Avian malaria (Plasmodium spp.) in the Auckland region : host-parasite associations, capture technique bias, and landscape disease dynamics : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Science in Conservation Biology, Massey University, Auckland, New Zealand
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Date
2011
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Massey University
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Abstract
Avian malaria parasites (Plasmodium spp.) are distributed throughout the world and
affect a vast range of bird species. However many aspects of avian malaria in New
Zealand, such as the extent of parasite diversity, distribution and prevalence in host
populations, are currently unknown. Thus, the first aim of this study was to examine
these parameters in native and exotic bird species of the Auckland Region, North Island.
A total of 21 species were sampled at two sites: Tiritiri Matangi Island and Waharau
Regional Park. Of these, five native (bellbird Anthornis melanura, tui Prosthemadera
novaeseelandiae, New Zealand fantail Rhipidura fuliginosa placabilis, North Island
tomtit Petroica macrocephala toitoi and silvereye Zosterops lateralis) and three exotic
(myna Acridotheres tristis, blackbird Turdus merula and song thrush T. philomelos)
species were infected. This is the first reported incidence of avian malaria in the New
Zealand fantail, and only the second record in tui. The parasite morphospecies identified
in this survey were P. (Haemamoeba) relictum, P. (Huffia) elongatum, P. (Novyella)
rouxi and two P. (Novyella) spp. not yet formally taxonomically described, one of which
appears to be specific to the endemic bellbird. Parasite prevalence within the two most
heavily sampled species varied strikingly: bellbird prevalence was estimated at 41.5% (N
= 51/123) in the Tiritiri Matangi population and silvereye prevalence at 9.2% (N =
22/240) within the Waharau population.
The other two objectives of this study addressed: 1) the potential bias that choice
of capture technique may have in avian malaria surveys and 2) the effects of forest
fragmentation on avian malaria and vector distributions. The first objective was
investigated by comparing prevalence and parasitaemia in adult male bellbirds on Tiritiri
Matangi Island caught via two live-capture techniques: mist netting and supplementary
feeder trapping. In this instance it was found that the choice of capture method did
influence results: mist netting of bellbirds yielded significantly higher parasitaemia than
feeder trapping. The second objective was investigated through a comparison of mosquito
species abundance, composition, and avian malaria prevalence in silvereyes at forest edge
versus interior sites in Waharau Regional Park. A total of five mosquito species, three
native (Aedes antipodeus, Culex asteliae and Cx. pervigilans) and two exotic (Ae.
notoscriptus and Cx. quinquefasciatus), were trapped in this study. Significantly more
exotic mosquitoes were trapped at the forest edge, with almost complete absence in the
interior. Furthermore, analysis of the individual species showed a significant edgeassociation
for Cx. quinquefasciatus. Although significantly more native mosquitoes
were trapped in the forest interior versus the edge, this was due to high Ae. antipodeus
abundance in one interior site. Consequently, no edge- or interior-associations were
found for the individual native species. Finally, avian malaria prevalence in silvereyes did
not significantly differ between forest edge and interior.
The outcomes of this study included: a) additional baseline prevalence data for
New Zealand; b) records of two new parasite-native bird associations; c) a demonstration
that different live-capture techniques can bias estimates of parasitaemia; d) confirmation
that forest edge habitats are more prone to exotic mosquito invasions in New Zealand;
and e) determination that avian malaria prevalence in the silvereye does not differ
between birds caught at forest edge and interior and is thus not closely correlated to
mosquito distribution at these sites. A discussion of the future avenues of avian malaria
research in New Zealand is provided at the end of this study.
Description
Keywords
Avian malaria parasites (Plasmodium spp.), Mosquitoes, Forest fragmentation, Parasite-bird associations, Avian malaria prevalence, Tiritiri Matangi Island, Waharau Regional Park, Auckland Region, New Zealand, Capture technique bias, Landscape disease dynamics, Forest sites