A host immune hormone modifies parasite species interactions and epidemics: insights from a field manipulation. Issue 1890 (7th November 2018)

• Record Type: Journal Article
• Authors: Halliday, Fletcher W.; Umbanhowar, James; Mitchell, Charles E.
• Is Part Of: Proceedings. Volume 285:Issue 1890(2018)
• Publication Date: 2018-11-07
• Subjects: disease ecology -- priority effects -- biotic interactions -- co-infection -- competition -- immunity; Biology -- Periodicals; 570.5
• DOI: 10.1098/rspb.2018.2075
• Languages: English
• ISSNs: 0962-8452

Abstract

Abstract : Parasite epidemics can depend on priority effects, and parasite priority effects can result from the host immune response to prior infection. Yet we lack experimental evidence that such immune-mediated priority effects influence epidemics. To address this research gap, we manipulated key host immune hormones, then measured the consequences for within-host parasite interactions, and ultimately parasite epidemics in the field. Specifically, we applied plant immune-signalling hormones to sentinel plants, embedded into a wild host population, and tracked foliar infections caused by two common fungal parasites. Within-host individuals, priority effects were altered by the immune-signalling hormone, salicylic acid (SA). Scaling up from within-host interactions, hosts treated with SA experienced a lower prevalence of a less aggressive parasite, increased burden of infection by a more aggressive parasite, and experienced fewer co-infections. Together, these results indicate that by altering within-host priority effects, host immune hormones can drive parasite epidemics. This study therefore experimentally links host immune hormones to within-host priority effects and parasite epidemics, advancing a more mechanistic understanding of how interactions among parasites alter their epidemics.