Dysentery Causes and Types

Dysentery

• Caused by bacteria Shigella, resulting in shigellosis
• Can also be caused by other bacteria, protozoa, or parasitic worms
• Bacillary dysentery is characterized by severe diarrhea containing blood or mucus
• Caused by gram-negative, facultatively anaerobic, non-motile rods of the genus Shigella

Shigellosis

• Estimated 150 million illnesses and 14,000 deaths worldwide
• Endemic in tropical and temperate climates
• S. dysenteriae type 1 causes the most severe disease and largest outbreaks
• Other species include S. Flexneri, S. Sonnei, and S. Boydii
• Most important cause of acute bloody diarrhea

Susceptibility and Transmission

• Immunity after infection is short and unsteady, with no cross-immunity
• High-risk groups include:
  • Children under 5 years
  • Severely malnourished patients
  • Elderly over 50 years
• Period of communicability: during acute infection and until the infectious agent is no longer present in feces (usually within 4 weeks)

Pathogenesis of Shigella

• Two-stage disease:
  1. Early stage: watery diarrhea and fever due to enterotoxic activity of Shiga toxin
  2. Second stage: adherence to and tissue invasion of the large intestine, resulting in bloody diarrhea and mucosal ulcerations

Laboratory Findings and Treatment

• Blood picture: increased total WBC count and neutrophils
• Stool examination: direct microscopic exam, WBC, RBC, and pus cells
• Bacteria culture: Shigella species
• Treatment: rest, fluids, and antimicrobials for severe cases; hospitalization for severely ill or malnourished patients

Amoebiasis

• Caused by the intestinal protozoan Entamoeba histolytica
• Geographic distribution: worldwide, with higher incidence in developing countries
• Risk groups: male homosexuals, travelers, recent immigrants, and institutionalized populations
• Incubation period: 2-4 weeks
• Period of communicability: while E. histolytica cysts are excreted (may continue for years)

Complications of Amoebiasis

• Severe ulceration of the gastrointestinal mucosal surfaces
• Invasion of soft tissues, most commonly the liver
• Formation of masses (amoebomas) leading to intestinal obstruction
• Local complications: pericolic and pericaecal abscess, pyogenic liver abscess, and subdiaphragmatic abscess
• Pulmonary amoebiasis: lung abscess, pulmono-pleural fistula, and empyema
• Brain abscess and amoebic meningoencephalitis

Diagnosis and Prevention of Amoebiasis

• Diagnosis: stool examination, blood tests, proctosigmoidoscopy or colonoscopy
• Prevention:
  • Sanitary disposal of human feces
  • Safe water supply
  • Proper chlorination of water supply
  • Education on personal hygiene
  • Health supervision of food handlers
  • Flies control
  • Washing vegetables to remove cysts
  • Cysts can be killed by desiccation and high temperatures

Treatment of Amoebiasis

• Primary therapy: hydration and metronidazole and/or tinidazole

Giardiasis

• Caused by the protozoal parasite Giardia intestinalis
• Found in humans, domestic animals, and wild animals
• Occurs worldwide, especially in warm climates
• Morbidity rate up to 20%
• Infections often resolve spontaneously, but chronic infections can occur
• Can be spread through:
  • Contaminated food or water
  • Close contact with infected individuals
  • Traveling to areas with poor sanitation
  • Exposure to contaminated surfaces
  • Animal contact or environments contaminated with feces