Resistance of Indonesian thin tail sheep against Fasciola gigantica and F. hepatica

Peritoneal Lavage Cells of Indonesian Thin-Tail Sheep Mediate Antibody-Dependent Superoxide Radical Cytotoxicity In Vitro against Newly Excysted Juvenile Fasciola gigantica but Not Juvenile Fasciola hepatica

“…Such a mechanism of rapidly induced killing is analogous to that proposed to act against F. hepatica in exposed rats, where killing occurs in the gut wall or peritoneum within 24 to 48 of challenge and before significant damage to the liver occurs (34,45,46,47,48). A curious and important aspect of our observations is that ITT sheep are fully susceptible to infection with F. hepatica (38,39) and, in parallel, NEJ F. hepatica parasites are resistant to the superoxide-mediated in vitro killing mechanism expressed by peritoneal cells of ITT sheep. Such a correlation suggests that the inability of ITT cells to kill NEJ F. hepatica in vitro and the inability of ITT sheep to resist F. hepatica infection are related phenomena.…”

“…Indeed, the experimental data obtained in vivo support this hypothesis. ITT sheep exhibit a rapid induction of eosinophilia and immunoglobulins G and E within 8 to 14 days of infection with F. gigantica (9), and significant killing of the invading parasites in ITT sheep occurs within 2 to 4 weeks of infection and before significant damage to the liver occurs (38,39,44). This lack of damage to the liver observed within 2 to 4 weeks of infection suggests that many invading parasites are killed in the perito- Interestingly, rats mediate effective immunity to F. hepatica and also have resident cells (monocytes/macrophages) which can kill parasites in vitro in the presence of a parasite-specific antibody, albeit the effector mechanism is nitric oxide and not superoxide radicals (33,34,41,46,47).…”

“…Our previous work showed that ITT sheep are susceptible to primary and secondary infections with the temperate liver fluke F. hepatica (38,39). Interestingly, we have also shown that NEJ F. hepatica parasites are highly resistant to oxygen free-radicalmediated killing in vitro (32,33).…”

“…Consequently, little is known about the humoral or cell-mediated responses important for host immunity against F. gigantica (34,42). However, studies of the natural hosts (sheep and cattle) provide evidence that ruminants do acquire resistance to F. gigantica infection (1,34,37,38,39,44). When the susceptibilities of sheep breeds to F. gigantica are compared, the Indonesian thin-tail (ITT) sheep exhibits a high degree of resistance to infection relative to other breeds such as St. Croix and merino (34,42).…”

“…When the susceptibilities of sheep breeds to F. gigantica are compared, the Indonesian thin-tail (ITT) sheep exhibits a high degree of resistance to infection relative to other breeds such as St. Croix and merino (34,42). For example, ITT sheep express high resistance to a primary infection with F. gigantica compared to Merino sheep and acquire further resistance to infection after exposure (34,37,38,39,49). Analysis of fluke burdens in sheep at various times following infection showed that significant killing of parasites occurs between 2 and 4 weeks of challenge, with little liver damage detected following infection, suggesting that many migrating flukes may not survive long enough to establish themselves in the liver (39).…”