Protozoan Parasites: Characteristics, Diseases, and Prevention
Protozoa: An Introduction
Protozoa are unicellular organisms. Some may be parasitic. They have core mitochondria, are eukaryotic, feed by phagocytosis, and reproduce by bipartition. Their vegetative form is the infective trophozoite cyst.
Entamoeba histolytica
Kingdom: Protista. Family: Entamoebidae. Genus: Entamoeba. Species: Entamoeba histolytica. It is an anaerobic eukaryotic parasite that lives in the lumen and the wall of the intestine. Its reservoir is humans only. It is found in three forms: trophozoite, cyst, and metacyst. The metacyst is derived from the cyst. What enters the body is the metacyst, which then passes to the cyst, and the trophozoite remains as the final form. Method of transmission: Fecal-oral and sexual transmission. Stages: When a person eats contaminated plants, the parasite enters the stomach and colon, locating itself in the cecum and becoming a metacyst. This divides into eight trophozoites, which can multiply and adhere to the intestine. The trophozoite causes the patient to develop Amebiasis. Diagnosis and treatment: Diagnosis is achieved by laboratory examination of stool using light microscopy. In some cases, imaging of the liver is needed. Prevention: Boiling water, washing vegetables and fruits thoroughly. The trophozoite feeds on the food bolus and intestinal bacteria. It has adhesins that allow it to attach to the mucosa, preventing it from being dragged out by diarrhea.
Amebiasis
Amebiasis is a parasitic disease of the intestine that is transmitted through contaminated food or water, via the mouth. Clinical presentation: It causes fever, chills, headache, diarrhea, dysentery, and fatigue. There are a few types of amebiasis, including intra- and extraintestinal. Therapy: Intestinal therapy for treatment when there is an abscess involves using an intraintestinal amebicide, such as metronidazole. Liver therapy also involves metronidazole. Prevention: Proper handwashing before cooking, after using the bathroom, and after changing a baby’s diaper. Boil vegetables at a temperature above 40°C. Use chlorinated water.
Acanthamoeba
Kingdom: Protista. Environmental reservoir: Water. Clinical picture: Includes headache, behavioral changes, and fever. It exists in both trophozoite and cyst forms. In the environment, it is found as a cyst. The cyst enters the body, and the trophozoite is the vegetative form in humans. It is anaerobic, requiring low oxygen tension. Transmission: Nasal, respiratory, and cutaneous routes. Diagnosis: Patient history. Biopsy. Treatment: Use of antimicrobial combinations, such as azoles (clotrimazole, miconazole).
Acanthamoeba Keratitis
Clinical presentation: Pain, photophobia, tearing, foreign body sensation. Risk group: Immunocompromised individuals (e.g., HIV). Symptoms: Headache, vomiting, nausea. Affected area: The central nervous system (CNS). Keratitis is an infection that occurs in the eye and is spread by poor handling of contact lenses or by infected water.
Naegleria fowleri
Naegleria fowleri is the most common species. Environmental reservoirs: Water. Clinical presentation: Amoebic meningitis. Causes: Swelling, hemorrhagic necrosis, and involvement of gray matter in the brain. Prevention: Avoid swimming in non-chlorinated standing water in places that are not recommended. Contagion: Direct water route to the nasal cavity. Treatment: Clotrimazole and Rifampin.
Giardiasis
Etiologic agent: Giardia lamblia. Reservoir: Humans and animals, such as beavers and rats. Transmission: Contaminated water or food, and fecal-oral route.
Giardiasis: Clinical Manifestations
Giardiasis produces explosive diarrhea, nausea, and fatigue. Stages: In the gut, it exists in the form of a trophozoite, where it feeds and reproduces. It is then eliminated in the feces as cysts, which can contaminate water or food and be transmitted to others. The main clinical picture is malabsorption syndrome. Prevention: Treat water of doubtful origin by boiling (chlorination does not affect Giardia). Wash your hands. Cook food properly.