Mini module - parasitology Flashcards
What % of animals are parasites?
> 50%
What is the name for organisms that aren’t parasites?
Hosts.
What are the world’s greatest killers?
Infectious diseases.
How many cases and deaths of malaria in 2020?
241 million cases and 627000 deaths.
What assesses overall burden of disease?
Disability-adjusted life year (DALY).
What is DALY?
Time-based measure that combines years of life lost due to premature mortality (YLLs) and years of healthy life lost due to disability (YLDs).
What is one DALY equal to?
Loss of one year of full health.
What is parasitology conventionally limited to?
Study of parasites from animal and Protista kingdoms - Protozoa, parasitic worms, arthropods, chordates.
What areas of microbiology does parasitology also cover?
Bacteria, viruses, fungi.
What does Symbiosis mean?
Living together.
What does symbiosis continuum mean?
Study of two organisms in association, one living in or on the other, usually different species.
What is Phoresis?
Two symbionts travel together, no harm, no physiological or biochemical dependence.
What is mutualism?
No harm, association not obligatory.
What is commensalism?
Only one partner benefits, no harm, association not obligatory.
What is parasitism (individual level)?
One partner lives at metabolic expense of host, harm, obligatory dependence.
Describe the relationship of feeding on ectoparasites.
Mutualism - both partners benefit, no harm to host.
Describe relationship of feeding on wounds.
Parasitism - one partner benefits, harm to host.
What is the definition of parasitism in population terms?
Parasites aggregated in host population, large numbers may kill host, higher reproductive rate than host.
What is the name for external parasites?
Ectoparasites.
What is the name for internal parasites?
Endoparasites.
What is an obligate (permanent) parasite?
Cannot complete life cycle without host.
What is a facultative (temporary) parasite?
Can become parasitic if accidentally ingested or enter an orifice/wound.
What is a definitive host?
Parasite reaches sexual maturity.
What is an intermediate host?
Parasite develops and often reproduces asexually.
What is a paratenic host?
Parasite undergoes no development but remains infective to another host.
What is a reservoir host?
Animal that harbours a parasite which can be transmitted to humans.
What is the name of the disease when parasites from animals are transmitted to humans?
Zoonosis.
What animals undergo the urban cycle?
Domestic animals.
What animals undergo the Sylvatic cycle?
Wild animals.
What is a vector?
Any agent that transmits a disease - insect can be definitive or intermediate host.
What kind of vector has no development?
Mechanical.
What kind of vector has development/ replication?
Biological.
Give examples of micro parasites.
Viruses, bacteria, Protozoa.
Give examples of macro parasites.
Worms, crustaceans, insects.
What are the defining characteristics of micro parasites?
Epidemic disease, specific resistance to infection, high reproductive potential.
What are the defining characteristics of macro parasites?
Endemic disease, non-specific host resistance, low reproduction potential, transmission dependent upon specific transmission stages.
What are the major prion micro parasites?
Creutzfeldt-Jakob disease, BSE.
What are major virus micro parasites?
HIV, COVID, flu, measles.
What are major bacteria micro parasites?
TB, anthrax, typhoid.
What are major Protozoa micro parasites?
Malaria, trypanosomiasis, leishmaniasis.
What kind of life cycle is the malarial parasite?
Sexual (gametes fuse, form sporocyst, develops 1000s sporozoites).
What are the two stages of malarial parasites?
Pre-erythrocytic cycle (liver) = asexual, post-erythrocytic cycle (blood) = asexual, gamete formation.
What is Haemozoin?
Waste product of malarial parasite reproduction cycle.
What are the three major classifications of macroparasites?
Phylum Platyhelminthes (flatworms), phylum Nematoda (round worms), phylum Arthropoda.
What are three example of flatworms?
Class monogenea, class Trematoda, class cestoidea.
What are the five areas of an ideal parasite?
Attachment, nutrition, evasion of immune response, reproduction, transmission.
What do all flatworms have?
Acoelomates, triploblsatic, bilaterally symmetrical.
What are different structures used for attachment?
Opisthaptor (monogenean), oral and ventral suckers (digenean) and scolex (cestode).
What is the downside of a complex attachment mechanism?
Restricted movement.
What is the bonus and downside of simple attachment mechanisms?
Increased mobility, risk of dislodgment.
What is necessary for parasite attachments?
Structure must exactly fit host tissue.
What is the posterior opisthaptor?
Monogenean attachment equipped with suckers, clamps, hooks, glands.
What is the strobila?
Chain of proglottids.
What can parasite feeding cause?
Anemia.
Where do micro parasites absorb their nutrients?
Via cell surface.
What ways can macroparasites get nutrients?
Surface browsing (Entobdella), blood feeding (polystoma adults), bulk tissue feeding (fasciola juveniles), nutrient uptake across body wall (cestodes).
What does Neoteny mean?
Reaches sexual maturity while retaining larval characteristics.
What does a dimorphic life cycle mean?
Two different adult morphs.
What are some problems with blood feeding?
Waste products of blood digestion, lack of B vitamins, clotting agents, exposure to hosts immune system.
What are two morphological adaptations for nutrition?
Increased body surface area, modified mouthparts.
What are three examples of increased body surface area?
Microthrix (cestodes), microvilli (monogeneans), surface folds.
What are five physiological and behavioural adaptations for nutrition?
Symbiotic micro-organisms to counteract vitamin B deficiency, production of anticoagulants, release of endogenous enzymes and binding, acidification of gut, migration along gut.
What is immunity?
Possession of tissues capable of recognising and protecting the animal against invaders - evoked by recognition of some part of parasite or secretory/excretory products.
What is innate immunity?
Defence is not dependant on previous exposure to infection.
What is acquired immunity?
Immune response develops after infection to particular parasite.
What is cross immunity?
Immunity between species and genera.
What is a susceptible host?
Can not eliminate the parasite.
What is resistant host?
Prevents establishment and survival of parasite.
What is premunition?
Host recovers from disease and is resistant to re-infection but some parasites remain and reproduce slow rate.
What is concomitant immunity?
Parasite elicits protection against re-infection but parasite itself remains unaffected by immune response.
What is inaccessibility in immune response?
Intracellular or located tissues have weak immune response, intracellular invasion of immune cells.
What is antigen disguise/mimicry?
Host antigens bound to surface of parasite.
What are four components of evasion of immune response?
Antigen polymorphism, shedding antigens, immunomodulation of host, anti complementary activity.
What is antigen polymorphism?
One attached, other survives, this one is attacked, new one survives, survived ones recognised by selection pressures, cycle continues.
In terms of reproduction, what do parasites have compared to hosts?
Higher reproductive potentials.
Are parasites r-strategists or k-strategists?
r-strategists.
What kind of reproduction do parasites employ?
Asexual, parthenogenesis and sexual.
What does reduced genetic variation do?
Ensures host-parasite co-evolution and maintains stability.
What are three modes of reproduction?
Oviparous, ovoviviparous, viviparous.
What is oviparous reproduction?
Eggs released into the environment and develop outside parent’s body.
What is ovoviviparous reproduction?
Encapsulated embryos develop within parent’s body.
What is viviparous reproduction?
Embryos develop within parents body.
What is hermaphrodites?
Occurrence of both sexes in same individual.
What are advantages of hermaphrodites?
Increases chances of finding a mate, increases egg output, potential for self-fertilisation.
What is sequential hermaphrodite?
One sex matures before the other.
What is protandry?
Male organs develop before female.
What is protogyny?
Female organs develop before male.
What does synchrony of parasite and host reproduction do?
Increases the success of parasite transmission.
What is neoteny?
Reaches sexual maturity while retaining larval characteristics.
What are different types of transmission?
Contact transfer, ingestion of intermediate and/or paratenic hosts, release of egg/spores/ cysts, free living larvae.
What is toxoplasma gondii epidemiology?
Intracellular protist parasite, global distribution, cosmopolitan in humans.
Characteristics of toxoplasma gondii?
Divides asexually to yeild haploid form that can infect, fields only definitive hosts, carnivores, insectivores, rodents, pigs, herbivores, birds, primates and others.
What is the behavioural manipulation hypothesis?
A parasite will specifically manipulate host behaviour essential for enhancing its own transmission.
What did the T.gondii infection do?
Converted the aversion to feline odours into attraction.
Epidemiology of toxoplasma gondii in humans?
Prevelance 13%, embryos susceptible, adults asymptomatic, infected males more impulsive, females more sociable.
What human behaviour does toxoplasma cause?
More likely to be involved in road traffic accidents, more prone to feelings of guilt.
What is the difference in gender for toxoplasma infection?
Infected women seem more intelligent, outgoing etc, men opposite.
What is a successful parasite?
Finds an appropriate host, establishes itself without detection, reproduces and gain nutrients without causing death to host.
What percentage of species on earth are parasites?
> 50%
What is the difference between predators and parasites?
Predators kill multiple prey, parasites obtain nourishment from single host.
What are advantages of parasitism?
Habitat, mobility, energy.
What must parasites respond to in order to adapt?
Discontinuity in space and time, host immunity and evolution.
What is preadaptation?
Would allow a proto-parasite to exploit host.
What is phoresis?
Starting point.
Why are parasite life cycles so complex?
Greater niche space for reproduction, increase the likelihood of transmission.
What is co-evolution?
A parasite may be associated with a host because the two share a long evolutionary history.
What is host-switching?
Recent colonisation of host group through ecological transfer.
What are geographical distributions of host and parasites influenced by?
Global events such as continental drift.
Why is sex favoured in hosts?
Produces rare phenotypes, which are expected to have greater resistance to parasites.
What does the Red Queen co-evolutionary hypothesis predict?
That parasites drive oscillations in host genotype frequencies due to common host disadvantage.
