Fasciola hepatica: The effect of challenge by the subcutaneous or intraperitoneal route with living adult flukes in sensitized rats

When rats, sensitized either by subcutaneous implantation of adult F. hepatica or by a normal oral infection with F. hepatica metacercariae, were challenged by implanting adult flukes in the peritoneal cavity, 23% of these flukes were killed in rats sensitized by subcutaneous implantation and 71% in the rats sensitized by the oral route. In contrast neither of these sensitization routes were effective against subcutaneous challenge with adult fluke. Histological evidence suggested that about half of the dead flukes found were killed shortly after transfer and these flukes were surrounded with mononuclear cells. The remaining dead flukes appear to have died after becoming surrounded with a cyst. These latter flukes were surrounded by neutrophils and this cell type was very prominent in the cysts of sensitized rats.