Eukaryotic Pathogens: Fungi & Parasites

Question 1

what are the fungal forms

Answer 1

yeasts, mould & fleshy fungi, Dimorphic fungi

Question 2

what is yeast

Answer 2

single-celled, reproduce asexually through budding

Question 3

what is mould and fleshy fungi

Answer 3

long filamentous structures (hyphae

Question 4

what is dimorphic fungi

Answer 4

grow as either yeast or mould depending on environmental conditions
Blastomyces dermatitidis, Candida spp.

Question 5

what is the study of fungi

Answer 5

mycology

Question 6

what ways do fungi reproduce

Answer 6

Fungi reproduce in many different ways

Asexual, sexual or both strategies at different times

Question 7

what is asexual reproduction

Answer 7

Elongation/fragmentation of hyphae

Budding/division of yeast cells

Production of asexual spores

Question 8

what is fungi sexual reproduction

Answer 8

Different from that of animals or plants

involves the production of sexual spores

Question 9

how do fungal infections spread

Answer 9

Fungal infections typically spread by spores

Enter the body through inhalation (typically soil-borne) or damaged skin

Person-to-person contact

Soil (spores) or insects bound with spores.

Question 10

what are food-based mycotoxins

Answer 10

Secondary toxic metabolites formed by moulds
>200 known mycotoxins

Infects cereals, nuts, figs, spices, coffee, dried fruits

Question 11

types of food-based mycotoxins

Answer 11

Aflatoxin B1 - produced by Aspergillus Flavus and Parasiticus.
potent carcinogens, associated with liver cancer

Ochratoxin A - produced by Penicillium spp. & Aspergillus spp.
kidney damage in humans & is a potential carcinogen

Patulin - produced by Penicillium spp. & Aspergillus spp.
potentailly carcinogenic, damage immune & nervous system

Question 12

what are the types of hallucinogenics

Answer 12

Ergot and magic mushrooms

Question 13

what is ergot

Answer 13

fungus that infects grains of rye & related grasses

Contains lysergic acid alkaloids (LSD precursors) ergotoxine: ergotamine; ergometrine

Question 14

what is ergotism

Answer 14

afflicted 100,000’s people in Europe during Middle Ages (ingestion of contaminated grain)

Vasoconstriction, gangrene, uterine contractions, nausea, convulsions, seizures, madness, hallucinations, death

Question 15

what are magic mushrooms

Answer 15

principle active compounds are psilocybin & psilocin

Similar to serotonin

Question 16

what is algae

Answer 16

• most are aquatic or live in moist conditions
• single or multi-cellular
• Distinct from higher plants as they lack tissue differentiation and are simple plants (no leaves, roots, no connective tissues)
• motile (flagella)

Question 17

Pathogenic algae

Answer 17

• very few pathogenic
• prototheca spp. colourless algae causes bursitis in joints
• Alexandrium tamarense & Karenia brevis produce a potent neurotoxin which accumulates in shellfish – paralysis if eaten

Question 18

what is a parasite

Answer 18

An organism that lives in or on the living tissue of a host organism at the
expense of that host

i.e. protozoa & helminths

Question 19

what is protozoa

Answer 19

Non-photosynthetic, unicellular eukaryotes
Despite uni-cellularity, complex organisation
Pinnacle of unicellular complexity

Question 20

is paramecium spp. a protozoa

Answer 20

yes

Question 21

what are the characteristics of protozoa

Answer 21

Cilia – cell motility & sweep food into oral groove
Cell Mouth - where food enters
Anal Pore - disposes of waste
Contractile Vacuole - contracts & forces extra water out of cell
Trichocysts - used for defence
Gullet - forms vacuoles for food storage
Macronucleus - larger nucleus, performs normal cell functions
Micronucleus - smaller nucleus, responsible for cell division

Question 22

what is Gardia Lamblia

Answer 22

Flagellated protozoan causing thick coating (non-invasive) on Gastrointestinal tract.

Transmitted: F-O-R and Outdoor leisure water.
explosive diarrhea, stomach cramps, upset stomach, bloating & flatulence
loss of appetite, lethargy, fever, gastroenteritis
2/3 people are asymptomatic

Question 23

what is entamoeba histolytica

Answer 23

Amoeba protozoan causing +/- invasion of GIT.

Transmitted: F-O-R and human reservoir
Three forms
-non-invasive colonisation/invasive form/extraintestinal disease

Question 24

what is Toxoplasma gondii_ Toxoplamosis

Answer 24

Non-motile parasite
Elaborate lifecycles: cat is definitive host; human intermediate host.

Toxoplasma gondii – toxoplasmosis (from cat faeces)

symptoms:
blindness, hydrocephalus, jaundice, eye lesions & neurological problems

Question 25

what is Plamodium spp Malaria

Answer 25

Tropical/sub-tropical infectious disease

from mosquitos

Symptoms
Destruction of red blood cells by merozoites
Synchronized release, every 48hrs, except for P. malariae every 72hrs
During attack: cyclic chills, high fever, drenching sweat
Anaemia, tachycardia, coma & death

No current vaccine; anti-malarial drugs = quinine or artemisinin derivatives

Question 26

what is the life cycle of plasmodium (malaria)

Answer 26

1. Sexual reproduction begins within mosquito
2. Sporozoites from mosquito bite enter human bloodstream
3. Migrate to liver, where they mature producing merozoite form
4. Liver cells rupture releasing merozoites, which invade RBC’s
5. Multiply further in RBC’s, rupture cells & infect new RBC’s
6. Some merozoites develop into male & female gametocytes
   - if consumed by a mosquito during a blood meal, the infectious cycle continues

4 species of malarial Plasmodium:
P. falciparum; P. vivax; P. ovale; P. malariae

Question 27

what are ciliate protozoa

Answer 27

Often have macronucleus & micronucleus

Macronucleus: polyploid, vegetative growth & cell division

Micronucleus: sexual reproduction

Cilia for locomotion & feeding

Question 28

what is the known pathogenic ciliated protozoon

Answer 28

Balantidium coli

Question 29

what is Balantidium coli

Answer 29

• causes inflammation of colon
• causes diarrhea
• transmission: F-O-R & zoonotic (esp pigs)
• no prevention
• diagnosis trophozoites/cysts in stool

Question 30

are helminths & arthropods microorganisms

Answer 30

No

Question 31

what do helminths and arthropods do

Answer 31

can cause parasitic/infectious disease

can transmit infectious disease

Question 32

what do arthropod vectors do

Answer 32

transmit infections between hosts

Mechanical – transports pathogen to host

Biological – essential link, due to importance in pathogen life-cycle

plasmodium –> Mosquito –> malaria

Question 33

what are arthropods reservoirs of infection

Answer 33

the pathogen can survive between human hosts

Question 34

what are examples of arthropods

Answer 34

tick, flea, louse, mosquito

Question 35

what are infective arthropods

Answer 35

mites: the female lays eggs in the skin causing rash
crabs: skin irritation, vectors for typhus
venom: bee stings, spider bite
tick: paralysis

Question 36

what are helminths

Answer 36

microscopic worms

Question 37

what are types of helminths

Answer 37

flukes, tapeworms, roundworms

Question 38

what are flukes

Answer 38

leaf-shaped hermaphroditic flatworms, except for bisexual blood flukes
complex life cycle includes a snail intermediate host