Parasitic nematode worms can cause significant damage to fish. How much damage worms can do depends on which species of nematode is concerned, which organs are affected and the number of worms involved.
This week we will talk about Ichthyouris bursata, a nematode from the family of Oxyuridea (Pharyngodonidae), belonging to the genus Ichthyouris, which parasitize Latin American fish – like discus, angelfish, geophagus and other cichlids of this region, as well as Siluridae and Loricariidae catfish. Particularly Symphysodon discus have a high incidence of infection. Ichthyouris bursate are small white worms, reaching a length of about 2-3 mm, which allows us to see the adults with the naked eye as well.
Due to the absence of special buccal capsules, Ichthyouris bursata does not attach to the intestinal wall of fish, but retains its position by locomotion. It feeds by sucking and grazing along the wall of the intestine. The feeding does not cause significant histological changes in the intestinal wall of the host fish, but if the number of worms increases to dozens or even hundreds, the fishes growth rate will diminish.
The determination of Ichthyouris bursata infections can be done with a microscopic examination of fish feces. The eggs of these worms are oval in shape and equipped with long polar filaments, present on either egg pole. Eggs are found either individually or in groups with intertwined filaments. If you see Ichthyouris eggs, it is recommended to administer an anthelmintic treatment, since mature female worms are able to lay dozens of eggs a day, which otherwise can lead to a significant increase of the parasites population in your aquarium.