In channel catfish (Ictalurus punctatus), the digenetic trematode B. damnificus, causes morality and reduced growth. Previous research has documented the hosts for B. damnificus are: the American white pelican (Pelecanus erythrorhynchos), the 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 fulfilling Koch’s postulates; determine if the snail, Biomphalaria havanensis-obstructa, could serve a host for B. damnificus, and examine the pathology of B. damnificus in channel catfish. American white pelicans (AWP) were artificially infected with B. damnificus metacercariae which matured to the adult stage (4 days) and shed ova. The ova hatched (12- 53 days), releasing miracidia which infected P. trivolvis and developed into B. damnificus cercariae which were shed (23 days), used to infect catfish and matured into metacercariae in the superficial muscle (23 days). Infected catfish were fed to AWP, and the metacercariae matured to patent adults (7 days) and shed ova, thus completing the life cycle. A second study was performed to determine if the snail, Biomphalaria havanensis- obstructa found in commercial catfish ponds could serve as an intermediate host for B. damnificus. Parasite free Biomphalaria havanensis- obstructa exposed to B. damnificus ova shed cercariae that were molecularly identified as B. damnificus; confirming Biomphalaria havanensis- obstructa is 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 200, 100, 50, 25 and 0 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 in fish challenged with 200 cercariae by day 6 post-infection. At day 6 post-infection, fish challenged with 100- 200 cercariae had loss of hepatocytes vacoulation and lymphoid depletion in the spleen. Metacercariae were not only present in the subcutaneous muscle but were also in the epidermis, behind the skull, within the muscular layers urinary bladder and around the heart.

No description available.

No description available.

Digenean eye-flukes of the genus <i>Diplostomum </i>(Family:  Diplostomatidae) are common in the eyes of freshwater fishes.  <i>Diplostomum </i>spp. infections can lead to severe detrimental deformities and even death to both farmed and wild fish species.  Identification of <i>Diplostomum</i> spp. in the fish host (metacercaria) is challenging because species are morphologically indistinguishable.  Since <i>Diplostomum</i> spp. are difficult to identify the literature is confounded by synonymy and as a result, the taxonomic status of the genus remains unclear.  Thus, it is difficult to ascertain the pathological status, diversity and geographical distribution of this economically important group of parasites. The purpose of this study was to define operational taxonomic units (OTU) using morphometric and molecular data collected from <i>Diplostomum </i>spp. metacercaria in the U.K.  Data was collected from ten fish species and four host locations:  lens humor retina and brain.  Four OTU were defined by host location using morphometric analysis.  Hence the morphometric analysis proved metacercaria from the four host locations were different in size and shape. Four OTU were discriminated using PCR-RFLP and sequence analysis.  However, with the exception of brain parasites, those in the fish eye (lens, humor and retina) could not be differentiated by host location.  Therefore, although parasites in the three fish eye locations were different in size and shape, they were not genetically different.  The OTU ITS1 sequence data was compared to published <i>Diplostomum</i> spp. sequences and the following genetic similarity was revealed:  OTU1 showed 99.4% similarity to <i>D. mergi</i>;  OTU2 99.7% similarity to <i>D. baeri</i> and OTU3 99.7% similarity to <i>D. paracaudum/D. spathaceum.  </i>OTU4 in the fish brain has previously been described as <i>D. phoxini.</i> The molecular approach was subsequently used in a temporal study to assess <i>Diplostomum </i>spp. metacercaria infections over the course of a year in a rainbow trout farm.

Cyathocotyle bushiensis and Sphaeridiotrema globulus were previously implicated in the annual mortality of wild ducks in southern Quebec. Of 21 snail species collected from nine aquatic communities in southern Quebec and southeastern Ontario, May to October 1989 and 1990, only Bithynia tentaculata was heavily and consistently infected with C. bushiensis metacercariae. Although infection levels varied spatially, a consistent concave seasonal pattern of prevalence and abundance was found which may be due to overwintering metacercariae and the almost simultaneous onset of cercarial transmission and recruitment of new snails in mid-summer. Even though S. globulus metacercariae were found in 18 of 21 snail species, B. tentaculata is believed to contribute most to transmission to ducks. The variety of seasonal patterns and large scale spatial heterogeneity in the prevalence and abundance of S. globulus suggested that cercariae may be from more than one source. Some of the spatial variation in metacercarial levels may be due to small scale processes; extensive spatial heterogeneity at a scale of 10 m was detected in S. globulus cercarial transmission to sentinel snails. This small scale heterogeneity may be due to B. tentaculata having small home ranges as suggested by mark-recapture studies on movement. In aquaria, even though smaller B. tentaculata were more active than larger ones and intraspecific microhabitat preferences were found, preliminary results from ducks (Anas discors) feeding on snail communities in pools suggested that snails are ingested in proportion to their presence. Therefore, the importance of a snail species or size class in the transmission of the two parasites to ducks may depend only on its density and metacercarial abundance. Finally, another mode of transmission is proposed for S. globulus: ducks may become infected by consuming empty snail shells containing viable cysts.

No description available.

No description available.

No description available.

Cyathocotyle bushiensis (Digenea) and Sphaeridiotrema globulus (Digenea) are gastrointestinal pathogens of waterfowl, and are known to co-occur in salvaged ducks. The intensity and time-dependent pathogenesis induced by single infections of the two digeneans, and concurrent infections were studied in two species of dabbling ducks. Gross tissue pathology by single C. bushiensis infection was found to be a function of both the intensity and the duration of infection. Infection with single species infections of C. bushiensis and S. globulus was associated with decreased weight gain, tendencies for increased body temperatures and increased hematological parameters in Pekin ducklings. The hematological parameters in blue winged teal infected with C. bushiensis were found to decrease. Infection with S. globulus did not induce any significant systemic changes in the blue winged teal. A preliminary study of the effects of concurrent infection on the duck hosts suggests that in general, concurrent infection enhances the detrimental aspects of single infection, decreasing weight gain, increasing body temperatures, and decreasing hematological parameters in both species.

Thesis (Ph.D.) - University of Queensland, 2005. / Includes bibliography.