Conventional Diagnosis of Parasites
Following are some conventional procedures for determining if parasites are present. I myself would tend to take
a regimen of antiparasitics ($20-40) if parasites are suspected and attempt to diagnose the condition empirically. However, for those who want to go the conventional route, this is how it is done.
It is usually worthwhile to look into more involved tests if parasites are
suspected. It is estimated by some experts that taking a fecal swab, which
is the maximum extent to which most MDs attempt to diagnose larger parasites,
results in less than a 5% detection rate even when there is an
infection in the digestive tract. Of course, this technique is competely
useless for parasites which are outside the digestive tract. This may explain
why conventional medicine is completely clueless on the potential extent of
The first method typically recommended for amoeba, worms, giardia, and such is the purged stool test. A strong purgative, like Fleet Phospho-Soda, is taken. The next day samples of the stool are preserved in formaldehyde after each evacuation and examined microscopically. Regardless of their type, parasites rarely appear before the
fourth evacuation, and often as many as twelve are required to yield a positive sample or rule out intestinal parasite involvement. Well, rule it out to a 50% degree of certainty anyway.
Even after the 12th purged stool tests negative, some physicians may still suspect parasite involvement (not in the US or course, where they usually don't make it past one fecal swab, much less 1, 4, or especially 12 purged stool samples). In this case, the Bueno-Parish test can be performed for identifying giardia or cryptosporidium. A small rectal speculum is used to gather rectal mucus and can often identify parasites that did not appear in the purged stool. In Gittleman's "Guess What Came To Dinner" she states, "Using this method, physicians (not in the US) found almost 50% of patients previously diagnosed as having IBS were in reality suffering from giardiasis. The patients had suffered with misdiagnosed bowel problems for an average of seven years."
For giardia and strongyloides that do not show up in the purged stool or rectal specula, the string test can be used. A capsule which contains a string is swallowed after the end of the string is pinned to the cheek. After four hours, the string is hauled back up and examined with a microscope. This often yields results when the purges and rectal speculation fail to.
Many parasites, likely the majority, do not inhabit or are only transitory visitors to the digestive tract and cannot be diagnosed with the above methods. When this is the case, other tests are used.
There are some blood parameters that, when skewed, may indicate parasites. Roundworm, hookworm, toxocara, pinworms, and strongyloides sometimes cause a high EOS count on a CBC. High EOS count is usually misdiagnosed by physicians in the US as an indicator of common allergy, not realizing that the primary allergen is the parasite itself.
Abnormal levels of vitamins, minerals, and enzymes can indicate parasitic
The most straightforward way to diagnose parasites with exposure to the blood is with microscopic examination. A sample of blood is taken at regular intervals, preferably every 4-6 hours for 72 hours around the clock, since some parasites only "come out to play" in the middle of the night. As with any microevaluation of body samples, as with feces, this also relies on someone happening to pick out the needle in the haystack by finding filaria, eggs, or other manifestations of parasites with blood exposure.
Immunological profiles of the blood can be used to indicate some parasites unless the immune system has been greatly
hampered, as is often the case with parasite infection. When this is used, antibodies to organisms are checked for pathogens like entamoeba, strongyloides, blood/liver/lung flukes, heartworm, toxoplasma, malaria, filaria, trichenella, etc.
When some parasites are suspected, like entamoeba, roundworm, hookworm, strongyloides, and pneumocystis, sputum tests may indicate the infection. Some parasites, notably roundworms, inhabit the lungs during part of their life cycle (causing bronchitis and potentially asthma). When the larvae are coughed up, they are typically swallowed and reinfest the digestive tract. They reproduce and start migrating to the lungs again.
Blood flukes can be diagnosed through urine sediment examination. Filaria and trichomonas infections can also be detected in this manner.
Swabbing the perineal area can often detect pinworms, even though they are rarely found with purge or rectal specula procedures. Since they come out the anus at night to lay eggs, the eggs can usually be detected with a tape swab of the perineal area taken first thing in the morning. This can also recover eggs of pork tapeworm, beef tapeworm, and blood fluke. Scrapings of the perineal area can reveal amoebal infection.
Since many parasites embed in the tissues they inhabit, detection is not possible without invasive procedures. Muscle biopsy can reveal pork tapeworm or trichenella. Rectal biopsy can reveal flukes, and liver biopsy is used for visceral larva migrans. Hydatid cysts are biopsied to determine the type of tapeworm which inhabits the cyst. Needle biopsy can show heartworm in the lungs as well as pneumocystis. Lymph biopsy can be used to detect toxoplasmosis.
Aspiration of fluids is necessary to get a reliable diagnosis for some parasites. Entamoeba may require aspirations of the colon, liver, rectum, or lung. Giardia and strongyloides can be aspirated from the duodenum or gall bladder. Toxoplasmosis or leishmania may be revealed through aspiration of the lymphs.
Some parasite can only be detected with CT scans or MRIs. Brain lesions can be caused by toxoplasmosis or tapeworms. A CT of the eye can show trapped ocular larva migrans, often mistaken as retinoblastoma. Given the dismal lack of training of MDs in the US on detecting parasites, I wonder how many people are treated for malignancies when these parasites, or others which produce growth factors, are a problem?
Here are a few synopses of studies done on diagnosing parasite conventionally.
Strongyloidiasis. The protean parasitic infection.
Schneider JH, Rogers AI
Division of gastroenterology, University of Miami School of Medicine, USA. JSchneigi@aol.com
To turn a well-known phrase regarding history, those who forget to diagnose strongyloidiasis will be condemned to rediscover it. The often protean manifestations of this disease cannot be emphasized enough. The parasite's unique life cycle enables it to live for decades in an unsuspecting host, presenting with symptomatic disease only occasionally. Making a definitive diagnosis may be difficult and requires persistence. A good history should reveal whether a patient belongs to a high-risk group. The physician should strongly suspect the diagnosis when nonspecific cutaneous, pulmonary, and gastrointestinal symptoms coexist. Unexplained enteric bacteremia or meningitis may be important clues to diagnosing disseminated disease, which carries a high mortality rate. Therapy is available, and advances are being made to make it more tolerable. Follow-up for eradication is laborious yet essential: In patients at high risk for disseminated disease, invasive procedures may be warranted to prove eradication. Incomplete therapy puts the patient at further risk for significant complications in the future.
Clin Lab Med 1995 Jun;15(2):307-31
The diagnosis of old and new gastrointestinal parasites.
Long EG, Christie JD
Division of Bacterial and Mycotic Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
For the foreseeable future, light microscopy will continue to be the method of choice for diagnosing gastrointestinal parasites. However, in selected circumstances, the use of commercially available immunofluorescent kits will supersede the use of routine light microscopy for diagnosis of Giardia lamblia and Cryptosporidium parvum. These techniques may used to diagnose invasive amebic infections caused by E. histolytica in the future. Pooling stool samples from the same or even different patients may offer a means to process specimens in a more efficient and cost-effective manner without lowering the predictive value of an ova and parasite examination. Although we suggest that, with some exceptions, stools for ova and parasite examination should not be accepted past the fourth day of hospitalization, we cannot recommend the use of a single stool sample for diagnosis without extensive studies in individual parasitology laboratories. Techniques have still not been developed for the optimum methods of concentration of stool for diagnosis of coccidian infections. For most laboratories, the diagnosis of microsporidian infections remains problematic because of the lack of a commercial source for oocysts to provide positive control material. (Note: There is now a commercial source for oocysts available.)
Eur J Clin Microbiol Infect Dis 1995 Jan;14(1):46-9
Evaluation of the optimal number of faecal specimens in the diagnosis of cryptosporidiosis in AIDS and immunocompetent patients.
Clavel A, Arnal AC, Sanchez EC, Varea M, Castillo FJ, Ramirez de Ocariz I, Quilez J, Cuesta J
Servicio de Microbiologia y Parasitologia, Hospital Clinico Universitario, Zaragoza, Spain.
This study determines the optimal number of faecal samples that should be examined in order to minimize the occurrence of false-negative results in the diagnosis of cryptosporidiosis using routine techniques. A total of 23,023 faecal samples from 10,870 patients submitted for parasitological examination were processed by the formalin-ethyl acetate concentration technique and stained using a modified Ziehl-Neelsen method. Cryptosporidiosis was diagnosed in 232 patients (2.13%), 44 of whom were infected by HIV, the prevalence rate in this population group being 15.54%. The increase in the number of diagnoses obtained by the examination of n and (n-1) specimens was evaluated statistically. This study found that three is the optimal number of faecal samples that should be examined when cryptosporidiosis is suspected in immunocompetent patients; whereas, only two samples are required for diagnosing this protozoosis in AIDS patients.
Schweiz Arch Tierheilkd 1995;137(9):438-44
Diagnosis of liver flukes in cows--a comparison of the findings in the liver, in the feces, and in the bile.
Braun U, Wolfensberger R, Hertzberg H
Klinik fur Wiederkauer- und Pferdemedizin, Universitat Zurich.
Percutaneous ultrasound-guided cholecystocentesis and aspiration of bile were attempted in 176 cows. These same procedures were performed in another 100 cows immediately after slaughter. The bile samples were examined microscopically for large and small liver fluke eggs. In addition, a fecal sample from each cow was examined for liver fluke eggs. The findings of both groups were summarized, and the results of the fecal and bile sample examinations were compared. In all cows the liver was examined for flukes, and the results were used as a reference. Of 41 cows in which adult flukes were found in the liver, 28 had F. hepatica eggs in fecal samples and 40 had F. hepatica eggs in bile samples. Of 204 cows in which no adult flukes were found in the liver, 23 had F. hepatica eggs in fecal samples and 27 had F. hepatica eggs in bile samples. The sensitivity of the determination of F. hepatica eggs in fecal and bile samples was 68 and 98%, respectively. The negative predictive values for fecal and bile examination were 93 and 99%, respectively. Of 49 cows in which adult flukes were observed in the liver, 13 had D. dendriticum eggs in fecal samples and 44 had D. dendriticum eggs in bile samples. Of 176 cows in which no adult flukes were found in the liver, 19 had D. dendriticum eggs in fecal samples and 49 had D. dendriticum eggs in bile samples. The sensitivity of the determination of D. dendriticum eggs in fecal and bile samples was 27 and 90%, respectively. The negative predictive values for fecal and bile examination were 81 and 96%, respectively. The results of this study indicate that the examination of bile is clearly a more reliable method of diagnosing liver fluke infections than microscopic examination of feces.
Indian J Gastroenterol 1993 Jul;12(3):77-9
Detection of Entamoeba histolytica antigens in stool in amebiasis.
Vinayak VK, Kumar P, Punj V, Vashist N, Kanwar JR, Bhasin DK, Singh K
Department of Experimental Medicine, Postgraduate Institute of Medical Education and Research, Chandigarh.
BACKGROUND: Stool microscopy, the conventional method of diagnosing intestinal amebiasis, fails to detect Entamoeba histolytica in more than 30-40% of clinically suspected cases. Demonstration of parasite products in clinical specimens has been suggested as an complementary. However, the usefulness of demonstrating amebic antigen in the stools of clinical cases needs to be assessed. METHODS: A double-antibody sandwich enzyme linked immunosorbent assay (ELISA) using anti-trophozoite antibodies to capture E histolytica specific coproantigen(s) was carried out on stools obtained from 31 patients with microscopically confirmed non-dysenteric amebic colitis, 18 patients with intestinal parasites other than E histolytica and 41 apparently healthy subjects. RESULTS: The assay detected E histolytica specific coproantigen(s) in stools of 23 (74.2%) of 31 subjects with non-dysenteric amebic colitis, none of 18 with other parasitic infections and 1 (2.4%) of 41 apparently healthy subjects. CONCLUSION: Our results provide evidence for the presence of E histolytica specific coproantigen(s) in stool eluates from patients with amebic infection; this finding can be exploited for confirming ongoing amebic infection. However, the sensitivity of the assay needs to be improved by the use of relevant monospecific/monoclonal antibodies.
Rev Hosp Clin Fac Med Sao Paulo 1993 Jul-Aug;48(4):175-82
[The importance of Strongyloides stercoralis revisited].
[Article in Portugese]
Pires ML, Dreyer G
Departamento de Parasitologia, Centro de Pesquisas Aggeu Magalhaes/FIOCRUZ, Recife, PE.
Strongyloidiasis is a worldwide parasitic disease and of great importance in Brasil. Among the diverse species of Strongyloides, only the following are of importance to man: S. stercoralis, S. fulleborni and S. fullerboni-like.
Even though S. stercoralis is an intestinal helminth, strongyloidiasis is a systemic infection that can affect, beside the gastrointestinal tract, lungs, CNS, liver and biliary tract, pancreas, genitourinary tract and skin. The great majority of cases are asymptomatic, having a chronic and benign course. Among the symptomatic subjects, the gastrointestinal and pulmonary symptoms prevail. For unknown reasons, strongyloides infection may result in severe, disseminated disease. Immunosuppressive, therapy was identified as an important risk factor for disseminated illness. Diagnosing strongyloidiasis may be difficult, and
even though the parasitological stool examination is the most used diagnostic test, sometimes larvae cannot be identified. Immunodiagnosis is not yet assessible for routine usage and is still a subject of research. Thiabendazole remains the drug of choice for treatment of strongyloidiasis, but other drugs, such as ivermectin, have been used. The purpose of this paper was to review the important aspects of the S.
stercoralis infection in man.