Microbiomes associated with avian malaria survival differ between susceptible Hawaiian honeycreepers and sympatric malaria-resistant introduced birds

Of the estimated 55 Hawaiian honeycreepers (subfamily Carduelinae) only 17
species remain, 9 of which the International Union for Conservation of
Nature considers endangered. Among the most pressing threats to
honeycreeper survival is avian malaria, caused by the introduced blood
parasite Plasmodium relictum, which is increasing in distribution in
Hawai`i as a result of climate change. Preventing further honeycreeper
decline will require innovative conservation strategies that confront
malaria from multiple angles. Research on mammals revealed strong
connections between gut microbiome composition and malaria susceptibility,
illuminating a potential novel approach to malaria control through the
manipulation of gut microbiota.  One honeycreeper species,
Hawai`i `amakihi (Chlorodrepanis virens), persists in some areas of high
malaria prevalence, indicating they have acquired some level of immunity.
To investigate if avian host-specific microbes may be associated with
malaria survival, we characterized cloacal microbiomes and malaria
infection for 174 `amakihi and 172 malaria-resistant warbling white-eyes
(Zosterops japonicus) from Hawai`i Island using 16S rRNA gene
metabarcoding and qPCR. Neither microbial alpha nor beta diversity
covaried with infection, but 149 microbes showed positive associations
with malaria survivors. Among these were Escherichia and Lactobacillus
spp., which appear to mitigate malaria severity in mammalian hosts,
revealing promising candidates for future probiotic research for
augmenting malaria immunity in sensitive endangered species.