The trematode Bolbophorus damnificus (Digenea: Bolbophoridae) has deleterious effects on production efficiency of farm-raised catfish. The effects of B. damnificus on channel and hybrid catfish, as well as the prevalence and longevity of the trematode stages impacting production, are not well understood. This study aimed to understand the prevalence of infected snails, determine the longevity and site specificity of B. damnificus cercaria in catfish, and compare mortality and physiological response between channel and hybrid catfish during infection. The infectivity and survival of B. damnificus cercariae declined significantly at 12h intervals from 12-36h, and subsequent trials were standardized using cercariae <12h old. Metacercariae persisted in both fish types for 13 months and were found commonly in the posterior midsection. Hybrid catfish exhibited lower mortality than channel catfish. Exposed catfish exhibited anemia corresponding to parasite encapsulation, however no difference was found between fish types in physiological response during infection and subsequent recovery.

The commercial production of channel catfish (Ictalurus punctatus) is major industry in Mississippi. Infections of channel catfish with the digenetic trematode Bolbophorus damnificus have often been associated with heavy economic losses in the industry. To efficiently control transmission of this trematode, the avian hosts need to be identified. In the first study, two American white pelicans, two double-crested cormorants, two great blue herons, and two great egrets were fed channel catfish infected with B. damnificus metacercariae. The presence of Bolbophorus damnificus ova in pelican feces at three days post infection (dpi) indicated the pelicans had patent infections. Mature B. damnificus were recovered from the intestines of both pelicans at 21 dpi. No B. damnificus infections were observed in the other bird species. In a second study, 33 American white pelicans, 34 double-crested cormorants, 35 great blue herons, and 32 great egrets were collected in the Mississippi Delta. The prevalence of B. damnificus in the American white pelican was 93.9%, with an average of 158 B. damnificus found per bird (range 0-681). Bolbophorus damnificus was not found in any of the other bird species. The results of these two studies confirm that the AWPE is the only proven natural host for B. damnificus. In a third study, two previously undescribed cercariae were found infecting rams-horn snails in commercial catfish ponds. In challenge studies, channel catfish were exposed to both cercariae types. Only one type of cercariae (type I) was infective to channel catfish. The first evidence of type I metacercariae was seen histologically at 14 dpi and grossly at 21 dpi. Development continued until 120 dpi, when both gross examination and histology suggested that the metacercariae were mature. The type I metacercariae appeared to cause little host damage. Molecular analysis of the 18S rRNA gene region indicated that the type I cercariae and metacercariae may be a species of Clinostomum. The data generated in these three studies provides additional information that can be used in the development of efficacious management schemes to control digenetic trematodes infecting commercial catfish.