Common parasites found in the gastrointestinal tract and alternative treatments

Review Article

Introduction

Human parasites include various protozoa and worms that infect the body and cause parasitic disease. Some parasites adapt to living in the lumen of the intestine where conditions are anaerobic, while others reside in the blood and tissues in aerobic conditions. While many parasites are considered harmless, others can have damaging effects on human health, such as giardia and Dientamoeba fragilis.1

Anthelmintics are a group of antiparasitic treatments that expel parasitic worms (helminths) and other internal parasites from the body without causing significant damage to the host. These forms of treatment often involve a range of traditional herbs and plants such as Artemesia absinthium (wormwood), Syzygium aromaticum (cloves), Juglans nigra (black walnut), berberine and Allium sativum (garlic).

Traditional approaches to intestinal parasitic infections are reviewed here with the objective of eradicating the parasite and strengthening gut immunity. While many traditional approaches may help in controlling or expelling the parasite, pharmaceutical drug interventions are required for hookworms (Necator americanus and Ancylostoma duodenale), tapeworms, nematodes, flukes and malaria (Plasmodium spp.).2

Giardia

Giardia is the most common parasite linked to intestinal diseases across the world, with cases estimated at 280 million per annum. 3,4,5 Giardia is a single-celled protozoan parasite that can cause acute giardiasis (diarrhoeal disease).6 It is found within the proximal small intestine of animals and humans, where it infects the mucosa.3 There are two stages in the life cycle of giardia: cysts that are transmitted through faeces; and trophozoites which infect the small intestinal mucosa.3 The disease is transmitted by contact with infected humans and animals or through water, soil, faeces or food.6 Water is the main medium of cross contamination and giardia cysts can survive in cold water and even water treated with chlorine.7

Common symptoms of giardia are fever, abdominal cramps, occasional vomiting, weakness, greasy stools, lack of appetite, weight loss, nausea, flatulence, dehydration and belching.6 Some patients do not present with symptoms, however patients who do develop symptoms can have them for two to six weeks or even longer.6 Patients with chronic giardia have been found to have impaired glucose absorption, affected epithelial barrier function and a 75% decrease in mucosal surface area.8 In most cases giardia is self-limiting, however in patients who are immunocompromised, elderly or infantile, symptoms can be persistent and life threatening.4 Data suggests that malnutrition and growth retardation can be caused by chronic giardiasis; in a study of Israeli infants, impaired growth was observed post giardia, indicating that giardia was causative.9,10,11,12

Giardia has been found to be resistant to drug treatment. A study analysing an outbreak of giardia in a non-endemic area found that one-third of the patients had symptoms recur post treatment.13 A large proportion of symptomatic patients are not cured by common drug treatments and are affected by irritable bowel syndrome (IBS).7,14

Blastocystis hominis

Blastocystis hominis is the most commonly found single-celled enteric parasite living in the intestines of humans and animals.15,16 The transmission of blastocystis is via the faecal–oral route and is associated with water contaminated with faecal cysts.17 The cysts of blastocystis can form resistance to chlorine disinfectant and are able to last for up to one month in pH levels of the stomach.18

Blastocystis has been linked to IBS and is associated with abdominal pain, lack of appetite, cramps, flatulence, fever, vomiting, growth retardation, nausea, itching, urticaria and diarrhoea.18 Symptoms from blastocystis can be chronic, lasting over several years.18
Blastocystis tends to be most prevalent in children aged seven to thirteen.18

In a study of individuals randomly selected from the general population, 19% hosted Blastocystis hominis.19 This study also found a significant correlation between IBS and Blastocystis hominis infection.19 Symptoms most commonly found were diarrhoea and abdominal pain, which lasted less than a month.19 After treatment with metronidazole, 59% of patients had recurring symptoms, indicating that this drug does not have a high success rate.19

In a study of over 12,000 patients, 17% had Blastocystis hominis in their stool and symptoms included constipation, abdominal pain, fatigue, diarrhoea, alternating diarrhoea and constipation, and vomiting.20

In the past blastocystis was regarded as harmless and recognition of it as a pathogenic parasite has been resisted.20 After studying the correlation of symptoms with blastocystis, a pathology specialist hospital and research centre discontinued their practice of stating that Blastocystis hominis is ‘generally considered as non-pathogenic’. 20 Specifically they found that symptoms associated with Blastocystis hominis resolved after the disappearance of the parasite in the faeces.20 This research group and pathology centre stated that this organism should be recognised as a causative pathogen, especially in cases without any other known cause and high counts of Blastocystis hominis in the stool.20

Dientamoeba fragilis

Dientamoeba fragilis is a common cause of intestinal illnesses, with the possibility of causing chronic infection.21 It is a facultative protozoan parasite that lives in the colon of humans and monkeys.21,22,23 Cross infection of Dientamoeba fragilis occurs with the oral uptake of infected faeces that contain cysts.22 In most cases that are positive for Dientamoeba fragilis, gastrointestinal symptoms are present.23 Diarrhoea and abdominal pain are the most common symptoms.24,25 Symptoms can be chronic and last for weeks or months depending on the case.23 Dientamoeba fragilis is most prevalent in patients under the age of ten.21,24,25 Detection of Dientamoeba fragilis is difficult because of irregular shedding; up to ten stool samples may be required to detect the parasite, increasing the percentage of positive results by 31%.21,25

In a faecal analysis of patients with gastrointestinal complaints presented to hospital, the prevalence of Dientamoeba fragilis was 5.2%, the second most common pathogenic parasite after Blastocystis hominis.21 Of the patients that were positive for Dientamoeba fragilis, 88% presented with intestinal symptoms.21 The most common symptoms were diarrhoea, abdominal pain, loose/abnormal stool, faecal urgency, fever and vomiting or nausea.21 Diarrhoea lasted on average from three days to a week.21 Twenty-five per cent of patients had chronic infections, with prolonged diarrhoea persisting for over a fortnight.21 Metronidazole was insufficient to treat Dientamoeba fragilis in 21% of patients; an insufficiency noted by other authors.21,26

Alternative treatments for intestinal parasites

Due to the developing resistance of parasites to drugs and reductions in chemical controls because of changing regulations, there is a need to develop new medications for effective parasite control.27 In particular, more effective anti-giardia drugs are now required to counteract the drug-resistant giardia strains that have emerged.28 In a randomised, single-blinded clinical trial it was found that Saccharomyces boulardii had a 94.4% success rate in treating the symptoms and presence of Blastocystis hominis parasites.29 In addition, the use of probiotics in combination with an anti-parasitic treatment may help prevent any adverse changes to normal gut flora which may lead to other infections.

Clove bud oil (eugenol)

Studies have found that eugenol (an essential oil found in cloves), which forms 88% of the clove plant Syzygium aromaticum, has effects on parasite growth and adherence.28,30 A study found that both Syzygium aromaticum and eugenol kill 50% of giardia parasites, specifically effecting trophozoite adherence after the first hour of incubation.28 Eugenol has also been effective for the treatment of other parasites such as Leishmania amazonensis.31

Wormwood

Artemisia absinthium (wormwood) has potential as an antiparasitic and was found to have high nematocidal activity while being non-cytotoxic to macrophage cells.27 Artemisia absinthium has been used as a medicinal herb across the world due to its antiprotozoal, cytotoxic, antimalarial, antipyretic, antioxidant, antimicrobial, anthelmintic, antidepressant and neurotropic properties.32 Artemisia absinthium has been found to reduce parasites such as Trichinella spiralis (roundworms) by 66%.27 The major components of Artemisia absinthium are (Z)-epoxyocimene and chrysanthenol.27 Artemisia absinthium has also been found to have antiparasitic activity against Trypanosoma cruzi and Trichomonas vaginalis, which are the parasitic agents of Chagas’ disease.33 Eight million people are affected by this parasite in Latin America, with infection spreading to the USA and Europe. There are approximately 1400 cases of Trypanosoma cruzi in Australia annually.34

In a study measuring the toxicity of Artemisia absinthium components they found two different chemotypes: sabinyl acetate + thujones and sabinyl acetate + (Z)-epoxyocimene.32 The most toxic compounds were found to contain thujones (12.3%).32 The Therapeutic Goods Association of Australia (TGA) only allows thujones to the level of 3.99%. Therefore, it is important to prescribe only TGA-listed artemisia products when concerned about toxicity.

Black walnut

Juglans nigra (black walnut) hulls are traditionally considered to be anti-parasitic. The hulls of the Juglans nigra tree contain the naphthoquinone compounds juglone and plumbagin, both of which exhibit anti-parasite properties. Juglans nigra is considered an anthelmintic herb used traditionally to help rid the body of worms. Studies indicate that plumbagin inhibits the motility of and hatching of first stage larvae of Haemonchus contortus. Plumbagin has also been found to partially inhibit embryonic development of Ascaris suum.35 Black walnut has a low potential to cause toxic reactions.2

Berberine

The alkaloid berberine is found in several plants including Hydrastis canadensis (goldenseal), Mahonia aquifolium (Oregon grape) and Coptis chinensis (goldthread). Several studies have found that berberine has growth-inhibiting activity against giardia, Entamoeba histolytica and Trichomonas vaginalis. An aqueous extract of C. chinensis has been shown to inhibit B. hominis in vitro.2

Garlic

The allicin compound derived from garlic appears to inhibit the sulfhydryl-dependent enzymes in protozoa.2 Garlic paralyses and has a moderate lethal effect on Ascaris lumbricoides in vitro.2 Garlic extract containing allicin has been found to be effective against Rhabditis spp. and the eggs of A. suum in vitro.36

References

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