Will Eating Oranges Kill Parasites?

Oranges are a popular and relatively
affordable fruit. It would be great if
claims that they kill parasites were
true. Image by Rosino: CC BY-SA 2.0

Have you read that oranges have antiparasitic properties, and that eating them can help keep parasites away? Is there any truth to this claim? It’s certainly true that many substances derived from plants are antiparasitic, so what’s the evidence for oranges?

Antiparasitic Oranges - The Science

A search for papers on the antiparasitic properties of oranges yields very little, but when I looked at orange essential oil and parasites, I found some research. Studies have used orange oil to treat parasites in fish, sheep, gerbils, and in the lab, but none (at least none that I could find) have used human subjects.

A study by Squires and colleagues investigated whether an orange oil emulsion would kill a roundworm parasite in gerbils and sheep. These researchers found that, at a high enough dosage, the treatment killed a significant number of the worms, suggesting that it might be useful in animal parasite control.

In contrast, in a 1990 Japanese study, “many essential oils were found to be nematocidal to the larvae of dog-roundworm, Toxocara canis,” but essential oil of oranges wasn’t one of the star examples. In the lab, only about a third of larvae were killed by orange oil, and only after 24 hours of exposure.

Hirazawa and colleagues studied whether plant essential oils could be used to kill a flatworm that infests puffer fish. They looked at caprylic acid (derived from palm and coconut oil, and human milk), orange oil, peppermint oil, and cinnamon oil, exposing the parasites to the oils in the lab. The researchers found that orange oil is the only one of the four that does not affect this parasite.

Other studies found orange oil to be ineffective at killing honey bee mites, and ineffective at killing kissing bugs, the vector of Chagas' disease. So it looks like orange oil may kill some parasites, under specific conditions, but it’s no panacea. The good news is that it does appear to be useful, if used properly, in the control of subterranean termites.

Oranges vs Orange Essential Oil

Essential oils are derived from plants using a distillation process. They are highly concentrated essences, and orange oil is generally made from the peel of the fruit. Obviously, eating an orange is very different from ingesting orange oil (and I’m not sure that this would be safe). I wonder how many oranges one would have to consume (including the peel) to get any benefit, assuming you had a parasite that they would kill.

I believe it’s safe to say that there is no convincing evidence that orange oil is a good way to keep parasites at bay, and there is no evidence at all for oranges.

Pity.

Sources

Hirazawa, N., T. Ohtaka, and K. Hata. 2000. “Challenge trials on the anthelmintic effect of drugs and natural agents against the monogenean Heterobothrium okamotoi in the tiger puffer Takifugu rigripes.” Aquaculture, 188, 2000

Nakamura N., F. Kiuchi, Y.Tsuda et al. 1990 "Nematocidal and bursting activities of essential oils on the larvae of Toxocara canis." Shoyakugaku Zasshi: 44(3).

Squires J., J. Foster, D. Lindsay et al. 2010. "Efficacy of an orange oil emulsion as an anthelminticagainst Haemonchus contortus in gerbils (Meriones unguiculatus) and in sheep."  Am.Vet Parasitol. Aug 27;172(1-2):95-9. doi: 10.1016/j.vetpar.2010.04.017. 

Cryptosporidium: A Parasite That Gets Into Drinking Water and Swimming Pools

Swimming pools become contaminated with infective
oocysts of Cryptosporidium when ill people have
accidents in the water.
Image courtesy of the US Dept of State.

Cryptosporidium spp. are tiny parasites that cause outbreaks of diarrhea. Contaminated drinking water is a common source of cryptosporidiosis, but there are others, including swimming pools and food.

At least two species of Cryptosporidium infect humans, and they are increasingly familiar causes of outbreaks. In recent years, online searches have constantly turned up swimming pool closures and boil water orders attributed to Cryptosporidium. Such outbreaks may indeed be more common; we may be getting better at identifying the parasites in outbreaks; and it may be that Internet reports mean that more people hear of it – all three factors likely play a part in the raised profile of these parasites.

When Cryptosporidium contaminates a municipal water supply, it can make many people sick at once, and this happens relatively easily because of the parasite’s small size and its ability to survive chlorination.

An oocyst (pronounced oo-oo-cyst) of  Cryptosporidium sp., the infective stage of the organism, is spherical and only about three to five one-thousandths of a millimetre wide. Environmentally resistant, it survives cold, chlorination, and salt water. It’s found in surface waters all over the globe - municipalities that use surface water supplies must do more than chlorinate water to avoid an outbreak. Most rely on filtration.

In the summer of 2013, an outbreak of cryprosporidiosis in Baker City, Oregon highlighted the risks of unfiltered water supplies, even when the watershed appears pristine. Even municipal water filtration systems can famously fail - more than 300,000 people got cryptosporidiosis in Milwaukee in 1993 due to inadequate treatment and filtration. In terms of numbers, a contaminated water supply is the most common source of human infections, but how does Cryptosporidium get into the water, and how else can we catch it?

Cryptosporidium in Livestock

Dairy and beef cattle suffer from and spread Cryptosporidium parvum. Young calves catch it and suffer severe diarrhea, while older cattle continue to carry the parasite and spread it. Runoff from pastures into rivers and wells after heavy rain is an important source of Cryptosporidium in surface waters. Ranched elk and bison also spread the parasite.

Cryptosporidium in Human Sewage

Untreated sewage from human communities often contains oocysts of Cryptosporidium. When sewage effluent is discharged into bodies of water without proper treatment, as it frequently is, especially after rainfall when treatment plants are overwhelmed, oocysts are discharged with it.

Canada Geese and other water birds could potentially
spread Cryptosporidium from cattle pastures to
distant surface waters.
Image by Robert Lawton; CC BY-SA 2.5.

Cryptosporidium in Wild Animals

Many species of wild animals can be infected with Cryptosporidium parvum, one of the species that infects humans. Dogs, cats, goats and mice are among them. Although this does not appear to be a significant source of water contamination, migratory birds may be a different story.

Cryptosporidium parvum is known to pass unharmed through the gut of a Canada goose without making the bird sick. Thus a goose can ingest millions of oocysts while pecking corn kernels from cow dung in Maryland, and discharge them into a watershed in Pennsylvania. It’s not clear how much geese and other migratory birds contribute to the spread of Cryptosporidium.

Direct Person to Person Spread of Cryptosporidium

Oocysts of Cryptosporidium are infective as soon as they are passed in stool. Thus, an infected person can pass on the parasite with dirty hands or objects contaminated with feces. Likewise, infected animals can pass the infection directly to other animals or to humans.

Cryptosporidium in Swimming Pools

It’s fairly common for swimming pools to become contaminated with Cryptosporidium - sometimes people go swimming and have minor “accidents” in the water, or feces work their way out of leaky diapers. Chemical treatment of swimming pools must reach high concentrations in order to kill the oocysts and pool filtration systems cannot remove them —or at least not fast enough to prevent some swimmers from swallowing some with a mouthful of water.

Food and Cryptosporidium

 

Food items can potentially be contaminated with oocysts of Cryptosporidium, particularly produce that has been irrigated with contaminated water. Because of this, and other disease-causing organisms that may be present, produce that will be eaten raw should be thoroughly washed.

Oocysts of Cryptosporidium have been found in oysters along the eastern seaboard of North America where human sewage effluent and runoff from agricultural lands flows into the ocean, probably because . oysters feed by filtering nutrients from the water around them. Eating raw oysters or other raw shellfish is, therefore, a potential source of cryptosporidiosis.

Though it is more common in warm climates,  Cryptosporidium is found in surface water everywhere - never drink untreated water and heed any boil water advisory issued by your local water utility.

Sources

Alberta Government. “Relationship Between Beef Production and Waterborne Parasites (Cryptosporidium spp. and Giardia spp.) in the North Saskatchewan River Basin.” Agriculture, Food and Rural Development. Apr 2006.

Graczyk, T. K. et al. “Giardia sp. Cysts and Infectious Cryptosporidium parvum Oocysts in the Feces of Migratory Canada Geese (Branta canadensis).” Applied and Environmental Microbiology 1998 Jul; 64(7), pp. 2736-8.

Roberts, Larry S. and John Janovy Jr. Foundations of Parasitology 8th Ed. Boston: McGraw Hill, 2009.

Terrey. Lynn. “Goats Not Behind Baker City Parasite Suspected of Sickening Thousands, Officials Say.” Oregon Live: The Oregonian; Aug 21, 2013 Accessed Aug 21, 2013.