Toxocara in the mouse: a model for parasite-altered host behaviour?

Area of Science:

• Parasitology
• Neuroscience
• Behavioral Science

Background:

• The Manipulation Hypothesis suggests parasites alter host behavior for their own benefit.
• Toxocara canis is a common helminth parasite with a complex life cycle.
• Understanding parasite-host interactions is crucial for disease ecology and public health.

Purpose of the Study:

• To critically evaluate parasite-altered host behavior in the Toxocara mouse model.
• To investigate the role of infection dose and larval brain accumulation in behavioral changes.
• To determine if observed behavioral modifications support the Manipulation Hypothesis.

Main Methods:

• Infection of outbred and inbred mice with varying doses of Toxocara canis ova.
• Assessment of diverse behaviors including activity, exploration, anxiety, learning, memory, and social behavior.
• Quantification of larval burden in the brain and correlation with behavioral outcomes.

Main Results:

• Significant variation in larval brain accumulation between individual mice and between mouse strains.
• Observed behavioral alterations in infected mice, linked to larval brain load.
• Outbred mice showed reduced aggression, increased defensive behaviors, and impaired learning with higher infections. Inbred mice displayed altered activity patterns (reduced immobility, increased digging/climbing).

Conclusions:

• Toxocara infection significantly impacts a wide range of murine behaviors.
• Evidence suggests behavioral changes are likely pathological side effects rather than adaptive manipulation.
• Observed behavioral alterations in mice may offer insights into human toxocariasis.