Table 1 Steps toward adaptive host manipulation compared against the known steps in Toxoplasma-rat, Leishmania-mouse, wasp-caterpillar and wasp-cockroach parasite-host systems. Additionally, tobacco addiction pathway included for comparison
From: The missing link in parasite manipulation of host behaviour
Steps to adaptive host manipulation | Case 1 | Case 2 | Case 3 | Jewel-wasp and cockroach | Tobacco addiction |
|---|---|---|---|---|---|
Step 1/Event A: Parasite/tobacco establishment | Toxoplasma gondii infects a rat (Rattus norvegicus) | Leishmania amazonensis infects a mouse | Wasp Cotesia congregata injects its larvae into the catepilliar Manduca sexta | Wasp Ampulex compressa stings cockroach Periplaneta americana | Inhalation of tobacco smoke |
Step 2: Manipulation factors released from source | ? | ? | ? | Venom stored in the glands released into CNS | Nicotine released into lungs/brain from tobacco root |
Step 3: Manipulation factors impacts physiological functioning | ? | ? | ? | Neurotoxin in venom impacts octopaminergic neurons | Nicotine saturates acetylcholine receptors |
Step 4/Event B: Molecular change in host | Testosterone release causes hypomethylation of the medial amygdala | Cytokine levels altered in pre-frontal cortex | Octopamine removal from hemolymph severely reduced | Sharp decrease in firing rate of affected neurons | Large dopamine release in the brain |
Step 5: Behavioural change | Loss of innate aversion to cat odor | Set of anxiety behaviours | Suppression of feeding | Loss of self-directed movement | Addiction to tobacco |