460 Parasitology Mid term 2

Cyst and trophozoites

Cyst - dormant, thick walled cell (infectious stage)

Trophozoite - active, feeding and multiplying form

Entamoeba histolytica (protozoa)

Causes invasive intestinal amebiasis

• Intestinal ulcers, dysentery, ulcerous colitis, Mega colon

Causes invasive extraintestinal amebiasis

• liver abscess, cutaneous and genital amebic lesions, brian hemorrhages

Diagnosis

• 3x stool exam, stool wet mount, fecal EIA, PCR

Entamoeba histolytica prevention and treatment

Prevention

• wash hands, boil water, chlorination does not help

Treatment

• Asymptomatic: Iodoquinol

• Symptomatic: Metronidazole

Entamoeba histolytica life cycle

1. Eat dirt with cysts

2. Cysts mature in environment

3. Cysts infect lungs, liver and GI as trophozoites

4. Excrete out cysts

Entamoeba histolytica morphology

Trophozoite

• 15-20uM in size, single nucleus

Cyst

• Four nuclei

Entamoaeba coli (protozoa)

Cyst: 8+ nuclei

Tropozoite: 1 nucleus with large/dirty cytoplasm

Endolimax nana

Cyst: 4 nuclei; lacks peripheral chromatin

Trophozoite: Irregular blot-like karyosome

Entamoeba polecki

Cysts: many small chromatid bodies with angular pointed ends
Trophozoite: empty looking

Iodamoeba buetschlii (protozoa)

Cyst: Single nuclei, large vacuole

Trophozoite: tall (wide) cell, 1 nuclei, vacuolated

Entamoaeba hartmanni (protozoa)

Cyst: small chromatid bodies

Trophozoite: Small, compact karyosome

Dientamoeba fragilis (protozoa)

• Flagellated protozoa

• Trophozoite stage only, no cysts

• Causes symptomatic and asymptomatic infections

• 2 nuclei inclusions possible in trophozoite form

Dientamoeba fragilis life cycle

1. Ingestion of trophozoites

2. Binary fission of trophozoites in GI

3. Trophozoites secreted in feces

Balantidum coli (protozoa)

• Ciliated parasite

• Parasite of pigs; not common in humans (but we can get infected)

• Treatment: Tetracycline

• Fecal-oral transmission

Balantidum coli life cycle

1. Consumption of contaminated produce (probable fecal contamination)

2. Cyst develops into trophozoite in GI

3. Trophozoite experiences binary fission and switched back into cyst

4. Cyst is excreted

Balantidum coli morphology

• Cilia on trophozoite surface

• Bean shaped macronucleus

• Cysts not often seen

Giardia duodenalis

• Intestinal flagellate

• Has ventral suction disk that allows for attachment to GI tract

• Causes

  • inflammation of the jejunum, watery stools, steatorrhea (as vilia go flat, leading to malabsoprtion)

• Diagnosis (up to 3 stool samples observed)

  • Antigen assay

  • Fluorescent antigen test kits

  • Multiplex PCR

Giardia duodenalis prevention and treatment

• Chlorination is not effective

• Boiling water is ok

• Iodination is the best method of cleaning

  • Wash hands, eat clean, cooked food

Giardia duodenalis morphology

Trophozoite: Pear shaped organism with tail

Cyst: 2 nuclei (immature)'; 4 nuclei (mature)

Giardia duodenalis life cycle

1. Ingestion of cysts

2. Cycst develop into trophozoite

3. Trophozoite experience longitudinal binary fission

4. Trophozoite becomes cyst

5. Cyst excreted in waste products

Trichomonas vaginalis

• Flagellated protozoan

• No cyst stage, only trophozoites

• Sexually transmitted infection; most common nonviral STD

• Men symptoms

  • Asymptomatic, rarely urethritis

• Women symptoms

  • Vaginitis, discharge, PID

• Neonates

  • Congenital transmission, preterm delivery, low-birthrates

• Diagnosis

  • wet mounts and viewing motility

  • Anaerobic culture (GOLD STANDARD)

  • PCR (Preferred method)

Trichomonas prevention and treatment

• Safe sex

• Metronidazole and trinidazole

Trichomonas vaginalis life cycle

1. Sexual intercourse leads to the swapping of trophozoites

2. Multiplication in the sexual tract via longitudinal binary fission

Trichomonas vaginalis morphology

Trophozoite: undulating membrane, 4 anterior flagella

Koch’s postulate (in the context of this lecture)

Clinical data can be non-specific; PCR diagnosis alone sometimes is not enough to confirm the identity of an organism

Dinoflagellates (Alexandrium Spp) and its life cycle

• Produces saxitoin concentrate in mollusks

• Causes

  • Nerve damage, some cases paralysis