Abstract
BackgroundParasitic infections may cause significant effects on behavior, learning, and memory of the host. In the brain of mice heavily infected with Angiostrongylus cantonensis, severe damage has been observed in the hippocampus. This component has been considered to have associations with spatial learning and memory in humans and vertebrates. This study was designed to determine the impairments in behavior, learning, and memory in BALB/c and C57BL/6 mice heavily infected with the parasite.MethodsEach mouse was inoculated with 50 third-stage larvae of A. cantonensis. After infection, daily changes in weight and dietary consumption, worm recoveries and survival rates were determined. The forced swimming test, open field test, and Morris water maze test were employed to evaluate depression- and anxiety-like behavior as well as impairments in spatial learning and memory, respectively.ResultsThe worm recovery rate in the BALB/c mice was significantly lower than that of C57BL/6 mice from day 14 post-infection. The survival rate in infected BALB/c mice decreased to 0% by day 25 whereas those with swim-training survived three more days. On day 42, the C57BL/6 mice had a survival rate of 85.7% in the swimming group and 70% in the non-swimming group. Significant differences were found in weight between infected and non-infected BALB/c and C57BL/6 mice from day 13 and day 12, respectively with corresponding changes in their dietary consumption. Depression-like behavior was found in the infected BALB/c mice but not in C57BL/6 mice. However, anxiety-like behavior was found to occur only in C57BL/6 mice. Impaired spatial learning and memory were also found in the two strains of mice which occurred from day 14 post-infection.ConclusionsResults of this study indicate that A. cantonensis causes depression, anxiety, and impairments in spatial learning and memory in heavily infected mice. Moreover, significantly higher severity was observed in the Th-2 dominant BALB/c mice.
Highlights
Parasitic infections may cause significant effects on behavior, learning, and memory of the host
We have reported that A. cantonensis causes significant pathological changes in the brain of infected mice especially in the hippocampus [15] and different temporal-spatial expressions of IL-4, IL-10, and IL-13 between of the infected Th-2 dominant BALB/c and Th-1 dominant C57BL/6 mice [16]
Worm recovery and survival rate The worm recovery rate in BALB/c mice tested with the Morris water maze significantly decreased with the time of infection (t(4) = 0.000169, P < 0.001) whereas that of C57BL/6 mice decreased only on day 21 postinfection (t(4) = 0.001452, P < 0.01)
Summary
Parasitic infections may cause significant effects on behavior, learning, and memory of the host. In the brain of mice heavily infected with Angiostrongylus cantonensis, severe damage has been observed in the hippocam‐ pus. This component has been considered to have associations with spatial learning and memory in humans and vertebrates. Parasitic infections have been reported to have significant effects on behavior, learning, and memory of the host. Inconsistent findings were obtained in infected rodents with gastrointestinal parasites, neurotropic parasites such as Toxocara canis [4] and Toxoplasma gondii [5,6,7] have been documented to cause learning impairments in their hosts. Association between T. gondii and anxiety and cognitive disorders has been reported [8, 9]
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