In vitro polarization of carp leucocytes in response to the blood fluke Sanguinicola inermis Plehn, 1905 (Trematoda: Sanguinicolidae)

An in vitro assay was used to determine the effects of Sanguinicola inermis adults and cercariae on the polarization responses of pronephric leucocytes of carp. Leucocytes were isolated and exposed to live adult flukes or cercariae for up to 48 h. Differences in polarization responses were related to the presence of the parasite, the presence or absence of carp serum and the time of incubation. The mean proportions of cells exhibiting polarization in unstimulated controls ranged from 5 to 30% over the experimental period. Within 15 min of exposure to adults or cercariae, significant increases in mean polarization responses were observed of up to 75% and levels remained higher than control values for over 24 h. Overall, the presence of normal carp serum, either untreated or heat inactivated, did not enhance the polarization responses of leucocytes incubated with only cercariae or adults. However, between 0.25 and 3 h, the presence of carp serum with cercariae significantly enhanced polarization responses when compared with cells incubated with cercariae alone.

Adherence of carp leucocytes to adults and cercariae of the blood fluke Sanguinicola inermis

Live adult and cercarial stages of Sanguinicola inermis Plehn, 1905 (Trematoda:Sanguinicolidae) were maintained in vitro in the presence of carp (Cyprinus carpio L.) leucocytes. Cells and parasites were fixed at intervals from 0.25 to 48 h and examined using light microscopy, SEM and TEM. Within 12 h of exposure, leucocytes were found attached to cercariae although, by 24 h, fewer cells were found attached to postcercarial, juvenile adult stages that had shed their tails. Neutrophils and macrophages were found attached to the damaged tegument of cercarie that had not transformed by 48 h. Few cells were attached to the tegument of adult flukes that were alive when fixed. However, there was extensive tegumental damage and numerous cells were attached to adult flukes that had died before fixation. The results are discussed with reference to parasite survival within the vascular system of the host.