Symptoms, Negative Tests, and Periodicity in Parasitic Infections

August 25, 2006

http://www.explorepub.com/articles/parasite_research1.html

(Explore Issue: Volume 9, Number 1)

Parasitological investigations of large patient populations are

rarely conducted in the United States where the illusion of freedom

from parasitic infections still predominate. Such investigations are

considerably more common in most third world countries where endemic

parasitosis are more readily documented.

Single and concurrent infections of 5 species of protozoans have

been diagnosed in 378 symptomatic and asymptomatic patients from 644

samples examined in the summer of 1996 at the Diagnostic and

Educational Laboratory (DEL) of the Phoenix based Institute of

Parasitic Diseases (IPD) using a concentration-sedimentation technique

(Amin, 1997). Fifty-four (8.4%) were infected with Blastocystis

hominis, 13 (2.0%) with Cyclospora cayetanensis, 50 (7.8%) with

Entamoeba coli, 53 (8.2%) with E. hartmanni, 99 (15.4%) with E.

histolytica/E. dispar, 28 (4.3%) with Entamoeba spp., 9 (1.4%) with E.

coli and E. hartmanni, 53 (8.2%) with B. hominis and Entamoeba spp.,

and 17 (2.6%) with other combinations of protozoan species. More

females were represented in the infected, especially the multiply

infected, patients than in the uninfected. The patient population

varied between 0 and 78 years of age. Very young children were not

multiply infected and only adults were infected with C. cayetanensis.

All single and multiple infections were represented in symptomatic and

asymptomatic patients. (Table 1)

Table 1. Prevalence of protozoan infections in stool samples of

644 symptomatic and asymptomatic patients examined during the summer

of 1996 at DEL-IPD.

Categories No. Tested (%)

Patients with Symptoms No. Tested (%)

Patients without Symptoms

Single infections 233 (43.8%) 38 (33.9%)

Blastocystis hominis 44 (8.3%) 10 (8.9%)

Cyclospora cayetanensis 10 (1.9%) 3 (2.7%)

Entamoeba coli 47 (8.8%) 3 (2.7%)

E. hartmanni 44 (8.3%) 9 (8.0%)

E. histolytica 88 (16.5%) 11 (9.8%)

Multiple infections (above) 95 (17.8%) 12 (10.7%)

Other combinations 14 (2.6%) 3 (2.7%)

Total infected 328 (61.6%) 50 (44.6%)

Not infected 204 (38.4%) 62 (55.4%)

Total examined 532 (100%) 112 (100%)

Enteric and extra-intestinal symptoms were associated with

presumably " harmless commensals " like E. coli and E. hartmanni.

Symptomatic patients infected with E. histolytica/E. dispar markedly

out-numbered those without symptoms.

It is clear from Table 1 that a number of patients had

sub-clinical infections and showed no overt intestinal or

extra-intestinal symptoms. These patients have been treated and their

overall health improved after having been tested, and their parasites

identified, at DEL-IPD.

The most common intestinal symptoms include bloating, diarrhea,

flatulence, cramps, constipation, maldigestion, and malabsorption.

Less frequently a patient may experience bleeding, irritable bowel,

ulcerative colitis, leaky gut, and excess mucus secretion.

Extra-intestinal symptoms often include fatigue, allergies, nausea,

nervous/sensory disorders (memory loss, brain fog, irritability, poor

coordination), skin disorders, pain, and muscle problems. Less

frequent extra-intestinal symptoms may include fever, headache, immune

deficiency, insomnia, weight changes, respiratory and hepatic

symptoms, and peritonitis.

It is also clear from Table 1 that a number of symptomatic

patients had no parasites that were detectable from fecal samples

provided. These cases are probably related to one or both of the

following reasons:

1. Other pathogenic organisms, ex., pathogenic bacteria, can

cause symptoms comparable to those produced by typical parasites.

These may include enterotoxigenic Escherichia coli, Salmonella,

Shigella and/or Campylobactor among others; see Paredes et al. (1996).

Like the typical parasites, these bacterial parasites are also

amenable to treatment with herbal products.

2. Because of the heterogeneous distribution and the cyclic

nature of some of the most common human parasites, infections may not

be detected in fecal samples if collected when parasites are not

running in the main fecal flow; e.g., intervals of many days may

intervene between amoebic " runs " which may make the microscopic

examination of many stool specimens necessary to confirm a positive

Entamoeba histolytica infection (Amin, 1994-95; Hiatt et al., 1995;

Kelsall and Ravdin, 1994). The same kind of periodicity and/or

adherence to the intestinal lining are also known to occur in Giardia

lamblia (see Amin, 1994-95, Walterspiel and Pickering,