Reduced spatial learning in mice infected with the nematode, Heligmosomoides polygyrus

Abstract

Parasite modification of host behaviour influences a number of critical responses, but little is known about the effects on host spatial abilities. This study examined the effects of infection with the intestinal trichostrongylid nematode, Heligmosomoides polygyrus, on spatial water maze learning by male laboratory mice, Mus musculus. In this task individual mice had to learn the spatial location of a submerged hidden platform using extramaze visual cues. Determinations of spatial performance were made on day 19 post-infection with mice that had been administered either 50 or 200 infective larvae of H. polygyrus. The infected mice displayed over 1 day of testing (6 blocks of 4 trials) significantly poorer acquisition and retention of the water maze task than either sham-infected or control mice, with mice that had received 200 infective larvae displaying significantly poorer spatial performance than individuals receiving 50 larvae. The decrease in spatial learning occurred in the absence of either any symptoms of illness and malaise, or any evident motor, visual and motivational impairments. It is suggested that in this single host system the parasitic infection-induced decrease in spatial learning arises as a side-effect of the host's immunological and neuromodulatory responses and represents a fitness cost of response to infection.

Behavioral changes induced by Toxoplasma infection of rodents are highly specific to aversion of cat odors

“…Similarly, mice infected with the protozoa Eimeria vermiformis exhibit decreased avoidance of cat odor when compared with uninfected controls (24). Specificity of these behavioral effects has not been investigated in either of the cases, although mice infected with E. vermiformis also show reduced spatial performance in nonaversive Morris water-maze task (25). Mice infected with the nematode Toxocara canis exhibit a variety of behavioral changes ranging from impaired motor performance and impaired learning to decreased neophobia (26).…”

Learned parasite avoidance is driven by host personality and resistance to infection in a fish–trematode interaction

“…This is in contrast with our predictions as it suggests that investment in cognitive abilities is not upregulated in individuals with low resistance, but that individuals with greater resources available for resistance also have more resources for cognitive skills. Generally, a trade-off between learning and immunity has often been observed in experiments exposing hosts to immune challenges or infections before or after undertaking different types of learning tasks [43,[58][59][60][61][62]. Here, the hosts were exposed to the parasite before, during and after the learning tasks, which may make the associations more complex.…”

The significance of cerebral toxocariasis: a model system for exploring the link between brain involvement, behaviour and the immune response

“…The open-field water maze or 'Morris water maze' has been used extensively to examine behavioural, neural and physiological substrates of spatial mapping and learning in rodents (Morris, 1984). Several studies, utilising a range of infectious agents including parasitic nematodes (Kavaliers and Colwell, 1995;Braithwaite et al, 1998) and immune deficiency virus (Sei et al, 1992) (Gundra et al, 2011). The wide availability of knockout mice would also allow for direct correlation between specific cytokines and behavioural alterations.…”