further insight into the natural history of AIVs in natural reservoirs.

Evidence of persistence and multiple genetic modifications of H7N7 low-pathogenic avian influenza virus in wild mallards in Poland provided by phylogenetic studies

Genetic characterization of the whole genome of four avian influenza H7N7 viruses isolated in three successive winter seasons (2007 to 2009) from wild mallards in three cities in Poland was performed. All of the tested strains were of low pathogenicity and no molecular marker associated with an increased adaptation to poultry, mammals or resistance to antiviral drugs was found. The major outcome of the phylogenetic studies was that the isolate A/mallard/Poland/446/09 (detected in December 2009) shared a recent common ancestor with A/mallard/Poland/41/09 (isolated in February 2009) in relation to HA and PB1 genes, with A/mallard/Poland/16/09 (found in January 2009) regarding NA and NS genes, and with A/mallard/Poland/01/08 (recovered in December 2007) as regards the NS gene. Interestingly, A/mallard/Poland/16/09 and A/mallard/Poland/446/09 were isolated at the same sampling site almost exactly 1 year apart, which points to resident population of mallards (and other resident waterfowl) as responsible for the perpetuation of avian influenza virus (AIV) in the given area between successive winters. On the other hand, the ornithological data discussed in detail in the paper strongly suggest that the virus transmission between close sites but located in different urban areas is most probably achieved by migratory birds, a fact additionally supported by a close relatedness between different gene segments of Polish H7N7 and AIV detected in wild birds in Europe. A high heterogeneity of the gene pool found in the study is indicative of frequent reassortment events. Additionally, two H7N7 isolates were shown to possess selected genes closely related to AIV detected in domestic poultry in Italy and the Czech Republic. The present study corroborates the importance of active surveillance in wild birds as a valuable tool for early warning of avian influenza in poultry.

Genome wide SNP discovery, analysis and evaluation in mallard (Anas platyrhynchos)

BackgroundNext generation sequencing technologies allow to obtain at low cost the genomic sequence information that currently lacks for most economically and ecologically important organisms. For the mallard duck genomic data is limited. The mallard is, besides a species of large agricultural and societal importance, also the focal species when it comes to long distance dispersal of Avian Influenza. For large scale identification of SNPs we performed Illumina sequencing of wild mallard DNA and compared our data with ongoing genome and EST sequencing of domesticated conspecifics. This is the first study of its kind for waterfowl.ResultsMore than one billion base pairs of sequence information were generated resulting in a 16× coverage of a reduced representation library of the mallard genome. Sequence reads were aligned to a draft domesticated duck reference genome and allowed for the detection of over 122,000 SNPs within our mallard sequence dataset. In addition, almost 62,000 nucleotide positions on the domesticated duck reference showed a different nucleotide compared to wild mallard. Approximately 20,000 SNPs identified within our data were shared with SNPs identified in the sequenced domestic duck or in EST sequencing projects. The shared SNPs were considered to be highly reliable and were used to benchmark non-shared SNPs for quality. Genotyping of a representative sample of 364 SNPs resulted in a SNP conversion rate of 99.7%. The correlation of the minor allele count and observed minor allele frequency in the SNP discovery pool was 0.72.ConclusionWe identified almost 150,000 SNPs in wild mallards that will likely yield good results in genotyping. Of these, ~101,000 SNPs were detected within our wild mallard sequences and ~49,000 were detected between wild and domesticated duck data. In the ~101,000 SNPs we found a subset of ~20,000 SNPs shared between wild mallards and the sequenced domesticated duck suggesting a low genetic divergence. Comparison of quality metrics between the total SNP set (122,000 + 62,000 = 184,000 SNPs) and the validated subset shows similar characteristics for both sets. This indicates that we have detected a large amount (~150,000) of accurately inferred mallard SNPs, which will benefit bird evolutionary studies, ecological studies (e.g. disentangling migratory connectivity) and industrial breeding programs.

Trends in Body Mass of Ducks over Time: The Hypotheses in Guillemain et al. Revisited

Trends in Body Mass of Ducks over Time: The Hypotheses in Guillemain et al. Revisited

Effect of a prior exposure to a low pathogenic avian influenza virus in the outcome of a heterosubtypic low pathogenic avian influenza infection in mallards (Anas platyrhynchos).

Wild birds, particularly Anseriformes and Charadriiformes, are considered the natural reservoir of low pathogenic avian influenza (LPAI) viruses. The high prevalence and subtype diversity of avian influenza viruses at premigrational staging areas provide the perfect opportunity for multiple exposures to different LPAI virus subtypes. Natural consecutive and concurrent infections of sentinel ducks with different LPAI virus subtypes have been reported. The protective immune response from different LPAI virus infections is not understood nor is the effect of such repeated exposures. This study experimentally evaluated the effect of a prior exposure to a LPAI virus on the outcome of a heterosubtypic LPAI virus infection in mallards (Anas platyrhynchos). The results of this investigation suggest that recent prior exposure to a LPAI virus may affect the outcome of a subsequent heterosubtypic LPAI infection in mallards by reducing the duration of cloacal and oropharyngeal viral shedding as well as the viral load excreted via the cloaca. Wild mallards are likely exposed to multiple subtypes of LPAI virus during the periods of peak viral circulation, and the results of this study suggest that the duration of viral shedding in subsequent exposures might be reduced.

Use of a Portable Tower and Remote-controlled Launcher to Improve Physical Conditioning in a Rehabilitating Wild Mallard (Anas platyrhynchos)

Prerelease reconditioning improves the chance of survival of rehabilitating raptors. Reconditioning may also help to rehabilitate waterfowl, including those that are threatened or endangered, especially if the birds are released during periods of migration. A flying harness, creance, remote-controlled launcher, and portable tower were used to create a means of reconditioning a rehabilitating 5-month-old female wild mallard duck (Anas platyrhynchos) that had been housed in a rehabilitation center for 7 weeks while recovering from an injury. Pre- and postflight serum lactate levels, body condition index scores, and controlled flight distances were used to assess the bird's degree of conditioning. Postflight serum lactate levels never returned to preflight levels and were not deemed a reliable indicator of physical fitness. However, the mallard showed an increase in endurance and strength as well as improved body condition index scores over the course of the reconditioning program.

Shedding light on avian influenza H4N6 infection in mallards: modes of transmission and implications for surveillance.

BackgroundWild mallards (Anas platyrhychos) are considered one of the primary reservoir species for avian influenza viruses (AIV). Because AIV circulating in wild birds pose an indirect threat to agriculture and human health, understanding the ecology of AIV and developing risk assessments and surveillance systems for prevention of disease is critical.Methodology/Principal FindingsIn this study, mallards were experimentally infected with an H4N6 subtype of AIV by oral inoculation or contact with an H4N6 contaminated water source. Cloacal swabs, oropharyngeal swabs, fecal samples, and water samples were collected daily and tested by real-time RT-PCR (RRT-PCR) for estimation of viral shedding. Fecal samples had significantly higher virus concentrations than oropharyngeal or cloacal swabs and 6 month old ducks shed significantly more viral RNA than 3 month old ducks regardless of sample type. Use of a water source contaminated by AIV infected mallards, was sufficient to transmit virus to naïve mallards, which shed AIV at higher or similar levels as orally-inoculated ducks.ConclusionsBodies of water could serve as a transmission pathway for AIV in waterfowl. For AIV surveillance purposes, water samples and fecal samples appear to be excellent alternatives or additions to cloacal and oropharyngeal swabbing. Furthermore, duck age (even within hatch-year birds) may be important when interpreting viral shedding results from experimental infections or surveillance. Differential shedding among hatch-year mallards could affect prevalence estimates, modeling of AIV spread, and subsequent risk assessments.

Origin and genetic diversity of Chinese domestic ducks

China is particularly rich in duck genetic resources. In order to reveal the genetic diversity and origin of Chinese domestic duck, the 667bp control region of mitochondrial DNA of 238 domestic ducks from 26 indigenous breeds, 25 wild mallards and nine spot-billed ducks were sequenced and analyzed them together with the published data for 12 mallards and nine spot-billed ducks. The haplotype diversity (Hd, 0.645) and average nucleotide diversity (Pi, 0.115%) indicate low genetic diversity of Chinese domestic ducks. The NJ phylogenetic tree and reduced median-joining network chart were constructed using a total of 72 haplotypes. The genetic contribution of mallard (Anas platyrhynchos) can be detected in most of Chinese indigenous duck breeds and that of spot-billed duck (Anas zonorhyncha) can also be detected in few Chinese indigenous duck breeds. The results indicated that the Chinese domestic ducks mainly derived from mallard (A. platyrhynchos) and few derived from spot-billed duck (A. zonorhyncha).

Relationships between dietary carotenoids, body tissue carotenoids, parasite burden, and health state in wild mallard ( Anas platyrhynchos) ducklings

While rodents and other mammals have traditionally served as models for studying carotenoid physiology, many wild animals from a variety of other taxa utilize carotenoids for self-maintenance and reproduction and accumulate far greater concentrations than those found in mammals. Though we have basic understandings of the control and value of carotenoids in some wild animal systems, many gaps remain. For example, parasites and pathogens impose severe survival constraints on free-ranging organisms, but little is known of how carotenoids work in concert with the immune system to combat natural infectious challenges. Furthermore, due to the high mortality rate from which many young animals suffer, health and carotenoid status during the early stages of development may be critical to survival. The relative importance of dietary versus physiological mechanisms for carotenoid uptake has also been understudied in the wild. To begin to shed light on these issues, we studied relationships between dietary and tissue carotenoids, hematological immune parameters, and endoparasitism of wild mallard ( Anas platyrhynchos) ducklings at a variety of ages. Lutein, zeaxanthin, β-cryptoxanthin, β-carotene, and canthaxanthin were the most common carotenoids in liver, plasma, and gut contents. We found that, early in development (when food intake is limited), carotenoids were comparatively concentrated in internal tissue (e.g., liver), presumably a carry-over from maternal contributions in yolk, but as ducklings approached independence (and increasingly fed on their own) concentrations were greatest in gut contents. Canthaxanthin concentrations were lower in the plasma and liver of older individuals compared to younger ducklings, even though gut canthaxanthin concentration did not change with age. Additionally, β-carotene was nearly absent from circulation, despite moderate levels within the gut, suggesting a high rate of conversion to retinol. Using principal components analysis, we revealed a correlation between an increased ability to assimilate dietary carotenoids and lower levels of chronic stress (as assessed by lower heterophil-to-lymphocyte ratios) and a correlation between a reduced carotenoid status and increased investment in the immune system (as assessed by higher total leukocyte count). We also found that individuals without parasites had an overall reduced carotenoid status. Thus, we demonstrate age-specific differences in carotenoid allocation in growing animals from a precocial bird species and provide correlational evidence that parasitism and health in wild animals are related to carotenoid status and assimilation ability.