Muscovy duck mortality not caused by Haemoproteus

Intracellular yeasts in endothelial cells of a great blue heron (Ardea herodias)

Intracellular organisms in the endothelial cells of several organs of an adult great blue heron (Ardea herodias) were identified as a yeast in the family Saccharomycetales based on ultrastructural morphology and sequence data from the ribosomal RNA operon. Morphologically similar organisms of unknown identity have been described previously in Muscovy (Cairina moschata) and domestic (Anas platyrhynchos domestica) ducks.

Avian malaria (Plasmodium spp) in yellow-eyed penguins: investigating the cause of high seroprevalence but low observed infection

AIM

To investigate the cause of a high seroprevalence of antibodies to Plasmodium spp known to cause avian malaria, but extremely low levels of observed infection, in yellow-eyed penguins, Megadyptes antipodes.

METHODS

A polymerase chain reaction (PCR) test specific for malarial parasites was applied to DNA extracted from blood samples collected from 143 yellow-eyed penguins from an area where seroprevalence for malarial antibodies was known to be high but no parasites were observed in blood smears.

RESULTS

None of the samples tested positive for malarial parasite DNA using the PCR test. Assuming a sensitivity of 90% for this test, this means that prevalence of infection was 95% likely to be <2.3% in this population during this sampling period.

CONCLUSIONS

Serological studies of a population of adult yellow-eyed penguins indicated a high level of exposure to avian malaria parasites, but a correspondingly high level of infection was not observed and no evidence of malarial parasite DNA was found in the current study. Discrepancies between these findings and historical records of Plasmodium spp found in blood smears and post mortem may be explained either by inaccuracy of the serological test used, or by infection occurring in juveniles which is subsequently cleared in surviving adults.

Microsporidiosis in a flock of tricolor parrot finches (Erythrura tricolor)

The lesions caused by a microsporidian infection in a flock of tricolor parrot finches (Erythrura tricolor) are described. Affected birds had a widespread nodular to diffuse granulomatous inflammation of the serosal surfaces of the gastrointestinal tract, peritoneum, perirenal airsacs and connective tissue, bone marrow, dura, and conjunctiva. This was composed predominantly of foamy macrophages containing numerous intracytoplasmic microsporidia measuring 1 to 2 microm. Ultrastructural features consistent with microsporidia were the presence of a coiled polar filament and an electrode-dense outer surface and thick electron-lucent capsule. Differential diagnoses included infection with intracellular organisms, including coccidian and other apicomplexan parasites, such as lsospora, Eimeria, and blood parasites; Chlamydophilosis; disseminated mycobacteriosis; and other bacterial and fungal species.

An unusual intracellular infection in ducks

An infection causing mortality was encountered on seven occasions in Muscovy (Cairina moschata) and domestic ducks (Anas platyrhynchos domestica). In all cases the principal lesion was a severe pneumonitis associated with the presence of numerous organisms in the cytoplasm of the blood capillary endothelial cells. Cultural examination for bacterial and fungal agents consistently failed to yield significant isolates. In tissue sections the organisms were poorly stained by haematoxylin and eosin but were strongly positive to the periodic acid-Schiff and periodic acid-silver methenamine methods. Electron microscopy showed round (0.5 microm to 1.0 microm diameter) or oval (1 microm x 1.7 microm) forms possessing a complex cell wall, cytoplasmic lamellar bodies and an apparently membrane-bound nuclear structure. On the available evidence, the identity of the organism and its classification as either a prokaryote or eukaryote were not resolved.