Food-Borne Parasites: The “Top Ten” List

By Roberta Attanasio

Food-born parasites affect the health of millions of people all around the world, causing huge social costs. However, we don’t know much about these parasites — where they come from, how they live in the human body, and how they make us sick.

Today (July 1, 2014), the Food and Agriculture Organization of the United Nations (FAO) released, along with the World Health Organization (WHO), a report — Multicriteria-based ranking for risk management of food-borne parasites — as a first step in tackling the problem.

Parasites are organisms that derive nourishment and protection from other living organisms known as hosts. Parasites that are present in food cause food-borne infectious diseases. They are classified biologically as protozoa (single-celled organisms) or helminths (better known as tapeworms, flatworms and roundworms). 

Infectious diseases caused by food-borne parasites have not received the same level of attention as other food-borne biological and chemical hazards. Nevertheless, they cause a high burden of disease in humans, may have prolonged, severe, and sometimes fatal outcomes, and result in considerable hardship in terms of food safety, security, quality of life, and negative impacts on livelihoods. It is difficult to know how widespread these parasites are globally — in many countries it is not compulsory to notify public health authorities of their presence.

• In Europe, more than 2,500 people are affected by food borne parasitic infections each year. In 2011 there were 268 cases of trichinellosis and 781 cases of echinococcosis recorded in the EU.
• In Asia, there is no precise national data but parasitic diseases are known to be widely spread and are recognized as major public health problems in many countries.
• In most African nations there is no data at all on the prevalence of food borne parasites in humans because there of a general lack of surveillance systems.
• In the United States, Neurocysticercosis, caused by Taenia solium, is the single most common infectious cause of seizures in some areas of the US where 2 000 people are diagnosed with neurocysticercosis every year. Toxoplasmosis is a leading cause of food-borne illness and death.

The FAO-WHO report was developed following a request by the global food standards body, the Codex Alimentarius Commission (Codex), to review the current status of knowledge on parasites in food and their public health and trade impacts. FAO’s food safety and quality unit and WHO responded by jointly organizing a global call for information on the problem. Twenty-two nations and one regional body responded, followed by an assessment and analysis by 21 experts on the impact of food-borne parasites.

From this work, an initial list of 93 parasites was developed. The list was then narrowed down to the 24 most damaging parasites based on the following criteria: 1) number of global illnesses, 2) global distribution 3) acute morbidity 4) chronic morbidity and 5) economic impact.

The top ten food-born parasites are:

1. Taenia solium (pork tapeworm): In pork
2. Echinococcus granulosus (hydatid worm or dog tapeworm): In fresh produce
3. Echinococcus multilocularis (a type of tapeworm): In fresh produce
4. Toxoplasma gondii (protozoa): In meat from small ruminants, pork, beef, game meat (red meat and organs)
5. Cryptosporidium spp.(protozoa): In fresh produce, fruit juice, milk
6. Entamoeba histolytica (protozoa): In fresh produce
7. Trichinella spiralis (pork worm): In pork
8. Opisthorchiidae (family of flatworms): In freshwater fish
9. Ascaris spp. (small intestinal roundworms): In fresh produce
10. Trypanosoma cruzi (protozoa): In fruit juices

“Obviously this top ten is a more general, global perspective and does not necessarily reflect parasite rankings at a national level where each country may have more precise information,” said Renata Clarke, head of food safety and quality at FAO.

“But considering the problems they cause, these parasites do not get the attention they deserve. We hope that by releasing a top ten ranking we can increase awareness among policy makers, the media and the general public about this major public health issue,” she added.

The FAO-WHO report lists a number of ways to reduce the risk of parasite infections. For farmers, it advises the use of organic fertilizer, particularly on produce, should be closely monitored to ensure it is composted properly and all fecal matter is removed. Water quality must also be closely monitored. For consumers, it advises that all meat should be well cooked and only clean water should be used to wash and prepare vegetables.