Pakistan’s First Nationwide STH Survey: Determining the Intensity and Prevalence of Worm Infections

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The World Health Organization (WHO) estimates that over 1.5 billion people are infected globally with soil-transmitted helminths (STH), with 835 million children in need of treatment (1). STH infections result from poor sanitation and hygiene conditions, and tend to have the highest prevalence in school-age children. The consequences of chronic worm infections in children are both widespread and debilitating; providing treatment improves children’s education, health, and long-term productivity.    

The WHO classifies Pakistan as a high-burden country for STH based on best available data, which has come from small scale surveys (2). To comprehensively determine the burden, intensity, and geographical distribution of STH in Pakistan and to inform an appropriate treatment strategy, Evidence Action’s Deworm the World Initiative collaborated with Interactive Research and Development (IRD), the Indus Hospital, and the Institute of Development and Economic Alternatives (IDEAS) to conduct the first nationwide STH survey in Pakistan in late 2016.

The survey

To conduct the survey, we used a microscope-based technique called ‘Kato-Katz’ to analyze stool samples, counting the number and types of worm eggs to determine STH prevalence and intensity. The Kato-Katz technique is a straightforward and cost-effective method recommended by the WHO (3). Prior to sending technicians out to schools, we conducted a comprehensive training course on the Kato-Katz technique at the Indus Hospital in Karachi to ensure sufficient knowledge of this important diagnostic tool.

Over the course of nearly five months, we deployed teams to 77 schools across four provinces and one territory to gather samples from over 4,000 students. While schools from all the administrative regions of Pakistan were not included in the survey, all ecological zones of Pakistan were represented. This sampling procedure followed WHO-recommended methodology. Using this methodology, epidemiological data gathered from schools spread across each ecological zone provides representative information for the whole country.

At each school, the teams explained worm infections to children and collected stool samples. Information about hygiene and sanitation infrastructure was collected at all schools, as well as at the household of each sampled child. In addition, teams provided deworming medication to all children at the survey schools, not just those who were recruited for the study. The deworming medication was provided through the WHO global drug donation program.

The remote location of some study sites presented challenges for the survey teams. In one case, the team stayed in one of the villager’s home for two days!  Elsewhere, in Gilgit-Baltistan, heavy rains caused landslides that blocked the only access road to a village the team was due to visit. Because the landslides were widespread in that province, the team had to abandon attempts at finding a suitable substitute school.

While our teams carried the necessary approvals from the health and education authorities, teachers were sometimes reluctant to grant permission to carry out the work; in a few schools, teachers did not permit deworming tablets to be distributed. We gained significant insights into cultural considerations needed to ensure the success of potential future deworming programs.

What did we learn?

The data collected indicates that STH is not widespread throughout the country; rather it is mostly confined to northern areas, with the highest prevalence focused in the area around the cities of Rawalpindi and Islamabad. Much of the southern region of Pakistan has very low levels of infection, with the notable exception of the vicinity of Karachi. In accordance with WHO recommendations, the data indicates annual treatment is required for an estimated 19 million school-age children (27% of the total, based on current population estimates). The data reveals that, while prevalence is high in Rawalpindi, Islamabad, and Karachi (three of the most populous cities of Pakistan), not all major urban areas exhibit high endemicity. Eleven of the top 20 most populous urban areas of Pakistan were included in the survey, with results indicating that only three of these urban areas are in need of MDA. 

Learn more about what makes mass, school-based deworming a cost-effective solution to fighting soil-transmitted helminths.

So, what’s next?

Based on the results of this survey, Evidence Action and IRD plan to work with health and education stakeholders at the national and provincial level to support the initiation of a school-based deworming program in areas recommended for mass treatment. As a result, our efforts will shift from scientific inquiry to the policy and operational foundation needed to support a successful public health intervention delivered in schools. We are excited about the prospect of reducing the harm caused by STH on millions of children in Pakistan in a cost-effective manner.

(1) World Health Organization. (2015). WHO PCT Databank Soil-transmitted Helminth Infections . Retrieved from:

(2) World Health Organization. (2015). Soil-transmitted Helminth Infections (PCT databank). Retrieved from:

(3) World Health Organization (2008). Action Against Worms Newsletter. (Preventive Chemotherapy and Transmission Control (PCT) unit)). Issue 11. Retrieved from:

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