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Poorer results of mice with latent toxoplasmosis in learning tests: impaired learning processes or the novelty discrimination mechanism?

Published online by Cambridge University Press:  20 April 2007

H. HODKOVA ,
P. KODYM  and
J. FLEGR
H. HODKOVA
Affiliation:
Department of Parasitology, Charles University, Viničná 7, Prague 128 44, Czech Republic
P. KODYM
Affiliation:
National Reference Laboratory for Toxoplasmosis, National Institute of Public Health, Šrobárova 48, Prague 10042, Czech Republic
J. FLEGR*
Affiliation:
Department of Parasitology, Charles University, Viničná 7, Prague 128 44, Czech Republic
*
*Corresponding author: Department of Parasitology, Charles University, Viničná 7, Prague 128 44, Czech Republic. Tel: +420-221951821. Fax: +420-224919704. E-mail: flegr@cesnet.cz
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Summary

The heteroxenous protozoan parasite Toxoplasma gondii is transmitted from the intermediate host (any warm-blooded animal) to the definitive host (members of the felidae) by carnivory. The infected intermediate hosts develop several specific behavioural changes that are usually considered products of manipulative activity of the parasite aimed to increase the probability of its transmission to the definitive host. Among other changes, the infected rodents were shown to have impaired learning capability. All previous studies were done 2–6 weeks after the infection. Therefore, it was difficult to resolve whether the observed impairment of learning processes was a result of acute or latent toxoplasmosis, i.e. whether it was a side-effect of the disease or a product of manipulation activity. Here we studied the learning capability of Toxoplasma-infected mice in the static rod test and 8-arm radial maze test and their spontaneous activity in the wheel running test 10 weeks after the infection. The infected mice achieved worse scores in the learning tests but showed higher spontaneous activity in the wheel running test. However, a detailed study of the obtained results as well as of the data reported by other authors suggested that the differences between infected and control mice were a result of impaired ability to recognize novel stimuli rather than of impaired learning capacity in animals with latent toxoplasmosis.

Keywords

Toxoplasmalatent toxoplasmosisnovelty seekingdopaminemanipulation hypothesisparasite
Type
Research Article
Information
Parasitology , Volume 134 , Issue 10 , September 2007 , pp. 1329 - 1337
Copyright
Copyright © Cambridge University Press 2007

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