Clinical signs, morphological and phylogenetic characterization of Myxozoan spp. infecting Nile tilapia, Oreochromis niloticus and African catfish, Clarias gariepinus in Qalyubia Governorate, Egypt.

Context: Myxosporean endoparasites (phylum cnidarian) are critical pathogens that affect both wild and cultured freshwater and marine water fishes globally causing huge economic losses and high mortalities.

Study objective: The present study investigated myxosporean infections in Nile tilapia and African catfish collected from the natural resources.

Methods: A total of four hundred Nile tilapia with an average weight (60 ± 5 g) and two hundred African catfish with an average weight (185 ± 30 g) were collected seasonally from Qalyubia Governorate, Egypt for parasitological and molecular diagnosis of isolated myxozoan species.

Results: Microscopic examination revealed Myxobolus heterosporous, Myxobolus brachysporus, Myxobolus tilapiae, and Myxobolus amieti in Nile tilapia and Henneguya suprabranchiae, and Myxobolus brachysporus in African catfish. Sequencing of 18S rDNA gene for isolated Myxozoan spp. from Nile tilapia revealed Myxobolus tilapiae deposited in GenBank under accession numbers (OR766325 and OR766326). In African catfish, the isolated Myxobolus brachysporus sequence was deposited under accession numbers (OR766327 and OR766328). Henneguya suprabranchiae was also identified in African catfish (accession. No. OR763724 and OR763433).

Conclusion: Overall, these results indicate a high prevalence of myxozoan infection in naturally inhabiting Nile tilapia and African catfish. Curiously, Henneguya suprabranchiae was detected in the digestive tract and kidneys of African catfish, which is considered a rare form.

Implication: This study highlighted the importance of parasitic surveys in natural resources that impact fish production.