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This article updates recent advances in the body of knowledge of diagnosis and treatment of intestinal parasites. The articles focus on the manifestations of disease in the immunocompetent adult host from developed countries. Specific pathogens discussed are Giardia lamblia and Dientamoeba fragilis, Entamoeba histolytica, Entamoeba dipar, Blastocystis hominis, Cyclospora cayetanensis, and Cryptosporidium parvum.
Most parasites of man in New Guinea are cosmopolitan species, widely distributed and highly prevalent in the island. Reports of other parasite infections are reviewed. This impoverished fauna includes anthroponotic species normally occurring at low prevalences, e.g. Isospora belli, Dientamoeba fragilis, Trichomonas hominis and a few zoonotic forms with pigs as reservoir hosts, notably Balantidium coli and Entamoeba polecki. Other zoonoses are very few and extremely rare. This may be due to the reduced placental mammal fauna. The potential for the spread of Taenia solium infection is highlighted, as is the unique zoogeographical distribution of the Strongloides species resembling S. fuelleborni. Enterobius gregorii is recorded for the first time from Papua New Guinea.
A comprehensive utilization review was done of all stool ova parasite examinations performed at a pediatric hospital during a 3-year period from June 1, 1989 to July 1, 1992. A total of 2,652 stool specimens were surveyed from 1,532 children. Forty-one percent (1,081) of the workload was from inpatients, 37% (976) was from emergency room (ER) visits/other outpatients, and 22% (233) was from patients attending the gastroenterology (GI) clinic. The prevalence of enteric parasites in hospitalized children was 4% (35 of 829) compared to rates of 10% (47 of 470) and 13% (30 of 233) for children attending the ER/other outpatient clinics and GI clinic, respectively. Giardia lamblia was found most often (31%[45 of 146]), followed by Dientamoeba fragilis (23%[33 of 146]), Entamoeba coli (16%[24 of 146]), Blastocystis hominis (13% [19 of 146]), Cryptosporidium (8% [12 of 146]), Endolimax nana (4% [6 of 146]), Enterobius vermicularis (2% [3 of 146]), Hymenolepis nana (2% [3 of 146]), and Iodamoeba buetschlii (1% [1 of 146]). Most children were colonized/infected with a single parasite (85%) with a much smaller number having two or more parasites. Only nine children (6%) who were immunocompetent and hospitalized for more than 4 days were found to have enteric parasites. Over the past 18 months, significant sustainable cost savings have resulted from the implementation of practice guidelines for ordering pediatric stool ova and parasite examinations.
We studied the frequency of parasitic infection and associated clinical symptoms in children who attended general pediatric and dental clinics at UCLA. Parasites were detected in stool specimens of 40 (38%) of the 1-4 children completing the study. Protozoan parasites were recovered in 39 (38%); one child had whipworm eggs. Parasites included Dientamoeba fragilis in 22 (21%) children and Giardia lamblia in 18 (17%) children; commensals were observed in 15 (14%) children. Parasitic infection was more frequent in younger children, those with a history of immigration or foreign travel and those attending a day care center. A significant proportion of children with parasites had vague gastrointestinal complaints; however, parasites had not been considered as the etiologic agent by the parent or child's physician. Anorexia, irritability and gas were frequent in children with G. lamblia; abdominal pain was more frequent in those with D fragilis. Intestinal parasitic infection should be considered in children with vague gastrointestional complaints, particularly those in endemic areas, with a history of foreign travel or immigration or attending a day care center. Siblings of infected children should have stool examination even if asymptomatic.
Twenty monoclonal antibodies were produced against trophozoites of Entamoeba histolytica strains HK-9 and HM-1: IMSS. When reactivity to various enteric protozoa was examined by an indirect fluorescence antibody test, 15 of the monoclonal antibodies were strongly reactive with E. histolytica trophozoites. Species-specific antigens recognized by these monoclonal antibodies were located on the plasma membrane, nucleus, cytoplasm, and cytoskeletal structures of the trophozoites. Two of the remaining five monoclonals reacted strongly with trophozoites of the E. histolytica-like Laredo strain. The determinant antigen was located in the cytoplasm. The three remaining monoclonal antibodies were found to recognize cross-reactive antigens between E. histolytica and E. histolytica-like Laredo, E. hartmanni, E. coli, Dientamoeba fragilis, Giardia lamblia, and Trichomonas hominis. These three antibodies were also reactive with T. vaginalis and mammalian cells such as HeLa cells. Thus, the combined use of monoclonal antibodies seems capable of distinguishing E. histolytica and/or E. histolytica-like Laredo from other enteric protozoa.
We determined small subunit ribosomal DNA sequences from three parabasalid species, Trichomitus batrachorum strain R105, Tetratrichomonas gallinarum, and Pentatrichomonas hominis belonging to the Trichomonadinae subfamily. Unrooted molecular phylogenetic trees inferred by distance, parsimony, and likelihood methods reveal four discrete clades among the parabasalids. The Trichomonadinae form a robust monophyletic group. Within this subfamily T. gallinarum is closely related to Trichomonas species as supported by morphological data, with P. hominis and Pseudotrypanosoma giganteum occupying basal positions. Our analysis does not place T. batrachorum within the Trichomonadinae. Trichomitus batrachorum (strains R105 and BUB) and Hypotrichomonas acosta form a well-separated cluster, suggesting the genus Trichomitus is polyphyletic. The emergence of T. batrachorum precedes the Trichomonadinae-Tritrichomonadinae dichotomy, emphasizing its pivotal evolutionary position among the Trichomonadidae. A third cluster unites the Devescovinidae and the Calonymphidae. The fourth clade contains the three hypermastigid sequences from the genus Trichonympha, which exhibit the earliest emergence among the parabasalids. The addition of these three new parabasalid species did not however resolve ambiguities regarding the relative branching order of the parabasalid clades. The phylogenetic positions of Tritrichomonas faetus, Monocercomonas sp., Dientamoeba fragilis, and the unidentified Reticulitermes flavipes gut symbiont 1 remain unclear.
Cultivation of luminal protistan parasites has a long history. In this review we discuss the methods and media that are most widely used for the establishment and maintenance of the following organisms in culture: Entamoeba histolytica, Giardia intestinalis, Trichomonas vaginalis, Dientamoeba fragilis, Blastocystis hominis, and Balantidium coli. While cultivation is of limited importance in the diagnostic laboratory, it is essential to most research laboratories, and it is toward the latter that this review is primarily aimed.
A monoclonal antibody (MAb) produced against trophozoites of Entamoeba histolytica strain HM-1:IMSS, reacted with all of 42 isolates and 4 clones showing pathogenic zymodeme (Z) patterns, i.e., Z-II, Z-II alpha-, Z-II (glucose phosphate isomerase: gamma +), Z-VII, Z-VII (glucose phosphate isomerase: alpha lack, gamma +), Z-XI, Z-XIV, and Z-XIX, regardless of culture conditions, geographical origins, or host symptoms in an indirect fluorescence antibody test. In contrast, the MAb failed to react with 14 isolates possessing nonpathogenic zymodemes Z-I and Z-VIII and did not react with other enteric protozoan parasites, such as E. histolytica-like Laredo, Entamoeba hartmanni, Entamoeba coli, Endolimax nana, Dientamoeba fragilis, Trichomonas hominis, and Giardia lamblia. Western immunoblotting analysis showed that the molecular weight of the antigenic component recognized by the MAb was exclusively 30,000 in pathogenic isolates of different zymodemes. These results suggest that the 30,000-molecular-weight antigen is a marker of pathogenic isolates and that the indirect fluorescent-antibody test with the MAb is useful for the accurate discrimination of pathogenic amebae.
A total of 372 pooled stool specimens from 274 homosexual men with diarrhea were submitted for parasitologic examination over a 2.5-year period. Each two-vial pooled specimen set contained portions of stool from 3 consecutive days in Formalin and polyvinyl alcohol. Of the 274 patients, 133 (48.5%) harbored one or more intestinal protozoa, with 161 (43.3%) of the 372 specimens submitted being positive for one or more organisms. The parasites identified included Entamoeba histolytica (71 patients), Giardia lamblia (22 patients), Endolimax nana (106 patients), Entamoeba coli (39 patients), Entamoeba hartmanni (25 patients), Dientamoeba fragilis (3 patients), Iodamoeba bütschlii (2 patients), and Chilomastix mesnili (2 patients). Cryptosporidium sp. (2 patients) and Isospora belli (1 patient) were also detected. Results of this study support the experience of other workers regarding high rates of infection with intestinal parasites in the homosexual population and also indicate that symptomatic individuals belonging to this acquired immunodeficiency syndrome risk group be screened for both common and uncommon intestinal pathogens.
As a result of disposal problems related to the use of mercury compounds, many laboratories have considered switching from mercuric chloride-based Schaudinn's and polyvinyl alcohol (PVA) stool preservatives to other non-mercury-based preservatives. The primary use for PVA-preserved specimens is the permanent stained smear, the most important technique in the routine ova and parasite examination for the identification and confirmation of intestinal protozoa. A comparison of organism recovery and morphology of the intestinal protozoa was undertaken with PVA containing either a zinc sulfate base or the "gold standard" mercuric chloride base. Paired positive fecal specimens (106 from 64 patients) were collected and examined microscopically by the trichrome stain technique. There were 161 instances in which organism trophozoite and/or cyst stages were identified and 3 in which human cells were identified. Morphology, clarity of nuclear and cytoplasmic detail, overall color differences, and the ease or difficulty in detecting intestinal protozoa in fecal debris, as well as the number of patients with a missed diagnosis, were assessed from the permanent stained smear. Overall organism morphology of the intestinal protozoa preserved in zinc sulfate-PVA was not always equal in nuclear and cytoplasmic detail or range of color after permanent staining to that seen with mercuric chloride-PVA. However, the same organisms were usually identified in both specimens, with the exception of situations in which organism numbers were characterized as rare (no organisms per 10 oil immersion fields at x1,000 magnification but at least one organism in the smear) [9 of 161 (5.6%)] or the organism was missed because of poor morphologic detail [12 of 161 (7.5%)]. In only six of these cases [6 of 161 (3.7%)] did the results involve pathogens. The patient diagnosis was missed in four cases of amebiasis and two cases of giardiasis; in both situations the organism numbers were rare. There were no discrepant results with Dientamoeba fragilis. Overall agreement between the two PVA-based results was 87.0% (140 of 161); when the instances of rare organisms were disregarded, the overall agreement was 92.5% (149 of 161). On the basis of these findings, zinc-PVA is viable substitute for mercuric chloride-PVA used for trichrome permanent stained smears.
Trichomonas vaginalis infection is the most prevalent nonviral sexually transmitted disease (STD) in the world. A PCR test using vaginal swab samples for the detection of T. vaginalis was developed to add T. vaginalis infection to the growing list of STDs that can be detected by DNA amplification techniques. A primer set, BTUB 9/2, was designed to target a well-conserved region in the beta-tubulin genes of T. vaginalis. All strains (15 of 15) of T. vaginalis tested were successfully detected by PCR giving a single predicted product of 112 bp in gel electrophoresis. No such targeted product was amplified with DNA from Trichomonas tenax, Trichomonas gallinae, Chlamydia trachomatis, Neisseria gonorrhoeae, Giardia lamblia, Chilomastix sulcatus, Dientamoeba fragilis, and Entamoeba histolytica. An optimal analytical sensitivity of one T. vaginalis organism per PCR was achieved. Culture, performed with the Inpouch TV culture system, was examined daily with a light microscope to identify T. vaginalis. Twenty-three of 350 (6.6%) vaginal swab samples from women attending an army medical clinic were culture positive for T. vaginalis. Of these culture positive specimens, PCR detected 22 of 23 (96%) with primer set BTUB 9/2, and wet preparation detected only 12 of 23 (52%). Seventeen specimens were BTUB 9/2-PCR positive and culture negative. Ten of these discordant specimens were determined to be as true positive by PCR using primer sets TVA 5-1/6 and/or AP65 A/B, which target different regions in the T. vaginalis genome, and seven were determined to be false positive. The sensitivity of BTUB 9/2-PCR was 97% and the specificity was 98%. The sensitivities of culture and wet preparation were 70 and 36%, respectively. The diagnosis of T. vaginalis infection by PCR is a sensitive and specific method that could be incorporated into a joint strategy for the screening of multiple STDs by using molecular amplification methods.
As a result of disposal problems related to the use of mercury compounds, many laboratories have switched from mercuric chloride-based Schaudinn's and polyvinyl alcohol (PVA) stool preservatives to other, non-mercury-based preservatives. A comparison of organism recoveries and morphologies of the intestinal protozoa was undertaken with PVA containing the EcoFix zinc-based Schaudinn's preservative (Meridian Diagnostics, Inc.); both Wheatley's modification of Gomori's trichrome stain (WT) and EcoStain (ES) were used to stain 51 human fecal specimens. Morphology, clarity of nuclear and cytoplasmic detail, overall color differences, and the ease or difficulty in detecting intestinal protozoa in fecal debris were assessed for the two permanent stained smears. Overall, organism morphology of the intestinal protozoa stained with WT and that of protozoa stained with ES were not equal in nuclear and cytoplasmic detail or range of color. However, the same organisms were identified in stained fecal smears with either WT or ES, with the exception of situations in which organism numbers were characterized as rare. Included were 67 protozoan challenges (number of organisms): Entamoeba histolytica-Entamoeba dispar (5), Entamoeba coli (9), Entamoeba hartmanni (6), Endolimax nana (12), Iodamoeba bütschlii (8), Blastocystis hominis (19), Giardia lamblia (6), Dientamoeba fragilis (2), yeast (2), and leukocytes (2). Five specimens were negative for parasites but contained fecal debris that was compared for morphologic detail and color range. The ES produces a more gray-green monotone with very little pink or red tone; contrast among the various colors is less than that seen with WT. Stain intensity for all organisms was acceptable, and there were no problems with stain deposition. The quality of the protozoan morphology with ES was often comparable to that with WT (36 of 67 [53.7%]) and, in some cases, better (24 of 67 [35.8%]). Organisms on the WT-stained smear exhibited better morphology in a few instances (4 of 67 [6%]), and in three instances, there were discrepant organism numbers.
From March to September 2001, 315 specimens from "nonrepeat" patients that were submitted for ova and parasite examination were stained using the Kinyoun modified acid-fast stain to detect the intestinal coccidians. Four patients (1.3%) were infected with coccidians, 2 with Cryptosporidium parvum and 2 with Cyclospora cayetanensis. No infections with Isospora belli were detected. In comparison, 15 patients (4.8%) had infections with one or more intestinal parasites detected by routine trichrome staining: 5 had Giardia lamblia; 2, Dientamoeba fragilis; 3, Strongyloides stercoralis; 1, Iodamoeba bütschlii; 3, Endolimax nana; 6, Blastocystis hominis; and 1, Entamoeba coli. Four patients were multiply infected. Coccidians made up 29% of the clinically significant parasitic infections. The coccidians were missed in all 4 cases because no special staining was ordered. Clinicians need to be reminded that additional tests should be ordered to fully evaluate patients with chronic diarrhea in which no diagnosis is found by routine testing.
A survey of intestinal parasites infection among Korean people has been carried out during July 1969 to December 1970. A total of 2,250 stool specimens (male 1,101, female 1,146) was collected from all the provinces and Seoul city in Korea. The specimens were examined routinely by direct fecal smear, zinc sulfate flotation and formalin-ether sedimentation techniques. The results are summarized as follows: 1. Of 2,250 specimens examined, l,803(80.l %) were positive for intestinal parasites. 2. The positive rates of intestinal helminths were 1,644(73.1 %) among 2,250; Ascaris lumbricoides 46.0 %, Trichocephalus trichiurus 46.8 percent, hookworm 6.8 %, Trichostrongylus orientalis 7.0 percent, Clonorchis sinensis 12.1 percent, Enterobius vermicularis 1.6 %, Hymenolepis nana 0.7 percent, Taenia species 0.3 %, Metagonimus yokogawai 0.04 percent, Fasciolidae 0.04 % and one case of lung fluke Paragonimu westermani. 3. The positive rstes of intestinal protozoa were 786(34.9 %); Entamoeba histolytica 6.4 %, Entamoeba coli 20.5 percent, Endolimax nana 10.0 %, Giardia lamblia 5.1 %, Trichomonas hominis 1.1 percent, Chilomastix mesnili 0.5 percent, Iodamoeba butschlii 0.6 percent, Enteromonas hominis 0.7 percent, Dientamoeba fragilis 0.1 % and one case of Isospora hominis. 4. Sexual distribution of helminths and protozoan infections showed higher rate in female than that of male, except C. sinensis, H. nana, Taenia species or G. lamblia. 5. Infections of T. trichiurus, hookworm, T. orientalis, C. sinensis, Taenia species, E. histolytica, E. coli and E. nana increased with age. Conversely, H. nana and G. lamblia infections were more predominent in younger ages.
A survey was conducted to determine the prevalence of protozoan parasites in a large semicommunal group in Los Angeles. Protozoan parasites were observed in 151 (69%) of the 220 group members in the study. Parasites were observed in stool specimens from 105 (76%) of the 138 children and 46 (56%) of the 82 adults. Dientamoeba fragilis was observed in 115 (52%), Giardia lamblia in 50 (23%), Entamoeba histolytica in 9 (4%), and commensals in 61 (28%). Parasitic infection was infrequent in infants less than 1 year old, was demonstrated in 33 (89%) of the 2- to 4-year-olds, 69 (78%) of the 89 school age children 8-15 years of age, and in 46 (56%) of the 82 adults. G. lamblia was most prevalent in children younger than 6 years; whereas D. fragilis was common in all age groups. The fecal-oral route was the most likely means for parasite transmission. Since the group at times serves meals to the public, spread of parasites outside the community is a potential public health problems. Diagnosis of parasitic infection is dependent on optimal stool collection, proper laboratory techniques and trained personnel.
Blastocystis hominis, an intestinal organism of uncertain taxonomic position, has long been considered nonpathogenic. Some recent studies suggest, however, that it may be associated with diarrhea and may respond to treatment with iodoquinol or metronidazole. To investigate this possibility, we identified 148 persons whose stools contained this organism. Of this number, 32 had at least 6 stool examinations performed. Twenty-seven of the 32 persons were later found to have greater than or equal to 1 recognized pathogens--Entamoeba histolytica, Giardia lamblia or Dientamoeba fragilis--and, after receiving appropriate therapy, became asymptomatic. The B hominis infection, however, was unaffected by therapy. Five persons with only B. hominis infection were treated with iodoquinol without effect; these persons fulfilled the medical criteria for irritable bowel syndrome. We believe that when an apparently symptomatic B. hominis infection responds to therapy, the improvement probably represents elimination of some other undetected organism causing the infection.
An epidemiologic field study was conducted in the village of Borbòn in Esmeraldas province in northern Ecuador to compare different parasitologic methods in the diagnosis of infection with the Entamoeba histolytica/Entamoeba dispar complex. The results of two stool antigen detection assays (the Prospect Entamoeba histolytica microplate assay and the E. histolytica II assay) were compared with isoenzyme characterization of the amebic isolates. Nearly all (176 of 178, 98.9%) subjects were positive for intestinal parasites on direct microscopic examination, and cysts and/or vegetative forms morphologically consistent with the E. histolytica/E. dispar complex were recorded in 48 of 178 cases (27%). Culture in Robinson's medium was positive for amebic stocks in 89 (50%) of the 178 samples tested. Of the 37 isolates successfully stabilized, cloned, and characterized by zymodeme analysis, seven (18.9%) showed isoenzyme patterns of E. histolytica, whereas 26 (70.3%) showed patterns of E. dispar. The remaining four strains were identified as Entamoeba coli (three isolates; 8.1%) and Dientamoeba fragilis (one strain; 2.7%).The immunochromatographic tests showed different degrees of sensitivity and specificity when compared with isoenzyme characterization as the reference technique. The microplate assay, which does not discriminate between E. histolytica and E.dispar, showed a sensitivity of 54.5% and a specificity of 94% for both these amebic species. In contrast, the second-generation E. histolytica II test had a sensitivity of 14.3% and a specificity of 98.4% for E. histolytica sensu stricto. Our survey clearly demonstrated that more specific and sensitive diagnostic tests, such as stool antigen detection assays and isoenzyme analysis, are needed to establish the actual worldwide distribution of E. histolytica and E. dispar.
With continuing emigration from endemic countries, screening for parasitic infections remains a priority in U.S. communities serving refugee and immigrant populations. We report the prevalence of helminths and protozoa as well as demographic risk factors associated with these infections among 533 refugees seen at the Santa Clara County, California, Refugee Clinic between October 2001 and January 2004. Stool parasites were identified from 14% of refugees, including 9% found to have one or more protozoa and 6% found to have at least one helminth. Most common protozoan infections were Giardia lamblia (6%) and Dientamoeba fragilis (3%), and for helminths, hookworm (2%). Protozoa were more frequent in refugees < 18 years of age (OR: 2.2 [1.2-4.2]), whereas helminths were more common in refugees from South Central Asia (OR: 8.0 [2.3-27.7]) and Africa (OR: 5.9 [1.6-21.6]) when compared with refugees from Eastern Europe and the Middle East. Among helminths, Ascaris lumbricoides and hookworm were concentrated among South Central Asians (6 of 7 and 10 of 11 cases, respectively), whereas Strongyloides stercoralis was predominantly found in Africans (5 of 7 cases). Although predeparture empirical treatment programs in Saharan Africa may have helped to reduce prevalence among arriving refugees from this region, parasitic infection is still common among refugees to the United States with helminth infections found in more specific populations. As refugees represent only a fraction of recent immigrants from endemic countries, current studies in nonrefugee groups are also needed.