Effect of various doses of infective Toxocara canis and Toxocara cati eggs on the humoral response and distribution of larvae in mice.

The effect of 5-2,500 infective Toxocara canis and 5-1,000 T. cati eggs on the humoral immune response and on the distribution of larvae in the organism was studied in paratenic hosts--inbred C57BL6/J mice. With each dose of T. canis eggs the maximal antibody level was recorded on day 56 post infection and was followed by a moderate decline that lasted until day 154 of the experiment. A correlation between the antibody level and the egg count was observed only with the infective dose of 5-50 eggs. A more rapid occurrence of antibodies was recorded in mice infected with a high dose of eggs. In those given 5 and 7 T. cati eggs the antibody level exceeded the extinction threshold value only from day 21 to day 84. Low doses of T. canis (n = 5) and T. cati (n = 7) eggs caused a comparable distribution of larvae in mice, and the larval recoveries on day 70 post infection ranged between 10.00% and 25.74%. Following a dose of 500 T. cati eggs, 22.28% of the larvae were recovered, although only 1.08% were localized in the brain. A dose of 1,000 T. canis eggs yielded 36.37% of the larvae, with as much as 28.13% being found in the brain.