Recovery of third-stage larvae of Anguillicola crassus (Nematoda : Dracunculoidea) from the flesh of fishes: Assessment of a digestive medium as a tool for the study of fish paratenic hosts.

The purpose of this study was to recover third-stage larvae (L3) of Anguill icola crassus alive from the flesh of fishes. Different digestive media hav e been tested on eel flesh for their efficiency and on living infective thi rd-stage larvae for their harmlessness. The results were : (1) Long-term survival of the L3 larvae was low, but their morphological fe atures were recognizable in each digestion runs. (2) Pepsin concentrations between 2.5 and 40 g/l proved to be without influ ence on the short-term (2-4 hours) survival of the L3 larvae of A. crassus. The digestion of the eel flesh was more advanced with the most concentrate d media, when applied for 12 hours. (3) L3 larvae survived longer at pH 1.8 than 1.5, and digestion appeared to be faster at the upper pH level. (4) L3 larvae survival was much longer at 20 degreesC than at 30 degreesC, but efficiency of the digestion process was poor at the lower temperature. For epidemiological studies, the optimal factors combination has been estab lished at pepsin concentration : 10 g/l, pH : 1.8 and temperature : 20-22 d egreesC, particularly when quantitative recovery of L3 larvae and work effi ciency were taken into account.