Dr. Murai Éva szerk.: Parasitologia Hungarica 25. (Budapest, 1992)

MATERIALS AND METHODS From 1987 to 1990, 7139 fish were analysed in the framework of exploratory testing conducted at the Research Centre (Centro de Pesquisas Ictiologicas Rodolpho von Ihering) of Pentecoste, Ceara State, and six other fish farms (Ceara, Piaui, Pernambuco, Rio Grande de Norte, Bahia States) and some water reservoirs of the state enterprise DNOCS (Departamento Nasional de Obras Contra as Secas), Brazil. Fish larvae and small fish were checked under a dissecting microscope. Older fishes were dissected, their organs removed and examined microscopically for the presence of parasites or other anomalies. The content of the alimentary tract was put in a conic glass and the sediment was examined. Formol fixed plankton samples were also checked for the presence of cestode larvae. Fish fry were fixed in 10% buffered neutral formol for histopathological examination. Sections were prepared and stained by haematoxylin-eosin according to the method described by Roberts (1978). RESULTS Plerocercoids (Fig. 1) were found in the abdominal cavity of several fish species in three locations (1140 cases, 15,9% ) during the three year period of testing (Békési 1990). The affected fish species were the following: common carp (Cyprinus carpio), tambaqui (Colossoma macropomum), pirapitinga (Colossoma brachipomum) tilapi spp. (Oreochromis spp.), curimata sp. (Prochilodus cearaensis), tucunare (Cichla ocellaris), apaiari (Astronotus ocellatus), and big head (Hypophthalmichthys nobilis). The heaviest infestation was found in a 10 day old tambaqui (12 mm) with some 250 plerocercoids in its abdominal cavity, whereas the intensity of infestation in most other affected fish was generally about 30-150 larvae. The plerocercoids were found in various developmental stages. Some were just pushing trough the intestinal wall, while some were found encysted on the visceral serosa or among the pyloric ceca. In the cyst the accumulated larvae measured 0.1-0.5 mm, and oval shaped calcareous inclusions could be seen in them (Fig. 1). Heavily infested fish fry had a distended abdomen, their movement was slow and often uncoordinated. Fishes older than thirty days did not present any clinical sign or external lesion. In the tucunare, adult tapeworms were found in the intestine besides plerocercoids encysted on the serosa. These parasites measured 3-6 mm in length, their strobila was segmented consisting of 3-6 proglottides only. Each segment contained one set of reproductive organ. On the scolex four suckers were located. As judged by their morphology, the adult worms belonged to different species, though they were similar in size. The intensity of infestation varied between 50-80 worms per fish. Smaller fishes were occasionally free of adult worms. We failed to identify the proteocephalid species found in tucunare.