unit 3: eukaryotic pathogens, viruses, and prions

list the eukaryotic pathogens

fungi

algae

protozoa

helminths

cell wall of fungi

chitin

cell membrane of fungi

ergosterol

what 2 forms does fungi come in

yeasts and molds

what does mold exist as

long threadlike structures of cells called hyphae

why are pathogenic fungi called dimorphic

can be yeast or mold

how can yeast grow

on agar plates

how do yeast reproduce

asexually through budding

what is budding reproduction

new genetically identical organism grows out from the body of a single parent

what gives mold their fuzzy appearance

hyphae

what is a tangled mass of hyphae called

mycelium

how does mold reproduce

spore formation and fragmentation

fragmentation

asexual reproduction, piece of hypha breaks off and will begin new growth

spore formation

aerial hyphae cells form spores (sexual or asexual) → get released and allow dispersal of fungi over long distance

what are fungal infections called

mycoses

systemic mycoses + example

deep within the body - cryptococcosis

subcutaneous mycoses

beneath the skin

cutaneous mycoses + example

affect hair, epidermis, and nails - tinea pedis (athlete foot)

superficial mycoses

on hair and skin

opportunistic mycoses + example

caused by normal microbiota or environmental fungi in immunosuppressed individuals - thrush (Candida albicans)

what is cutaneous mycoses caused by

a fungi called dermatophytes

what is ringworm actually called

tinea corporis

what is candida

apart of normal microbiota which grows in mouth, vagina, or skin of immunocompromised ppl

what causes cryptococcosis

lung infection or meningitis

what does the gelatinous capsule do in cryptococcosis

allows evasion of phagocytosis

what is cryptococcosis a problem for

immunosuppressed individuals

toxins produced by fungi causes disease: (2)

1. ergot toxin

2. alfatoxin

what does ergot toxin cause

ergotism

ergotism

-seizures

-hallucinations

-gangrene

what is ergot toxin produced by

claviceps purpurea

what is aflatoxin caused by

aspergillus flavus

what type of trophs are algae

photoautotrophs

algae does not cause infections but what instead?

intoxications

2 types of pathogenic algae:

diatoms

dinoflagellates

diatoms toxin name:

domoic acid - neurotoxin

disease of diatoms:

amnesiac shellfish poisioning

dinoflagellates toxin name:

saxitoxins - neurotoxin

disease of dinoflagellates

paralytic shellfish poisoning

do protozoa have cell wall

no

what can protozoa form

cysts - protective structure that enables survival in poor conditions

what are the 3 steps of parasitic protozoa life cycle

1. transmission to human host

2. multiplication within host

3. microbe leaves host and must re-enter new host

what variations may be included in parasitic protozoa lifecycle

• requiring more than 1 host

• sexual reproduction

• cyst production

what protozoa has one host life cycle

entamoeba histolytica

what is a definitive host:

organism that hosts the sexual reproductive stage of parasite

intermediate host:

organism that hosts the asexual reproductive stage of parasite

2 examples of an intermediate host:

plasmodium vivax + toxoplasma gondii

what is amoebic dysentry caused by

entamoeba histolytica

what is dysentery

blood mucoid diarrhea, cramping, nausea, vomit, fever

how does the fecal-oral transmission happen here:

human ingestion of cysts

how many hosts can amoebic dystentry have

1 host, human

what is the course of disease: amoebic dystentry

1. cysts germinate into amoeba → then multiply in large intestine

2. amoeba form new cysts → shed into faces + infect new hosts

3. invasive disease may occur → feed on intestinal epithelial → cause ulcer + bleeding

4. may penetrate other organs to cause abscesses

what is malaria caused by

plasmodium species

symptoms of malaria

fever and chills, anemia, joint pain

how many host life cycles in malaria

2, human (intermediate) and mosquito (definitive)

what is the plasmodium life cycle

1. transmission to human

2. multiplication in human host

3. exit human → re enter mosquito

explain the transmission to human:

infected female mosquito bites human → passes infectious form of plasmodium

what is the infectious form of plasmodium called scientifically

sporozoite

explain multiplication in human host

-plasmodium infect human liver cells + reproduce asexually

-plasmodium infect RBC + reproduce asexually

-plasmodium forms gametes (gametocytes) in RBC

explain how it exits human and re-enter mosquito host:

-infected human is bitten by another female mosquito and it picks up plasmodium gametocytes

-gametocytes get fertilized with sexual reproduction in mosquito intestine, mature into sporozoites → salivary glands → repeat

what is toxoplasmosis caused by

toxoplasma gondii

how many life cycles do toxoplasmosis have

2

what are they

cat (definitive host)

humans (intermediate host)

after the cysts are picked up by a human, what can they lead to?

congenital infections in pregnant women or grow in immunocompromised ppl

what are the 2 main groups of helminths (worms)

platyhelminths (flat worms)

nematodes (round worms)

who are flat and round worms

Platyhelminthes and nematodes

2 kinds of pathogenic platyhelminthes

1. schistosoma

2. taenia solium

2 kinds of pathogenic nematodes

1. enterobius vermicularis

2. ascaris lubricoides

what are flukes

• non segmented worm with oral sucker

• known as trematodes

what is an example of a fluke

schistosoma

explain a schistosoma

• cause schistosomiasis

• human is definitive host

• water snail is intermediate host

explain the lifecycle of a schistosoma

1. egg released feces or urine

2. egg hatch in fresh water

3. miricidia infect water snails

4. cercariae are shed and invade skin of human bathers

5. larvae enter blood vessels

6. adult larvae move to intestine or bladder to mate

7. fertilized egg shed or enter different organs

8. cycle repeats

what are tapeworms also known as

cestodes

explain tapeworms

• cestodes

• segmented with suckers or hooks

• small intestine parasites

how does the head (scolex) help tapeworms do its thang

sucks and hooks to attach to intestinal wall of definitive host

head is aka?

scolex

segments aka?

proglottids

what do segments closer to head have

male and female reproductive organs

why are tapeworms considered hermaphrodite

because they contain male and female reproductive organs

what do segments at the end of worm have

sacs of fertilized eggs

what is the intermediate + definitive host of tapeworm

intermediate: where egg hatches into larvae and gets buried in tissue to form cysticerci

definitive: where it consumes cysticerci and develop into adult tapeworm in small intestines

what is cysticerci

undercooked larvae infested meat

dioecious

separate male and female animals

when can a human get Taenia solium

if human ingests undercooked larvae infested meat

what is taeniasis

abdominal discomfort, weight loss, fatigue

explain the lifecycle of a pork tapeworm

1. adult tapeworm grows in small intestine

2. fertilized egg passed in feces

3. pig eat egg contaminated grass

4. egg → larvae and burrow into muscle and become cysticerci

5. human eat infected undercook mean

6. digest all but scolex

7. head sucks onto intestinal wall

which is intermediate and definitive host in pork tapeworm?

pigs - intermediate

human - definitive

how could humans be intermediate and definitive hosts? and what is the disease called?

if human were to ingest tapeworm eggs

cysticerosis

tapeworm lifecycle when human is intermediate host

adult tapeworm grows in small intestine

egg passed in feces

another human consumes eggs

egg hatch → larvae burrow into organs and brain to develop cysts

cysticerosis

what is pinworm called

enterobius vermicularis

how many hosts does EV have

only 1 human host

where do adults mature in EV

large intestine

how does EV reproduce

male and females mate (dioecious)

lifecycle of EV

adult female → eggs planted at anus

eggs passed in feces or fingernails

human consume egg

larvae → mature in large intestine

adult male and female worm mate

adult female → anus

cycle repeat

who is the intermediate and definitive host In EV?

human - definitive

NO INTERMEDIATE

describe ascaris lumbricoides

one human host

ascariasis

lifecycle of ascaris lumbricoides

adult female lay egg in intestine

egg passed in feces

human consume egg

hatch in intestine

immature larvae burrow into circulatory

migrate to lungs

migrate to pharynx + swallowed

adult worms mate in small intestine

repeat

what is the word virus derived from

latin word meaning poison

size of viruses

10-900 nano meters

what are viruses visible with

electron microscope