Photo: Tomás León (MS GHE 2014) and Sujittra Chaiyadet (Khon Kaen University) take water samples from fish ponds near Lawa Lake in northeast Thailand to assess contamination and the presence of Opisthorchis viverrini.
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Tomás León (MS GHE 2014) and Sujittra Chaiyadet (Khon Kaen University) take water samples from fish ponds near Lawa Lake in northeast Thailand to assess contamination and the presence of Opisthorchis viverrini.
Photo: Fish ponds like this one near Taishan, Guangdong Province, China, are fertilized with animal waste and can therefore be reservoirs of waterborne parasites such as Clonorchis sinensis.
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Fish ponds like this one near Taishan, Guangdong Province, China, are fertilized with animal waste and can therefore be reservoirs of waterborne parasites such as Clonorchis sinensis.
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Understanding Disease Transmission in China and Thailand

Tomás León always wanted to work internationally. It all started with a trip to Latin America as an undergrad in engineering. Opportunity knocked again with a trip to Asia in 2013 to investigate the environmental factors shaping the transmission of liver flukes, specifically Opisthorchis viverrini in Thailand and Clonorchis sinensis in China.

León, a masters student in Environmental Health Sciences, aims to discover if hydrology and the construction of fish ponds affects the burden of these parasites, which spread to humans by eating fish that is raw or under cooked. Fish is a dietary staple in many Asian cultures and as populations have risen, so has the appetite for farmed fish and crustaceans.

“There is a lot of research on these particular parasites to understand the medical side of the picture, namely, how they affect people’s health,” says León. “But there is limited research on the environmental factors that influence their transmission cycle in the lakes and ponds of Thailand and China.”

In Khon Kaen, Thailand, León worked with Dr. Banchob Sripa on a study at Lawa Lake, the site of a larger project conducted by the Tropical Disease Research Laboratory at Khon Kaen University. Fishing is one of the main industries in the area. It’s also one of two “hot spots” in Thailand for the prevalence of cholangiocarcinoma, a form of liver cancer on the increase worldwide often triggered by liver flukes, León’s parasite of interest.

“I’ve always wanted to work internationally. I’m living my dream.” Tomás León

León leveraged his experience in Thailand to lead a second project in the city of Jiangmen located in South China. Working with the local department of public health, he drew up plans to sample water, fish, and fresh water snails – quantitative data he would later analyze as part of his thesis.

In addition to honing his technical skills, León says his field work reinforced the challenge of changing behaviors. “If we could convince everyone to stop eating raw and under cooked fish, there wouldn’t really be a need for our research,” says León. “The reality is people have been trying to do this for decades, but it’s a deeply embedded cultural tradition. In global health we come up against behaviors that might seem undesirable or are unhealthy, but we have to work within the context of these cultures and understand change comes slowly.”

Health Effects of Indoor Insecticides in South Africa

Photo: DDT is sprayed indoors to control the spread of malaria.
DDT is sprayed indoors to control the spread of malaria.

In South Africa, the government sprays the indoor walls of people’s homes with insecticides to control malaria, a disease that in some regions of the country proves fatal in over ninety percent of cases. Yet scientists like Fraser Gaspar are increasingly concerned about the health impacts, particularly among susceptible populations such as children and pregnant women.

Gaspar, a PhD student in Environmental Health Sciences at UC Berkeley, travelled to rural villages in the Province of Limpopo in South Africa, just south of the Zimbabwe border. As part of his thesis field work, he measured indoor levels of the insecticide dichlorodiphenyl trichloroethane, or DDT, in dust samples taken from 50 homes and assessed prenatal serum levels in 750 women living in local villages in collaboration with Brenda Eskenazi and Jonathan Chevrier at the Center for Environmental Research and Children’s Health, and Riana Bornman at the University of Pretoria.

“I went to South Africa as an undergrad and fell in love with the culture,” says Fraser Gaspar. “When this project came up I was interested in the research and the area. It’s a win-win.”

DDT has previously been associated with developmental delays in early childhood. Gaspar hopes his research will help inform risk assessment debates on the implications of indoor residual spraying with a goal of controlling malaria in a way that is effective, but still safe.

Gaspar says it’s key to tailor global health projects to include issues important to the local community. “We are interested in neurodevelopment, for example, but we make sure our study collects other useful information on HIV and malaria. For example, we’re working with the malaria control department tracking the areas sprayed for malaria control – we’re interested in exposures and health effects, but the malaria control department is interested in covering areas they need to spray.”

Global Environment and Obesity

Funded by the Center for Global Public Health, Jenna Hua travelled in July to Kunming, the capital of Yunnan province in southwest China. Her goal was to collect a third round of data for her dissertation examining how food environments influence childhood obesity and metabolic risk. Hua is a PhD student in Environmental Health Sciences.

Photo: Fried street food found in Kunming.
Fried street food found in Kunming.

China’s rapidly growing obesity levels - greater than twenty-five percent in some cities – make it “a natural laboratory for studying how developments in the built environment affect health,” says Hua. Her study compares children’s height and weight over time with physical activity patterns and changes to their food environment.

The increasing globalization of China has impacted food choices in Hua’s study neighborhoods. “We have definitely seen more stores popping up with imported food, and there’s a new diabetic specialty store, signifying diabetes rates are on the rise.”

“It’s important to be flexible and explore your options on the ground,” says Jenna Hua, who received a Suzanne Llewellyn COEH Student Project Award.

In China for ten months on a Fulbright Scholarship, Hua says “for anyone who wants to work internationally, it’s important to be flexible.” For example, her collaborators at Kunming Medical College originally said she could access electronic medical records for all kindergarteners in the city, but without warning, they limited enrollment to one school. Undeterred, she tapped into local contacts to recruit high school students to meet her objectives. “The best way of getting data is to build connections,” says Hua. “You have to explore your options on the ground.”

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