Mapping Areas of High Risk for Waterborne Zoonoses in the Eastern Cape: Integrating Multi-Criteria Decision Analysis with GIS to Identify Critical Rivers
1
Institute for Water Research, Rhodes University, Grahamstown, South Africa
Popul. Med. 2026;8(Supplement Supplement 1):
ABSTRACT
INTRODUCTION:
Waterborne zoonotic diseases remain a major global public health concern, contributing to approximately 2.5 billion infections and 2.7 million deaths annually. The Eastern Cape Province of South Africa is particularly vulnerable due to extensive rural settlements, high livestock density, and inadequate water and sanitation infrastructure. Many communities depend on river systems that are frequently contaminated with zoonotic pathogens, yet spatial tools to identify high-risk areas are limited. This study aimed to develop and validate a spatial risk map for waterborne zoonotic diseases in the Eastern Cape Province.
METHODS:
A multi-criteria decision analysis (MCDA) integrated with geographic information systems (GIS) was applied to develop a provincial risk map. Eight environmental drivers, including flooding, temperature, rainfall, wastewater treatment plants, population density, drought, livestock presence, and agricultural activities, were weighted using the analytic hierarchy process (AHP). The resulting composite map classified the province into five risk levels. Validation was conducted at eight sampling sites along the Bloukrans and Buffalo rivers during winter and summer using microbiological and molecular analyses.
RESULTS:
Strong positive correlations were observed between predicted risk levels and measured concentrations of Escherichia coli O157:H7, particularly during summer (Bloukrans River R = 0.92 p = 1.8 × 10⁻⁵; Buffalo River R = 0.93 p = 1.6 × 10⁻⁵). Turbidity also correlated significantly with site risk level. Polymerase chain reaction analysis confirmed the presence of the fliC H7 gene in 97.9% of isolates and the invA gene for Salmonella enterica in 43.8% of presumptive isolates. The eaeA virulence gene was detected in 29.8% of Bloukrans River isolates.
CONCLUSIONS:
The integration of MCDA and GIS effectively identified and predicted areas vulnerable to waterborne zoonotic contamination in the Eastern Cape Province, providing a useful decision-support tool for targeted intervention and public health planning.
Waterborne zoonotic diseases remain a major global public health concern, contributing to approximately 2.5 billion infections and 2.7 million deaths annually. The Eastern Cape Province of South Africa is particularly vulnerable due to extensive rural settlements, high livestock density, and inadequate water and sanitation infrastructure. Many communities depend on river systems that are frequently contaminated with zoonotic pathogens, yet spatial tools to identify high-risk areas are limited. This study aimed to develop and validate a spatial risk map for waterborne zoonotic diseases in the Eastern Cape Province.
METHODS:
A multi-criteria decision analysis (MCDA) integrated with geographic information systems (GIS) was applied to develop a provincial risk map. Eight environmental drivers, including flooding, temperature, rainfall, wastewater treatment plants, population density, drought, livestock presence, and agricultural activities, were weighted using the analytic hierarchy process (AHP). The resulting composite map classified the province into five risk levels. Validation was conducted at eight sampling sites along the Bloukrans and Buffalo rivers during winter and summer using microbiological and molecular analyses.
RESULTS:
Strong positive correlations were observed between predicted risk levels and measured concentrations of Escherichia coli O157:H7, particularly during summer (Bloukrans River R = 0.92 p = 1.8 × 10⁻⁵; Buffalo River R = 0.93 p = 1.6 × 10⁻⁵). Turbidity also correlated significantly with site risk level. Polymerase chain reaction analysis confirmed the presence of the fliC H7 gene in 97.9% of isolates and the invA gene for Salmonella enterica in 43.8% of presumptive isolates. The eaeA virulence gene was detected in 29.8% of Bloukrans River isolates.
CONCLUSIONS:
The integration of MCDA and GIS effectively identified and predicted areas vulnerable to waterborne zoonotic contamination in the Eastern Cape Province, providing a useful decision-support tool for targeted intervention and public health planning.
| eISSN: | 2654-1459 |
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