Environmental surveillance for Salmonella Typhi and its association with typhoid fever incidence in India and Malawi

Uzzell, Christopher B, Abraham, Dilip, Rigby, Jonathan, Troman, Catherine M, Nair, Satheesh, Elviss, Nicola, Kathiresan, Lalithambigai, Srinivasan, Rajan, Balaji, Veeraraghavan, Zhou, Nicolette A, Meschke, John Scott, John, Jacob, Kang, Gagandeep, Feasey, Nicholas ORCID: https://orcid.org/0000-0003-4041-1405, Mohan, Venkata Raghava and Grassly, Nicholas C (2023) 'Environmental surveillance for Salmonella Typhi and its association with typhoid fever incidence in India and Malawi'. The Journal of Infectious Diseases. (In Press)

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Abstract

Background
Environmental surveillance (ES) for Salmonella Typhi potentially offers a low-cost tool to identify communities with a high burden of typhoid fever.

Methods
We developed standardised protocols for typhoid ES, including sampling site selection, validation, characterisation; grab or trap sample collection, concentration; and quantitative PCR targeting Salmonella genes (ttr, staG and tviB) and a marker of human faecal contamination (HF183). ES was implemented over 12-months in a historically high typhoid fever incidence setting (Vellore, India) and a lower incidence setting (Blantyre, Malawi) during 2021-2022.

Results
S. Typhi prevalence in ES samples was higher in Vellore compared with Blantyre; 39/520 (7.5%, 95% Confidence Interval 4.4-12.4%) vs. 11/533 (2.1%, 1.1-4.0%) in grab and 79/517 (15.3%, 9.8-23.0%) vs. 23/594 (3.9%, 1.9-7.9%) in trap samples. Detection was clustered by ES site and correlated with site catchment population in Vellore but not Blantyre. Incidence of culture-confirmed typhoid in local hospitals was low during the study and zero some months in Vellore despite S. Typhi detection in ES.

Conclusions
ES describes the prevalence and distribution of S. Typhi even in the absence of typhoid cases and could inform vaccine introduction. Expanded implementation and comparison with clinical and serological surveillance will further establish its public health utility.

Item Type:	Article
Subjects:	QW Microbiology and Immunology > Immunotherapy and Hypersensitivity > QW 806 Vaccination WA Public Health > Water > WA 675 Water. Water supply. Sources WC Communicable Diseases > Infection. Bacterial Infections > Enteric Infections > WC 269 Salmonella infections WC Communicable Diseases > Infection. Bacterial Infections > Enteric Infections > WC 270 Typhoid fever
Faculty: Department:	Clinical Sciences & International Health > Clinical Sciences Department Clinical Sciences & International Health > Malawi-Liverpool-Wellcome Programme (MLW)
Digital Object Identifer (DOI):	https://doi.org/10.1093/infdis/jiad427
SWORD Depositor:	JISC Pubrouter
Depositing User:	JISC Pubrouter
Date Deposited:	09 Oct 2023 08:37
Last Modified:	16 Feb 2024 14:34
URI:	https://archive.lstmed.ac.uk/id/eprint/23298

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