Document Type

Journal Article

Publication Title

The Lancet Regional Health - Western Pacific

Volume

24

Publisher

Elsevier

School

Centre for Ecosystem Management

Funders

Coalition Against Typhoid through the Bill and Melinda Gates Foundation [grant number OPP1017518] / Victorian Government / National Health and Medical Research Council Australia / Australian Research Council / Fiji Ministry of Health and Medical Services

Comments

Davies, M. R., Duchene, S., Valcanis, M., Jenkins, A. P., Jenney, A., Rosa, V., ... & Strugnell, R. A. (2022). Genomic epidemiology of salmonella typhi in central division, Fiji, 2012 to 2016. The Lancet Regional Health-Western Pacific, 24, 100488. https://doi.org/10.1016/j.lanwpc.2022.100488

Abstract

Background: Typhoid fever is endemic in some Pacific Island Countries including Fiji and Samoa yet genomic surveillance is not routine in such settings. Previous studies suggested imports of the global H58 clade of Salmonella enterica var Typhi (Salmonella Typhi) contribute to disease in these countries which, given the MDR potential of H58, does not auger well for treatment. The objective of the study was to define the genomic epidemiology of Salmonella Typhi in Fiji. Methods: Genomic sequencing approaches were implemented to study the distribution of 255 Salmonella Typhi isolates from the Central Division of Fiji. We augmented epidemiological surveillance and Bayesian phylogenomic approaches with a multi-year typhoid case-control study to define geospatial patterns among typhoid cases. Findings: Genomic analyses showed Salmonella Typhi from Fiji resolved into 2 non-H58 genotypes with isolates from the two dominant ethnic groups, the Indigenous (iTaukei) and non-iTaukei genetically indistinguishable. Low rates of international importation of clones was observed and overall, there were very low levels an antibiotic resistance within the endemic Fijian typhoid genotypes. Genomic epidemiological investigations were able to identify previously unlinked case clusters. Bayesian phylodynamic analyses suggested that genomic variation within the larger endemic Salmonella Typhi genotype expanded at discreet times, then contracted. Interpretation: Cyclones and flooding drove ‘waves’ of typhoid outbreaks in Fiji which, through population aggregation, poor sanitation and water safety, and then mobility of the population, spread clones more widely. Minimal international importations of new typhoid clones suggest that targeted local intervention strategies may be useful in controlling endemic typhoid infection. These findings add to our understanding of typhoid transmission networks in an endemic island country with broad implications, particularly across Pacific Island Countries.

DOI

10.1016/j.lanwpc.2022.100488

Creative Commons License

Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.

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