Gram Research analysis found that Cryptosporidium parvum, a parasite causing severe diarrhea, was detected in 22 out of 96 fresh produce samples tested in Costa Rica using advanced DNA methods. Cilantro showed the highest bacterial contamination, with E. coli found in 14 samples. The findings demonstrate that raw vegetables and fruits can carry dangerous parasites and bacteria, making thorough washing essential before consumption, especially for people with weakened immune systems.
Researchers in Costa Rica tested fresh produce like strawberries, lettuce, and cilantro to see if they contained a parasite called Cryptosporidium that causes severe diarrhea. They examined 96 samples using advanced laboratory techniques and found the parasite on some vegetables and fruits. The study also checked for harmful bacteria like E. coli. The findings show that raw produce can carry dangerous germs, especially cilantro, which had the most bacterial contamination. This research highlights why washing produce carefully and improving food safety practices are so important for protecting public health.
Key Statistics
A 2026 study of 96 produce samples from Costa Rica’s Metropolitan Area found Cryptosporidium parvum in 22 samples using molecular DNA testing, more than four times higher than the 5 samples detected by microscopy alone.
Among 82 produce samples tested for bacterial contamination in a 2026 Costa Rican study, E. coli was identified in 14 samples, with cilantro showing the highest counts of total and heat-resistant coliforms.
Research published in the Journal of Food Protection in 2026 confirmed that Cryptosporidium parvum was present in strawberries, lettuce, and cilantro from different provinces across Costa Rica, indicating widespread contamination in the fresh produce supply.
The Quick Take
- What they studied: Whether fresh produce sold in Costa Rica’s main cities contained a parasite called Cryptosporidium parvum that makes people sick with severe diarrhea.
- Who participated: 96 samples of strawberries, lettuce, and cilantro purchased from markets in the Metropolitan Area of Costa Rica.
- Key finding: Researchers found Cryptosporidium parvum on 22 samples using advanced DNA testing methods, and cilantro had the most bacterial contamination with E. coli found in 14 samples.
- What it means for you: Washing fresh produce thoroughly before eating is important. People with weak immune systems should be especially careful with raw vegetables and fruits. Better safety practices are needed at farms and markets to prevent contamination.
The Research Details
Scientists collected 96 samples of strawberries, lettuce, and cilantro from stores in Costa Rica’s main metropolitan area. They used two main methods to test for Cryptosporidium: first, they looked at the samples under a microscope using special stains that make the parasite visible, and second, they used a more sensitive DNA test called nested PCR that can detect even tiny amounts of the parasite’s genetic material. They also tested all samples for harmful bacteria like E. coli and other coliforms, which are bacteria found in human waste that indicate contamination.
The researchers chose these three produce items because they are commonly eaten raw in Costa Rica and are known to be high-risk foods for parasite transmission. Strawberries are eaten whole without cooking, lettuce is typically served fresh in salads, and cilantro is used as a fresh garnish. All three foods can easily pick up parasites and bacteria if they come into contact with contaminated water during growing, harvesting, or handling.
This type of study is important because it gives real-world information about actual food safety risks in a specific region. By testing produce that people actually buy and eat, researchers can identify where contamination happens and what needs to be fixed.
This research approach matters because it looks at actual food that people purchase and eat, not just theoretical risks. By testing real produce from real markets, scientists can identify specific contamination problems and help improve food safety practices. The use of both microscopy and DNA testing is important because the DNA method is much more sensitive and can catch parasites that the microscope might miss.
The study used well-established laboratory methods that are recognized internationally for detecting parasites and bacteria. The nested PCR technique used is considered highly reliable for identifying Cryptosporidium. However, the study did not specify exactly how many samples of each produce type were tested, which would have been helpful for understanding the risk level for each food. The research was published in the Journal of Food Protection, a respected scientific journal focused on food safety.
What the Results Show
When researchers looked at the produce samples under a microscope, they found Cryptosporidium in 5 samples. However, when they used the more sensitive DNA testing method, they found the parasite in 22 samples, which is more than four times higher. This shows that the parasite can be present in amounts too small to see under a microscope but still large enough to make someone sick. All of the Cryptosporidium found was identified as Cryptosporidium parvum, which is the species that most commonly infects humans and causes serious diarrhea.
The bacterial contamination results were also concerning. Cilantro had the highest levels of total bacteria and heat-resistant bacteria. E. coli, a bacterium found in human waste that indicates fecal contamination, was found in 14 samples out of 82 that were tested for bacteria. This means that about 17 percent of the samples tested positive for E. coli, suggesting that these foods came into contact with human or animal waste at some point.
The presence of both parasites and bacteria on the same produce items is particularly worrying because it shows multiple pathways for contamination. If produce can carry parasites from one contamination event and bacteria from another, it means the food safety problems are widespread throughout the production and distribution system.
Cilantro stood out as having the most contamination overall, with the highest counts of total coliforms and thermotolerant coliforms. This is important because cilantro is often used as a fresh garnish and is rarely cooked, meaning any parasites or bacteria on it would go directly into people’s mouths. The fact that different produce items had different contamination levels suggests that some crops or growing practices may be riskier than others. The study also showed that contamination was found in produce from different provinces across Costa Rica, indicating this is not just a local problem but a regional issue.
This research updates previous findings about Cryptosporidium in Costa Rican produce. The use of molecular DNA testing in this study is more advanced than older methods, which means researchers can now detect contamination that previous studies might have missed. The finding that Cryptosporidium parvum is present in fresh produce confirms what scientists have observed in other countries, showing this is a global food safety concern, not unique to Costa Rica. However, the specific contamination rates found in this study provide new information about the current risk level in this region.
The study did not clearly specify how many samples of each produce type were tested, making it difficult to know if strawberries, lettuce, and cilantro had equal risk or if one was tested more than others. The research did not identify where the contamination came from, such as whether it happened at the farm, during transport, or at the market. The study also did not test for other parasites or viruses that might be present on produce. Additionally, the research was conducted in one specific region of Costa Rica, so the results may not apply to other parts of the country or other countries with different farming and food handling practices.
The Bottom Line
Wash all fresh produce thoroughly under running water before eating, even if you plan to peel it. For people with weak immune systems, including those with HIV, cancer patients receiving treatment, or very young children, consider cooking vegetables instead of eating them raw, or consult a doctor about which raw foods are safe. Food producers and markets should implement stronger safety practices to prevent contamination at the farm and during distribution. Government agencies should increase testing and monitoring of fresh produce.
Everyone should care about this research, but it is especially important for people with weakened immune systems who can develop severe, long-lasting infections from Cryptosporidium. Parents of young children should be aware of the risks. Food producers, market managers, and government food safety officials need this information to improve practices. People who eat a lot of raw vegetables and salads should take extra care with washing produce.
If you become infected with Cryptosporidium from contaminated produce, symptoms typically appear within 2 to 10 days and can last from a few days to several weeks in healthy people. For people with weak immune systems, the infection can become chronic and life-threatening. Proper washing of produce can reduce but may not completely eliminate the risk, so combining washing with other safety practices is important.
Frequently Asked Questions
Can you get sick from eating unwashed strawberries and lettuce?
Yes, unwashed produce can carry Cryptosporidium parvum and E. coli bacteria. A 2026 Costa Rican study found these contaminants in fresh produce samples. Washing produce under running water reduces risk significantly, though people with weak immune systems should consider cooking vegetables instead.
What are the symptoms of Cryptosporidium infection from contaminated food?
Symptoms typically appear within 2 to 10 days and include severe diarrhea, stomach cramps, nausea, and vomiting. In healthy people, symptoms usually last days to weeks. In people with weakened immune systems, the infection can become chronic and life-threatening, requiring medical treatment.
How do I properly wash fresh produce to remove parasites?
Wash all produce under running water for at least 20 seconds, rubbing it with your hands or a clean brush. For leafy greens like lettuce and cilantro, rinse each leaf separately. While washing reduces risk, it may not eliminate all parasites, so people at high risk should consider cooking vegetables instead.
Which fresh produce has the most contamination risk?
According to a 2026 Costa Rican study, cilantro had the highest bacterial contamination levels. Produce eaten raw without cooking, like strawberries and lettuce, carries higher risk than cooked vegetables. People with weak immune systems should be especially cautious with all raw produce.
Is Cryptosporidium only a problem in Costa Rica?
No, Cryptosporidium parvum is found worldwide and causes diarrheal disease globally. The Costa Rican study confirms this is an international food safety concern. Proper produce washing and food safety practices are important everywhere, not just in Costa Rica.
Want to Apply This Research?
- Track your produce washing routine by logging each time you wash vegetables and fruits before eating them, noting the type of produce and whether you used running water and rubbing with hands or a brush.
- Set a daily reminder to wash all fresh produce under running water for at least 20 seconds before eating or cooking. For high-risk groups, add a reminder to consider cooking vegetables instead of eating them raw.
- Monitor your gastrointestinal health by tracking any unusual digestive symptoms and correlating them with the types of raw produce consumed. If symptoms like diarrhea develop, note what produce was eaten in the previous 2 to 10 days and report it to a healthcare provider.
This research describes the presence of parasites and bacteria on fresh produce in Costa Rica. While the findings are important for food safety awareness, this article is for educational purposes and should not replace professional medical advice. If you experience symptoms of foodborne illness such as severe diarrhea, stomach cramps, or vomiting lasting more than a few days, contact a healthcare provider immediately. People with weakened immune systems, including those with HIV, cancer patients, pregnant women, and very young children, should consult their doctor about safe food handling practices. This study was conducted in Costa Rica and results may not apply to all regions or countries.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.