Table 1.
Prevalence of protozoa as described by various studies from developed countries
| Reference | Study location; period | Cases and samples | Lab method(s) | Overall pathogen isolation rate (%) | No. of samples | Parasites detected (%)a,b |
|---|---|---|---|---|---|---|
| 184 | Melbourne, Australia; 1997 | Fecal specimens from community-based asymptomatic individuals | Modified iron-hemotoxylin stain to detect Giardia, Cryptosporidium, Blastocystis, Entamoeba, and other protozoa | 11.8 | 1,091 | Protozoa (8.3), Giardia spp. (1.6), Blastocystis spp. (6.0), Cryptosporidium (0.4), D. fragilis (0.4) |
| 335 | Helsinki, Finland; 1985-1986 | Diarrhea in adult out- and inpatients attending three health centers and a municipal hospital | Formalin-ether concentration method and modified Ziehl-Neelsen method for Cryptosporidium | 35.2 | 253 | G. intestinalis (2.0), Cryptosporidium sp. (2.8), E. histolytica/E. dispar (0.4) (majority of isolates were imported from other countries) |
| 452 | Madrid, Spain; 1980–1983 | Fecal samples from infected persons (50% children) in hospital | Microscopic examination for parasitesc | 46.1 | 5,022 cases | Giardia intestinalis (2.7), Entamoeba histolytica/E. dispar (<1) |
| 247 | Ljubljana, Slovenia; 1992-1993 | Patients with diarrhea | Permanent staining, Gomori's trichrome modification for Blastocystis sp., and safranin-methylene blue stain for Cryptosporidium, with bright-field microscopy | 3.7 (39/1,066 patients) | 1,066 cases, 150 controls | Blastocystis spp. (3.7 [cases] and <1 [controls]) |
| 11 | Population of England; 1993-1996 | Fecal samples from patients with diarrhea and controls | Novel real-time PCR for Giardia sp., real-time nested PCR for Cryptosporidium sp. | 20 (population), 51 (pathogen isolated) | 2,422 cases, 2,205 controls | Cases: Giardia (2), Cryptosporidium spp. (2); controls: Giardia (1), Cryptosporidium spp. (0.5) |
| 396 | Sydney, Australia; 2003–2006 | HIV-positive and HIV-negative MSM with diarrhea, presenting at general medical practice (GP) | Molecular methods, modified iron-hematoxylin stain, and a carbol-fuschin staining step to detect coccidian parasites | 23.98 (448 pathogens isolated) | 1,868 total, 628 from HIV-negative patients, 618 from HIV-positive patients, 622 from non-MSM | Entamoeba histolytica/E. dispar complex (2.9), Cryptosporidium species (1), Giardia intestinalis (2.9), Dientamoeba fragilis (0.8), Blastocystis spp.(16.9) |
| 425 | Northeast region of England; 2003–2005 | Humans | Cryptosporidium screen using auramine staining, microscopic examination for OCP | NA | 279 outbreaks, 2,889 cases tested | Cryptosporidium (3.0) |
| 90 | Ankara, Turkey; 2005–2007 | Hospital patients presenting with IBS, inflammatory bowel disease (5), and chronic diarrhea | Native Lugol's, trichrome, and Kinyoun's acid-fast staining; genomic DNA preparation; subtyping by PCR with STS primers | 18.1 (cases), 16.7% (controls) | 105 cases, 96 controls | Blastocystis (18 [cases]) and 16.7 [controls]) |
| 442 | Uppsala, Sweden; 1981 | Hospital inpatients and outpatient Swedish children of <15 years of age with acute gastroenteritis | Parasitic studies, formalin-ether concentration method; Cryptosporidium detected by light microscopy and Kinyoun's acid-fast stainingd | 68 | 416 cases, 200 controls | Giardia intestinalis (1 [cases] and 1 [controls]) |
| 355 | Brisbane, QLD, Australia; circa 1992 | 260 nonhospital patients with diarrhea sent to a private laboratory in Brisbane | Fecal culture and microscopy (trichrome staining for identification by oil immersion microscopy) | 15 | 260 specimens | G. intestinalis (1.5), Blastocystis spp. (10.8), G. intestinalis (1.5) |
| 416 | Stockholm, Sweden; 1996-1997 | Consecutive adult patients of >15 years of age with diarrhea and healthy control subjects | OCP by direct microscopy and Cryptosporidium oocysts by a modified Ziehl-Nielsen technique | 56 (cases), 16 (controls), 8 (protozoa) | 851 cases, 203 controls | Cases: E. histolytica (1), G. intestinalis (2), Blastocystis spp. (4), Cryptosporidium (2), microsporidia (<1); controls: E. histolytica (<1), Blastocystis spp. (9) |
| 417 | 42 specialized travel or tropical medicine sites located on six continents; 1996–2005 | Returned travelers diagnosed with an “infectious gastrointestinal disease” | Best available reference diagnostics; there was considerable heterogeneity between centers in terms of availability and sophistication of diagnostic (e.g., molecular) testing | 39 (65% of isolates were parasitic) | 7,442; 2,902 tested for parasites | Giardia (27.9), E. histolytica (12.5), Dientamoeba fragilis (4.0), Cryptosporidium spp. (1.1), Cyclospora (1.1), Cystoisospora belli (0.1) |
| 12 | 26 U.S. states and two Canadian provinces; 1996 | Fecal samples from infected and noninfected persons | Formalin-ethyl acetate concentration sedimentation procedure and confirmatory permanent smears when necessary | 5,250 cases | C. cayetanensis (4.3); note that 91% of infected patients had gastroenteritis symptoms | |
| 144 | Noumea, New Caledonia; 1990-1991 | Patients of all ages with diarrhea | Formalin-ether concentrates/smears stained with merthiolate-iodine-formaldehyde solution and examined microscopicallye | 40.4 | 2,088 cases | E. histolytica/dispar (3.5), Giardia intestinalis (7.8) |
| 60 | Republic of Korea; 2004–2006 | Diarrheal patients hospitalized in 96 hospitals | Enzyme immunoassay kit | 36.8 | 76,652 cases | Protozoa (2.3), Cryptosporidium spp. (0.8), Entamoeba histolytica/E. disparf (0.6), Giardia (1.7) |
| 81 | Netherlands; 1996–1999 | Stool samples from patients who consulted with a GP regarding gastroenteritis | Microscopic examination of SAF-fixated samplesg | 37.5 (cases), 9.8 (controls) | 857 cases, 574 controls | Cases: G. intestinalis (5.4), Cryptosporidium spp. (2.1), Cyclospora (0.2), Entamoeba spp. (0.9), D. fragilis (10.3); controls: G. intestinalis (3.3), Cryptosporidium (0.2), Cyclospora (0.2), Entamoeba spp. (0.7), D. fragilis (14.6) |
| 192 | Gyeonggi-do, South Korea; 2004–2006 | Gastroenteritis patients in hospital | ELISA | 3.4 | 6,071 cases | Protozoa (3.4), G. intestinalis (2.5), E. histolytica/E. dispar (0.4), Cryptosporidium parvum (0.4) |
| 301 | 16 Danish counties, Denmark; 2000-2001 | Stool samples from children of less than 5 years of age from hospitals and general practice offices | Microscopyh plus Ziehl-Neelsen acid-fast staining for Cryptosporidium and Cyclospora sp. | 54 (cases), 22 (controls) | 424 cases, 866 controls | Cases: G. intestinalis (<1), Cryptosporidium (1.7), Blastocystis spp. (<1); controls: G. intestinalis (<1), Blastocystis spp. (1.3) |
| 24 | Melbourne, Victoria, Australia; 1980–1993 | Hospitalized children (0 to 14 years old) | Microscopyi for OCP, modified acid-fast smears for cryptosporidia | 56.6 | 3,785 | Cryptosporidium (0.5), G. intestinalis (0.3) |
| 264 | Sydney, Australia; 2001 | 412 children under 6 years of age with diarrhea, either hospitalized or outpatients at The Sydney Children's Hospital | Giardia-specific enzyme immunoassay and microscopy with modified Ziehl-Neelsen stain for cryptosporidia | 33 | 412 | Cryptosporidium spp. (2.4), G. intestinalis (2.7) |
| 370 | Melbourne, Australia; 1997–1999 | Fecal samples from family units (community) of at least two children (≤15 years old) and two adults each | A modified iron-hematoxylin stain was used to detect Giardia and Cryptosporidium in concentrated specimens | 25 | 791 | Cryptosporidium spp. (1.6), Giardia intestinalis (2.5) |
| 193 | Neusiedl am See, rural eastern Austria; January to December 2007 | Patients who consulted general practitioners for gastroenteritis | Giardia intestinalis plus Cryptosporidium parvum (RIDA Quick Cryptosporidium/Giardia Combi test) | 23.2 | 306 | Protozoa (1.3), Cryptosporidium spp. (1.6), Giardia intestinalis (2.5) |
| 128 | Canadian hospital morbidity database (HMDB); 1995–2004 | Population hospitalized in Canada for gastorintestinal illness (acute, chronic, and rehabilitation care) | Not given | 21.7 | 927,645 hospitalizations | Entamoeba spp. (0.05), Giardia intestinalis (0.15), Cryptosporidium spp. (0.08) |
| 467 | England; 1993–1996 | Patients with diarrhea in the community and seen by GP | Microscopyj (12) | 24 | 1,262 | Protozoa (1.6), Cryptosporidium spp. (1.3), Giardia intestinalis (0.32) |
| 204 | Berlin, Germany; 2005–2007 | Patients of ≥18 years of age hospitalized with community-acquired gastroenteritis | SAF fixation-concentration and microscopy for OCP; direct immunofluorescence antibody test for G. intestinalis and Cryptosporidium; Kinyoun's staining method for Cryptosporidium, C. cayetanensis, and I. belli | 59.8 | 132 | Blastocystis spp. (7.6), Giardia intestinalis (7.6) |
| 255 | Parma, Italy; 1983-1984 | Hospitalized patients with acute enteritis | Microscopy | 26.2 | 797 | Protozoa (3.1), Giardia intestinalis (1.4) |
| 225 | Seattle, WA, USA; 1998–2001 | Children with diarrhea who presented to a pediatric emergency department | Trichrome stains and formalin-ethyl acetate sedimentation for OCPD and fluorescence antibody testing for Giardia and Cryptosporidium sp. | 19.5 | 656 (from 1,626 patients) | Protozoa (2.13), Blastocystis spp. (1.1), Cryptosporidium spp. (0.15), Giardia spp. (0.46), E. histolytica/E. dispar (0.15) |
| 265 | United States; 1996-1997 | National surveillance data for food-borne illness cases | Not given | Not given | Estimated 38,629,641 cases | Parasites (6.6), Cryptosporidium parvum (0.8), Cyclospora cayetanensis (0.4), Giardia intestinalis (5.2) |
| 215 | Helsinki, Finland; 1982-1983 | Fecal samples sent by GPs for routine parasitological examination | Ritchie's formalin ether concentration method, used along with a modified Ziehl-Neelsen method | Not given | 154 | Cryptosporidium spp. (9.1), Giardia (29.2), Blastocystis spp. (13), E. histolytica/E. dispar (2) |
| 1 | Tenerife, Canary Islands, Spain; ∼2004 | Clinical samples (156 stools) | Light microscopy, staining with Weber's chromotrope and PCR-hybridization for the identification of Enterocytozoon bieneusi | 11.54 | 156 | Protozoa (11.54), E. bieneusi (11.54) |
| 96 | United States (10 cities); 1998-1999 | Diarrheal stool specimens from HIV-infected patients in 3 U.S. hospitals and a database | Moura's quick-hot Gram chromotrope technique, modified trichrome blue stain (confirmed by chromotrope 2R staining and oil immersion microscopy) | 1.5 | 737 | Microsporidian species (1.5) |
| 248 | Vigo, Spain; ∼2001 | Elderly HIV-negative patients; 47 of 60 had diarrhea | Light microscopy with Weber's chromotrope-based stain and PCR-hybridization | 17.02 | 60 | E. bieneusi (17.02) |
| 448 | Central area of Brussels, Belgium; 2002-2003 | Patients suspected of suffering from a parasitic gastrointestinal illness | Bright-field microscopy and PCR | 37 | 1,207 stool samples from 448 outpatients | D. fragilis (6.3), G. intestinalis (7.1), C. parvum (1.6%), E. hystolytica (0.2%), Blastocystis sp. (9.8%), Entamoeba coli (5.4%) |
a
In some reports, some patients had multiple pathogens isolated; hence, the percentages may not add up to 100%.
b
The designation E. histolytica is reported as E. histolytica/E. dispar for consistency, unless the study's methodology indicated clearly that the test was specific for E. histolytica.
c
Incomplete techniques and no permanent stained smears used. The methods were described as follows. “Wet mounts of 5,022 freshly passed stools were examined for leukocytes or parasites or both. The samples which were not immediately processed were stored at 4degrees Celcius for a maximum of 36 h.”
d
Permanent stains were not performed for routine investigations of protozoa.
e
No permanent stains performed. Although the authors indicate the presence of E. histolytica, there is nothing in the article to indicate that the organisms were confirmed as E. histolytica versus E. histolytica/E. dispar.
f
A Ridascreen immunoassay kit was used, and this test detects E. dispar trophozoites. However, the authors reported that the organisms were E. histolytica.
g
Microscopic examination included a combination of (i) a wet film (iodine stained or unstained); (ii) Ridley concentration (iodine staining); (iii) modified Ziehl-Neelsen staining of Ridley concentrate; and (iv) permanent staining by hematoxylin.
h
Microscopy of concentration sediment wet mount for protozoa only, other than special stains for coccidia.
i
Microscopy for wet mount examination only, other than special stains for coccidia.
j
Microscopy not defined.