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Intestinal Protozoa, Molecular Testing

Protozoan infections can cause significant gastrointestinal issues and are prevalent worldwide, especially in regions with poor sanitation and hygiene practices. This test covers the most critical intestinal protozoa using an accurate molecular method (PCR): Entamoeba histolytica, Cryptosporidium parvum, Isospora/Cystoisospora belli, Dientamoeba fragilis, Blastocystis hominis, Giardia lamblia, and Entamoeba dispar.

Entamoeba histolytica

Entamoeba histolytica is a protozoan parasite causing amoebiasis, which can lead to both intestinal and extra-intestinal infections.

  • Transmission: Fecal-oral route, through contaminated food and water, and person-to-person contact.
  • Symptoms: Ranges from asymptomatic infection to severe dysentery with bloody diarrhea, abdominal pain, fever, and, in chronic cases, liver abscesses.
  • Treatment: Metronidazole or tinidazole followed by a luminal agent such as paromomycin or iodoquinol to eliminate cysts in the intestine.

Cryptosporidium parvum

Cryptosporidium parvum is a protozoan that causes cryptosporidiosis, leading to gastrointestinal illness.

  • Transmission: Fecal-oral route, commonly through contaminated water, including recreational water sources like swimming pools.
  • Symptoms: Watery diarrhea, abdominal cramps, nausea, vomiting, fever, and weight loss. Symptoms are particularly severe in immunocompromised individuals.
  • Treatment: Nitazoxanide is used for immunocompetent patients, while supportive care are critical for immunocompromised individuals.

Isospora/Cystoisospora belli

Cystoisospora belli (formerly Isospora belli) causes cystoisosporiasis, leading to gastrointestinal symptoms.

  • Transmission: Fecal-oral route, through ingestion of contaminated food or water.
  • Symptoms: Watery diarrhea, abdominal pain, weight loss, fever, and eosinophilia. Chronic infection can occur in immunocompromised patients.
  • Treatment: Trimethoprim-sulfamethoxazole (TMP-SMX) is the treatment of choice, with supportive care for hydration.

Dientamoeba fragilis

Dientamoeba fragilis is a protozoan parasite associated with gastrointestinal symptoms, though its pathogenicity is debated.

  • Transmission: Uncertain, but possibly via fecal-oral route or through helminth eggs like those of Enterobius vermicularis.
  • Symptoms: Diarrhea, abdominal pain, bloating, and nausea. Some individuals may remain asymptomatic.
  • Treatment: Metronidazole or iodoquinol are commonly used treatments, with consideration for treating concomitant helminth infections.

Blastocystis hominis

Blastocystis hominis is a common protozoan found in the intestines of humans and many animals. Its clinical significance is often unclear.

  • Transmission: Fecal-oral route through contaminated food and water.
  • Symptoms: Diarrhea, abdominal pain, bloating, nausea, and fatigue, though many infections are asymptomatic.
  • Treatment: Often not required for asymptomatic individuals. Symptomatic cases may be treated with metronidazole or trimethoprim-sulfamethoxazole (TMP-SMX).

Giardia lamblia

Giardia lamblia (also known as Giardia intestinalis or Giardia duodenalis) causes giardiasis, a common intestinal infection.

  • Transmission: Fecal-oral route, through contaminated water, food, and person-to-person contact.
  • Symptoms: Watery diarrhea, abdominal cramps, bloating, nausea, weight loss, and fatigue.
  • Treatment: Metronidazole, tinidazole, or nitazoxanide are commonly used treatments. Hydration is essential for managing symptoms.

Entamoeba dispar

Entamoeba dispar is a non-pathogenic amoeba morphologically identical to Entamoeba histolytica.

  • Transmission: Fecal-oral route, through contaminated food and water.
  • Symptoms: Generally asymptomatic, as E. dispar is considered non-pathogenic.
  • Treatment: It is not typically required due to its non-pathogenic nature, but accurate diagnosis is essential to avoid unnecessary treatment.

Protozoan infections like those caused by Entamoeba histolytica, Cryptosporidium parvum, Cystoisospora belli, Dientamoeba fragilis, Blastocystis hominis, Giardia lamblia, and Entamoeba dispar present a significant health concern, particularly in areas with poor sanitation. Diagnosis often relies on stool examination, with advanced methods like PCR providing more accurate identification. Treatment varies by pathogen, focusing on specific antimicrobial agents and supportive care. Improved sanitation, hygiene practices, and access to clean water are crucial for preventing these infections.

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