INVESTIGATING THE ROLE OF THE CLOACAL MICROBIOME IN AVIAN MALARIA SUSCEPTIBILITY IN HAWAIIAN HONEYCREEPERS

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2021-12

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Anthropogenic disturbance has led to an increase in the frequency and severity of infectious wildlife diseases in naive ecosystems, posing major threats to global biodiversity. For a poignant example, of the 55 Hawaiian honeycreeper species (subfamily Carduelinae) that have been documented across the Hawaiian archipelago, only 17 remain, and 9 of them are endangered. Among the most pressing threats to honeycreeper survival is avian malaria, caused by the introduced blood parasite Plasmodium relictum, which is expanding in distribution in Hawaiʻi as a result of climate change. Recent research on mammals has revealed strong connections between gut microbiome composition and malaria susceptibility, illuminating a potential novel approach to malaria control through the administration of antimalarial probiotics. One honeycreeper species, the Hawai‘i ‘Amakihi (Chlorodrepanis virens), persists in some areas of high malaria prevalence, indicating they have acquired some level of immunity to this disease. To investigate if avian host-specific microbes may be associated with malaria survival, I characterized cloacal microbiomes and malaria infection for 174 ‘amakihi and 171 malaria-resistant Warbling White-eyes (Zosterops japonicus) from Hawai‘i Island using 16S rRNA gene sequencing and qPCR. Neither microbiome alpha nor beta diversity covaried with malaria infection, but 71 microbes showed positive associations with survivors of malaria, revealing promising targets for future probiotic research. Among these were Escherichia and Lactobacillus spp., which have supported potential to mitigate malaria severity in mammalian hosts, and Pseudomonas spp., which have been linked to Plasmodium suppression in mosquito vectors. My findings suggest targeted probiotics warrant further investigation for their potential to provide practical and effective methods of augmenting immunity in malaria sensitive species to prevent imminent extinctions.

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Wildlife conservation, Microbiology, Parasitology, 16S rRNA gene sequencing, Chlorodrepanis virens, metabarcoding, Microbiota, Plasmodium relictum, probiotics

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49 pages

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