Introduction:
Conventionally most infections in humans occur through parasites. However, parasitic infections are defined as those caused by helminths or protozoa. In addition, protozoal infections are classified based on the mode of transmission, such as enteric transmission (Balantidium, Cryptosporidium, Toxoplasma, Giardia, Entamoeba, Cyclospora, and Microsporidia), sexual transmission (Trichomonas), arthropod transmission (Babesia, Plasmodium, Leishmania, and Trypanosomes), and other modes of transmission (Naegleria, Acanthamoeba, and Toxoplasma).
What Are the Causes of Intestinal Protozoal Infections?
Intestinal protozoal diseases are primarily transmitted through the fecal-oral route. Food and water contamination also leads to most of the outbreaks. Immunologic factors like T-cell responses and immunoglobulin A (IgA) are essential for spore-forming protozoa and giardiasis. Another risk factor associated with intestinal protozoal infection is malnutrition. Swine also act as an important reservoir for balantidiasis and dientamoebiasis is usually associated with pinworm co-infection.
What Are the Symptoms of Intestinal Protozoal Infections?
The symptoms of intestinal protozoal infections depend on the different types of protozoal infections.
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Amebiasis: Noninvasive intestinal infections usually do not show any symptoms. However, gastrointestinal symptoms are present in some instances, including mild diarrhea and constipation with or without mild abdominal pain, and most patients tolerate the infection. In intestinal amebiasis or amebic colitis, the individuals suffer from diarrhea for one to three weeks, bloody stools with abdominal pain, and weight loss. Acute fulminant or necrotizing colitis is associated with improper treatment involving corticosteroids. The patient suddenly develops constipation after a severe episode of dysenteric diarrhea followed by episodes of shock. Amoeboma, a mass of granulation tissue, is formed in the cecum or ascending colon. It is in less than one percent of patients with intestinal amoebiasis. A liver abscess is seen in ten percent or less of the patients with invasive E. histolytica infections. Patients present with symptoms of fever, abdominal pain, and poor appetite. Diarrhea is associated with a liver abscess in 20 percent of cases.
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Giardiasis: Symptoms of these infections are seen more commonly in children than in adults. In the United States, the asymptomatic carrier rate of G. lamblia is estimated to be three to seven percent, but in southern regions, it can be as high as 20 percent. Most infections produce no symptoms in endemic giardiasis. In acute infectious diarrhea, patients generally show symptoms within ten days of exposure, and the symptoms develop within three weeks in more than 90 percent of the patients. The symptoms are acute diarrhea include low-grade fever, nausea, abdominal pain, and anorexia. Acute giardiasis may resolve spontaneously. Chronic giardiasis includes intermittent, loose, and foul-smelling stools. Symptoms of abdominal pain, flatulence, epigastric pain, nausea, and anorexia are commonly noticed. Studies have revealed that giardiasis may also be associated with chronic urticaria, gallbladder disease, and treatment failures due to antibiotic malabsorptions in otitis media.
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Spore-Forming Protozoa: These protozoa usually produce an asymptomatic infection. Cryptosporidia usually causes asymptomatic infection in normal and immunodeficient individuals. All spore-forming protozoa are more common and severe in patients who are immunodeficient. Most cases are documented in patients with autoimmune deficiency syndrome (AIDS). Studies have revealed that severe cryptosporidia infections are seen in individuals with renal transplantation and deficiency of immunoglobulin A (IgA). Biliary tract Infection has been associated with Cryptosporidium, Isospora, and Microsporidia, causing abdominal pain along with jaundice and fever.
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Dientamoebiasis: The D. fragilis infection includes abdominal pain, diarrhea, anorexia, nausea, and vomiting. Less commonly occurring symptoms include fever, weight loss, and fatigue. Diarrhea takes around one to two weeks to subside. However, abdominal pain can last for one to two months. This infection is highly associated with pinworms, causing anal pruritus or lower urinary tract infections in many individuals (especially young girls).
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Balantidiasis: These infections are usually asymptomatic. However, in some individuals, an acute or chronic illness may develop. The patient complains of diarrhea in acute illness with abundant mucus and blood in the stool. Patients may also experience nausea and vomiting. In most cases, patients recover without any treatment. However, in some cases (immunodeficient or malnourished individuals), the infection can be sudden, severe, and fatal. Generally, the infection occurs with episodes of intermittent diarrhea and constipation. An appendicitis-like illness may be seen in some cases, but extraintestinal infection rarely occurs.
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Blastocystosis: It is believed that B. hominis causes infection only when it is present in huge numbers. However, some studies show that the quantity or number of parasites does not give an accurate prediction of the severity of the infection. Common symptoms include abdominal pain, diarrhea, and flatulence. Fever and bloating may also be seen in some patients.
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Amebic or Balantidic Colitis: The infection presents with nonlocalized abdominal tenderness, and one-third of patients usually have a low-grade fever. In young infants, dehydration may also be seen. Individuals with acute or fulminant colitis present with severe abdominal pain, distension, and tenderness, with or without fever. Signs of shock may also be present. Tender hepatomegaly is present in almost all cases of amebic liver abscess, and fever is present in 80 to 90 percent of cases, with or without hypoventilation of the lower right lung. In severe cases, jaundice is also present.
How Are Intestinal Protozoal Infections Treated?
It is essential to follow standard pediatric assessments for treating children with diarrhea caused by intestinal protozoa. Children usually show symptoms of dehydration, tachycardia (heart beat more than 100 times per minute), decreased tears, lethargy, decreased urine output, and altered mental status. Hypovolemic shock may also occur with these infections, and treatment should be provided accordingly. Oral rehydration therapy (ORT) is given to children with mild-to-moderate dehydration. For immediate fluid resuscitation for dehydration, the physician should look for potential nutritional deficiencies and administer nutrition to the child with acute or chronic diarrhea. Protozoal gastrointestinal infections in immunocompetent patients are usually self-limiting, and no special precautions are needed. The treatment of choice for this infection is specific antiprotozoal therapy. Patients with severe amoebic or balanitis colitis should not be given oral nutrition, and proper monitoring for potential surgical complications should be done. Parenteral nutrition can be administered in some patients. Patients with amoebic liver abscesses should be hospitalized to avoid further complications.
Conclusion:
Protozoan parasites can thrive in most environmental conditions, including refrigerated storage. Therefore, various treatments are employed to inactivate protozoan parasites in food, water, and ecological systems. For the inactivation of protozoan parasites in the water, ozone is the most effective chemical disinfectant besides chlorine or chlorine dioxide. Additional prevention methods should be used for children with gastroenteritis, including wearing gowns and gloves for patient care and washing hands properly after contact.
