The study of the life cycle of <i>Bolbophorus damnificus</i> and its pathology in the channel catfish (<i>Ictalurus punctatus</i>)
In channel catfish (Ictalurus punctatus), the digenetic trematode Bolbophorus damnificus, causes morality and reduced growth. Previous research has documented that the hosts for B. damnificus are: the American white pelican (Pelecanus erythrorhynchos ), the Ram's horn snail (Planorbella trivolvis) and the channel catfish. The goals of this research were to confirm the life cycle of B. damnificus in a single life cycle study, determine if the snail Biomphalaria havanensis could serve as host for B. damnificus, and examine the pathology of B. damnificus in channel catfish.
American white pelicans (AWPE) were artificially infected with B. damnificus metacercariae which matured to the adult stage in four days and shed ova. The ova hatched in 12-53 days, releasing miracidia which infected P. trivolvis and developed into B. damnificus cercariae which were shed in 23 days, used to infect catfish and matured into metacercariae in the superficial muscle in 23 days. Infected catfish were fed to AWPE, and the metacercariae matured to patent adults in seven days and shed ova, thus completing the life cycle.
A second study was done to determine if the snail B. havanensis found in commercial catfish ponds, could serve as an intermediate host for B. damnificus. Parasite free B. havanensis exposed to B. damnificus ova shed cercariae that were molecularly identified as B. damnificus; confirming B. havanensis as a potential intermediate host for B. damnificus .
A third study examined the pathology associated with B. damnificus infections in channel catfish. Cercariae, confirmed by PCR to be B. damnificus, were used to infect fingerling catfish at 0, 25, 50, 100 and cercariae/fish. The fish were euthanized 3, 4, 5 and 6 days post-infection, gross observations were noted and tissues were collected for histology. Mortalities of 20-100% occurred by day 6 post-infection in fish challenged with 200 cercariae. At day 6 post-infection, fish challenged with 100-200 cercariae had loss of hepatocyte vacoulation and lymphoid depletion in the spleen. Metacercariae were not only present in the subcutaneous muscle but were also in the dermis, behind the skull, within the muscular layers of the urinary bladder and around the heart.