Pigs & Parasites
(Credit: John Openshaw)
Neurocysticercosis and Taenia solium: Developing Interventions to End Cycles of Poverty
Objectives
1. Understand the transmission pathways of neurocysticercosis in adults and children
2. Better define the burden of neurocysticercosis including cognitive deficits in pediatric populations
3. Develop and pilot interventions to stop the transmission of taeniasis and neurocysticercosis
Rationale
Affecting millions living in low-income communities consuming pork throughout Asia, Africa, and Latin America, neurocysticercosis (NCC) is a neglected infectious disease caused by larval forms of the pig tapeworm, Taenia solium, infecting the human brain. Spread via a fecal-oral route as humans with gastrointestinal tapeworm infestation shed thousands of eggs contaminating hands, food sources, and the environment, the disease causes a spectrum of neurologic symptoms include seizures; headaches; and deficits in attention, motor control, impulsivity, and mental and social functioning. NCC is the cause of the majority of cases of acquired epilepsy in endemic areas, and has been identified by the World Health Organization as a leading cause of mortality and morbidity from food-borne diseases. However, measures of burden fail include cognitive deficits, and we hypothesize that the global cost of NCC infection is vastly underestimated. Finally, NCC is an eradicable disease, and successful implementation of improved hygienic standards, pig husbandry techniques which limit pigs’ access to human feces, safe meat handling and preparation, and appropriate treatment of both exposed pigs as well as humans harboring the tapeworm in their GI track would lead to measurable decreased disease burden.
Project Dates
2015 to current
Stage of Work
We have established school- and village-based study sites in poor, rural Tibetan areas in Western Sichuan, China, to study the burden of NCC and to pilot methods of disease elimination. The population in these areas consist of poor Tibetan smallholder farmers who raise pigs and partake in small-scale agriculture.
Data from our field work suggest widespread disease, cognitive impairment, and signs of likely transmission within schools. Overall, 6% of children (180/2867) had serologic evidence of cysticercosis IgG antibodies, with three schools having prevalences of 15% or higher. MRI scans on a subset of students visualized parasites in the brains in 9% (6/63). Children meeting clinical criteria for neurocysticercosis scored significantly lower on a standardized math test compared to their uninfected classmates, suggesting that the disease is causing cognitive deficits and that children affected by NCC are scholastically one year behind their healthy classmates (average score difference of 0.65 standard deviations, p = 0.02).
Based on self-reporting, 11% (283/2606) of children reported having worms or worm segments in their feces. In an in-depth survey of a school where we tested children for GI tapeworms, we found that 4% of the overall school population had T. solium GI carriage (16/362), although the prevalence was 15% amongst fourth graders. Analysis of a school social networks, revealed that 22% of children with serologic evidence of cysticercosis IgG antibodies had identifiable school-based close contacts with infectious tapeworm carriers consistent with school based transmission.
We have developed and are trialing culturally appropriate interventions packages at both the school and village level. Our school based interventions are aimed at decreasing transmission of disease within schools by improving hygiene and handwashing. In pilot schools, we have installed and maintained handwashing stations outside restrooms; devised plans to keep water flowing to hand washing stations despite freezing temperatures in winter; implemented delivery protocols for soap at all hand washing stations; developed educational campaigns using lecture and audiovisual components for both students and teachers; designed materials to encourage handwashing including posters and behavioral nudges; and tested monitoring and enforcement protocols to ensure compliance of hand washing in the student body. In observations our interventions at the school level have led to increases in hand washing and, based on principal and teacher report, evidence of habit formation amongst students.
Our village based efforts aim to decrease burden of infectious cysts in pork as well as educating villagers regarding safe meat handling and preparation. In collaboration with veterinary services at the village and county level, we have developed protocols to treat pigs with an anti-helminthic drug which clears infectious cysts from pig muscle prior to slaughter at the New Year holiday.
People
Primary Contact: John Openshaw
Stanford University Based Project Team
John Openshaw is a physician trained in infectious diseases and internal medicine. He is interested in the ecology and public health burden of zoonotic infectious diseases. He has experience implementing large projects in resource limited settings.
Alexis Medina has been researching the economics of social issues in China for over ten years. She has extensive experience in international program management, including leading survey teams in rural China, overseeing the design and development of field projects, and coordinating data collection and analysis. She has co-authored several academic publications on the intersection of health and education in rural China. Alexis speaks fluent Mandarin, and holds a Master’s in East Asian Studies from Yale University.
Stephen Felt’s research interest focuses on infectious diseases, particularly zoonoses, and refining experimental techniques to improve animal health and welfare. Prior to arriving at Stanford, he served as the Director for the Animal Resources Program at the Naval Medical Research Unit No. 3 in Cairo, Egypt.
Scott Rozelle is the co-director of the Rural Education Action Program. His research focuses almost exclusively on China and is concerned with: agricultural policy, including the supply, demand, and trade in agricultural projects; the emergence and evolution of markets and other economic institutions in the transition process and their implications for equity and efficiency; and the economics of poverty and inequality, with an emphasis on rural education, health and nutrition.
Stephen Luby is a medical epidemiologist trained in internal medicine, epidemiology and preventive medicine. He has extensive experience implementing large studies in resource limited settings. His previous positions include directing the Centre for Communicable Diseases at the International Centre for Diarrhoeal Diseases Research, Bangladesh in Dhaka, Bangladesh from 2004 - 2012, conducting research and teaching epidemiology at the Aga Khan University in Karachi, Pakistan from 1993 - 1998, and working as an epidemiologist in the Foodborne and Diarrheal Diseases Branch of the U.S. Centers for Disease Control and Prevention.
China Based Project Team
Professor Huan Zhou, Sichuan University, is a professor at the Sichuan University School of Public Health. She has extensive experience leading public health related projects across China.
Dr. Tiaoying Li, Sichuan Centers for Disease Control and Prevention, works on Taenia infections at the Sichuan Centers for Disease Control and Prevention. She has extensive experience working on Taenia solium both in the field and laboratory.
To Learn More About This Work
Disease in Schools: Toward a solution for common tapeworm infection
Funding
The pigs and parasites project is funded from an initial grant from Stanford’s Global Development and Poverty Initiative (now the Stanford King Center on Global Development).