Evaluate how parasites modify host behaviour to aid their transmission Flashcards
What is host manipulation by a parasite?
Any alteration in the host phenotype, induced by a parasite and that provides a fitness benefit to the parasite
What does the infected host facilitate the parasite with?
Dispersal, ability to carry out its lifecycle and transmission
How are phenotypic traits altered by the parasite?
Genomes
What are the three major parasitic lineages whereby host manipulation has been seen?
Nematoda, Platyhelmintha and Arthropoda - ecto and endo parasites
What are the three explanations for why host behaviour changes when a host is infected?
- Manipulation genome in parasite that benefits parasite
- The change may be an adaptive response by host to the infection
- By product of pathology that aids the parasite
How does toxoplasma gondii manipulate its host? Citation
Increases rats exploratory behaviour, therefore they are more likely to be predated on by definitive host (Cat)
Berdoy (1995)
How does Eimeria spp manipulate its host? Citation
Sporozoan - Reduces anxiety in rodents which makes them more likely to be predated - Serotonin neurotransmitter affected and opioid mediated analgesia
Kavaliers (1994)
How do trypanosomes affect their vector Tsetse flies? (Citation)
Higher activity of feeding induced which spreads their transmission
(Jenni, 1980)
How does Polymorphus paradoxus increase visibility of amphipods?
Manipulates them to move to the photic zone of the lake where mallards (DH) can spot them more easily and eat them
(Bethel and Holmes, 1977)
What is trophic transmission?
Juvenile stages of the parasite live inside the IH and have to be transmitted to the DH by predation
How does the parasite achieve trophic transmission?
Makes the IH more attractive/visible to DH so it’s more likely to be preyed on
What is an example of trophic transmission?
Parasitic flatworm (Leucochloridium paradoxum) infects snails eyes and pulsates to attract birds (DH), birds peck off the eyes and they are transmitted to the birds.
What are the four implications of host manipulation in a population? Interest in this area?
- Shape host evolution
- Influence the ecology of other parasite species
- Alter the structure of the surrounding animal community
- Have veterinary implications
What happens when transmission means parasite must exit the host?
Parasites must exit the host to disperse themselves into a new environment as their lifecycle forces them to change environment. Usually habitat is unsuitable for the host
Whats an example of the exit transmission?
Nematode hair worm larvae develop in orthopterans and then lead them to water whereby they drown in order for the parasite to be released and carry out its adult life in water.
What is vector-borne transmission in regards to manipulation?
Pathogens transmitted from vector to vector - blood meals taken by mosquito
Parasites can manipulate the duration of blood meals to be shorter so that the vector can visit more individuals in a short amount of time.
What is an example of manipulation by vector borne transmission
Malaria plasmodium - affects mosquito seeking behaviour - Impairs the mosquitoes ability to obtain a full blood meal so moves from host to host - aids transmission
What happens when transmission involves the parasite living inside the host and then exiting and leaving pupates on its surface?
Common in Diptera and Hymenoptera
Manipulation involves the parasite making the host move to places that will protect the pupae
What are three ways the host performs protecting parasitic pupae?
- Host moving to specific microhabitats
- Host producing physical structures protecting their emergence
- Host staying with pupae to defend them from predators
What is the biological way that parasites can manipulate the host?
Parasites might secrete neuroactive substances
If they live in the CNS - allows for behaviour manipulation
Affect release of certain hormones
e.g. Rabies - cytokine increase which leads to aggression
Protein sequences affected
What is the best mode of transmission imo?
Vector bourne transmission as malaria so prevalent.
