Skip to:


Intestinal Worms

Poor sanitation breeds trouble.

Intestinal worms are a significant public health problem in many developing countries, with about one quarter of the world’s population infected. Invisible to the naked eye, intestinal worms quietly sap valuable nutrients from their host, often leading to stunted growth and malnutrition.


Moreover, intestinal roundworm infection is associated with poorer academic performance, lower scores on memory and intelligence tests, and lower school attendance rates.

Despite the serious implications of infection, no comprehensive study has been undertaken to explore the impacts of intestinal roundworm infection in China. With this goal in mind, REAP began investigating intestinal worms in 2010, focusing on hot, humid, worm-friendly areas of rural Guizhou province.

In collaboration with the National Institute of Parasitic Diseases (NIPD) at the Chinese Center for Disease Control and Prevention (CDC), REAP surveyed 1701 children from 46 schools and found that 35 percent were infected with intestinal worms. Some villages in Guizhou province showed infection rates as high as 80 percent (read more about this study here). National Chinese government officials called these findings “shocking” and earmarked $10 million for a worm eradication project.

However, intestinal worm infection continues to be a subject of speculation and debate among national-level policymakers. Some argue that intestinal roundworm infection is harmless and does not require government intervention. Others are hesitant to proceed without sufficient evidence on the best overall strategy to combat intestinal worms.

Given the serious implications for children’s health and school performance, and even China’s economic growth, REAP has partnered with the NIPD to find the most effective strategy to reduce infection rates. We believe providing hard evidence can help tip the scales toward decisive action to eliminate intestinal worms in rural China.


The overall goal of our project is to assess the relationship between worm prevalence and indicators of rural Chinese children’s health, academic performance, and raw cognitive function. We will assess: 

Can a health education campaign and/or a deworming program give her a better future?

1) Worm prevalence by worm type, county, and ethnicity

2) Performance of schoolchildren with a focus on:
       a) Anemia
Height and Body Mass Index (BMI)
Executive Function
Working Memory
Processing Speed
       d) Academic performance - 
Standardized math test score

3) The correlation between worm prevalence and children’s performance  


We carried out a cluster randomized controlled trial to identify the impact of strategies designed to reduce intestinal worm infection. By comparing the performance of children who received a worm reduction intervention with those who did not, we were able to determine the effect of the intervention and identify the causal impact of intestinal worms on children’s health and development.

Project Sample

Our sample comprised 112 townships scattered across 7 southeastern counties in rural Guizhou province. One of China’s poorest provinces, Guizhou province was chosen due to its low levels of health and education and high prevalence of intestinal worms.

Project Interventions

Our intervention group received health education and deworming pills. We distributed colorful health education brochures about the dangers of worm infection and how to prevent it to students, teachers, and parents. Members of the intervention group were also individually trained by the research group, and village doctors watched an educational DVD produced by the Ministry of Health. Local doctors then distributed deworming pills to sample children and all siblings aged 3-18 every six months, per WHO guidelines.

The control group received neither health education nor deworming pills.

Data Collection

In May 2013, we conducted a baseline survey of all sample children, collecting information on:

1) Worm infection (type)
2) Physical health (hemoglobin count [Hb], height, weight)
3) Anemia status

Cognitive Development
1) Executive function (working memory, processing speed)
2) School performance (standardized math test)
3) School attendance

Socioeconomic Characteristics
1) Individual basics: gender, DOB, ethnicity, boarding status
2) Household characteristics: size, siblings, education of parents, presence of parents

Eating and Sanitation Habits
1) Dietary intake
2) Hand washing; bare feet
3) Type of toilet; use of night soil

Worm Knowledge and Deworming History 
1) Questions on perceptions about worm prevalence and transmission
2) Deworming experience over past 6 or 12 months

In May 2014, we administered an endline survey—identical to that administered at baseline—to all study participants. By comparing the change from baseline to endline in the control versus the treatment groups, we measured the change in performance level due to the deworming intervention. 


The high rate of worm infections in rural Guizhou Province spells bad news for the health and cognitive development of its young residents.

We used data from our baseline survey to measure the correlation between worm prevalence and children’s performance level. Our first finding showed that the prevalence of worm infections in our study areas is quite high, around 42%. We also found that some population groups were more likely to be infected than others, specifically:

  • Older children and Shui minority children 
  • ​Children who wash their hands less often, who have eaten uncooked meat, and whose households use nightsoil 
  • ​Children who live with their father but not with their mother 

This information is helpful for targeting anti-worm policies toward those most at risk. Our most disturbing results center around the extremely strong link we have identified between worm infection and various measures of health and cognitive development.

After controlling for socioeconomic status, we found that children infected with worms are more likely than their non-infected peers to:

  • Suffer from iron-deficiency anemia
  • Fail their test of raw cognitive function (WISC)
  • Be severely stunted or malnourished
  • Scored lower than their peers on a standardized math test
  • ​Be absent from school

We then measured the impact of our health education and deworming intervention on both infection rates and children's performance. The intervention effectively lowered infection prevalence (from 43 percent to 28 percent in the intervention group) and intensity (from an average of 703 eggs per gram to 300epg among positive samples in the intervention group).

However, the intervention had no significant impact on outcomes of nutrition, cognitive abilities, nor school performance. This may be because, according to WHO standards, both our intervention and control groups had light-intensity infections. It is possible that due to baseline low infection intensity in our sample population, deworming did induce an impact on our outcome variables, but that this impact was not observable because the absolute change in infection intensity was relatively low.

Our analysis identified a significant correlation between higher STH infection intensity and worse cognitive and school performance outcomes. Therefore, more research is needed in areas of moderate- to high-intensity infection.

*Executive Function

Executive function is measured through the internationally-recognized Wechsler Intelligence Scale for Children (WISC). Through this test, we measured children’s working memory and processing speed.

Working memory is the ability to actively maintain information in conscious awareness, perform some operation or manipulation with it, and produce a result. Contemporary research has shown that working memory is closely related to achievement and learning.

Processing speed is related to mental capacity, and has been identified as an important domain of cognitive functioning.