Inflammatory cell stimulation and wound healing in Sphaeridiotrema globulus experimentally infected mallard ducks (Anas platyrhynchos)

Thirty laboratory-reared mallard ducks (Anas platyrhynchos) were experimentally infected with Sphaeridiotrema globulus. Host cell-mediated immunity and wound healing in S. globulus infected ducks were evaluated by gross and histological examination. Establishment, location, and life span of S. globulus differed from previous reports of sphaeridiotremiasis in both naturally and experimentally infected waterfowl. No worms were recovered from the ceca, and worm migration occurred anterior to the ileo-cecal valve with greater dispersion (less worm crowding) at higher rates of infectivity. Parasite death and host lesion resolution were evident at days 8 to 10 postinfection (PI) in ducks fed a moderate dose (200 metacercariae, group A) with a 5% mean parasite recovery rate. Host death occurred at days 3 to 6 in ducks fed a high dose (550 metacercariae, group B) with a 16% mean parasite recovery rate. Mast cells increased significantly (P less than 0.005) in group A ducks from days 4 to 10 PI. Eosinophil proliferation was greater in group B than in group A on day 4 PI, but comparatively fewer eosinophils were identifiable in group B ducks on day 6 PI.     

Susceptibility of the gray wolf (Canis lupus) to infection with the Lyme disease agent, Borrelia burgdorferi

Four juvenile gray wolves (Canis lupus) were inoculated with live Borrelia burgdorferi. One received an intravenous inoculum, a second was inoculated subcutaneously, and two more were fed Peromyscus maniculatus sucklings which had earlier been inoculated with B. burgdorferi. The intravenously inoculated wolf developed a generalized lymphadenopathy and a persistent serum antibody titer to the spirochete which peaked at 1:512. Borrelia burgdorferi was visualized in liver sections of this wolf using direct immunofluorescent staining. The subcutaneously inoculated wolf showed a low and transient antibody response which peaked at 1:64, and manifested no clinical or postmortem abnormalities. The wolves which were fed inoculated mice showed no detectable antibody response. They were clinically normal throughout the project, and there were no detectable lesions at necropsy. Two control wolves were inoculated intravenously with formalin killed B. burgdorferi. Serum antibody titers of these controls peaked at 1:64 and 1:32, respectively, and fell to 1:16 by day 48 postinoculation. A survey of serum samples from 78 wild-trapped wolves from Wisconsin and Minnesota revealed that one was positive and another was suspect for B. burgdorferi infection based on presence of antibody to the spirochete. We conclude that the wolf is susceptible to infection by B. burgdorferi and that wolves are being infected in the wild.     

Acute toxicity of lead, steel, and an iron-tungsten-nickel shot to mallard ducks (Anas platyrhynchos)

Twenty mallards (Anas platyrhynchos) of both sexes were dosed by oral gavage with Heavi-Shot (H-S; Environ-Metal, Inc., Sweet Home, Oregon, USA) pellets, 20 with steel shot, and 10 with lead (Pb) pellets, all of equal size. All pellets were fired from a shotgun into an absorbent material, retrieved, and weighed prior to introduction into the ducks. Birds were fed whole kernel corn and grit and observed for signs of toxicity for 30 days following dosing. Hevi-Shot pellets lost an average of 6.2% of their mass and steel shot pellets lost 57% of their mass in the birds' gizzards. Almost all (90%) of the Pb shot dosed birds died before the end of the study, while no mortality was observed in the steel or H-S dosed groups. Even though total food consumption differed between the H-S and steel shot groups, mean bird weight change was not different. There were no significant morphologic or histopathologic abnormalities of the liver and kidney in the H-S and steel shot groups. Results indicated that mallards dosed orally with eight No. 4 H-S pellets were not adversely affected over a 30-day period, and that H-S provides another environmentally safe nontoxic shot for use in waterfowl hunting.     

Comparative toxicity of lead shot in black ducks (Anas rubripes) and mallards (Anas platyrhynchos)

In winter, pen-reared and wild black ducks (Anas rubripes), and game farm and wild mallards (Anas platyrhynchos), maintained on pelleted feed, were sham-dosed or given one number 4 lead shot. After 14 days, dosed birds were redosed with two or four additional lead shot. This dosing regimen also was repeated in summer using pen-reared black ducks and game farm mallards. Based upon mortality, overt intoxication, weight change, delta-aminolevulinic acid dehydratase activity and protoporphyrin concentration, black ducks and mallards were found to be equally tolerant to lead shot. However, captive wild ducks were more sensitive than their domesticated counterparts, as evidenced by greater mortality and weight loss following lead shot administration. This difference may be related to stress associated with captivity and unnatural diet.     

Effects of ingested lead on antibody production in mallards (Anas platyrhynchos)

We examined the effects of lead ingestion on in vitro and in vivo indices of immune function in mallards (Anas platyrhynchos). Twenty-four mallard drakes were randomly divided into three groups (I, II, III), then assigned to treatment or control subgroups (n = 4). On day 0, all treatment birds were dosed orally with one number 4 lead shot (mean = 0.2 g). We challenged all individuals in each group with washed sheep red blood cells (SRBC) injected intraperitoneally on days 0 (Group I), 7 (Group II) or 14 (Group III), and collected blood for analyses 7 and 8 days after SRBC challenge. We measured and compared blood lead concentrations, in vitro lymphocyte transformation responses to phytohemagglutinin A and lipopolysaccharide, and hemagglutination titers to SRBC. Mean blood lead concentrations were elevated (P less than or equal to 0.04) in treatment birds at each sampling period. Large individual variability in lymphocyte stimulation responses precluded further analysis of those data. Hemagglutination titers to SRBC were lower (P less than 0.0001) in lead-poisoned ducks than in controls, suggesting that ingested lead may have immunosuppressive effects on mallards.     

Transmission of Salmonid Whirling Disease by Birds Fed Trout Infected with Myxosoma cerebralis

SYNOPSIS. Mallard ducks, Anas platyrhynchos and a black crested night heron, Nycticorax nycticorax were fed trout infected with Myxosoma cerebralis (Hofer) in 2 separate experiments. Feces from the birds were deposited in troughs containing M. cerebralis -free mud as well as in 1 trough without mud. Spore suspensions were also added directly to mud in 1 trough and to another trough without mud. Susceptible rainbow trout, Salmo gairdneri , developed whirling disease in all troughs containing mud contaminated with M. cerebralis but remained free of infection when exposed to M. cerebralis in troughs without mud. This demonstrates the possibility of bird transmission of the organism causing whirling disease to previously non-contaminated waters.     

Reproductive effects and duckling survivability following chronic dosing with tungsten-iron and tungsten-polymer shot in adult game-farm mallards

Tungsten-iron and tungsten-polymer shot were given conditional approval for waterfowl hunting by the U.S. Fish and Wildlife Service based partly on the results of a 30-day acute toxicity trial utilizing mallards (Anas platyrhynchos). Final approval of the two tungsten-containing shot was contingent on the results of a 150-day study that assessed the health and reproductive effects of tungsten-iron and tungsten-polymer shot in adult mallards. Reproductive data are presented in this paper. Sixteen male and 16 female adult mallards were dosed orally with eight #4 steel shot (control), eight #4 tungsten-iron shot, or eight #4 tungsten-polymer shot on days 0, 30, 60, 90, and 120 of a 150-day trial (26 January 1998 to 25 June 1998). Reproductive performance was assessed during the last 90 days (day 61 to day 150) of the trial. There were no significant differences in egg production and fertility and hatchability of eggs from tungsten-iron- and tungsten-polymer-dosed ducks compared to control ducks. There was no evidence of differences in percent survivability and body weight of ducklings from tungsten-iron and tungsten-polymer mallards compared to ducklings from control ducks. Tungsten-iron or tungsten-polymer shot repeatedly administered to adult mallards during the 150 day trial did not adversely affect reproduction or their offspring.     

Genomic Characterization of H14 Subtype Influenza A Viruses in New World Waterfowl and Experimental Infectivity in Mallards (Anas platyrhynchos)

Recent repeated isolation of H14 hemagglutinin subtype influenza A viruses (IAVs) in the New World waterfowl provides evidence to suggest that host and/or geographic ranges for viruses of this subtype may be expanding. In this study, we used genomic analyses to gain inference on the origin and evolution of H14 viruses in New World waterfowl and conducted an experimental challenge study in mallards (Anas platyrhynchos) to evaluate pathogenicity, viral replication, and transmissibility of a representative viral strain in a natural host species. Genomic characterization of H14 subtype IAVs isolated from New World waterfowl, including three isolates sequenced specifically for this study, revealed high nucleotide identity among individual gene segments (e.g. ≥95% shared identity among H14 HA gene segments). In contrast, lower shared identity was observed among internal gene segments. Furthermore, multiple neuraminidase subtypes were observed for H14 IAVs isolated in the New World. Gene segments of H14 viruses isolated after 2010 shared ancestral genetic lineages with IAVs isolated from wild birds throughout North America. Thus, genomic characterization provided evidence for viral evolution in New World waterfowl through genetic drift and genetic shift since purported introduction from Eurasia. In the challenge study, no clinical disease or lesions were observed among mallards experimentally inoculated with A/blue-winged teal/Texas/AI13-1028/2013(H14N5) or exposed via contact with infected birds. Titers of viral shedding for mallards challenged with the H14N5 IAV were highest at two days post-inoculation (DPI); however shedding was detected up to nine DPI using cloacal swabs. The distribution of viral antigen among mallards infected with H14N5 IAV was largely restricted to enterocytes lining the villi in the lower intestinal tract and in the epithelium of the bursa of Fabricius. Characterization of the infectivity of A/blue-winged teal/Texas/AI13-1028/2013(H14N5) in mallards provides support for similarities in viral replication and shedding as compared to previously described waterfowl-adapted, low pathogenic IAV strains in ducks.     

Health effects following chronic dosing with tungsten-iron and tungsten-polymer shot in adult game-farm mallards

Permanent approval of shot composed of tungsten-iron and tungsten-polymer for waterfowl hunting by the U.S. Fish and Wildlife Service was pending the results of the present study that examined the health and reproductive effects of the two shot types on mallards (Anas platyrhynchos) over a 150-day period. We collected data pertaining to the effects of tungsten-iron and tungsten-polymer shot on mortality, body weight, organ weight, tissue pathology, and shot erosion. Thirty-two bird groups (sexes equal) of adult mallards were dosed orally with eight #4 steel shot (control), eight #4 tungsten-iron shot, or eight #4 tungsten-polymer shot on days 0, 30, 60, 90, and 120 of a 150-day trial (26 January 1998 to 25 June 1998). An additional 12 mallards (sexes equal) were dosed orally with eight #4 lead shot (positive control) on day 0 of the study. All lead-dosed ducks died by day 25, whereas no ducks died in the other treatment groups. Significant liver hemosiderosis was present in all control and tungsten-iron-dosed males, in five of eight control and three of eight tungsten-iron-dosed females, and in one tungsten-polymer-dosed male examined. The rate of shot erosion was highest for tungsten-polymer shot (99%), followed by tungsten-iron (72%), and steel (55%) shot. Tungsten-iron or tungsten-polymer shot repeatedly administered to adult mallards did not have deleterious health effects during the 150-day trial based on mortality, body weights, organ weights, and histology of the liver and kidneys.     

Experimental infections of waterfowl with Sphaeridiotrema globulus (Digenea)

Sphaeridiotrema globulus in experimentally infected mute swans (Cygnus olor), mallard ducks (Anas platyrhynchos) and Canada geese (Branta canadensis) induced ulcerative hemorrhagic enteritis. Sites of infection include the jejunum and ileum. The digeneans ulcerated the intestine. The inflammatory response was primarily lymphocytic with some eosinophils. Severe hemorrhage from damaged submucosal capillaries provided a blood meal for the parasite and caused anemia in the host. Extra-medullary hematopoiesis occurred in the liver, and an erythroid hyperplasia occurred in the bone marrow of infected birds. Infected birds exhibited muscular weakness and died from shock associated with severe blood loss. Mallards and Canada geese were less susceptible to fatal infection than the mute swan as evidenced by survivors in the higher dose groups.     

Mallard ducklings (Anas platyrhynchos) experimentally infected with Echinostoma trivolvis (Digenea)

Of 8, day-old mallard ducklings, each fed 50 encysted metacercariae of Echinostoma trivolvis, 4 (50%) were infected 15-31 days postinfection (PI) with a total of 10 (2.5%) worms. The worms were attached loosely to the mucosa of the lower ileum and rectum-cloaca, and some were ovigerous by day 15 PI. Ducklings, 4-14 days old when fed encysted metacercariae, became infected with E. trivolvis adults, but ducks 150 days old were refractory to infection. Compared to our previous studies on experimental infections of echinostomes, mallard ducklings were less susceptible than golden hamsters to E. trivolvis.     

The hamster immune response to tick-transmitted Borrelia burgdorferi differs from the response to needle-inoculated, cultured organisms.

The human immune response to natural infection with Borrelia burgdorferi appears to differ from that seen in small mammals infected by needle inoculation. In humans, antibody to outer surface proteins A and B (OspA and OspB) is not detectable until late in infection, but small mammals inoculated with B. burgdorferi produce early antibody to OspA and OspB. To investigate this disparity we compared the immune response in hamsters to B. burgdorferi after needle inoculation with cultured organisms or infected tick homogenates with the immune response after tick transmitted (natural) infection. We determined that the antibody response to OspA and OspB after natural infection of hamsters is similar to that seen in humans, and differs from the antibody response after hamster infection by needle inoculation. High titers of antibody to OspA and OspB were undetectable even 42 wk after bite by B. burgdorferi-infected ticks. The failure to produce antibody to OspA and OspB was not dependent on challenge dose, because animals inoculated by needle with low doses (1 x 10(5) to 1 x 10(6) cells) of B. burgdorferi produced antibody to OspA and OspB. A rapid but limited anti-41-kDa response was observed. One possible new Ag, 43 kDa (p43), was identified. The antibody response to p43 was independent of the route of inoculation. Our results suggest that the hamster immune response to tick-transmitted Borrelia burgdorferi differs from the response to needle inoculated, cultured organisms.     

Immunization of ducks for type C botulism

A single subcutaneous immunization with a vaccine used for protecting ranch mink (Mustela vison) against type C botulism reduced morbidity and mortality in mallard (Anas platyrhynchos) and northern pintail (Anas acuta) ducks challenged with approximately 4.5 x 10(4) and 2.25 x 10(4) mouse lethal doses (MLD50), respectively, of botulinum toxin at 10 and 15 days post-immunization (pi). There was no significant protection at 5 days pi. Protection persisted in mallards for 90 days pi. To simulate use of vaccine as a part of treatment of sick birds in the field, mallards were exposed to toxin and, when clinical signs were evident, each bird was treated by intraperitoneal injection of type C botulinum antitoxin and one-half of the birds were immunized. Immunization had no significant effect on recovery from intoxication. At 10 days posttreatment, all birds were challenged with toxin. Clinical signs and mortality were significantly less frequent among immunized birds than among non-immunized birds after the second exposure. Immunization might be useful as part of the treatment regimen in botulism outbreaks.     

Transmission of avian influenza A viruses among species in an artificial barnyard

Waterfowl and shorebirds harbor and shed all hemagglutinin and neuraminidase subtypes of influenza A viruses and interact in nature with a broad range of other avian and mammalian species to which they might transmit such viruses. Estimating the efficiency and importance of such cross-species transmission using epidemiological approaches is difficult. We therefore addressed this question by studying transmission of low pathogenic H5 and H7 viruses from infected ducks to other common animals in a quasi-natural laboratory environment designed to mimic a common barnyard. Mallards (Anas platyrhynchos) recently infected with H5N2 or H7N3 viruses were introduced into a room housing other mallards plus chickens, blackbirds, rats and pigeons, and transmission was assessed by monitoring virus shedding (ducks) or seroconversion (other species) over the following 4 weeks. Additional animals of each species were directly inoculated with virus to characterize the effect of a known exposure. In both barnyard experiments, virus accumulated to high titers in the shared water pool. The H5N2 virus was transmitted from infected ducks to other ducks and chickens in the room either directly or through environmental contamination, but not to rats or blackbirds. Ducks infected with the H7N2 virus transmitted directly or indirectly to all other species present. Chickens and blackbirds directly inoculated with these viruses shed significant amounts of virus and seroconverted; rats and pigeons developed antiviral antibodies, but, except for one pigeon, failed to shed virus.     

A comparison of two methods to establish the prevalence of lead shot ingestion in mallards (Anas platyrhynchos) from The Netherlands

Two collection methods for screening the mallard (Anas platyrhynchos) population in the Netherlands for the ingestion of spent lead shot were compared. One method consisted of examination of gizzards from mallards shot by hunters (n = 2,859) and the other method consisted of examination of gizzards from mallards caught in duck traps (n = 865). The 95% confidence interval of lead shot ingestion in the mallard population estimated by the first method was 1.7 to 2.9% and by the second method 1.1 to 3.1%. These values were not significantly different. From the numbers of lead pellets embedded in the gizzard wall in hunter-killed and trapped mallards it was estimated that at least 22 to 68% of the trapped ducks had been hit by lead shot previously, but survived. Furthermore, this study shows that it is reasonable to assume that a substantial part of the pellets which are identified (in this study and other studies) as ingested, may well have been shot into the gizzard lumen at some time before the birds were actually killed. To avoid lead poisoning in mallards and in raptors depredating waterfowl hit by lead shot, a change to steel shot is advocated.     

Are ducks contributing to the endemicity of highly pathogenic H5N1 influenza virus in Asia?

Wild waterfowl are the natural reservoir of all influenza A viruses, and these viruses are usually nonpathogenic in these birds. However, since late 2002, H5N1 outbreaks in Asia have resulted in mortality among waterfowl in recreational parks, domestic flocks, and wild migratory birds. The evolutionary stasis between influenza virus and its natural host may have been disrupted, prompting us to ask whether waterfowl are resistant to H5N1 influenza virus disease and whether they can still act as a reservoir for these viruses. To better understand the biology of H5N1 viruses in ducks and attempt to answer this question, we inoculated juvenile mallards with 23 different H5N1 influenza viruses isolated in Asia between 2003 and 2004. All virus isolates replicated efficiently in inoculated ducks, and 22 were transmitted to susceptible contacts. Viruses replicated to higher levels in the trachea than in the cloaca of both inoculated and contact birds, suggesting that the digestive tract is not the main site of H5N1 influenza virus replication in ducks and that the fecal-oral route may no longer be the main transmission path. The virus isolates' pathogenicities varied from completely nonpathogenic to highly lethal and were positively correlated with tracheal virus titers. Nevertheless, the eight virus isolates that were nonpathogenic in ducks replicated and transmitted efficiently to na?ve contacts, suggesting that highly pathogenic H5N1 viruses causing minimal signs of disease in ducks can propagate silently and efficiently among domestic and wild ducks in Asia and that they represent a serious threat to human and veterinary public health.     

Viability and infectivity of Cryptosporidium parvum oocysts are retained upon intestinal passage through a refractory avian host.

Six Cryptosporidium-free Peking ducks (Anas platyrhynchos) were each orally inoculated with 2.0 x 10(6) Cryptosporidium parvum oocysts infectious to neonatal BALB/c mice. Histological examination of the stomachs jejunums, ilea, ceca, cloacae, larynges, tracheae, and lungs of the ducks euthanized on day 7 postinoculation (p.i.) revealed no life-cycle stages of C. parvum. However, inoculum-derived oocysts extracted from duck feces established severe infection in eight neonatal BALB/c mice (inoculum dose, 2.5 x 10(5) per mouse). On the basis of acid-fast stained direct wet smears, 73% of the oocysts in duck feces were intact (27% were oocyst shells), and their morphological features conformed to those of viable and infectious oocysts of the original inoculum. The fluorescence scores of the inoculated oocysts, obtained by use of the MERIFLUOR test, were identical to those obtained for the feces-recovered oocysts (the majority were 3+ to 4+). The dynamics of oocyst shedding showed that the birds released a significantly higher number of intact oocysts than the oocyst shells (P < 0.01). The number of intact oocysts shed (87%) during the first 2 days p.i. was significantly higher than the number shed during the remaining 5 days p.i. (P < 0.01) and significantly decreased from day 1 to day 2 p.i. (P < 0.01). The number of oocyst shells shed during 7 days p.i. did not vary significantly (P > 0.05). The retention of infectivity of C. parvum oocysts after intestinal passage through an aquatic bird has serious epidemiological and epizootiological implications. Waterfowl may serve as mechanical vectors for the waterborne oocysts and may enhance contamination of surface waters with C. parvum. As the concentration of Cryptosporidium oocysts in source waters is attributable to watershed management practices, the watershed protection program should consider waterfowl as a potential factor enhancing contamination of the source water with C. parvum.     

Second intermediate host land snails and definitive host animals of Brachylaima cribbi in southern Australia

This study of infection of southern Australian land snails with Brachylaima cribbi metacercariae has shown that all commonly encountered native and introduced snails are susceptible second intermediate hosts. The range of infected snails is extensive with metacercariae-infected snails being present in all districts across southern Australia. C. virgata has the highest average natural metacercarial infection intensity of 6.1 metacercariae per infected snail. The susceptibility of birds, mammals and reptiles to B. cribbi infection was studied in South Australia by capturing, dissecting and examining the intestinal tract contents of animals which commonly eat land snails as a food source. Indigenous Australian little ravens (Corvus mellori), which are a common scavenger bird, and two other passeriform birds, the black bird (Turdus merula) and the starling (Sturnus vulgaris), which are both introduced European birds, were found to have the highest infection rates of all animals examined. Other birds found infected with B. cribbi were an emu (Dromaius novaehollandiae), chickens (Gallus gallus) and a pigeon (Columba livia). Natural infections were also detected in field mice (Mus domesticus) and shingleback lizards (Tiliqua rugosa) although the intensity of infection was lower than that observed in birds. Susceptibility studies of laboratory mice, rats and ducks showed that mice developed patent infections which persisted for several weeks, rats developed a short-lived infection of three weeks' duration and ducks did not support infection. This study has shown for the first time that a brachylaimid can infect a wide host range of birds, mammals and reptiles in nature.     

The influence of seven environmental and physiological factors on duck plague virus shedding by carrier mallards

Duck plague (DP) carrier mallards (Anas platyrhynchos) were subjected to seven environmental and physiological conditions in an attempt to stimulate DP virus shedding. The conditions were: food quality, social interaction, reproductive state, time dependency of food and water, noise, exercise, and sex of bird. Cloacal and oral swabs were taken daily for 10 days and assayed for DP virus content. The stimulated carrier ducks shed DP virus intermittently in amounts up to 10(8) ffus/swab/day (the highest 10-fold dilution still showing specific fluorescence). Unstimulated DP carrier ducks shed only up to 10(3) ffus/swab/day. Reproductive state and exercise were the only two factors that acted in concert to stimulate the shedding of virus in oral secretions.