Host-parasite Behaviour Flashcards
1
Q
Parasitism
A
-relationship between species, where one organism (parasite) lives on or in another organism (host) causing some harm, and is adapted structurally to living this way
2
Q
Host-parasite strategies
A
- Resistance
- involves active defence mechanisms
- Tolerance
- host learning to live with parasite
- may compromise ability to reproduce
- Avoidance
- avoiding places and conspecifics which are associated with risk
3
Q
Host-pathogen interaction
A
- evolving process
- parasite develops strategies to infest host
- host modify defence response to avoid infestation
- some parasites can change host behaviour so that it is disadvantageous to host
- parasites never stope evolving into forms that achieves higher success in parasitizing their hosts
4
Q
Toxoplasmosis
A
- toxoplasma Gondii is an intracellular protozoan that infects Rattus novergicus (intermediate host) and Felis catus (domestic cat - definitive host)
- capable of infecting all mammals as intermediate note
- cats only mammals that emit it through feces
- in intermediate hosts, cysts grow in brain and viable for life of host
- most infectious in immunocompromised patients
5
Q
T gondii invasion of the brain
A
- unicellular/intracellular parasite
- must enter cell to replicate
- 3 proposed mechanisms
1. Transcellular migration
2. Trojan horse (use immune cell to get through BBB)
3. Paracellular entry (between cells) - parasite (tachyzoites) rapidly replicate
- bradyzoites are slowly replicating and can remain in host for lifetime
6
Q
T. Gondii and rodent behaviour
A
- infection high across species (56% in domestic/wildcats)
- in humans prevalence increases with age, lower in cold regions and hot/arid/ high elevation
- inhibit strong aversion to cat odour
- increased activity, decreased fear in novel environment
- Induced suicidal behaviour in rodent linked to amygdala
- infected humans increase activity, increase reaction times, altered personality
- linked to increased accident rated and suicide attempts
7
Q
T gondii and DA and NE dysregulation
A
- significantly reduces NE and increases DA
- may be caused by reduced expression of dopamine B hydroxylase (DBH) in infected animals
-DBH synthesizes NE from DA
- NE deficits seem more important in locomotion of T.gondii infected rates
- DBH-/- knockouts show similar decrease in locomotion
- female rats dont show same decrease
8
Q
T gondii and cAMP expression
A
- reduces cAMP in hippocampus
- elevates cAMP in amygdala and cortex
- may account for behavioural differences
9
Q
Acoustic startle response
A
- reflec caused by unexpected loud sound
- associated with protection of sensitive organs
- recorded by eye blink
- prepulse inhibition (PPI is an attenuation of startle Response by using a warning sounds shortly before
- PPI measure can be useful in schizophrenia and hippocampal damage (reduced), neuroleptics increase PPI
10
Q
T gondii and PPI
A
-infected individuals had increased reaction time
- prevalence of infection in schizophrenia patients is 2.7x higher
- infected schizophrenia shows slower reaction than non-infected
11
Q
T gondii and excessive alcohol consumption
A
- individuals who were more ser opposite effects for parasite has also significantly more often alcohol detected in their blood
- risky behaviour group (suicide, drunk driving, drug overdose) that was seropositive has significantly higher concentration of alcohol detected in their system compared to seronegative
12
Q
T gondii and alcohol preference
A
- relative odour pleasantness had no change in women except for reduced scores for cat odour
- in infected men more odours received higher scores
13
Q
T gondii and host neuroimmune Response
A
- infection associated with abnormal monoamine levels
- parasite expresses 2 hydroxylases (could be degrading 5HT)
- possible that host reduces tryptophan availability for parasite to stop growth
- innate immunity is present in different forms in all animals and makes first line of defence against pathogens
- adaptive immunity believed to be achievement of vertebrates
14
Q
Schistocephalus solidus lifecycle
A
- tapeworm that uses three-spinner sticklebacks as second intermediate host
- become infected after ingesting infected copepods (first intermediate host)
- parasite grows in fish body cavity over months to form large plerocercoids causing deformations of fish abdomen
- parasite can only attain sexual maturation and reproduce following ingestion of its sticklack host by a suitable definitive host
-infected fish approach water surface and are inattentive to predatory birds that usually serve as definitive host
15
Q
Fish parasitism reduces fear in host
A
- More likely to become bird prey
- over week 9-15 infected fish showed slower escape
- explanation of risky behaviour may be driven by increased demand of parasite for food
- or that parasite manipulates host brain to make it more vulnerable
