MIDTERMS TOPIC

• Protozoans in general


  • Characterize the protozoans in general
• Protozoans that are medically important

  • Enumerate and classify the protozoans that are medically important
• Amoeba, flagellates, ciliates


  • Describe the general morphology
• Pathophysiology, life cycle, infective stages, modes of transmission, prevention and control

  Explain the pathophysiology, life cycle, infective stages, modes of transmission, prevention and control
• Diagnostic features of each parasite

  • Describe the diagnostic features of each parasite
• Different specimens used for identification of parasites

  • Enumerate the different specimens used for identification of parasites

  
• Identify correctly the diagnostic features of each parasite

  
• Specimen collection, handling, processing, preservation and its disposal


  Discuss specimen collection, handling, processing, preservation and its disposal
• Flagella


  Locomotory organelles
• Axoneme


  Root of flagellum
• Undulating membrane


  Flagellum fin like structure that generates a wavelike motion
• Cytostome


  Serves as oral cavity
• Kinetoplast


  Constitute the neuromotor apparatus (blepharoplast and parabasal body), serve as sensory organ
• Giardia lamblia


  • Only intestinal flagellate that is pathogenic but non-invasive
• Trophozoite


  Rounded anteriorly, tapering at the posterior end (pear-shaped), bilaterally symmetrical, binucleated (centrally nucleated), with 4 pairs of flagella; 8 flagella, parabasal bodies: with sucking disc (for attachment), motility: falling leaf motion, measure 8 to 12 um

  
• Cyst


  Oval, double-walled organism, with 2-4 nuclei (young cysts: 2 nuclei, mature cysts: 4 nuclei), centrally located karyosome, with parabasal body

  
• Giardia lamblia is pathogenic but non-invasive
• Giardia lamblia possesses the sucking disk


  On intestinal wall, the parasite would attach on the intestinal wall and that would destroy the intestinal villi
• Destruction of intestinal villi

  Leads to malabsorption that causes diarrhea
• Giardia lamblia does not produce tissue lesions but it destructs intestinal villi
• Giardia lamblia does not cause blood ingestion or tissue invasion
• Transmission of Giardia lamblia

  Trophozoite or cyst stage may be excreted through defecation, contaminate food and drink, cyst stage is the infective stage, upon ingestion of the cyst, there is transformation of trophozoite (excystation)

  
• Cysts from animals or human feces are transferred to the mouth via contaminated hands, food, or water
• Life cycle of Giardia lamblia


  Mature cysts (infective stage) are ingested, they pass through the stomach and excyst in the duodenum developing into trophozoites which rapidly multiply and attach to the intestinal villi, trophozoites may then be found in the jejunum, as the feces enters the colon and dehydrates, the parasite then encysts, after encystment, mature cysts are passed out in the feces and are infectious

  
• Cyst is resistant to the acidity of the stomach, trophozoite is fragile and can be destroyed in the low pH of the stomach
• Life cycle of Giardia lamblia

  Portal of Entry - Mouth, Mode of Transmission - Ingestion of (quadrinucleated) infective cyst, Habitat - Intestine, Portal of Exit - Anus
• Giardia lamblia is non-tissue invading but with mechanical irritation of the intestine, destructing the intestinal villi
• Diagnostic stage: cyst and trophozoite, Infective stage: cyst
• Giardiasis


  The disease caused by Giardia lamblia, a significant but not life-threatening gastrointestinal disease
• Giardiasis is the causative agent of Traveller's diarrhea
• Ingestion of the cysts

  Takes 1-4 weeks for disease to manifest (Average: 9 days)
• Giardia lamblia may be asymptomatic (cyst passer)
• Mechanical irritation of the sucking disc to the microvilli

  Leads to deficiencies in the digestive enzymes, malabsorption (steatorrhea)
• Acute cases of giardiasis


  • Abdominal pain, cramping with diarrhea, flatus with an odor of H2S (Hydrogen sulfide), bloating, nausea and anorexia followed by malaise and flatulence, diarrhea for weeks or months if untreated
• Diarrhea is the most common symptom of giardiasis, occurring in 89% of cases
• Chronic cases of giardiasis

  • Steatorrhea or the passage of greasy, frothy stool that float on toilet water, weight loss, profound malaise and fever
• Diagnosis of giardiasis


  Stool examination (demonstration of cyst and trophozoite) - DFS, Conc. Tec, diagnostic test: demonstration of the parasite in duodeno-jejunal aspirate (Entero-test) or biopsy specimen

  
• Prevalence of giardiasis is associated with poor environmental sanitation
• Control and prevention of giardiasis

  Treatment of cases (Metronidazole), proper or sanitary waste disposal to prevent contamination of water supply and food, avoid the use of night soil as fertilizer
• Chilomastix mesnili


  • Commensal, non-pathogenic, inhabits the cecal region of the large intestine