Evaluate how parasites modify host behaviour to aid their transmission

Question 1

What is host manipulation by a parasite?

Answer 1

Any alteration in the host phenotype, induced by a parasite and that provides a fitness benefit to the parasite

Question 2

What does the infected host facilitate the parasite with?

Answer 2

Dispersal, ability to carry out its lifecycle and transmission

Question 3

How are phenotypic traits altered by the parasite?

Answer 3

Genomes

Question 4

What are the three major parasitic lineages whereby host manipulation has been seen?

Answer 4

Nematoda, Platyhelmintha and Arthropoda - ecto and endo parasites

Question 5

What are the three explanations for why host behaviour changes when a host is infected?

Answer 5

1. Manipulation genome in parasite that benefits parasite
2. The change may be an adaptive response by host to the infection
3. By product of pathology that aids the parasite

Question 6

How does toxoplasma gondii manipulate its host? Citation

Answer 6

Increases rats exploratory behaviour, therefore they are more likely to be predated on by definitive host (Cat)
Berdoy (1995)

Question 7

How does Eimeria spp manipulate its host? Citation

Answer 7

Sporozoan - Reduces anxiety in rodents which makes them more likely to be predated - Serotonin neurotransmitter affected and opioid mediated analgesia
Kavaliers (1994)

Question 8

How do trypanosomes affect their vector Tsetse flies? (Citation)

Answer 8

Higher activity of feeding induced which spreads their transmission
(Jenni, 1980)

Question 9

How does Polymorphus paradoxus increase visibility of amphipods?

Answer 9

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)

Question 10

What is trophic transmission?

Answer 10

Juvenile stages of the parasite live inside the IH and have to be transmitted to the DH by predation

Question 11

How does the parasite achieve trophic transmission?

Answer 11

Makes the IH more attractive/visible to DH so it’s more likely to be preyed on

Question 12

What is an example of trophic transmission?

Answer 12

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.

Question 13

What are the four implications of host manipulation in a population? Interest in this area?

Answer 13

1. Shape host evolution
2. Influence the ecology of other parasite species
3. Alter the structure of the surrounding animal community
4. Have veterinary implications

Question 14

What happens when transmission means parasite must exit the host?

Answer 14

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

Question 15

Whats an example of the exit transmission?

Answer 15

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.

Question 16

What is vector-borne transmission in regards to manipulation?

Answer 16

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.

Question 17

What is an example of manipulation by vector borne transmission

Answer 17

Malaria plasmodium - affects mosquito seeking behaviour - Impairs the mosquitoes ability to obtain a full blood meal so moves from host to host - aids transmission

Question 18

What happens when transmission involves the parasite living inside the host and then exiting and leaving pupates on its surface?

Answer 18

Common in Diptera and Hymenoptera

Manipulation involves the parasite making the host move to places that will protect the pupae

Question 19

What are three ways the host performs protecting parasitic pupae?

Answer 19

1. Host moving to specific microhabitats
2. Host producing physical structures protecting their emergence
3. Host staying with pupae to defend them from predators

Question 20

What is the biological way that parasites can manipulate the host?

Answer 20

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

Question 21

What is the best mode of transmission imo?

Answer 21

Vector bourne transmission as malaria so prevalent.