Eukaryotes

antigenic variation and example

changing surface proteins to evade immune system

ex: giardia’s VSPs (variant-specific surface proteins)

apicomplexan life cycle (and example)

ex: Plasmodium - malaria

T. gandii and Cryptosporidium

S → M → T → M

1) Sporozoite infects

2) Merozoite forms and multiplies via binary fission in schizont

3) Trophozoite stage

4) Merozoite release again → some mature into macrogametocytes ♀ and microgametocytes ♂

dimorphism and example

fungi alter between yeast like unicellular organisms (higher temps) and temperature mycelial forms (lower temps)

Candida dublinienis

Saprolengia “fish fuzz”

→ sapro- loves water! spores shaped like pears (primary) and kidneys (secondary)

hyphae collection makes cotton tufts on infected fish

water mold that forms oomycetes and causes major aquaculture industry harm

malachite green used to treat, but has been banned 

Giardia lamblia “beaver fever”

→ 2 nuclei, 4 flagella, no mitochondria = double trouble diarrhea

uses VSPs

diplomonad - 2 stages

1) trophozoite - motile, 2 nuclei + 4 flagella

2) cyst - 4 nuclei

T. cruzi “Chaga’s Disease”

→ chagas kisses your heart forever

one cell and one flagella

vector: kissing bug poops out trypomastigote after feeding

forms:

• amastigote (intracellular, no flagella)

• trypomastigote (flagella, motile, infective)

hides in heart and digestive muscles

more dehibilitating than malaria

Paragonimus westermani “Oriental Lung Fluke”

→ cercariae crustacean = crusty cough

eggs → miracidium → snail

cercariae → invade crustaceans → encyst as metacercariae

eating them = lung infection

mimics TB (peural effusion, blood stained septum, pneumonia, fibrous nodules)

Leishmania dovani

→ Leish loves macrophages, fever, and dark

female sandfly bites infect 1 million annually

2 forms: triggered by temp difference between fly and host

• promastigote (flagellated, in fly)

• amastigote (nonflagellated, in humans)

Kinetoplast (mitochondrial DNA) used to identify 

replicates in macrophages 

causes fever, organ swelling, darkened skin

Balamuthia mandrillaris “Brain Eating Amoeba”

→ brain eating amoeba = balamuthia = bad news/bad wounds

free living ameoba enters human through wounds/inhalation causes Granulomatous Amebic Encephalitis

2 forms use psuedopodia to move

1) trophozoite (infective)

2) cyst (dormant)

90% fatality

Plasmodium falciparum “Malaria”

→ falciparum = fever from female anopheles

infects 250 M a year through Anopheles mosquito

most virulent Apicomplexan

causes multiorgan failure

release/rerelease of merozoites causes fever/chills

new R21 vaccine 70% effective

Piscinoodinium pillulare (Velvet/Gold Dust Disease)

dioflagellate algae in freshwater

mixotrophic (photosynthetic and parasitic)

attatches to fish w/ rhizoids

3 life stages:

• tomont (encysted, reproductive)

• dinospore (free-swimming infective)

• trophont (feeding)

secretes proteases/lipases that cause necrosis

Ascaris lumbricoides “Nematode roundworm”

900M cases annually, 10K deaths

Neglected Tropical disease

Male: small curved tail 

Female: long straight tail

uses Ascaris Trypsin Inhibitor (ATI) to inhibit host digestive system

follows Hepato-Tracheal-Migration

Enterobius vermicularis “Pinworm”

→ pin scotch tape to itchy butt

females lay eggs in jelly like substance around anus

females are longer w/ pin shaped tail

causes perianal pruritus (anal itching)

self infection through scratching

Diphyllobothrium latum “Fish Tapeworm”

recall tapeworm anatomy

eggs hatch in cold water → coracidia → ingested by crustaceans

larvae hatch in crustaceans → humans pick up uncooked 

freeze at -18C for 24 hrs to kill

causes gastrointestinal pain, vomiting, diarrhea

Naegleria fowleri “Brain-eating Amoeba”

causes Primary Amoebi meningoencephalitis

freshwater 

3 stages:

• trophozoite (feeding/reproductive)

• flagellate (motile)

• cyst 

humans accidental hosts

attaches to nasal epitheliam via Nfa1

destroys tissue with trogocytosis, proteases, and phospholipases

Schistosoma mansoni “Blood fluke”

flatworm (Platyhelminth)

causes intestinal/hepatosplenic schistosomiasis

200M people annually affected

eggs→  miricidia → infect snails → sporocysts → cercariae → infect humans (liver)

eggs trigger immune response

candida dubliniensis

dimorphic fungi → mycelial and unicellular forms

in mouth and GI as normal flora

forms chlamydospores to survive harsh conditions

filamentous hyphae form is most invasive 

antibiotic can allow growth 

Taenia solium “Pig tapeworm”

platyhelminth

causes taeniasis and cysticerosis (larvae migrate to brain tissue)

4 suckers and double row of hooklets 

Pfiesteria piscicida “non-photosynthetic Dinoflagellate algae”

East coast issue — 1 B fish killed in 1991

2 flagella

2 forms: 

• motile — naked cell w/out cellulose plates

• cyst 

attaches to wounded fish and secretes neurotoxins 

Rhizocephalans “Parasitic barnacle”

crustacean host (unsclerotizes cuticles)

grows root system in host from vermigon which is injected into host

males enter crustation by a separate system

causes shrinking of sexual organs