Further Outpatient Care
Symptoms usually resolve within 3-4 days after initiation of antiprotozoal therapy in immunocompetent patients with protozoal gastroenteritis. Nevertheless, especially in cases of giardiasis, patients should be monitored with a repeat stool examination if symptoms reappear.
In amebic liver abscess, ultrasonographic abnormalities can persist for months, and another ultrasound is usually not recommended after successful completion of therapy.
Further Inpatient Care
Patients with either necrotizing colitis or liver abscess caused by E histolytica may require further inpatient care only if surgical procedures were performed.
Patients with AIDS or other immunodeficiencies who have spore-forming protozoal infections may require prolonged hospitalization to correct electrolyte imbalance or accompanying conditions.
Inpatient & Outpatient Medications
Inpatient medications
Intravenous medications are indicated only in cases of severe amebic or balantidic colitis or in patients with amebic liver abscess.
Intravenous metronidazole with or without intramuscular dehydroemetine can be used until the patient can start oral therapy.
In some patients with AIDS and in unusual cases in immunocompetent hosts, hospitalization is required, and intravenous solutions are indicated to correct electrolyte imbalance.
Outpatient medications
Oral antiprotozoal therapy is usually administered at home.
Deterrence/Prevention
Standard hospital precautions are used for all hospitalized patients.
Additional control precautions are implemented for children with gastroenteritis, especially for patients using diapers or who have incontinence. This includes use of gowns and gloves for patient care, and hands must be washed after contact. A single room is indicated, if possible.
Prevention of exposure in persons infected with HIV consists in the following: [26]
-
Avoid contact with human and animal feces.
-
Request a veterinarian to examine the stools for Cryptosporidium in puppies or kittens younger than 6 months.
-
Avoid exposure to calves and lambs.
-
Avoid drinking water from lakes or rivers.
No chemoprophylactic agents are available for any of these diseases.
Protozoan parasites can survive under ambient and refrigerated storage conditions when associated with a range of substrates. Consequently, various treatments have been used to inactivate protozoan parasites in food, water, and environmental systems. Ozone is a more effective chemical disinfectant than chlorine or chlorine dioxide for inactivation of protozoan parasites in water systems. However, sequential inactivation treatments can optimize existing methods through synergistic effects.
Vaccination
Cryptosporidiosis
Several Cryptosporidium sporozoite antigens have been identified as potential vaccine candidates using traditional methods such as analysis of serum specificities after Cryptosporidium infection. [27] However, despite the considerable amount of structural and immunological data obtained from characterizations of multiple sporozoite surface antigens, a vaccine is not yet available.
A “reverse vaccinology” strategy using in silico analyses based on the genome sequence information of the organism represents a novel approach to identifying vaccinogens. This approach is particularly useful in organisms like Cryptosporidium, which are difficult to cultivate continuously in the laboratory. The strategy is based on the ability to predict proteins that are associated with the parasite surface and therefore have the potential for interaction with the host immune mechanisms, by in silico screening for signal peptides, glycosylphosphatidylinositol (GPI) signal anchors, and similarities with known pathogenic factors. This strategy has identified 3 promising Cryptosporidium vaccinogens that induce strong humoral and cellular immune responses, although these potential vaccines are still under investigation.
Amebiasis
Vaccinations using native and recombinant forms of the parasite Gal-lectin have been successful in protecting animals against intestinal amebiasis and amebic liver abscess. To date, this immunological approach holds the most promise, but clinical trials are required to validate its efficacy in humans. [28]
Giardiasis
By the year 2000, a Giardia vaccine was available in the United States for prevention of clinical signs of giardiasis and reduction of cyst shedding in dogs and cats. The vaccine is based on the current state of knowledge of Giardia antigenicity and immunology. However, studies done in humans are still ongoing. [29]
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This micrograph stained with chlorazol black, revealed an Entamoeba histolytica cyst.
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This is a scanning electron micrograph (SEM) of an in vitro Giardia lamblia culture. This photograph contains both trophozoites and a cluster of maturing cysts (bottom right). At far left, the 2 trophozoite-staged organisms are positionally situated opposite to one another, with the farthest left G lamblia displaying its dorsal, or upper surface, and the protozoan to its immediate right, its ventral, or bottom surface.
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This photomicrograph revealed the morphologic details of Cryptosporidium parvum oocysts.
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This is an illustration of the life cycle of Isospora belli, the causal agent of isosporiasis.
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This photomicrograph of a fresh stool sample, which had been prepared using a 10% formalin solution, and stained with safranin, revealed the presence of 3 uniformly stained Cyclospora cayetanensis oocysts in the field of view.
Tables
Name |
Mode of Transmission |
Symptoms |
Flagellates |
|
|
G lamblia |
Contaminated water, fecal-oral |
Nausea, bloating, gas, diarrhea, anorexia |
Dientamoeba fragilis |
Fecal-oral, associated with Enterobius |
Previously thought commensal; may cause diarrhea, abdominal, pain, nausea |
Amebas |
|
|
Entamoeba histolytica |
Contaminated water, fecal-oral, contaminated food |
Colitis, dysentery, diarrhea, liver abscess, other extraintestinal disease |
Spore-forming (Coccidia) |
|
|
Cryptosporidium parvum |
Contaminated water, swimming pools, fecal-oral |
Immunocompetent patients: Self-limited diarrhea Immunosuppressed patients: Severe and interminable diarrhea |
Isospora belli |
Fecal-oral |
Same as in Cryptosporidium |
Cyclospora cayetanensis |
Fecal-oral, contaminated water and food |
Same as in Cryptosporidium |
Microsporidia (Septata intestinalis, Enterocytozoon bieneusi) |
Fecal-oral, contaminated water |
Same as in Cryptosporidium |
Ciliates |
|
|
Balantidium coli |
Fecal-oral (frequently associated with pigs) |
Colitis, diarrhea |
Other |
|
|
Blastocystis hominis |
Fecal-oral |
May cause mild diarrhea |
Organism |
Size (mm) |
Stain Used |
Other Tests |
E histolytica |
Trophozoite: 10-60 Cyst: 10-20 |
Wet mount,* trichrome, periodic Schiff |
Enzyme-linked immunosorbent assay (ELISA) |
G lamblia |
Trophozoite: 9-21 Cyst: 7-12 |
Wet mount,* trichrome, hematoxylin, Lugol |
ELISA* |
C parvum |
2-5 |
Modified acid-fast,* auramine-rhodamine, Sheafer method |
ELISA* |
I belli |
30x12 |
Wet mount,* modified acid-fast* |
None |
C cayetanensis |
8-10 |
Modified acid-fast,* wet mount |
Electron microscopy |
Microsporidia |
1-2 |
Modified trichrome* |
Electron microscopy, fluorescence methods, small intestine biopsy |
D fragilis |
7-12 |
Iron hematoxylin,* trichrome* |
None |
B. coli |
50-200 |
Wet mount,* concentration techniques |
None |
B hominis |
5-30 |
Trichrome,* iron hematoxylin* |
None |
*Preferred screening test in clinical settings. |
|||
Organism |
Drugs, Pediatric Dose, and Treatment Duration |
E histolytica (Luminal disease or colonization) |
Iodoquinol: 40 mg/kg/d PO divided tid for 20 d; not to exceed 2 g/d |
Paromomycin: 25-30 mg/kg/d PO divided tid for 7 d |
|
E histolytica (Moderate colitis) |
Metronidazole: 50 mg/kg/d PO divided tid for 10 d |
Tinidazole: 50 mg/kg/d PO for 3 d; not to exceed 2 g/d |
|
E histolytica (Severe colitis or liver abscess) |
Metronidazole: 50 mg/kg/d PO divided tid for 10 d |
Dehydroemetine*: 1-1.5 mg/kg/d divided bid PO for 5 d |
|
Tinidazole†: 50 mg/kg/d PO for 3-5 d; not to exceed 2 g/d |
|
G lamblia |
Tinidazole: 50 mg/kg/d PO once; not to exceed 2 g/dose |
Metronidazole: 15-20 mg/kg/d PO divided tid for 5 |
|
Albendazole: 15 mg/k/d (not exceed 400 mg) PO q24 h, for 5-7 days |
|
Furazolidone: 6 mg/kg/d PO divided qid for 7-10 d |
|
Paromomycin: 40 mg/kg/d PO divided tid for 7 d |
|
Nitazoxanide: 200-400 mg/d PO divided bid for 3 d |
|
D fragilis |
Iodoquinol: 50 mg/kg/d PO divided tid for 20 d; not to exceed 2 g/d |
Paromomycin: 30 mg/kg/d PO divided tid for 7 d |
|
Tetracycline: 40 mg/kg/d PO divided qid for 10 d; not to exceed 2 g/d |
|
C parvum§ |
Paromomycin*: 30 mg/kg/d PO divided tid (duration unknown) |
Nitazoxanide: 200-400 mg/d PO divided bid for 3 d |
|
I belli |
Trimethoprim/sulfamethoxazole (TMP/SMZ): 20/100 mg/kg/d PO divided bid for 10 d, followed by 10/50 mg/kg/d PO divided bid for 21 d |
C cayetanensis |
TMP/SMZ: 10/50 mg/kg/d PO divided bid for 3 d |
Microsporidia S intestinalis |
Albendazole* (adult dose): 800 mg/d PO divided bid |
Microsporidia E bieneusi |
No treatment recommended; albendazole may decrease the number of organisms |
B coli |
Tetracycline: 40 mg/kg/d PO divided qid for 10 d; not to exceed 2 g/d |
Metronidazole: 35-50 mg/kg/d PO divided tid for 5 d |
|
Iodoquinol: 40 mg/kg/d PO divided tid for 20 d |
|
B hominis |
Metronidazole: 35-50 mg/kg/d PO divided tid for 10 d |
Iodoquinol: 40 mg/kg/d PO divided tid for 20 d |
|
Nitazoxanide||: 500 mg/d PO divided bid for 3 d |
|
*Efficacy is unknown. †Drug is available from the CDC Drug Service (phone: 404-639-3670; evenings, weekends, and holidays: 404-639-2888). ‡ Drug is not available in the United States. §Recommended regimens are indicated only in patients who are immunosuppressed. A recent meta-analysis has not shown evidence for a reduction in the duration or frequency of diarrhea by nitazoxanide or paromomycin when compared with placebo in immunosuppressed patients, nevertheless, oocyst clearance was significantly reduced. [25] ||Recent studies have shown effective outcomes when compared to placebo, but no clinical trials have compared with other antiparasitic drugs. |
|
