T2 - Micro - Parasites 3 - Coccidia And Aids

Front 1

When you hear about coccidia, what bad guys should you immediately think of?

Back 1

Cryptosporidium

Cyclospora

Isospora

and Toxoplasma.

Front 2

briefly, describe the major difference between cryptosporidum, cyclospora, isospora, and toxoplasma. which are dangerous?

Back 2

cryptospora, cyclospora, and isospora all live out their life cycles within intestinal epithelia and are pooped out as cysts. Fecal/Oral route transmission, simple.

Toxoplasma is far more complicated.

all can cause disease, but in AIDS patients, all these can cause life threatening diarrhea. Note that crypto and toxo are the most notoriosu (and that toxo is way bad for pregnancy).

Front 3

Describe the life cycle of crypto - how is it different from the others?

Back 3

fecal/oral.

eat the oocyte-containing cysts (which have 4 sporozoites). break out, attach to intestinal epithelium.

unlike the other coccidia, IT DOES NOT INVADE CELLS - it induces the formation of host membrane around it, making it EXTRACYTOPLASMIC with a junction connecting it to the host epi.

after attaching, asexually reproduce and make MEROGONY - these go and attach elsewhere.

Merogonizites become macro/microgametocytes and spit out lots of little gametes, which fertilize other microgametes, making oocytes which sporulate and get pooped out.

Front 4

in crytposporidium, this action of by microgamete fertilization can allow what?

Back 4

auto-infection! keep yourself infected with these if immunocompromised and can't keep replication in check.

Front 5

what causes the notable cryptosporidium outbreaks?

Back 5

if asked on the test, the example most likely is of WATER - in the US, problems with sewage treatment can lead to massive outbreaks of cryptosporidium.

though human to human transmission is probably most common.

Front 6

how does cryptosporidium cause disease?

Back 6

get what looks like an osmotic diarrhea.

two ways - one is BLUNTING OF VILI and stopping absorption.

Also, there's HYPERPLASIA of the CRYPT cells and greater numbers of them. Crypt cells secrete Cl-, which will bring Na+ and H20 with it - so get secretion of water.

Block absorption, increase secretion = diarrhea.

Easy to remember that crypotosporidium causes CRYPT CELL hyperplasia.

also, inflammation leads to increased intracellular permeability and leakage.

Front 7

how do we diagnose crypotosporidium?

Back 7

Cryptosporidium, cyclospora, and isospora ARE ALL ACID FAST, so this will be the option on the test.

Find oocytes in the feces that are acid fast and you've got your culprit.

Front 8

who's infected with toxo?

Back 8

25% of people by age 25 in the US. No biggie.

Front 9

describe the complicated life cycle of toxoplasmosis

Back 9

start in cat, which is the "definitive" host, with the sexual form of the bug. Replicates like crypto - Undergoes merogany (asexual) and lots of gamogony (sexual, produces micro/macro gametes) - they fertilize each other and make OOCYSTS which are pooped out.

These have to develop for 24 hours in the soil (sporgony) - now infectious.

Intermediate host now eats it...lots of animals, including humans, count. SPOROZYTES are released, infect macrophages, SPREAD ALL OVER = TACHYZOITES. Cause disease/immune response.

Immune response checks them, become BRADYZOITES and sit inside tissues DORMANT. Found mostly in brain and muscle. PERMANENT CHRONIC INFECTION is now established. Cat eats animal, and process starts all over again.

Front 10

How do most humans get infected with toxoplasma?

Back 10

mostly from undercooked meat, from animals that ate oocysts that have sporulated and sat in the moist soil for months.

Or, you're a fetus and get it from mom.

Or from organ transplant.

Front 11

Toxoplasma clinical symptoms in adults?

Back 11

Mostly asymptomatic. 90% of france is infected, afterall.

sometimes during acute infection, you can have mono-like symptoms (remember that toxoplasma trophozoites infect macrophages and spread around). In healthy people, usually unnoticed and quickly chronic.

can BOUNCE BACK and become bad if you get immunosuppressed for any reason. AIDS = ENCEPHALITIS.

Front 12

Toxoplasma is a TORCHES organism. What happens?

Back 12

Mom can only transmit WHEN ACUTE INFECTION is happening - so a chronically infected mom is at no risk of passing it on.

The earlier in pregnancy infected, the worse (though transmission is easier later on).

Still birth, CNS problems...big one is RETINOCHOROIDITIS - this eventually develops in 82% of kids infected in uretro with toxo.

brain calcifications, hydrocephaly, microcephaly all possible.

Front 13

how do you diagnose toxo?

Back 13

serology is the main way - rarely can you find organisms (they're all bound up in the muscles during bradyzoite stage. though because lots of people are infected, it's hard to tell chronic from acute.

usually find HIGH TITERS if acute. ALso use imaging to find encephalitis in AIDS patients.

Front 14

how do you not get toxo?

Back 14

cook your food, stay away from cat poop.

but remember that it takes 24 hours for oocysts to sporulate and become sporozoites (infective) - so if you clean cat box every day, you can't get infected with toxo.