miscellaneous protozoa Flashcards

Question

life cycle of Sarcocystis spp

Answer 1

1. Begins when the sporocysts and oocysts are passed in the feces coming from humans 2. Sporocysts and oocysts can contaminate grass and the cows and pigs can ingest them 3. In the intermediate host, the sporocysts rupture and release sporozoites which will invade the intestinal mucosa and reach the vascular epithelial cells where they undergo schizogony 4. Schizonts rupture and release merozoites 5. Merozoites will penetrate muscle cells and develop into cysts with bradyzoites 6. Cysts with bradyzoites ingested in undercooked meat for the sarcocystis 7. When the sarcocysts are ingested by humans (definitive host), the merozoites are released in the intestines and enter intestinal cells and develop into male and female gametocytes (microgametes and macrogametes) 8. Fertilization will happen and then zygote will develop into an oocyst 9. Oocyst contains 2 sporocysts which have 4 sporozoites 10. Oocysts are shed in feces and are ingested by intermediate host (cattle and pigs)

Answer 2

S. hominis: (Intestinal form) - eating undercooked beef (cattle/pig) w sarcocysts - definitive host *cattle/ pig - intermediate host - intestines (Destroys the intestinal lining (epithelial cells) May cause mild intestinal symptoms like diarrhea or stomach pain.) S. lindemanni: (Muscular form / Extra-intestinal) - ingesting oocyst from animals - intermediate host *definitive host is unknown - striated muscle (muscular form) !! (Sarcocysts develop in skeletal or cardiac muscle (but usually not both). Causes: - Myositis (muscle inflammation) - Muscle pain - Allergic reactions (like swelling, fever, or rash) Diagnosis: - Muscle biopsy - Use PAS stain (special stain for detecting cysts) Treatment: No specific cure. Give supportive care (rest, pain relief, manage symptoms))

Answer 3

Cryptosporidium parvum

Answer 4

Cryptosporidium parvum: ● Ubiquitous presence worldwide ● C. hominis: human-specific ● C. parvum: zoonotic (affects multiple mammals) Blastocystis hominis: ● worldwide Cyclospora cayetanensis: ● tropical and subtropical countries ● first reported in Nepal Microsporidia: ● worldwide (opportunistic infection, especially in AIDS patients)

Answer 5

● Roundish in shape; may resemble yeast ● Contains 4 sporozoites, but no sporocysts ● Surrounded by a thick cell wall ● May have 1-6 dark granules

Answer 6

thick-walled sporulated oocysts - which is responsible for autoinfection * resistant to chlorine and many disinfectants; ozone effective - water-borne transmission = hard to combat !! other forms (not commonly seen in clinical samples ) ● Schizonts with merozoites ● Microgametocytes and macrogametocytes

Answer 7

1. Infective stage: humans ingest thick-walled sporulated oocysts through contaminated water or food - immediately infectious when excreted in feces 2. Excystation: in the small intestine, sporozoites are released from the oocyst. 3. Intestinal invasion: sporozoites enter the intestinal cells and become trophozoites. 4. Asexual cycle (schizogony): trophozoites multiply into meronts, which release merozoites to infect more cells. 5. Sexual cycle (gametogony): some merozoites develop into gamonts → microgametes (male) and macrogametes (female). Fertilization forms a zygote. 6. Oocyst formation: zygote develops into either: - thick-walled oocyst excreted in feces (Diagnostic stage; Infective stage) ○ Thin-walled oocyst → causes auto-infection inside the host

Answer 8

mammals birds

Answer 9

Villous atrophy: The finger-like projections (villi) in the small intestine get shorter. Crypt hyperplasia: The valleys between villi (crypts) get deeper and wider. Lymphocyte infiltration: White blood cells gather in the area (sign of inflammation).

Answer 10

Blastocystis hominis

Answer 11

4 forms - vacuolated (most common) - amoeboid - granular - cystic

Answer 12

cyst ingestion → trophozoite replication (binary fission, sporulation)

Answer 13

1. Vacuolated Form ● Most common in stool specimens ● Has a large central vacuole with cytoplasm and nuclei pushed to the edge ● Reproduces by binary fission 2. Amoeboid Form ● Polymorphous, slightly larger than vacuolated ● Seen occasionally in feces ● Reproduces by sporulation 3. Granular Form ● 10-60 um in diameter ● Observed in old cultures 4. Cystic Form ● Smallest form ● Thick multilayered cyst wall ● Important for transmission and resistance

Answer 14

1. Cyst and vacuolar forms are excreted or shed in feces - cyst – infective and diagnostic stage 2. Infection occurs via fecal-oral transmission by ingestion of contaminated food and water 3. Infectious stage is not yet confirmed but some articles support that the ingestion of cyst is the infective stage 4. Once ingested, the cyst reaches the small and large intestines where excystation will occur 5. Vacuolar form develops and multiplies that acts like a trophozoite - engages in nutrient update, undergoes binary fission, and may convert into other forms like granular, amoeboid forms 6. For the infection to continue, some vacuolar forms may encyst again and can be passed out in the feces, continuing the life cycle

Answer 15

Blastocystis hominis - polymorphism = many form *participates in sexual and asexual reproduction, and exhibits pseudopod extension and retraction

Answer 16

sporulated oocyst (8-10 um, 2 sporocysts each with 2 sporozoites)

Answer 17

ingestion of sporulated oocysts → sporozoites infect intestine → asexual/sexual phases → unsporulated oocyst excreted

Answer 18

1. Begins during the excretion of unsporulated oocysts in the stool 2. Oocysts will contaminate and sporulate in the environment 3. Sporulated oocysts will enter the food chain (can be mixed with cilantro, basil, raspberries, water) 4. Humans acquire infection by the ingestion of food and water contaminated with sporulated oocyst 5. Excystation of the sporocysts will release sporozoites that infect the enterocytes of the small intestine where sexual and asexual phases will occur 6. Sporozoites will undergo asexual reproduction first forming meront I and meront II and then meront II will become a zygote 7. After the sexual phase, unsporulated oocyst develop and are excreted in the feces ● Summary of life cycle: ingestion of sporulated oocyst → excystation → release sporozoites → infect enterocytes in the small intestine → asexual → sexual → zygote from microgametes and macrogametes → unsporulated oocyst that will be shed in the stool

Answer 19

Microsporidia

Answer 20

spores (1-5 um) oval to cylindrical thick double-layered wall contain polar filament (tubule) that injects infective sporoplasm into host cells - infection will start by swallowing or breathing in spores

Answer 21

1. Ingestion and inhalation of spores can happen from dirty water, contaminated food, or close contact with infected surfaces or people with Microsporidia 2. Once inside the body, the spores pops open and uses a special structure called polar filament 3. The extrusion of polar filament injects its content or sporoplasm into one of the body cells 4. Inside the cell, the parasites start multiplying by binary fission and new spores will be formed each with their polar filament ready to infect other cells - release of new spores can either be into the body or into the stool (ingestion or inhalation of spores → extrusion of polar filament → injection of sporoplasm → replication (binary fission) → release of new spores)

Answer 22

1. Enterocytozoon bieneusi - Causes enteritis (intestinal infection) - Common in AIDS patients - Leads to diarrhea and malabsorption 2. Encephalitozoon spp. - Causes systemic infections (spreads to many organs) - Reported in transplant patients or through blood (donor-derived infections) 3. Pleistophora spp. - Infects muscle and other tissues - Seen in immunocompromised people 4. Microsporidium spp. and Nosema spp. - Can cause eye infections (especially corneal infections) - May also cause rare but serious systemic infections - Can be fatal in immunocompromised infants

Answer 23

1. Tachyzoites: rapidly divide and spread in tissues, causing initial damage. 2. Bradyzoites: form cysts in brain, muscles, eyes — may remain dormant for years ● Oocyst: 10-15 um x 8-12 um - similar to l. belli ● Tachyzoite: Crescent-shaped, 3-7 um ● Bradyzoite cyst: 12-100 um, clustered bradyzoite *All 3 forms are infectious to humans aside from oocyst

Answer 24

1. Starts during oocysts are passed out in feces of cats 2. The oocysts are ingested by rodents and follow life cycle to form tissue cysts 3. The definitive hosts which are the cats ingest tissue cysts present in the intermediate host 4. Oocysts ingested by other intermediate hosts such as sheep and pigs will follow life cycle and become tissue oocysts 5. Humans can acquire the infection and when they ingest uncooked meat containing tissue cyst or ingestion of oocyst via drinking contaminated water or eating unwashed fruits and vegetables 6. Humans can also acquire the infection via blood transfusion, organ transplant, or congenital infection

Answer 25

- Cleaning cat litter boxes - Playing in sandboxes or soil contaminated with cat poop - Touching your mouth with unwashed hands after contact *Important: Fresh cat poop does not contain infectious oocysts. Oocysts need 1–5 days in the environment to become mature and infectious.

Answer 26

parasite becomes a tissue cyst. - resting (dormant) form that stays hidden in the body. - tissues found in: Brain Eyes Skeletal muscles Other organs *cysts can stay in the body for years, especially during the chronic stage of infection.

Answer 27

Definitive host = Cats - both sexual and asexual reproduction in cats’ intestines. (Tissue cysts release zoites Asexual reproduction (schizogony) makes merozoites Some merozoites → tissue cysts Others → male (microgamete) and female (macrogamete) After fertilization → oocyst Oocysts are shed in feces and become infectious after sporulation in the environment.) - cats are the only animals that can shed oocysts in feces. Intermediate hosts = Humans, pigs, sheep, etc. - in these hosts, only asexual reproduction happens. - the parasite forms tissue cysts in organs like the brain, eyes, and muscles. (Humans ingest oocysts (from cat feces) or bradyzoites (from meat). In the intestines, they turn into tachyzoites (fast-replicating form). Tachyzoites spread through the blood to the: - Brain - Eyes - Muscles They form tissue cysts (bradyzoites), which stay dormant. If the person becomes immunocompromised, the cysts may reactivate and cause disease.) MOT: 1. Eating undercooked meat (especially pork or lamb) that contains tissue cysts. 2. Swallowing oocysts from contaminated: - Water - Food - Soil - Unwashed hands 3. Congenital transmission (mother to fetus): - Happens if the mother gets infected for the first time during pregnancy. - IgG antibodies can cross the placenta. 4. Blood transfusion or organ transplant from infected donors: - Involves tachyzoites (the active form). - Rare.

Answer 28

Pneumocystis jiroveci

Answer 29

● Trophozoite: 2-4 um, ovoid - commonly seen form ● Cyst: 4-12 um, 4-8 intracystic bodies

Answer 30

● Presumed: alveolar colonization → trophozoites multiply → cyst formation ● At-risk: immunocompromised patients (e.g., HIV/AIDS) ● Transmission: likely airborne

Answer 31

likely airborne

Answer 32

Cryptosporidium

Answer 33

Cyclospora

Answer 34

Microsporidia

Answer 35

Pneumocystis

miscellaneous protozoa Flashcards

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