Parasitology of the yellow-eyed penguin (Megadyptes antipodes)

Abstract

The goal of this study was to determine whether parasites represent a threat to the continued existence of the Yellow-Eyed Penguin, Megadyptes antipodes. The population of this rare penguin has suffered from two severe mass-mortalities in the past decade, resulting in the deaths of a significant proportion of breeding adults, and consequently their chicks. One of the suspected agents of these mortalities is avian malaria (Plasmodium spp.), which is a major cause of death in captive penguin populations.

In this study, I examined blood samples drawn from penguins on Boulder Beach, on the Otago Peninsula. Blood smears were examined for the presence of haematozoa, and ELISAs were performed to detect antibodies to Plasmodium spp. There was no evidence of blood parasites on any examined smears, but 169 of the 171 samples tested were seropositive for anti-Plasmodium antibodies according to the ELISA technique used in this study.

PCR analysis indicated that avian malaria was present in the Yellow-Eyed Penguin population, but was unable to identify the agent responsible beyond the genus. Initial investigation suggests a species of Plasmodium other than P. relictum is involved.

All birds sampled were in good health, suggesting that even if these birds have been exposed to avian malaria, it does not cause significant harm. Avian malaria may be sustained in the penguin population at a sub-clinical level, resulting in birds which carry the disease, but do not show any symptoms under normal conditions.

In addition to blood samples, faecal samples were taken from live birds at the same time. These indicated that twelve of the sixty-five birds examined were infected with the coccidian Eimeria sp. Nematode eggs of Contracaecum sp. were also recovered in the faecal sample of one of these birds. There was no evidence to suggest that these parasites harm their hosts in a measurable manner.

Twenty adult Yellow-Eyed Penguins were dissected in order to determine what helminth parasites were present in these birds. One species of nematode and one species of acanthocephalan were recovered. These were respectively identified as Contracaecum eudyptes and Corynosoma hannae. The majority of the penguins dissected were infected with one or both of these parasites. Again, there was no evidence that these parasites result in significant harm to their hosts, only one bird showing signs of inflammation as a result of a heavy nematode infection.

Ectoparasites were rarely recovered from these birds. Lice (Austrogonioides conci) were recovered from one live bird in the course of the study. No mites or fleas were detected on any penguin examined in this study.

The parasites of the Yellow-Eyed Penguin recovered in this study did not appear to inflict measurable harm on their hosts, but their potential impact cannot be ignored, especially when the host is under stress.