Balantidiasis

Balantidiasis is a zoonotic parasitic infection caused by the protozoan Balantioides coli. It is most prevalent in warm and humid climates. Transmission primarily occurs through the ingestion of food or water contaminated with cysts from the feces of reservoir hosts, most commonly pigs. The intestine is usually the primary site of infection, but extraintestinal infections can occur in various organ systems. While many infections are asymptomatic, clinical presentations can vary. Manifestations of symptomatic intestinal balantidiasis range from intermittent diarrhea (chronic form) to bloody diarrhea (acute dysenteric form). Diagnosis is typically confirmed by direct microscopic identification of trophozoites in stool samples. Treatment options include tetracycline, metronidazole, and iodoquinol, but data on the efficacy of pharmacological treatment is very limited. Severe complications include intestinal ulceration, perforation, and peritonitis.

• Pathogen: Balantioides coli (parasitic ciliated protozoan)
• Primary reservoir: pigs and nonhuman primates
• Transmission
  • Primary: ingestion of contaminated food or water
  • Less common: direct contact with infected animals or their feces (e.g., animal handlers)
• Risk factors
  • Close proximity to pigs or their feces ^[1]
  • Immunocompromised status ^[2]

• Geography: worldwide; most prevalent in tropical and humid climates (e.g., Asia, South America, Africa) ^[2]
• Age: children > adults ^[1]

Epidemiological data refers to the US, unless otherwise specified.

Many infections are asymptomatic, with hosts acting as carriers.^[2]

• Intestinal infection ^[1][2]
  • Typically affects the large intestine (cecum and colon)
  • Acute (dysenteric) form
    • Diarrhea with mucus and blood
    • Tenesmus
    • Severe cases: intestinal wall ulceration and perforation
  • Chronic form
    • Intermittent diarrhea
    • Colic
    • Abdominal pain
• Extraintestinal infection: less common; symptoms vary by location and may include the following ^[1]
  • Genitourinary: dysuria
  • Pulmonary: dyspnea, hemoptysis
  • Ocular: red eyes, photophobia, foreign body sensation
  • Hepatic: pain in the right upper quadrant
  • Peritoneal: abdominal distention

Diagnosis is typically made by microscopic identification of the parasite in stool samples. ^[2]

• Stool microscopy ^[2]
  • Gold standard for routine diagnosis
  • Direct examination of a fresh fecal sample without preservation is the preferred method for trophozoite identification.
  • Sedimentation techniques: may detect cysts; less sensitive and generally not recommended
• Biopsy: can confirm tissue invasion; helpful for suspected extraintestinal infection ^[2]
• Analysis of other biological samples (e.g., urinary sediment, BAL): Consider for extraintestinal infection. ^[2]

Protozoan culture in vitro is not routinely recommended for clinical diagnosis. ^[2]

There is limited data on the efficacy of pharmacological treatment; specialist consultation is advised.

• Tetracycline is most commonly used. ^[2]
• Alternatives include metronidazole and iodoquinol.

• Intestinal perforation
• Peritonitis
• Intestinal ulceration
• Abscess formation
• Rarely: fulminant infection and death within 3–5 days ^[1][2]

We list the most important complications. The selection is not exhaustive.