Neurobehavioral Disorders and Pathological Changes in the Brain of Mice Are Caused by Chronic Toxocara Canis Larval Invasion with Low to Moderate Inoculum

Toxocara canis larvae are one of the most overlooked agents of nervous system infection in paratenic hosts. Previous studies in mouse models have shown that infection with various (mainly high) numbers of larvae leads to neurobehavioral disturbances and pathological changes. Our study investigated whether the infection with low and moderate numbers of larvae could affect the physical condition, motor skills, and pathogenesis in the brains of experimentally infected mice. Two groups of BALB/c mice were orally infected with 10 and 100 T. canis larvae per animal and examined regularly until the 97th week after infection. General appearance, specific antibody responses, and motor/balance skills were assessed. The number and viability of larvae in the liver, spleen, lungs, and brain were assessed by quantitative compressed biopsy technique, while the pathological changes of the brain infection were studied histologically. As a result, changes were observed in overall appearance, activity, as well as motor and balance ability. The infections were associated with an increased IgG antibody response to the specific anti-T. canis excretory/secretory antigen and tissue damage in the brain characterized by necrosis, cell infiltrations, including foamy cells, and hemorrhages. The study demonstrated the effects of low and moderate T. canis infection in a paratenic host during the chronic phase of infection, which lasted up to 97 weeks for the first time.