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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