Abstract
Kenya, just like other countries with endemic soil-transmitted helminths (STH), has conducted regular mass drug administration (MDA) program for the last 5 years among school aged children as a way to reduce STH infections burden in the country. However, the point of interruption of transmission of these infections still remains unclear. In this study, we developed and analyzed an age structured mathematical model to predict the elimination period (i.e., time taken to interrupt STH transmission) of these infections in Kenya. The study utilized a deterministic age structured model of the STH population dynamics under a regular treatment program. The model was applied to three main age groups: pre-school age children (2–4 years), school age children (5–14 years), and adult populations (≥15 years) and compared the impact of two interventions on worm burden and elimination period. The model-simulated results were compared with the 5 year field data from the Kenyan deworming program for all the three types of STH (Ascaris lumbricoides, Trichuris trichiura, and hookworm). The model demonstrated that the reduction of worm burden and elimination period depended heavily on four parameter groups; drug efficacy, number of treatment rounds, MDA and water, sanitation and hygiene (WASH) coverage. The analysis showed that for STH infections to be eliminated using MDA alone in a short time period, 3-monthly MDA plan is desired. However, complementation of MDA with WASH at an optimal (95%) coverage level was most effective. These results are important to the Kenyan STH control program as it will guide the recently launched Breaking Transmission Strategy.
Highlights
Soil-transmitted helminths (STH) are part of a group of diseases categorized by the World Health Organization (WHO) as neglected tropical diseases (NTDs)
In this paper we developed an age-structured mathematical model based on ordinary differential equations (ODE), which are part of deterministic models, to determine the impact of mass drug administration (MDA) and WASH interventions on worm burden and elimination period specific to Kenyan infection transmission dynamics
The process and impact of the program is continuously being evaluated through a robust monitoring and evaluation (M&E) program which is independently conducted by the Kenya Medical Research Institute (KEMRI) as described elsewhere (19)
Summary
Soil-transmitted helminths (STH) are part of a group of diseases categorized by the World Health Organization (WHO) as neglected tropical diseases (NTDs). Soil-Transmitted Helminths Transmission Interruption Model countries and affect more than two billion people globally (1). A further four billion people are estimated to be at risk. These infections occur mainly in the rural areas of Sub-Saharan Africa, Latin America, China, and South East Asia (3). STH are mainly caused by lack of safe drinking water, proper sanitation (practice of open defecation), and hygiene (poor practice of handwashing and walking barefoot on contaminated soil) (4). STH are generally transmitted through ingestion of nematode eggs from contaminated soil (A. lumbricoides and T. trichiura) or through active penetration of the skin by larvae in the soil (hookworm) (5). The infection prevalence and intensity are strongly inversely correlated with the access to and use of improved sources of water, sanitation and hygiene (WASH) (6). Infected individuals show a broad range of symptoms including nausea, tiredness, abdominal pain, and loss of appetite that can attenuate malnutrition and increased rates of anemia (7)
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