Carp coccidiosis: Activity of phagocytic cells from common carp infected with Goussia carpelli

Abstract

Pronephric phagocytes from common carp Cyprinus carpio L. infected with the gut-dwelling coccidian Goussia carpelli showed enhanced phagocytic activity during the period of merogonic and gamogonic development of the parasite from Days 10 to 15 post exposure (PE) to the parasite. The respiratory burst activity was enhanced during excretion of oocysts at Days 15 to 25 PE. The addition of parasite lysates to assays resulted in an increase of phagocyte activity in cells from carp infected with gamogonic and sporogonic stages of the parasite and from carp which, at Day 35 PE, had recovered from a G. carpelli infection. The addition of immune serum sampled from fish at Days 5, 10, 15, 20, and 25 PE had no clear stimulatory effect on phagocyte activity. This suggests an activation of pronephric phagocytes on infection with the parasite. In carp with gamogonic and sporogonic parasite stages, activated macrophages show an increased cytotoxic reactivity, and activated macrophages rather than non-activated resident macrophages can be enhanced by opsonization with parasite molecules.