“Aspects of the histopathology of the rectum of Clarias gariepinus infected with the camallanid parasite Paracamallanus cyathopharynx (Baylis,1923) (6952)”

Aspects of the histopathology of the rectum of Clarias gariepinus infected with the camallanid parasite Paracamallanus cyathopharynx (Baylis,1923)

Various studies have reported on Paracamallanus cyathopharynx (Baylis,1923) morphology in various river systems all over the African continent. The data on the impact of the parasite on the host is incomplete and includes mixed species infections. Therefore, this study focuses on aspects of the histopathology of the rectum of Clarias gariepinus (Burchell, 1822) infected with P. cyathopharynx in South Africa. Twenty fish were collected from Lake Heritage (10 fish) (Crocodile River) and Vaal River below the Vaal Dam (10 fish). Infected and uninfected tissue as well as unattached parasite were collected. Specimens and tissues were fixed in 10% neutral buffered formalin or 70% alcohol, for histological assessment and scanning electron microscopy respectively. Samples for histological assessment were embedded in TAAB epoxy resin and sections were stained with haematoxylin and eosin. Prevalence and mean intensity in Lake Heritage (Crocodile River) were 80% and 3.3 and in the Vaal River 60% and 2.5 respectively. Macroscopically, attached parasites have a red tinge. The buccal capsule consists of two parts separated by an isthmus and the anterior part has longitudinal ridges dorsally and ventrally but lacks teeth. The buccal capsule has a slit like opening that can be closed. Externally, a pair of tridents can be seen as bumps on the lateral side of the parasite. The parasite attaches to the columnar epithelial lining of the rectum and apply negative pressure exerted by the muscular oesophagus, to suck the host’s epithelial cells and connective tissue into the buccal capsule. The longitudinal ridges create imprints on the host tissue. Furthermore, the shape of the columnar cells sucked into the buccal capsule is altered. The surrounding epithelium and the submucosa remain intact. None of the specimens sectioned contained blood in the buccal capsule or intestine. There is no inflammation, haemorrhage, or cellular infiltration at the attachment site. There is also no statistical difference between the number of goblet cells in infected and uninfected tissue. It is concluded that contrary to previous reports P. cyathopharynx does not infect the stomach but instead the rectum of C. gariepinus. The low intensity and limited impact indicate that the parasite does not pose threat to its host and will probably not impact on catfish aquaculture. The origin of the red coloration in the parasites remains unsolved.

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