Intestinal Protozoal Diseases Follow-up

Updated: Apr 26, 2017
  • Author: Enrique Chacon-Cruz, MD; Chief Editor: Russell W Steele, MD  more...
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Further Outpatient Care

See the list below:

  • 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

See the list below:

  • 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

See the list below:

  • 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.



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: [24]

  • 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.



Several Cryptosporidium sporozoite antigens have been identified as potential vaccine candidates using traditional methods such as analysis of serum specificities after Cryptosporidium infection. [25] 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.


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. [26]


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. [27]



See the list below:

  • Amebiasis

    • Amebic colitis - Electrolyte imbalance and dehydration

    • Necrotizing colitis - Intestinal perforation leading to peritonitis, septicemia leading to shock

    • Ameboma - Intestinal obstruction

  • Extraintestinal amebiasis

    • Liver abscess (most common complication, associated with high morbidity rates) - Rupture to pleura, pericardium (leading to tamponade), bronchia, or peritoneal cavity (leading to peritonitis); amebic hepatitis

    • Perianal perirectal abscess

    • Abscesses in other organs (eg, brain, kidney)

  • Giardiasis

    • Acute giardiasis - Dehydration and electrolyte imbalance, mainly in young infants

    • Chronic giardiasis - Transitory disaccharidase deficiency; malnutrition; malabsorption of fats, carbohydrates, vitamin B-12, folic acid, and vitamin A; malabsorption of antibiotics leading to failure in treatment for otitis media; chronic urticaria; arthritis (resolves after successful antiprotozoal therapy)

    • Complications in giardiasis are much more common in patients with predisposing conditions such as IgA deficiency and hypogammaglobulinemia.

  • Spore-forming protozoa

    • In the immunocompetent host - Dehydration and electrolyte imbalance, transitory malabsorption, and transitory disaccharidase deficiency

    • In the immunodeficient host - Severe dehydration and electrolyte imbalance during acute episodes; malabsorption of fats, carbohydrates, and vitamins, leading to severe malnutrition; disaccharidase deficiency; biliary disease (with cryptosporidia, microsporidia, and Isospora) leading to sclerosing cholangitis, acalculous cholecystitis, or pancreatic duct involvement (very rare); extraintestinal invasion (very rare, observed only with microsporidia in patients with AIDS), eg, to the liver or lung

  • Dientamoebiasis - Dehydration and electrolyte imbalance (rare)

  • Balantidiasis

    • Severe colitis (can lead to necrotizing colitis) - Same complications as in amebic colitis

    • Disseminated disease - Liver, lung

  • Blastocystosis - Complications are very rare and usually are associated with electrolyte imbalance and, when present, are only in patients who are malnourished or immunocompromised.



See the list below:

  • Following adequate therapy, acute protozoal gastroenteritis in the immunocompetent host has an excellent outcome.

  • Exceptions are complicated cases of amebiasis and inadequately treated chronic giardiasis.

  • Symptomatic spore-forming protozoal infection in immunocompromised hosts, especially in patients with AIDS, is associated with progression of the disease, particularly when low CD4 counts (< 100/mL) are present. The mortality rate in this group of patients is high, although these individuals may improve significantly because of recovery of immune status with HAART.


Patient Education

See the list below:

  • Prevention of all intestinal protozoal infection requires disruption of the fecal-oral spread (hand washing), as well as decontamination of water (by heating at 55°C for 5 min or with saturated crystalline iodine, 12.5 mL/L/30 min) and food and adequate sanitation.

  • Amebiasis: Advise individuals traveling to endemic areas to avoid uncooked foods that might have been grown, washed, or prepared with potentially contaminated water.

  • Giardiasis

    • Children with acute symptomatic giardiasis should not attend childcare centers.

    • Infected persons and persons at risk should adhere to strict handwashing techniques after any contact with feces. This is especially important for caregivers of diapered infants in childcare centers, in which diarrhea is common and the carrier rates are high.

    • To date, antigiardial therapy for asymptomatic carriers has not been proven to reduce outbreaks in childcare centers.

    • Methods to adequately purify public water supplies include chlorination, sedimentation, and filtration.

    • Advise travelers to endemic areas to avoid uncooked foods that might have been grown, washed, or prepared with potentially contaminated water.

  • Spore-forming protozoa

    • These organisms are most commonly spread by person-to-person transmission; therefore, hand washing helps prevent infection.

    • Enteric precautions should be used for hospitalized patients, and children with diarrhea should not attend childcare centers.

    • Immunocompromised patients should take special precautions around animals and use only appropriately filtered water. This is important because regular chlorination does not kill C parvum.

  • Dientamoebiasis: Adequate sanitation, handwashing, and decontamination of water should be performed, as in giardiasis.

  • Balantidiasis: Useful methods of control include reducing human contact with infected pigs and with contaminated food and water, as well as improving conditions of personal hygiene and nutrition.

  • Blastocystosis: Adequate sanitation, handwashing, and enteric precautions interrupt person-to-person transmission.