Top 10 food parasites

When many people think about properly preparing their food to help eliminate food safety risks, they are often worried about key pathogens, such as E. coli or Salmonella. These pathogens can be very dangerous—most of the illnesses, hospitalizations and deaths from food poisoning are caused by major pathogens.

But a new report from the World Health Organization (WHO) and the Food and Agriculture Organization (FAO) of the United Nations zeroes in on the risk of foodborne parasites—and the most dangerous ones to look out for.

The report compiled a list of 24 foodborne parasites and rated them based on several criteria: the number of global illnesses, global distribution, morbidity-acute, morbidity-chronic, percentage chronic, mortality, increasing illness potential, trade relevance and socio-economic impact.

These parasites are transmitted to humans through fresh or processed foods by animals (typically from feces) or people (usually from inadequate hygiene). The top 10 to found to be of a greatest risk are highlighted below.

  1. Taenia solium—Ranked number one on the list, this parasite is estimated to infect millions worldwide. Most often found in South American, Central American, Southeast Asian and sub-Sarahan African regions, this parasite can infect both humans and pigs. Humans most often come into contact with this particular type of tapeworm through consuming raw or undercooked pork (although other variations of the species exist in beef as well).
    Symptoms: Diarrhea, constipation, indigestion or other mild symptoms. In severe cases, epilepsy, seizures and lesions on the brain.
  2. Echinococcus granulosus—This tropical parasite has been estimated to have been the cause of loss of life of 1–3 million per year. Most human contact comes from dogs, or from ingesting soil, water or vegetables contaminated with infected dog feces. Those who swallow the eggs of the tapeworm are also at risk for infection. Dogs come into contact with the tapeworm by eating home-slaughtered sheep or other livestock.
    Symptoms: Once ingested, the eggs are carried to the liver where cysts can form. Cysts may also appear in the brain, bones, kidney, lungs, etc., all of which may produce no symptoms for years until it’s large enough to be felt by physical examination. Additional symptoms can include pain in the abdomen, bloody sputum, chest pain and severe skin itching.
  3. Echinococcus multilocularis—This parasite can be found in Europe, Asia and North America. Like E. granulosus, dogs and cats can be good hosts for this parasite, along with voles, muskrats, deer mice and gerbils. Humans come into contact with the coat of the animal, or breathe in eggs from the dog’s coat that has gotten into the air or ingesting dog feces.
    Symptoms: See E. granulosus.
  4. Taxoplasma gondii—This is a single-celled parasite found throughout the world. Millions in the U.S. are infected every year, although most with healthy immune systems can keep the parasite from causing illness. Infection occurs through consuming undercooked meat, such as pork, lamb or venison; not washing hands or utensils thoroughly after touching raw meat product or through cat feces that contain the parasite.
    Symptoms: Many who have been infected may feel like they have a flu that lasts for a month or more, but the parasite can also cause damage to the brain, eyes or other organs.
  5. Cryptosporidium spp.Commonly known as “Crypto,” these species can infect animals and humans. Water is the most common method of transition, and is a frequent cause of waterborne disease in the United States.
    Symptoms: While some who are infected show no signs at all, others can experience stomach cramps, dehydration, nausea and fever that can last anywhere from a few days to a month.
  6. Entamoeba histolytica—This single-celled organism can infect humans and primates. The name of the infection it causes is amebiasis (or amoebiasis). Transmission occurs through fecal contamination of water or foods, as well as direct contact with dirty hands or objects and even sexual contact.
    Symptoms: Infections can last for years and may be accompanied by no symptoms. Those with symptoms can have gastrointestinal issues or dysentery.
  7. Trichinella spialis—Prevalent mostly in Mexico, but also found in southern Asia and Africa, South America and the Middle East, this parasite has a very broad host range. The parasite particularly gravitates to carnivorous or omnivorous animals, but is usually transmitted to humans through eating raw or undercooked pork.
    Symptoms: Muscular weakness and twitching, edema around the eyes, puffy face, swelling extremities and/or damage to the heart, nervous system and other organs.
  8. Opisthorchiidae—This family includes various dignean parasites, according to the report, most important of which are Clonorchis sinensis, Opisthorchis viverrini and Opisthorchis felineus. The parasite is transmitted to humans via ingestion of the flesh or skin of freshwater fish.
    Symptoms: This parasite has the potential to be carcinogenic. Less severe infections can include indigestion, abdominal pain or diarrhea.
  9. Ascaris spp.—According to the Centers for Disease Control and Prevention (CDC), an estimated 807—1,221 million people worldwide are infected with this parasite. They are parasitic worms often found in the soil, transmitted by ingestion of the eggs. As of now, it is uncommon in the United States.
    Symptoms: Often those infected show no symptoms. However, some can experience mild abdominal discomfort. In severe cases, the parasite can cause intestinal blockage or impaired growth in children.
  10. Trypanosoma cruzi—One of the five parasitic diseases targeted by the CDC for public health action is Chagas disease, caused by the Typanosoma cruzi parasite. This parasite is only found in the Americas, and is transmitted by insect vectors.
    Symptoms:  Chagas disease has two types: acute or chronic. Those with the acute form of the disease can have symptoms that last for weeks or months, which include fever, swelling around where parasite entered. Rarely, the acute infection may result in inflammation of the heart, brain or lining of the brain. Those who have the chronic form of the disease may not even be aware they have it and may have no symptoms for life. However, some may develop severe problems, including heart rhythm abnormalities or a dilated heart, esophagus or colon.

For more information on the parasites and the United Nations report, please click here.  

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