Massey Documents by Type

Permanent URI for this communityhttps://mro.massey.ac.nz/handle/10179/294

Browse

Has files: YesSubject: search.filters.subject.Avian malaria

Search Results

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Indirect interaction between an endemic and an invading pathogen: A case study of Plasmodium and Usutu virus dynamics in a shared bird host population.
    (Elsevier B.V., 2024-04-18) Dimas Martins A; Roberts M; Ten Bosch Q; Heesterbeek H
    Infectious disease agents can influence each other's dynamics in shared host populations. We consider such influence for two mosquito-borne infections where one pathogen is endemic at the time that a second pathogen invades. We regard a setting where the vector has a bias towards biting host individuals infected with the endemic pathogen and where there is a cost to co-infected hosts. As a motivating case study, we regard Plasmodium spp., that cause avian malaria, as the endemic pathogen, and Usutu virus (USUV) as the invading pathogen. Hosts with malaria attract more mosquitoes compared to susceptible hosts, a phenomenon named vector bias. The possible trade-off between the vector-bias effect and the co-infection mortality is studied using a compartmental epidemic model. We focus first on the basic reproduction number R0 for Usutu virus invading into a malaria-endemic population, and then explore the long-term dynamics of both pathogens once Usutu virus has become established. We find that the vector bias facilitates the introduction of malaria into a susceptible population, as well as the introduction of Usutu in a malaria-endemic population. In the long term, however, both a vector bias and co-infection mortality lead to a decrease in the number of individuals infected with either pathogen, suggesting that avian malaria is unlikely to be a promoter of Usutu invasion. This proposed approach is general and allows for new insights into other negative associations between endemic and invading vector-borne pathogens.
  • Thumbnail Image
    Item
    The impact of conservation translocations on vector-borne parasites : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Ecology at Massey University, Palmerston North, New Zealand
    (Massey University, 2015) Schoener, Ellen Renate
    Wildlife conservation in New Zealand relies on translocations of endangered species to safe sites. While knowledge of the biology and behaviour of translocated hosts has steadily increased, the role of parasites in wildlife translocations has been largely overlooked. Parasites can affect their host’s survivorship during translocations by causing disease. However, failure to translocate or reintroduce a host specific parasite with its endangered host can contribute to the extinction of the parasite with unforeseen consequences for the future of the host or even the whole ecosystem. The main aims of this study were to establish baseline data on the impact of North Island saddleback translocations on their avian malaria (Plasmodium spp.) parasites as well as gaining further insight into potential vectors in New Zealand. The study was also intended to contribute to the development of recommendations for future parasite screening programmes for native passerine translocations. Saddlebacks and Plasmodium were chosen because of the detailed saddleback translocation history and its known relationship with the parasite. As a result of this study, several Plasmodium lineages previously unrecorded in saddlebacks and New Zealand were identified, for example, the native Kokako01 and one lineage closest related to two lineages from the Americas. Nonetheless, the most frequent lineages found were the cosmopolitan P. elongatum GRW6 and LINN1, and P. vaughani SYAT05, common in birds introduced to New Zealand. This finding suggests that endemic parasites may have already become rare or extinct. In addition, Plasmodium DNA was detected in both native and introduced mosquitoes that may act as vectors. A qPCR assay was developed that was found to be a cost effective and rapid screening tool for the detection of Plasmodium in native birds suffering from acute infection, presenting with clinical symptoms, and in birds that were found dead. . I conclude that future translocations should consider the movement of endemic parasites with their hosts. How this should happen is open for future studies. However, I urge managers to start considering this issue now as New Zealand has already recorded the extinction of one endemic parasite and many more may have already been lost without knowledge.
  • Thumbnail Image
    Item
    Host-parasite interactions between Plasmodium species and New Zealand birds : prevalence, parasite load and pathology : a thesis presented in partial fulfilment of the requirements for the degree of Master of Veterinary Science in Wildlife Health at Massey University, Palmerston North, New Zealand
    (Massey University, 2015) Sijbranda, Danielle Charlotte
    Avian malaria, caused by Plasmodium spp., is an emerging disease in New Zealand and has been reported as a cause of morbidity and mortality in New Zealand bird populations. This research was initiated after P. (Haemamoeba) relictum lineage GRW4, a suspected highly pathogenic lineage of Plasmodium spp. was detected in a North Island robin of the Waimarino Forest in 2011. Using nested PCR (nPCR), the prevalence of Plasmodium lineages in the Waimarino Forest was evaluated by testing 222 birds of 14 bird species. Plasmodium sp. lineage LINN1, P. (Huffia) elongatum lineage GRW06 and P. (Novyella) sp. lineage SYATO5 were detected; Plasmodium relictum lineage GRW4 was not found. A real-time PCR (qPCR) protocol to quantify the level of parasitaemia of Plasmodium spp. in different bird species was trialled. The qPCR had a sensitivity and specificity of 96.7% and 98% respectively when compared to nPCR, and proved more sensitive in detecting low parasitaemias compared to the nPCR. The mean parasite load was significantly higher in introduced bird species compared to native and endemic species. The data suggests that introduced bird species such as blackbirds have a higher tolerance for Plasmodium spp. infections than endemic and native species. The high prevalence of infection and high parasite load in introduced passerines confirmed that they are important reservoirs for avian malaria in the New Zealand. A clinical case of avian malaria in a captive wildlife setting was described for a little penguin (Eudyptula minor) at Wellington Zoo. Nested PCR results and DNA sequencing confirmed infection of the deceased penguin with Plasmodium (Huffia) elongatum GRW06. A retrospective analysis of little penguin cases in the Massey University post mortem database, combined with nested PCR for Plasmodium spp. on stored liver tissue samples and DNA sequencing, revealed three additional mortality cases due to P. elongatum lineage GRW06, P. relictum lineage SGS1 and P. sp. lineage LINN1 in one captive and two wild little penguins. Our results suggest that avian malaria causes sporadic mortality in New Zealand’s little penguins, but there is no evidence of mass mortality events due to avian malaria in this species.
  • Thumbnail Image
    Item
    Population genetics, biogeography and ecological interactions of the New Zealand bellbird (Anthornis melanura) and their avian malaria parasites : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy (Ph.D.) in Zoology at Massey University, Albany, New Zealand
    (Massey University, 2011) Baillie, Shauna Maureen
    Habitat loss and redistribution of species has lead to population declines and loss of genetic diversity with serious implications to species survival on ecological and evolutionary scales. While there is no doubt that rapidly dwindling endangered populations require our immediate attention, studies on common species are equally important. The purpose of this thesis is to investigate the genetic connectivity, biogeographical relationships and host-parasite interactions of a common and widely distributed bird species, mainly because we want common species to remain common. Furthermore, I illustrate how studies such as this provide invaluable comparisons for sympatric endangered species. In this thesis, patterns of genetic variation of the New Zealand bellbird (Anthornis melanura) are delineated to assess their re-colonization potential among fragmented landscapes. Using a phylogeographic perspective I show how dispersal ability and secondary contact among isolated population fragments shape the evolutionary trajectory of a species. I also determine the biogeographical relationships between the bellbird host and its malaria parasites with key emphasis on host-parasite specificity. Finally, immunological trade-offs are investigated in disease epidemiology by examining host factors that influence malaria prevalence. I show that an immense capacity for dispersal has prevented divergence and shaped the high levels of genetic diversity and connectivity in bellbirds today. However, substantial genetic differentiation among subpopulations reflects recent habitat fragmentation. Based on these findings I conclude that continued habitat loss can lead to further reductions in gene flow, despite dispersal. Though restricted to northern populations, I provide evidence that the most abundant avian malaria lineage infecting bellbirds is likely an endemic Plasmodium (Novyella). This parasite exhibits bimodal seasonality and male-biased infections, but these relationships vary among subpopulations. Malaria prevalence appears to be governed by food availability and territory stability, thus habitat disturbance has repercussions to immune phenotype. With this thesis I advocate a re-thinking of conservation strategies toward spatial planning that enables ‘natural’ secondary contact among habitat fragments. Translocation is not necessary for all species. In addition to being the first study on seasonal and host factors affecting malaria patterns in the Southern Hemisphere, this thesis makes major contributions to science by elucidating some ecological relationships that underpin the evolution of immunity.