Widespread exposure to lead affects the body condition of free-living whooper swans Cygnus cygnus wintering in Britain.

Lead poisoning, through the ingestion of spent lead gunshot, is an established cause of morbidity and mortality in waterbirds globally, but the thresholds at which blood levels begin to affect the physiology of birds in the wild are less well known. Here we determine the prevalence of lead exposure in whooper swans and, for the first time, identify the level of blood lead associated with initial reductions in body condition. Blood lead elevated above background levels (i.e. >20 µg dL(-1)) was found in 41.7% (125/300) of swans tested. Blood lead was significantly negatively associated with winter body condition when levels were ≥44 µg dL(-1) (27/260 = 10%). Our findings indicating that sub-lethal impacts of lead on body condition occur at the lower end of previously established clinical thresholds and that a relatively high proportion of individuals in this population may be affected, reaffirm the importance of reducing contamination of the environment with lead shot.

The transport and culture conditions for optimum transformation responses of wildfowl lymphocytes to mycobacterial antigens.

A method has been developed for increasing the survival of wildfowl lymphocytes during transport over considerable distances. Blood in an equal volume of heparinised RPMI was maintained at close to avian body temperature, i.e., approximately 40 degrees C. Using this system lymphocyte transformation in the presence of antigen (mycobacterial) has been successfully performed with wildfowl mononuclear cells for the first time. Duck cells were cultured in 10% autologous sera with 8 x 10(5) cells/well for 4 days. Cells from Hawaiian geese (Branta sandvicensis) required similar culture conditions but were incubated for 3 days.

Avian immune responses to Mycobacterium avium: the wildfowl example.

Immunological responses of wildfowl (Order Anseriformes: ducks, geese, swans and screamers) to mycobacteria have been investigated as part of studies to develop a vaccine and diagnostic assay for avian tuberculosis. 10(9) killed Mycobacterium vaccae protected the Cairinini (perching ducks) from avian tuberculosis (p<0.02) but did not achieve statistically significant protection in the other taxonomic tribes. The Cairinini includes the threatened, yet highly susceptible, white-winged duck (Cairina scutulata).Together, loss of cell-mediated responses to common mycobacterial antigens, increased responsiveness to the species specific antigens of M. avium, and increased antibody production are reminiscent of the T(H1) to T(H2) shift seen in mammalian mycobacterial infections. It is speculated that excessive exposure to environmental mycobacteria prior to vaccination is detrimental and common antigens play an important role in wildfowl immunity to mycobacteria. A new vaccination trial using killed M. vaccae is being undertaken. Antibody responses are a useful ante mortem diagnostic indicator in most taxonomic tribes with the exception of the primitive Dendrocygnini (whistling ducks).

An examination of the immune system of the duck (Anas platyrhynchos) for factors resembling some defined mammalian cytokines.

Duck lymphoblasts generated by phytohaemagglutinin (PHA) did not respond to recombinant or Jurkat cell line human interleukin (IL)-2 or possess surface antigens resembling mammalian IL-2 receptors or IL-1 beta. Supernatant fluids from normal and PHA-stimulated duck lymphocyte cultures, and normal and lipopolysaccharide (LPS)-stimulated monocytes, gave negative results in a range of assays for biological activity and immunochemical presence of factors resembling mammalian IL-1 and IL-2. However, supernatant fluids from LPS-stimulated duck monocytes contained IL-6-like activity (up to 35 units/mL) assessed on the 7TD-1 murine cell line. We were unable to demonstrate mRNA that would hybridize to cDNA probes for human IL-1 beta, IL-6, and tumour necrosis factor (TNF) in extracts of blood and lymphoid organs from normal and antigen-stimulated ducks. Because homologous serum or plasma is essential for duck lymphocytes and macrophages to respond to mitogens in vitro, we asked whether this growth-factor-like activity might be caused by substances resembling mammalian cytokines. Serum and plasma were examined for activity consistent with IL-1 and IL-6 on mammalian target cells. None was detected. Instead, both serum and plasma contained inhibitors of human IL-1 beta and IL-6, detected at dilutions up to 1:100. Inhibition by serum was heat (56 degrees C, 30 min) labile but inhibition by plasma was heat stable. The identities and biological functions of these inhibitors remain to be defined.

Purification of duck immunoglobulins: an evaluation of protein A and protein G affinity chromatography.

Duck serum proteins binding to protein A Sepharose CL-4B and protein G Sepharose 4 Fast Flow and eluted at pH 2.8 or 11.5 were characterized by sodium dodecyl sulphate polyacrylamide gel electrophoresis, radial/immunodiffusion against defined anti-immunoglobulin (Ig) reagents, and by the reactivity in immunoelectrophoresis of antisera raised in rabbits inoculated with the eluates. The results indicated that IgY (previous nomenclature 7.8S IgG) and IgY (delta Fc) (previously 5.7S IgG) bound to protein A efficiently and to protein G weakly, while IgM bound to protein A and protein G weakly. Some binding of non-Ig proteins also occurred. Attempts to separate the non-Ig proteins from the Igs by elution at different pHs (5.0, 4.0, 3.0 and 2.5) were unsuccessful, but it was found that precipitation of Igs in day-old duck serum with Na2SO4, followed by chromatography on protein A Sepharose, yielded relatively pure IgY. The efficient binding of the duck IgYs to protein A resembles high affinity binding of mammalian Igs but cannot be attributed to the Fc, as it is in mammals, since the IgY (delta Fc) does not have an Fc region. Instead, binding probably occurs through unique histidine residues occurring predominantly in the CH1 domain.

Mycobacteriosis in birds.

Avian mycobacteriosis is an important disease which affects companion, captive exotic, wild and domestic birds. The disease is most commonly caused by Mycobacterium avium and Mycobacterium genavense. Lesions are typically found in the liver and gastrointestinal tract, although many other organ systems can potentially be affected. The authors review those species of Mycobacterium reported to affect birds, the epidemiology of avian mycobacteriosis, immunological responses to mycobacterial infection, ante- and post-mortem diagnosis, treatment and prevention or control of the disease.

Use of an enzyme-linked immunosorbent assay to diagnose avian tuberculosis in a captive collection of wildfowl.

The current study assessed the diagnostic accuracy of an enzyme-linked immunosorbent assay (ELISA) and evaluated it as a diagnostic screening aid for avian tuberculosis (TB) in a wildfowl collection at the Wildfowl and Wetlands Trust Centre at Llanelli, Wales, U.K.. Four hundred and eighteen birds of the collection, including geese, ducks, and swans, were screened for mycobacterial antibody levels. Of those birds tested, 40 died during the period of this study and gross post mortem examinations were performed. The ELISA showed a sensitivity of 76.9% and a specificity of 55.6% using post-mortem findings as the 'gold standard'. Thirteen of the examined birds showed evidence of avian TB at necropsy. In addition, liver and spleen biopsies of 19 birds were examined histopathologically. There was minimal agreement between gross post mortem and histopathological findings. PCR performed on 13 of the specimens prepared for histopathology did not identify the presence of mycobacterial DNA. The findings reveal a need for further research to improve the sensitivity and specificity of this ELISA and the accurate diagnosis of avian TB.

Susceptibility of captive wildfowl to avian tuberculosis: the importance of genetic and environmental factors.

This study reports the findings of an epidemiological survey of death due to avian tuberculosis in the captive collection of wildfowl at The Wildfowl and Wetlands Trust Centre, Slimbridge, Gloucestershire. Both genetic and environmental factors have been shown to affect the incidence of, and the birds' susceptibility to, the disease. Seasonal body condition was related to the occurrence of death due to the disease in both males and females. Birds from either hot or cold climates appeared to have a higher incidence than those from temperate climates. What the birds ate did not affect incidence but the method they used for obtaining their food did. Higher susceptibility was found in those species evolved for marine or arboreal habitats. Anomalies in susceptibility which suggest a higher level of genetic immunity in some groups have also been found. Reasons are put forward to explain these findings.

A comparison and evaluation of techniques for diagnosis of avian tuberculosis in wildfowl.

To control the epizootic of avian tuberculosis within the collections of captive wildfowl of The Wildfowl and Wetlands Trust an efficacious vaccine and a reliable diagnostic test are required. A number of potential diagnostic tests were compared for sensitivity and specificity using a flock of 178 feral barnacle geese (Branta leucopsis) at The Wildfowl and Wetland Trust's centre at Slimbridge, Gloucestershire. Evaluations were made of: serodiagnosis by an enzyme-linked immunosorbent assay (ELISA); agglutination of a suspension of killed Mycobacterium avium using both whole blood and serum; and haematological analysis. Necropsy findings confirmed the ELISA to be sensitive and specific, and capable of detecting the disease even at an early stage. The agglutination tests were quick and easy to perform although a number of false positives and negatives did occur. The haematological analysis was found to be less sensitive. ELISA and agglutination tests are now being used to screen the birds in the collections.