Digestive Conditions / Parasites

The two major classifications, predator and scavenger, are differentiated by their nutritional relationships.7 Further modification leads to symbiosis and commensalism. Parasitism is where the host is injured through the activities of the parasite during an intimate and protracted relationship between the two.

Some organisms have a changing interaction with their host — sometimes as a parasite and sometimes commensal.

Few people realize the enormous impact of parasites and diarrheal diseases on human health. Diarrheal diseases ( bacterial as well as parasitic) constitute the greatest worldwide cause of morbidity and mortality.1 Numerous studies show parasitic infection up to 99% in undeveloped countries.2

In the United States, diarrheal diseases caused by intestinal infections are the third leading cause of morbidity and mortality. Most Americans have grown up with modern sanitation, and it is often assumed parasitic infections are encountered only in impoverished foreign countries.3 According to Neva, "The United States citizen can acquire amebiasis, giardiasis, pinworms, and strongyloides, for example, without so much as a passport application."4

The increase in worldwide travel, coupled with increasing immigration into the United States, contributes to the spread and incidence of parasitic infections. In a study of outpatients at the Gastroenterology Clinic in Elmhurst, N.Y., a 74% incidence of parasites was found.5 A total of 20% of this population harbored pathogens. One survey of public health laboratories reported that 15.6% of specimens examined contained a parasite.6 At Great Smokies Diagnostic Laboratory, almost 30% of specimens examined are positive for a parasite.

The prevalence of parasitic infections in the United States is difficult to quantify. Most figures are underestimates that can be traced to inadequate parasitologic training of physicians and laboratory technicians.3 As detection methods become more accurate and sophisticated, physicians are recognizing the increased incidence of parasitic infection and its relationship to a broad spectrum of diseases.

Common Protozoal Parasites

Information on parasites is available in several excellent texts.^24,32 The protozoa that parasitize the intestinal lumen belong to five groups: amoebae, flagellates, ciliates, coccidia and microsporidia. Most are transmitted through fecally contaminated food, water or other materials. Contaminated water supplies are a particular problem because many cysts are not killed by usual levels of chlorination.

Blastocystis hominis

Blastocystis hominis is the most prevalent parasite but often isn’t detected due to poor laboratory techniques. ³³ At Great Smokies Lab, Blastocystis is found in more than 20% of clinical specimens.³⁴ The weight of evidence supports treating it as a potential pathogen (disease causing organism).³⁵ Together with other weak pathogens, it is associated with many chronic conditions, including irritable bowel, chronic fatigue and arthritic/rheumatoid complaints.

Three forms have been identified, and the vacuolated form is most commonly seen in fecal specimens. Blastocystis has been found to produce gastrointestinal cramps, vomiting, sleeplessness, nausea, weight loss, lassitude, dizziness, flatus, anorexia, and pruritus. B. hominis is often found in patients with classic symptoms of irritable bowel syndrome.³⁶ Treatment with metronidazole has been found to eradicate the organism.

Blastocystis hominis may be highly variable in its pathogenicity (its ability to cause disease). The organism is present in a number of healthy individuals, and an asymptomatic carrier state has been postulated. ³⁷ In many patients with gastrointestinal illness, this organism is the only identifiable parasite, and these patients improve when Blastocystis is eradicated.³⁵ We find its presence highly correlates with gastrointestinal symptoms; and, along with others, suggest it may be a pathogen in symptomatic patients.^14,38

Dientamoeba fragilis

Dientamoeba fragilis, a pathogenic flagellate and one of the most frequent parasitic infections, often goes undetected due to poor laboratory technique.^39-41 Symptoms include diarrhea and abdominal discomfort. It resides in the colon, has a cosmopolitan distribution, is found as a trophozoite and has no cyst stage. Transmission is by direct ingestion of the trophozoite and can be found within the eggs of some helminths, especially pinworms.

Amoeba

Amoeba including Endolimax nana, Entamoeba histolytica, E. coli and E. hartmanni are cosmopolitan in distribution. E. histolytica is linked to acute diarrhea and GI distress. However, individuals may harbor E. histolytica without obvious symptoms. Lesser known organisms Entamoeba coli, E. hartmanni and Endolimax nana are associated with chronic GI symptoms, although not generally recognized as pathogens. There is an association between E. nana infection and reactive arthritis.⁴² Variations in an organism’s virulence and/or the host resistance may explain variations in the degree of pathogenicity.

There are two forms of amoeba — the motile trophozoite and the cyst - and transmission is by ingestion of the cyst stage. The cyst, the infective form of the organism, resists environmental changes and may spread from person to person or indirectly via food or water. Symptoms occur primarily with tissue invasion and include intermittent diarrhea and constipation, flatulence and cramping. Intestinal infection symptoms include mild diarrhea, food intolerance, fatigue and dysentery.

Giardia lamblia

Giardia lamblia, a flagellate with cosmopolitan geographic distribution, is found in duodenal contents and bile. In the duodenum it can be demonstrated in the mucosal crypts where it attaches itself to the mucosal cells, causing gastroenteritis. When swept into the fecal stream, the trophozoite encysts. Consequently, most fecal specimens contain the encysted parasite rather than the flagellated trophozoite form, which is usually found only in severe diarrhea. In the cyst (resistant) form, they spread the disease from host to host by fecal/oral routes, either directly (as between children in day-care centers or between sexual partners) or by food and water.⁴³ Waterborne epidemics involve mountain streams, well water and even some chlorinated community water systems.

Iodamoeba butschlii

Iodamoeba butschlii is an amoeba with a low pathogenicity associated with chronic complaints. It has a cosmopolitan distribution and is located in the lumen of the colon and cecum. Transmission is by ingestion of the cyst stage.

Fungal conidia

Fungal conidia are yeast. They are very small (two to four microns), have considerable structure (typically with pointed ends and an interior vacuole), and are difficult to culture. The few studies on this organism cite its ability to ferment complex polysaccharides to produce alcohol. In a recent review of Great Smokies’ parasitology results, we found fungal conidia in 5.4% of the samples.⁴⁴ They were more prevalent in women and frequently found in the absence of other parasites. Almost all the patients suffered from gastrointestinal complaints, but diarrhea (38%), gas (33%), and bloating (33%) were most common.

At this time we know little about fungal conidia pathogenicity. Our advice is to put fungal conidia in the same category as Blastocystis hominis or yeast overgrowth and treat (or not treat) with the same criteria.

Intestinal helminths

Intestinal worms are a leading cause of morbidity and mortality and usually diagnosed by detection of eggs or larvae in fecal specimens. Some of the more common helminths are Nematodes, including Enterobius vermicularis, Ascaris lumbricoides, Trichuris trichiura, Necator americanus and Strongyloides stercoralis.

Shown below are microscopic images of actual parasites:

Click on each image for a larger image This image shows a small parasite on the wall of the large intestine. Endolimax nana Endolimax nana Entamoeba histolytica Entamoeba histolytica

In general, a parasite interferes with the host's vital processes through secretions, excretions or other products.⁷ These products include proteolytic enzymes that erode the intestinal wall, enterocytotoxins (from E. histolytica), and serotonin-like products.⁸

Parasitic infections can trigger autoimmune reactivity. The parasite might cause tissue destruction, thus releasing high amounts of self antigens which stimulate the autoreactivity.⁹