ABSTRACT: To examine the pathogenic capacity of Goussia carpelli, a gut-dwelling coccidian parasite of common carp Cyprinus carpio, hematological parameters were recorded from carp following a laboratory-induced infection with this parasite. With the development of the parasite, serum sodium and protein levels decreased, thus indicating an ion loss and the hydration of blood plasma in infected fish. On Days 8 and 11 post exposure (PE) to the parasite, Aeromonas spp.-like bacteria were detected in the liver and the spleen of 8 infected carp out of the 10 carp sampled, while uninfected control carp remained bacteria-free. On these dates, infected carp were listless, and their intestines appeared dilated and were filled with a whitish-yellow gelatinous content. In intestinal scrapings, gamogonic and sporogonic developmental stages of the coccidia were found. Differential white blood cell counts of peripheral blood leukocytes showed an increase in granulocyte numbers on Days 11 and 14 PE. On Days 21 and 28 PE, when the carp had already excreted most of the oocysts, a clear leucocytosis was found. Owing to the osmotic challenge of infected carp, which is caused by ion loss and plasma hydration, and to the invasion of opportunistic bacteria, the infection of carp with G. carpelli should be taken as a serious pathogen affecting stressed or juvenile fish.

KEY WORDS: Goussia carpelli · Coccidia · Hematology · Serum electrolytes · Serum proteins · Carp · Pathology

Published in DAO Vol. 30, No. 2 (1997) on August 28
ISSN: 0177-5103. Copyright © Inter-Research, Oldendorf/Luhe, 1997