Intestinal Protozoal Diseases Follow-up

Updated: Sep 21, 2022
  • Author: Enrique Chacon-Cruz, MD, MSc; Chief Editor: Russell W Steele, MD  more...
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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.



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.



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.


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]


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]