[Effect of infection rate on parasite-host relations in opisthorchiasis]

The adaptation of the immunity system to recurrent helminth contamination in the natural development of opisthorchiasis accords with that of the underlying adaptation syndrome in chronic stress. The established correlation makes itself evident in the fact that in recurrent infections with Opisthorchis, the acute (a mobilization phase) and particularly chronic (a depletion phase) stages of infestation are characterized by a significant reduction in the overall and specific immunological responsiveness of the host, which is followed by the enhanced biological activity of the parasite. In recurrent infections with metacercaria at the stage of invasion (an adaptation phase), the host's organism is able to retard the biological activity of the parasite by straining the immune system against specific Opisthorchis) and heterological (sheep red blood cells):antigens. With this, Opisthorchis eggs double in number after the third contamination while those increase by 10 times after the third contamination and by 26 times in the presence of chronic infection just after the second contamination with helminths.