Infection with Toxoplasma gondii does not elicit predator aversion in male mice nor increase their attractiveness in terms of mate choice

Abstract

Behavioral manipulation hypothesis posits that some parasites induce behavioral changes in the host to increase transmission efficiency of the parasite. Protozoan parasite Toxoplasma gondii infecting rats has been widely studied in this context. T. gondii increases attractiveness of infected male rats and reduces innate aversion of rats to cat odor, likely increasing transmission of the parasite by sexual and trophic routes respectively. It is currently unexplored if T. gondii induces gain of male attractiveness in experimental models other than rats. Here we show that laboratory infection of two strains of mice does not induce behavioral manipulation. Moreover, T. gondii infection results in reduction of male attractiveness in one of the strains. In agreement with this observation, T. gondii infection also fails to induce reduction in innate aversion to cat odors in mice. Effects of the parasite on mice mate choice are similar to effects of several other parasites in this animal model. Thus, behavioral change induced by the parasite may be specific to the rodent species.

The aromatic amino acid hydroxylase genes AAH1 and AAH2 in Toxoplasma gondii contribute to transmission in the cat

“…gondii have been proposed as candidate effectors for the parasite’s ability to manipulate host behavior via manipulating dopamine in the host [23, 25, 41, 43–48], our previous work failed to reproduce the parasite’s described ability to exert effects upon host dopamine levels [24], consistent with other reports [25, 26]. Further, inconsistencies in cat-aversive behavior and other reported behavioral changes including anxiety, activity level, learning, memory, and more, challenge the robustness of this behavioral manipulation [25, 26, 46, 49–53]. Finally, the hypothesis that tissue cysts of brain-resident parasites actively alter host dopamine to exert behavioral control faces exceptional challenge from the observation that parasites defective in their ability to establish lifelong residency in the brain still result in abnormal cat attraction [51].…”

Behavioral biology of Toxoplasma gondii infection

“…Accordingly, T. gondii infection of outbred rats or infection with lowvirulence parasites produce remarkably specific behavioral effects with minimal sickness behavior [4,5,31]. On the other hand, infection of inbred mice with virulent type I parasite strains causes much acute sickness and less specific behavioral effects [22,28,32,33]. Thus, the behavioral outcome of T. gondii infection systematically varies with the host-parasite strain combinations.…”

Sex Steroids Mediate Bidirectional Interactions Between Hosts and Microbes

“…Upregulation of testosterone production following T. gondii infection may also enhance trophic transmission through decreased predator avoidance behavior (Hari Dass and Vyas, 2014). These effects, however, may be species specific as T. gondii infection in mice resulted in decreased testosterone levels (Kankova et al, 2011) and fails to alter predator avoidance or reproductive potential (Soh et al, 2013). How pathogens utilize and even produce sex steroids to promote transmission differentially between the sexes or during different reproductive states requires consideration.…”