“Aspects of the histopathology of the stomach of Clarias gariepinus (Burchell, 1822) infected by Procamallanus (Procamallanus) pseudolaeviconchus Moravec & Van As, 2015. (6951)”

Aspects of the histopathology of the stomach of Clarias gariepinus (Burchell, 1822) infected by Procamallanus (Procamallanus) pseudolaeviconchus Moravec & Van As, 2015.

African sharptooth catfish is a preferred aquaculture species. They are omnivorous and host many parasite species. The current study reports on the impact of Procamallanus (Procamallanus) pseudolaeviconchus Moravec & Van As, 2015 on the stomach of Clarias gariepinus (Burchell, 1822) and identifies the wound inflicting structures. Fishwere collected from Lake Heritage (Crocodile River), and Vaal River below Vaal Dam. Infected and uninfected stomach tissue as well as unattached parasites were fixed in 10% neutral buffered formalin for histological assessment or 70% alcohol for scanning electron microscope respectively. Specimens were embedded in TAAB epoxy resin and stained with Periodic-Acid Schiff or haematoxylin and eosin. No P. (P.) pseudolaeviconchus were found in the fish from the Vaal River therefore these fish were used as control.In Lake Heritage prevalence was 80% and mean intensity 2.5. The buccal capsule is large, lacks teeth, and has a round opening that cannot be closed and bears unlobed peribuccal flanges. The oesophagus is muscular. The parasites attach to the columnar epithelial lining of the mucosa and perforates it at the interface with the buccal capsule while the surrounding epithelium remains intact. The columnar epithelial cells and connective tissue are sucked into the buccal capsule, their shape is altered, and cells are sloughed off. The underlying gastric glands show signs of trauma. The impact is localized to the attachment site. There’s no inflammation, haemorrhage or cellular infiltration at the attachment site. Host tissue is present in the intestinum of the parasites. It is deduced that the nematode uses the peribuccal flanges, solid sturdy buccal capsule, and the vacuum created by the muscular oesophagus to attach and ingest host tissue. These structures create a suction cup which enables the parasites to ingest the host’s tissue into the buccal capsule and eventually into the intestine.It is concluded that the low intensity, localised trauma and absence of an immune response indicate limited impact on the host. The life cycle has not been studied but probably involves one or more intermediate host/s (copepods and/or smaller fish species) which can be excluded in fish culture. Therefore, the parasite poses a limited threat to aquaculture.

1. MATEA, KENNETH, UNIVERSITY OF JOHANNESNURG, Presenter
2. Avenant-Oldewage, Annemariè, UNIVERSITY OF JOHANNESBURG, Author