An Investigation into the distribution and environmental niches of pathogenic Salmonellae in Blantyre
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Date
2020-10-16
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Kamuzu University of Health Sciences
Abstract
Type of Study: Observational cohort study of all cases of Typhoid Fever presenting to
Queen’s Hospital
The problem: Invasive Salmonellae are amongst the most important bloodstream pathogens
in Africa. There have previously been two confirmed epidemics of Nontyphoidal Salmonella
(NTS) bloodstream infection in Malawi and Multidrug Resistant Typhoid Fever became
prominent from 2011, thus invasive Salmonella disease (iSD) remains the most important
cause of bacterial bloodstream infection in the city. Our data demonstrate that Typhoid is not
evenly distributed across Blantyre and that there are specific risk factors, including age
(most common aged 5-15), use of river water for cooking and cleaning and one’s social
networks, for example attendance at child day care. Following the identification of these risk
factors by statistical association in a case-control study, the next step is to confirm the
environmental niches of these pathogens by microbiological surveillance in order to inform
public health policy and reduce transmission.
Objectives and Methodology: We propose to undertake an observational cohort study of all
cases of Typhoid Fever presenting to Queen’s Hospital from patients within Blantyre. Having
previously conducted a case control study that has identified risk factors for Typhoid, we plan
to extend this classical outbreak investigation by looking for the causative pathogen in the
community as requested by the district health officer, by undertaking a detailed
microbiological survey of the households and the broader environment of cases to identify
environmental niches of Salmonellae. Lastly, we plan to describe the geographical
distribution of Typhoid within Blantyre to continue our surveillance of hotspots within the city
and to use Whole Genome Sequence data from isolates of Salmonella Typhi to model the
transmission of the pathogen in Blantyre.
Expected outcomes and dissemination: We will describe “hotspots” of iSD in Blantyre,
observing both Typhoid and NTS as there are important differences between households
affected by NTS compared to those affected by S. Typhi, particularly that NTS may show a
higher rate of carriage of Salmonella in the stool of household animals. Lastly, we hope to
produce a model of Typhoid transmission in Blantyre.
More detailed information about risk factors and environmental niches of S. Typhi and NTS
will help to inform public health strategy to control Salmonella infections in Blantyre. Indeed,
this study was specifically requested by the District Health Officer of Blantyre when I
presented the results of the case control study (then Medson Machaya). This information will
be distributed to the College of Medicine, COMREC, the Malawi Ministry of Health and
submitted for peer-reviewed publication.
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Research Subject Categories::MEDICINE