Lecture 2 Parasite diversity 1 ( viruses, fungi) Flashcards
how many parasites?
40% known parasites
individual hosts have 10s or 100s of parasites -> more parasite spp than host sp
How can we categorize parasites?
- size (micro- vs. macro-): generation time, infection intensity (load), transmission, pathology
- habitat (ecto- vs. endo-)
- behaviour (parasitoids, social)
Differentiate microparasite and macroparasite in categorizing parasites?
micro: - small (< 500 μm) • _SHORT_ generation time • accumulate large numbers – ignore individual growth (focus on replication) --> epidemiology – host infected or not (intensity not considered) • often _direct_ transmission ----> no vector/intermediate host
macro:
• relatively large (with eye)
• long generation time (comparable to host)
• low numbers – consider individual growth
–>epidemiology – parasite growth as important as
reproduction
• often complex life cycles
—> vector or intermediate host (separate asexual & sexual reproduction)
what are examples of microparasites?
fungi, protozoa, viruses, prokaryotes
Differentiate habitat of endoparasites vs ectoparasites in categorizing parasites?
(a) endoparasites • size not important • challenges: establishment, dispersal (b) ectoparasites • size not important • challenges: persistence, abiotic factors (temperature, dryness)
What are examples of macroparasites?
helminths, arthropods, other
Differentiate behaviour (parasitoids, social) in categorizing parasites?
(a) Parasitoids
• free-living adult but parasitic juvenile
–> often insects
—> usually kill host to progress to next life cycle stage
(b) Social parasites
• exploit host social behaviour
—-> often “brood parasites”
Why can viruses act as parasites?
-complete parasites (or symbionts) no metabolism (but alive, have genetic material)
-host cell does all tasks
• same basic structure
• protein shell
—-> some distinction (morphology)
—-> holds genetic information (single or
double-stranded)
—–> sometimes also viral envelope (_host
cell membrane parts)
• aid in host cell attachment & introduction of genetic material
• aid in host cell attachment & introduction of genetic material
How do viruses work?
- picture
4. viral dna is transported across the nucleaus and integrates into the host DNA
5. new viral RNA is used as genomic RNA and to make viral proteins
6. New viral RNA and proteins move to the cell surface and a new, immature HIV forms
7. MATURE VIRION: virus matures by protease releasing individual HIV proteins
Why are viruses important as parasites
• replication: can replicate extremely quickly
• intensity: can reach very high loads/intensity
• pathology: host cell usually dies after use
—>often easily transmissible (direct, vector-borne)
• antigenic drift: rapid evolution
——->antigenic drift: virus -> small mutations
——–>shift: several viruses -> new strain
ex. Hiv evolution , zoonosis, issue for new strains (epidemics and pandemics)
• resistance: issue for control, resistance within 6 months
HIV example of resistance and treatment
-use drug “_cocktails__” to treat HIV instead
• multiple mutations conferring multiple resistance unlikely
• new treatments actually take advantage of evolution
strains once resistant
–>strains once resistant to drug A should evolve
effective again
What are notable examples of viruses as parasites?
- West Nile
- Smallpox
- Foot and mouth disease
- Dengue fever
- Hantavirus
- Ranavirus
- PRV (piscine reovirus)
Fungi as parasites and name 4 groups:
most are symbionts and decomposers but also parasites.
Chytridiomycota, Ascomycota,Zygomycota, Microsporidia)
Describe the life cycle of parasitic fungi Chytridiomycota? Give an example.
• aquatic fungi warm, moist
conditions
ex. BD, spores are evolved
Describe the life cycle of parasitic fungi Ascomycota? Give an example.
- largest fungal group includes _yeasts
- spores are evolved
- EX. Aspergillis- fungal infections eating at coral
EX. Pneumocystis carinii (PC) - huge lesions of where fungus destroy lung tissue, HIV died of secondary infections from PC, through breathing
