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Abstract The introduction of nonnative species and reductions in native biodiversity have resulted in substantial changes in vector and host communities globally, but the consequences for pathogen transmission are poorly understood. In lowland Hawaii, bird communities are composed of primarily introduced species, with scattered populations of abundant native species. We examined the influence of avian host community composition, specifically the role of native and introduced species, as well as host diversity, on the prevalence of avian malaria (Plasmodium relictum) in the southern house mosquito (Culex quinquefasciatus). We also explored the reciprocal effect of malaria transmission on native host populations and demography. Avian malaria infection prevalence in mosquitoes increased with the density and relative abundance of native birds, as well as host community competence, but was uncorrelated with host diversity. Avian malaria transmission was estimated to reduce population growth rates of Hawai‘i ʻamakihi (Chlorodrepanis virens) by 7–14%, but mortality from malaria could not explain gaps in this species’ distribution at our sites. Our results suggest that, in Hawaii, native host species increase pathogen transmission to mosquitoes, but introduced species can also support malaria transmission alone. The increase in pathogen transmission with native bird abundance leads to additional disease mortality in native birds, further increasing disease impacts in an ecological feedback cycle. In addition, vector abundance was higher at sites without native birds and this overwhelmed the effects of host community composition on transmission such that infected mosquito abundance was highest at sites without native birds. Higher disease risk at these sites due to higher vector abundance could inhibit recolonization and recovery of native species to these areas. More broadly, this work shows how differences in host competence for a pathogen among native and introduced taxa can influence transmission and highlights the need to examine this question in other systems to determine the generality of this result.
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Transinfection of Wolbachia wAlbB into Culex quinquefasciatus mosquitoes does not alter vector competence for Hawaiian avian malaria (Plasmodium relictum GRW4)
Avian malaria is expanding upslope with warmer temperatures and driving multiple species of Hawaiian birds towards extinction. Methods to reduce malaria transmission are urgently needed to prevent further declines. ReleasingWolbachia-infected incompatible male mosquitoes could suppress mosquito populations and releasingWolbachia-infected female mosquitoes (or both sexes) could reduce pathogen transmission if theWolbachiastrain reduced vector competence. We clearedCulex quinquefasciatusof their naturalWolbachia pipientis wPip infection and transinfected them withWolbachia wAlbB isolated fromAedes albopictus. We show thatwAlbB infection was transmitted transovarially, and demonstrate cytoplasmic incompatibility with wild-type mosquitoes infected withwPip from Oahu and Maui, Hawaii. We measured vector competence for avian malaria,Plasmodium relictum, lineage GRW4, of seven mosquito lines (two withwAlbB; three with naturalwPip infection, and two cleared ofWolbachiainfection) by allowing them to feed on canaries infected with recently collected field isolates of HawaiianP.relictum. We tested 73 groups (Ntotal= 1176) of mosquitoes forP.relictuminfection in abdomens and thoraxes 6–14 days after feeding on a range of parasitemias from 0.028% to 2.49%, as well as a smaller subset of salivary glands. We found no measurable effect ofWolbachiaon any endpoint, but strong effects of parasitemia, days post feeding, and mosquito strain on both abdomen and thorax infection prevalence. These results suggest that releasing malewAlbB-infectedC.quinquefasciatusmosquitoes could suppresswPip-infected mosquito populations, but would have little positive or negative impact on mosquito vector competence forP.relictumifwAlbB became established in local mosquito populations. More broadly, the lack ofWolbachiaeffects on vector competence we observed highlights the variable impacts of both native and transinfectedWolbachiainfections in mosquitoes.
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- Award ID(s):
- 1911853
- PAR ID:
- 10601058
- Editor(s):
- Vernick, Kenneth D
- Publisher / Repository:
- PLOS
- Date Published:
- Journal Name:
- PLOS Pathogens
- Volume:
- 20
- Issue:
- 8
- ISSN:
- 1553-7374
- Page Range / eLocation ID:
- e1012052
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1371/journal.ppat.1012052
