Changes in worm burden, haematological and serological response in rats after single and multiple Angiostrongylus cantonensis infections.

Thirteen groups of rats were first sensitized with single or double doses of 5--30 third-stage larvae of Angiostrongylus cantonensis, followed by a challenge infection with 100 larvae at various periods after the primary infection. Seven other groups of rats receiving only the sensitizing infection served as the controls. In all the sensitized rats, a significantly (p less than 0.05) smaller mean number of adult worms was found established in the challenge infection as compared to the control. The frequency of the sensitizing dose and timing of the challenge infection appeared to influence the intensity of the host's response. There was no conclusive evidence to indicate that the immune response could retard the growth, development, or sex ratios of the worms established in subsequent infections. A positive haemagglutinating antibody response was first observed in some rats as early as four weeks post-infection with 100 larvae when the worms began migrating from the brain to the lungs. The antibody response and eosinophilia were most pronounced during the oviposition of the female worms and hatching of first-stage-larvae. Changes in white blood cell, lymphocyte, and neutrophil counts were also followed in some groups.