HCM 124 lecture 5 .ppt
- 1. HCM 124: MEDICAL PARASITOLOGY AND ENTOMOLOGY JACKSON C. KORIR (PhD) 0721- 413 606 jcheruiyot@mmust.ac.ke Masinde Muliro University of Science and Technology (MMUST) University of Choice
- 2. The Protozoa Introduction: The Phylum Protozoa is classified into four subdivisions according to the methods of locomotion. The amoebae (Sarcodina) move by means of pseudopodia. The flagellates (Mastigophora) typically move by long, whiplike flagellae. The ciliates (Ciliata) are propelled by rows of cilia that beat with a synchronized wavelike motion. The sporozoans (Sporozoa) lack specialized organelles of motility.
- 4. The Protozoa General: There are about 45,000 protozoan species; around 8000 are parasitic, and around 25 species are important to humans. Diagnosis - must learn to differentiate between the harmless and the medically important. This is most often based upon the morphology of respective organisms. Transmission - mostly person-to-person, via fecal-oral route; fecally contaminated food or water; other means include sexual transmission, insect bites or insect feces.
- 5. The Protozoa General: Exist in 2 forms: Trophozoite - the motile vegetative stage; multiplies via binary fission; colonizes host. Cyst - the inactive, non-motile, infective stage; survives the environment due to the presence of a cyst wall. Cysts do not multiply, however, some organisms divide within the cyst wall.
- 6. The Protozoa Diagnostic Features: Nuclear structure - important in species differentiation. Size - helpful in identifying organisms; must have calibrated objectives on the microscope in order to measure accurately. Cytoplasmic inclusions - chromatoid bars (coalesced RNA); red blood cells; food vacuoles containing bacteria, yeast, etc. Appearance of cytoplasm - smooth & clean or vacuolated. Type of motility - directional or non-directional; sluggish or fast.
- 7. The Protozoa Nuclear Structure: Chromatin - nuclear DNA. Present as “peripheral” chromatin and the karyosome. Karyosome - a small mass of chromatin within the nuclear space. Also called “endosome” or “centrosome.” Peripheral Chromatin - chromatin adhering to the nuclear membrane. Nuclear membrane - membrane surrounding all nuclear material. Chromatoid body or “bar” - coalesced RNA within the cytoplasm of the cyst stage.
- 8. Intestinal Protozoa - The Amoebae General Life cycle - The definitive host ingests the infective cyst stage from fecal contamination in environment. The cyst passes into the small intestine & excystation occurs with transformation to the trophozoite stage. Trophozoites colonize the host, multiplying asexually via binary fission. They can remain near the lumen (non- pathogens) or invade the wall of the intestine & multiply (pathogens). Cysts and trophozoites are passed in the feces of the infected host.
- 9. Life cycle
- 10. Intestinal Protozoa - The Amoebae Entamoeba histolytica Epidemiology - Occurs worldwide; the highest incidence and prevalence is in areas with poor sanitation. Pathology and Clinical Manifestations - the most pathogenic of all; causes amoebic dysentery; can become extra-intestinal; can be fatal. Hepatic abscess is the most common and dangerous complication. Chronic infections may last for years; often confused with colitis, cancer. Distribution - worldwide, mostly in tropics and sub-tropics.
- 11. Intestinal Protozoa - The Amoebae Entamoeba histolytica Morphology & Laboratory Identification - trophozoites range 12 to 30 microns in diameter; - nucleus has an even distribution of peripheral chromatin and a small, compact, centrally located karyosome; - cytoplasm is smooth and granular; - inclusions, if present, are red blood cells; - Motility is rapid, progressive, and unidirectional, through pseudopods - cysts range 10 to 20 microns in diameter and contains four nuclei when mature. - immature cyst has inclusions namely; glycogen mass and chromatoidal bars. - Cigar-shaped chromatoid bars may be present in some cysts.
- 12. Intestinal Protozoa - The Amoebae Entamoeba hartmanni Epidemiology - similar to E. histolytica Formerly called the “small race” of Entamoeba histolytica. Technologists must be able to differentiate this organism from E. histolytica because E. hartmanni is non- pathogenic.
- 13. Intestinal Protozoa - The Amoebae Entamoeba hartmanni Morphology & Laboratory Identification - This organism is morphologically similar to E. histolytica. The difference lies in the sizes of the respective organisms. Trophozoites will measure less than 12 microns, while cysts will measure less than 10 microns.
- 14. Intestinal Protozoa - The Amoebae Entamoeba coli Significance - this is a harmless commensal; must be differentiated from pathogens. Morphology – - trophozoites range from 10 to 35 microns in diameter; - cysts range from 10 to 30 microns in diameter and contain 8 to 16 nuclei when mature; the nucleus exhibits an eccentric karyosome with irregular, coarse chromatin. The cytoplasm is heavily vacuolated, containing yeast, bacteria, and debris.
- 15. Intestinal Protozoa - The Amoebae Entamoeba gingivalis Infective site - the mouth; the organism thrives in diseased gums, but is not considered a causal agent. It is destroyed in stomach if swallowed. Transmission - contact with fomites (drinking glasses, eating utensils, etc.); kissing. Morphology - resembles E. histolytica, but has no cyst stage. It is the only species which ingests leucocytes.
- 16. Intestinal Protozoa - The Amoebae Endolimax nana Occurrence - occurs in about 14% of the US population; 21% worldwide. Pathogenicity - none. Morphology - trophozoites range from 5 to 10 microns in diameter. The nucleus contains a large, blot-like karyosome; there is little or no peripheral chromatin. Cysts are usually sub-oval, measuring 4 to 6 by 6 to 10 microns.
- 17. Intestinal Protozoa - The Amoebae Iodamoeba butschlii Pathogenicity - none. Morphology - the cyst is often called the “iodine cyst” due to the presence of a large glycogen vacuole which stains dark brown with iodine.
- 18. - E. histolytica E. hartmanni E. coli E. polecki E.nana l. butsch lii Tropho zoiteM oveme nt Active especially in acute dysentery Sluggish Sluggish sluggish Sluggish Active Inclusi ons Red cell in case of tissue invasion No red cells No red cells No red cell No red cell No red cell Morphology of Trophozites of intestinal Amoebae (Live specimens)
- 19. - E. histolytica E. hartmanni E. coli E. polecki E. nana I.butschlii Trophozoite No. of nuclei 1 1 1 1 1 1 Karysome(N ucleolus) Usually central small Usually central small Usually central small Usually central small Large Large generally irregular Peripheral chromatin Usually symmetrical fine Usually symmetrical fine Usually symmetrical fine Usually symmetrical fine Usually symmetrical fine Incon- spicuous Cyst No. nuclei 4 4 8 1 1 1 Shape Circular Circular Circular Circular Usually oval Irregular Size(dia.) 12-20 um 2-8 um 15-25 um 11-15 um 8-12 um 10-16 um Chromatoid body Usually large rounded ends Usually large rounded ends Usually small splintered ends Variable shape Absent Absent Glycogen vacuole Diffuse Diffuse Diffuse Diffuse Absent large and sharply demarcated Other inclusions Nil Nil Nil Usually large faintly staining mass Nil Sometimes minute rod like bodies Differential characteristics of intestinal amoebae (stained specimens)
- 20. Treatment & prevention of pathogenic amoeba Treatment- metronidazole marketed under brand name flagyl followed by Iodoquinol Prevention- Introduction of adequate sanitation measures and education about the routes of transmission. - Avoid eating raw vegetables grown by sewerage irrigation and night soil.
- 21. Tissue Dwelling Amoebae Naegleria fowleri Classification - an ameboflagellate; a free-living organism alternating between amoeboid and flagellated forms; only the amoeboid form is found in tissues. Life cycle - the amoeba gains entry via the nasal mucosa, usually during a swimming event; it moves along the olfactory nerve, gaining access to the brain via the cribriform plate. Cases are invariably fatal. Infections do not spread from person-to-person. Naegleria fowleri trophozoite in CSF
- 22. The Protozoa Tissue Dwelling Amoebae Naegleria fowleri Symptoms - Dramatic and rapidly progressive. Headache, fever, nausea & vomiting occur within 1 to 2 days. Meningoencephalitis, irrational behavior, coma & death usually occur within 9 days of exposure. Diagnosis - Usually made at autopsy. CSF contain motile amoebae. Early diagnosis is critical. Amoebae in CSF specimens can be cultured on non- nutrient agar containing bacteria.
- 23. Tissue Dwelling Amoebae Acanthamoeba spp. Life cycle - also a free-living amoeba. The amoeba reaches the brain hematogenously after entering a wound or lesion on the skin. More commonly, the organism is associated with getting into eyes via contaminated or homemade cleaning solutions. Symptoms - slow onset (10 or more days). Presents as chronic, granulomatous lesions in brain. In eye lesions, the infection resembles a herpes virus infection. Acanthamoeba keratitis - associated with users of extended-wear contact lenses.
- 24. Superclass Mastigophora - the flagellates. Inhabit the mouth, bloodstream, gastrointestinal, or urogenital tracts. Morphological Characteristics Flagellum(ae) - organelles of locomotion; an extension of ectoplasm; moves with a whip-like motion. Axostyle - a supporting mechanism, a rod-shaped structure; not all flagellates have these. Undulating membrane - a protoplasmic membrane with a flagellar rim extending out like a fin along the outer edge of the body of some flagellates. Costa - a thin, firm rod-like structure running along the base of the undulating membrane. Cytosome - a rudimentary mouth; also referred to as a gullet.
- 25. Superclass Mastigophora - the flagellates. Identification of a flagellate is based upon: Size. Shape. Motility. Number and morphology of nuclei. Number and location of flagellae. Location in the body of the host.
- 26. Superclass Mastigophora - the flagellates. There are three groups of flagellates: • Luminal flagellates -Giardia duodenalis -Dientmoeaba fragilis • Hemoflagellates -Trypanosoma species. -Leishmania species. • Genital flagellates -Trichomonas vaginalis
- 27. Intestinal flagellates Giardia duodenalis Most common protozoan parasite Life cycle - man ingests cysts from fecally contaminated environment; the organism excysts in the upper intestine; trophozoites multiply and attach to the intestinal mucosa; often enter the gall bladder. Trophozoites and cysts are passed in the feces. Diagnosis - identification of cysts or trophozoites in stool specimens or duodenal contents.
- 28. 1-2. Giardia cysts are the infective stage of G. intestinalis. As few as 10 cysts can cause infection (1). These cysts are ingested by consuming contaminated food or water, or fecal-orally. They can survive outside the body for several months, and are also relatively resistant to chlorination, UV exposure and freezing. 3. When cysts are ingested, the low pH of the stomach acid produces excystation, in which the activated flagella breaks through the cyst wall (1). This occurs in the small intestine, specifically the duodenum. Excystation releases trophozoites, with each cyst producing two trophozoites. 4. Within the small intestine, the trophozoites reproduce asexually (longitudinal binary fission) and either float free or are attached to the mucosa of the lumen. 5. Some trophozoites then encyst in the small intestine. Encystation occurs most likely as a result of exposure to bile salts and fatty acids, and a more alkaline environment. Both cysts and trophozoites are then passed in the feces, and are infectious immediately or shortly afterward. Person-to-person transmission is possible. Life cycle of Giardia
- 29. Intestinal flagellates Giardia duodenalis Morphology - very distinctive. Dorsal-ventrally flattened, and Bi- laterally symmetrical. Cyst - 9 x 12 micrometers and contain 2 to 4 nuclei; parabasal bodies are present. Trophozoite - Four pairs of flagella - one pair located anterior, two pair located ventrally, and one pair located posteriorly. An axostyle and parabasal bodies are present. Trophozoite Cyst
- 30. Intestinal flagellates- Giardia duodenalis Epidemiology - prevalence 1 to 30%, common in children’s day care centers; can be transmitted in water. Sexual transmission has been well documented. Pathology and Clinical Manifestations - symptoms can be severe; diarrhea, foul-smelling, greasy, mucus-laden stools, flatulence, nausea, cramps. Most infections are asymptomatic; chronic cases experience weight loss, malabsorption of fat, protein, folic acid, and fat-soluble vitamins. Laboratory diagnosis- Examination of diarrhoeal stool- trophozoite or cyst, or both may be recovered in wet preparation. Treatment- quinacrinehydrochloride or metronidazole.
- 31. Intestinal flagellates- Dientamoeba fragilis General - Formerly classified as an amoeba; electron microscopy and immunological studies have suggested a flagellate nature. Laboratory diagnosis - detection of bi- nucleated trophozoites; fragmented karyosomes consisting of 4 to 8 granules of chromatin.
- 32. Intestinal flagellates Dientamoeba fragilis Diagnostic stage - the trophozoite in feces. There is no cyst stage. Morphology - 1 or 2 nuclei, with little or no peripheral chromatin; karyosome is divided into 4 to 8 distinct granules. May rarely ingest rbc’s.
- 33. Intestinal flagellates Dientamoeba fragilis Pathology - infection is usually asymptomatic; can be associated with diarrhea, anorexia, abdominal pain. Association with pinworm - the organism may be transmitted from host to host within the egg of Enterobius vermicularis. Distribution - worldwide, there is a 1% to 20% prevalence.
- 34. Intestinal flagellates- Chilomastix mesnili A non-pathogen - must be differentiated from Giardia. Found in cecum and colon. Transmission - by ingestion of mature cysts.
- 35. Intestinal flagellates- Chilomastix mesnili Morphology - Trophozoite - 4 flagella (3 anterior, 1 associated with the cytostome; one nucleus, always located anteriorly. Cyst - lemon shape; 1 nucleus; cytostome may be seen.
- 36. The Trichomonads Characteristics - Undulating membrane - protoplasmic membrane with flagellar rim extending out like a fin along outer edge of body. Flagella - several in a tuft, provides locomotion. Axostyle - functions for support. Costa - firm rod-like structure running along base of the undulating membrane. Cytostome - rudimentary mouth.
- 37. The Trichomonads- Trichomonas hominis Commensal - must differentiate from pathogens. Transmission - direct person-to-person fecal transmission; no cyst stage. Morphology - “arc-shaped” exhibits a wobbly, jerky, motility. Must differentiate from T. vaginalis - in instances where feces is contaminated with urine.
- 38. TheThe Trichomonads- Trichomonas vaginalis Life cycle - trophozoite lives in the vagina, urethra, epididymis, and prostate; multiplies via longitudinal fission; no cyst stage. Mode of infection - sexual intercourse or fomites. Diagnosis - identification of trophozoites in body fluids (wet mounts of discharges) or on PAP smears.
- 39. Trophozoite
- 40. The Trichomonads Trichomonas vaginalis Pathology - Females: vaginal discharge; burning, Itching, or chafing. Frequency of urination or dysuria. Males: frequently asymptomatic. If the prostate is involved, the patient may develop discharge, dysuria, and enlargement of prostate with tenderness. Morphology - has an axostyle and short undulating membrane that extends less than half the body length; 4 flagellae. Treatment- Metronidazole
- 41. Class Ciliophora - The Ciliates Balantidium coli Epidemiology - Rarely found. This is the only ciliate parasite of humans. Largest parasitic protozoan - trophozoite is 30-120 x 25-125 microns; the cyst averages 50 - 70 microns in diameter. Life cycle - The cyst is ingested via fecal contamination in environment; cysts excyst in the small intestine; trophozoites migrate to large intestine.
- 42. Class Ciliophora - The Ciliates Balantidium coli Pathology & Symptoms - Many infections are asymptomatic, organism feeding on bacteria at surface of mucosa. Severe infections - with the aid of hyaluronidase, the organism burrows into submucosa, producing ulcers. Symptoms - dysentery, abdominal pain, nausea & vomiting, fever, headache. Diagnosis - Diagnosed by observing cysts & trophozoites in fecal samples. Treatment-The drug of choice is tetracycline; iodoquinol and metronidazole are alternative agents.
- 43. Class Ciliophora - The Ciliates Balantidium coli Morphology - Large, oval shape; two nuclei, 1 large kidney shaped (macronucleus) & 1 small micronucleus (micronucleus not often seen); body surface covered by longitudinal rows of cilia; cytostome present. Primary animal reservoir - pigs, monkeys.