A natural parasitic infection with the external ciliate protozoan, Chilodonella hexasticha , was recorded 3 days post‐transportation (PT) in the gills and skin of African catfish ( Clarias gariepinus ). Infected fish displayed behavioural changes and typical signs of infection. Mortalities started on day 7 PT and stopped on day 13 PT, where cumulative mortality reached 62.2%. The expression of immune‐relevant genes, interleuki...