Phylum Apicomplexa Flashcards
Phylum Apicomplexa
Apical complex serving for attachment to host cells
Tissue parasite
Complex life cycle - alternating sexual & assexual gen
Characteristic secretory organelle at 1 end
Toxoplasma gondii
Class conoidasida
Luminal protozoa, obligate intracellular coccidian parasite (sexual sporogonic phase, asexual schizogonic phase)
Morphology - schizonts, tissue cysts, gamonts, oocysts
Schizonts (sporozoan trophozoite that replicates via schizogony)- sm basophillic intracellular bodies. Divide rapidly > sm collection of trophozoites (tachyzoite)
Tropozoite
- 2-7um, crescent shaped (1 pointed (apical complex here) + 1 rounded end)
- pseudocysts in acute infection
- nucleus, mitochondria, golgi, rhoptry, micronemes, 3 polar rings in conoid
- susecptible to drying, freezing + gastric digestion
Tissue cysts (schizogony)
- resting form (found in chronic stage of infection in brain, sk msc etc)
- surrounded by thin 1o eosinophillic cyst wall
- contain 100’s basophillic bradyzoites (slow multiplying parasites within the cyst)
- round/oval 10-20um
- suseptible to desiccation, freezing, thawing and heat >60oc
Gamonts - exhib sex differentiation
Oocyst
- develop in definite host (I of feline)
- formed from sexual repro
- sm ovoid 10-12um
- thick resistant wall
- millions shed in cat faeces/day
- Sporulation in soil > 2 round sporocyts w/ 4 elongated sporozoites (sporulated oocyst is infective)
- v resistant to environ conditions
T gondii
Host
1 - definite = felines (sexual + asexual)
2 - intermediate = man + other mammals (asexial)
Two life cycles (enteric - cat, exoenteric - human)
1 - cat ingest tissue cysts in meat/ingest oocysts in faeces
2 - bradyzoits released in SI > asexual shizogony > merozoites
3 - some merozoites > extraintestinal tissue > tissue cysts in organs of body
4 - merozoites > M + F gametocytes > gametogony (micro + macrogamete > oocyst w/ sporoblast)
5 - oocyst excreted in faeces + develop in soil > sporulated oocyst (infective) > ingested by birds/rats
6 - Man acquire by ingest contam food/water w/ sporulated oocyst/ undercooked meat w/ tissue cyst
7 - Excystation in SI > bradyzoites released from tissue cyst/ sporozoite released from oocyst
8 - Sporozoites + bradyzoites infect intestinal mucosa > multiply by endodyogeny ( 2 daughter cell w/i 1 mother) > tachyzoites > multiply
9 - spread to other organs > tissue cyst forms > dead end
[zoonosis]
T gondii - Disease
Toxoplasmosis (zoonosis)
Human transmission
- congential transplacental m>f
- acquired
Symptoms
- most human infections are asymptomatic
- flu like symptoms w/ swollen lymph glans/ msc aches + pains lasting month/ more
- fever, sore throat
- reduced/ blurred vision, pain, redness of eye
- can cause damage to brain, eyes + other organs (severe cases with those who have weak immune systems)
Diagnosis
- serology test for antibodies :IgG antibody, IgM, IgA (ELISA, IFAT)
- Molecular - PCR
Microscopy - tachyzoites + tissue cysts in blood, dputum, BM (stain w/ giemsa, PAS)
- MRI + CT CNS
Prevention
- don’t eat undercooked meat, wash fruit + veg, X unpasteurized milk, cover sandboxes, gloves for gardening, wash hands
Treatment
Congential - pyrimethamine + sulfadiazine
Immunocomp - w/o lymphadenopathy x req specific therapy unless severe
Immunocompromised - 1o prophylaxis, sulfamethoxazole
Genus Plasmodium - Lifecycle
Class sporozoa
Host - Definite=F anaopheles mosquito, intermediate= vertebraes
Schizogony (asexual in verbrate host)
1) Sporozoite (infective) F anophales salivary gland > bloodstream via blood meal
2) >invade liver hepatocytes> initiate exoerythrocytic schizogony (no pigment in liver schizonts)
3) sporozoite > schizgony > many uninucleated merozoites (schizont)
4) Parasitized liver cell rupture > free merozoites
5) Erythocytic schizogony > merozoites invade RBC as by invag RBC membrane
6) > ring form (young trophozoites) > trophozoites > schizgony > merozoites (schizonts) (hemozin pigment as feed on Hb)
7) > rupture cell > reinvade new cells
NB. Some parasite which don’t invade RBC X divide but > M + F Gametocytes
Sporogony (sexual in mosquito) - 10-17 D
1) Blood meal > gametocytes enter mosquito
2) Nucleus of male microgametocytes >divide to 6-8 nuclei > migrate to periphery of parasite
3) Exflagellation - uninucleur microgamete thrust out and detached from parental cell
4) F microgame mature > macro
5) Fertilisation - M microgamete + Macrogamete > zygote
6) After blood meal zygote > wormlike ookinete
7) Penetrate gut wall > spherical oocyst between epithelium + BM > increase in size + develop sporozoites
8) oocyst rupture > free sporozoites into body cavity > migrate to salivary glands
9) when take next blood meal > sporozoites enter blood stream > exoerythrocytic cycle
Genus Plasmodium, Class sporozoa - General morphology
Ring (i.e. young trophozoite) - bluish cytoplasm w/ dotlike nucleus of red chromatin
Trophozoite: hemozoin produced as byproduct of digesting host Hb (dark staining malarial pigment)
Schizont: multiple masses of nucleur chromatin
Gametocyte: compact cytoplasm, no nucleur division
Which parasites can cause malaria in humans
Plasmodium vivax > vivax malaria (benign tertian malaria)
Plasmodium Malariae > malariae malaria (quartan malaria)
Plasmodium Falciparum > falciparum malaria (malignant tertian malaria)
Plasmodium oval
Falciparum + vivax are the main agent of malaria
Blood stages can be used to differentiate the different species
Plasmodium Vivax
Blood stages
Larger infected RBC larger, Schuffer’s dots over RBC cytoplasm (manifestations of caveola-vesicle complexes that form on RBC membrane)
Young trophozoite - growing signet ring appearence
Trophozoite - signet ring appearence w/ ameboid extensions of cytoplasm
Schizont - troph>after 36 hours parasite filled over 1/2 RBC, nucleus divided
Schuffner’s dots (fine, round, pink or reddish granules). After 48 hours, schizont segmented into 16 merozoites each w/ red nucleus + blue cytoplasm
Gametocyte - oval, nearly fill RBC. Macro - darker blue cytoplasm + more compact nucleus than micro
Plasmodium Falcipuram
Blood stages
Infected RBC normal size - infects all ages
Rings - Slightly smaller + more numerous ring, frequently w/ 2 nuclei
Schizonts - Similar to vivax but smaller + more merozoites when mature
Immature gametocyte - Elliptical shape
Mature Gametocyte - banana shape (crescent), sometimes Maurer’s dots (irregularly distributed red dots or clefts)
Plasmodium malariae
Infected RBC normal/smaller
Early stage - smaller, less irregular, more compact and cytoplasm deeper blue that P. vivax
Trophozoite - dark brown/black granules , elongated and stetch across RBC (band shape across cell)
Schizont - after 72 hours daisy/rosette mature schizont w/ 8-10 oval merozoites, mass of greenish black pigments located centrally surrounded by merozoites
Gametocytes - similar to P vivax
Malaria
Symptoms
Headache, lassitude, vague pains in joints + bones, chilly sensation, fever, vomitting, rapid pulse, malarial paroxysms
