Protozoology

Protozoology

1. Structure of Protozoa

• Nucleus and cytoplasm: These are the two basic components of a protozoan cell.

• Size: Most protozoa are less than 50 micrometers in size.

2. Two Forms of Protozoa

• Cyst form: This is the inactive form, with a thick wall, that can survive for a long time in the environment. This form is the infectious form of amoebas, flagellates, and ciliates.

• Active form/ Trophozoite: This is the active form, with cytoplasm surrounded by a cell membrane.

• Ectoplasm: Responsible for excretion and respiration.

• Endoplasm: Contains the nucleus and is responsible for the cell’s nutrition.

3. Nutrition of Protozoa

• All protozoa are holozoic – they use organic matter for nutrition.

4. Classification of Protozoa

• By mode of locomotion:

• Amoebas: Examples: Naegleria, Acanthamoeba, Entamoeba, Endolimax, Pseudolimax.

• Flagellates: Examples: Giardia lamblia, Trichomonas vaginalis.

• Ciliates: Examples: Balantidium coli.

• Sporozoans: Examples: Cryptosporidium, Isospora, Cyclospora, Toxoplasma gondii, Plasmodium, Babesia.

• By mode of reproduction:

• Asexual reproduction: Common in amoebas, flagellates, and ciliates. There are two forms: cyst and active form.

• Sexual reproduction: Common in sporozoans. There are four forms: fission, trophozoite, gamete fusion, and oocyst.

5. Amoebas

• Free-living amoebas: Naegleria, Acanthamoeba.

• Intestinal amoebas: Entamoeba (histolytica), Endolimax, Pseudolimax.

• Entamoeba gingivalis: Lives in the gums.

6. Flagellates

• Intestinal parasites: Only Giardia lamblia causes disease.

• Genitourinary parasites: Trichomonas vaginalis.

7. Ciliates

• Balantidium coli: Causes diarrhea and is an intestinal parasite.

8. Sporozoans

• Intestinal parasites: Cryptosporidium, Isospora, Cyclospora.

• Parasite in multiple organs: Toxoplasma gondii.

• Parasite in blood: Plasmodium causes malaria, Babesia.

9. Entamoeba histolytica

• Active form that eats red blood cells (Trophozoite): Moves in one direction with the help of pseudopodia, has clearly distinguishable ecto/ endoplasm, is less resistant, causes disease, and reproduces by binary fission.

• Active form minuta: Lives saprophytically in the colon, smaller than the active form that eats red blood cells, can transform into a cyst.

• Cyst: Spherical/ slightly oval, with a thick wall, resistant to the environment, is the infectious form.

10. Life cycle of Entamoeba histolytica

• Non-disease-causing cycle: People ingest a 4-nucleated cyst, the cyst divides into minuta, when faced with unfavorable conditions, minuta can transform into a cyst and be excreted in feces. When favorable conditions are met, minuta can transform into the active form that eats red blood cells.

• Disease-causing cycle: The active form that eats red blood cells causes necrosis, bleeding, invades the colon wall and reproduces by binary fission, and can travel through the blood to other organs.

11. Epidemiology of Entamoeba histolytica

• Host: Healthy carriers, external environment.

• Mode of transmission: Contaminated water, food contaminated with human feces, male-to-male sexual contact.

12. Clinical manifestations of Amoebic dysentery

• Dysentery syndrome: Abdominal pain, straining, mucus and bloody stools.

13. Diagnosis of Amoebic dysentery

• Fresh smear: Finding the active form histolytica in mucus, blood, and stool.

• Monoclonal antibody technique: Finding amoebic antigens in fresh stool.

• PCR: Detecting E. histolytica DNA.

14. Complications of Entamoeba histolytica

• Gastrointestinal bleeding, intestinal obstruction, amoebic tumor, chronic colitis.

15. Visceral amoebas

• Most common in the right upper lobe of the liver.

16. Clinical manifestations of liver abscess caused by Entamoeba histolytica

• Pain in the upper right abdomen, high fever.

• Complications: Abscess rupture into the pleural cavity.

17. Diagnosis of liver abscess caused by Entamoeba histolytica

• Imaging: X-ray, CT, ultrasound.

• Abscess aspiration: Finding Entamoeba histolytica.

• ELISA: Finding antibodies in the blood.

18. Naegleria fowleri

• Form: Has 3 stages: amoeba form (infectious), flagellate form (free-living), and cyst form.

• Epidemiology: Contaminated water, enters through wounds in the nose and sinuses.

• Disease caused by Naegleria: Primary amoebic meningoencephalitis.

• Clinical manifestations: Acute headache, fever, vomiting, stiff neck, coma.

• Diagnosis: Cerebrospinal fluid examination, direct observation, brain autopsy.

• Prevention: Swimming pool disinfection, preventing water from entering the nose and throat.

19. Acanthamoeba

• Form: 2 stages: active form, cyst form.

• Epidemiology: Contaminated soil, water, dust, contact lenses.

• Disease caused by Acanthamoeba: Granulomatous amoebic encephalitis, secondary keratitis, otitis, skin ulcers, myocarditis, pneumonia.

• Clinical manifestations: Slow progression, often seen in immunocompromised people.

• Diagnosis: Brain tissue biopsy, direct observation, culture of the sample.

20. Trichomonas vaginalis

• Form: Only the active form exists, which is both infectious and disease-causing.

• Life cycle: Lives in the vagina (female) and urethra (male), feeds on bacteria, white blood cells, and secretions.

• Transmission: Direct sexual contact, indirect contact through towels, etc.

• Reproduction: Binary fission longitudinally.

• Host: Human.

• Clinical manifestations: Vaginitis (female), urethritis (male).

• Diagnosis: Direct microscopic examination of samples to find the parasite.

21. Cryptosporidium

• Form: Oocyst, spherical/ oval, with 4 sporozoites.

• Life cycle: Direct short cycle, inhalation/ ingestion of oocysts, oocysts excyst in the small intestine, transform into active form, asexual/ sexual reproduction, create oocysts.

• Epidemiological factors: Oocysts have thick walls, are resistant, contain 4 sporozoites, short direct transmission.

• Clinical manifestations: Gastroenteritis, fibrosing cholangitis, cholecystitis, interstitial pneumonia.

• Diagnosis: Stool examination, intestinal biopsy, PCR, fluorescence PCR, serological testing.

22. Toxoplasma gondii

• Form: 3 forms: Bradyzoite (slow-moving), Tachyzoite (active form), oocyst.

• Life cycle: Has 2 cycles: sexual in cats, asexual in other animals.

• Transmission: Eating/ drinking food contaminated with oocysts, eating raw meat contaminated with oocysts, pseudocysts, blood transfusion, mother to fetus via the placenta.

• Clinical manifestations: Encephalitis, meningoencephalitis, tumors, epilepsy, mild paralysis, visual impairment.

• Diagnosis: Direct detection of the parasite, detection of antibodies.

23. Plasmodium sp.

• Form: Trophozoite, merozoite, schizont, gametocyte.

• Development cycle: Has 2 stages: asexual in humans, sexual in female Anopheles mosquitoes.

• 5 types of malaria parasites that cause disease in humans: P. malariae, P. vivax, P. falciparum, P. ovale, P. knowlesi.

• Clinical manifestations: Typical malaria attack (chills, fever, sweating), anemia, thrombocytopenia, increased blood bilirubin, increased alkaline phosphatase.

• Diagnosis: Blood tests, immune diagnosis, thick blood smear.

• Treatment: Termination of attack, prevention of recurrence, prevention of transmission.

24. Giardia lamblia

• Form: Active form (infectious), cyst form (infectious).

• Life cycle: Active form attaches to the duodenum and jejunum, divides longitudinally, transforms into a cyst in the colon.

• Epidemiology: Children, water sources, food, close contact.

• Clinical manifestations: Chronic diarrhea, watery, foul-smelling, foamy stools, malabsorption, vomiting, poor appetite, mild fever, chills, epigastric pain, bloating.

• Diagnosis: Stool examination, duodenal fluid examination, detection of antigens in fresh stool.

• Treatment: Metronidazole, Ornidazole, Tinidazole, Albendazole, Paromomycin.

Note: This article provides basic knowledge about protozoology. The diagnosis and treatment of diseases caused by protozoa should be performed by a specialist.