This study investigates the infestation by Anguillicoloïde crassus of eels from Tonga Lake and El Kebir Wadi, with a focus on epidemiological indexes, seasonal trends and evaluates the current infection rate (by lumen worms of the swim bladders) and past infections (e.g., as evidenced by damage to the swim bladders). During this study, A seasonal assessment was conducted by collecting parasites and measuring morphological parameters, including the length and weight of the fish. A total of 213 eels were examined, and the fish length ranged between 336- 740 and 297 – 601 mm from Tonga Lake and El Kebir Wadi respectively. The SDI and the classical epidemiological parameters were computed following dissection. The epidemiological indexes were: A=58.47% and 55.84 %, I=3.41 and 3.267 per infected host and A=2.01 and 1 per examined eel in Tonga Lake and El Kebir wadi respectively. Concerning the seasonal evolution, winter showed the highest values rates of A. crassus abundance and infestation intensity. On the other hand, more than a third of the swim bladders eels from El Kebir Wadi were intact, while 63.9% of indicate a moderate damage in Lake Tonga