Defeating diplostomoid dangers in USA catfish aquaculture

Abstract

Abstract. Diplostomoid digenean metacercariae have caused widescale mortalities of channel catfish, Ictalurus punctatus (Rafinesque), at aquaculture farms in Louisiana, Mississippi and Arkansas, USA. Originally, based on a tentative diagnosis, the industry considered the primary harmful agent to be an introduced species from Europe, Bolbophorus confusus (Krause, 1914), frequently reported from the American white pelican, Pelecanus erythrorhynchos Gmelin. Our group has now shown, using ITS 1-2 plus three more-conservative gene fragments, that two sympatric species of Bolbophorus exist in the American white pelican. One, B. damnificus Overstreet et Curran, 2002, infects the musculature of catfish, and the other, probably not B. confusus, does not infect catfish. However, at least four other pathogenic diplostomoids and a clinostomoid infect the catfish, and they use at least four different snail hosts, including the planorbids Planorbella trivolvis (Say) and Gyraulus parvus (Say), the physid Physella gyrina (Say) and a lymnaeid. Two metacercariae, B. damnificus and Bursacetabulus pelecanus Dronen, Tehrany et Wardle, 1999, infect the catfish and mature in the pelican; two others, Austrodiplostomum compactum (Lutz, 1928) and Hysteromorpha cf. triloba (Rudolphi, 1819), mature in cormorants; one, Diplostomum sp., matures in seagulls and at least one, Clinostomum marginatum (Rudolphi, 1819), matures in herons, egrets and other wading birds. Consequently, management of catfish ponds relative to digenean infections requires considerable biological information on the fish, bird, and snail hosts as well as the parasites.

Infection levels ofAustrodiplostomum compactum(Digenea, Diplostomidae) metacercariae inPlagioscion squamosissimus(Teleostei, Sciaenidae) from the Nova Avanhandava reservoir, São Paulo State, Brazil

“…The same (no damage, cataracts or blindness) was observed in this study despite the record of up to 136 metacercariae in a single eyeball. It is noteworthy that metacercariae of other species of the Diplostomidae family have caused mortality and decreases in condition factors in catfish Ictalurus punctatus (Rafinesque, 1818) at fish farms in the USA (Overstreet & Curran, 2004).…”

New host records and a checklist of fishes infected with Austrodiplostomum compactum (Digenea: Diplostomidae) in Brazil

“…Specifically, the Paraná basin is the most studied region for A. compactum in Brazil, and this is possibly related to the distribution of researchers in Brazil. Despite the large number of studies, further investigations are necessary to understand the relationship between environmental aspects and life strategies because diplostomiasis causes large aquaculture losses each year worldwide (PAPERNA; DZIKOWSKI, 1995;OVERSTREET;CURRAN, 2004).…”

Parasites of the American White Pelican

“…Whether B. confusus, which we consider to be a European species, exists in North America still has to be determined (Overstreet et al 2002). One of the two species previously reported in part as B. confusus by at least some authors (e.g., reviews by Olson 1966, Overstreet et al 2002, Appendix 1) was considered as B. damnificus, and it can be readily acquired by the AWP from feeding on infected channel catfish (Ictalurus punctatus) (Overstreet et al 2002, Overstreet andCurran 2004). The other species is referred to as Bolbophorus sp.…”

“…Good examples include two diplostomatid digeneans that infect catfish and a cathaemasiid digenean that infects amphibians. These diplostomatids, Bolbophorus damnificus and Bursacetabulus pelecanus, both can produce mass mortalities of the channel catfish, at least in aquaculture conditions (Overstreet et al 2002, Overstreet andCurran 2004). The problem with B. damnificus is more confusing than originally presumed by fish farmers and managers because more than one species of Bolbophorus infects the AWP (Overstreet et al 2002), with a single individual bird capable of harboring at least two of those species.…”

“…Those for B. damnificus enter the fish and finally lodge and encyst, typically in the muscle adjacent to the dermis in the caudal region, and those of B. pelecanus end up unencysted in the vitreous humor of the eye. Infection by B. damnificus also results in pathological alterations in the kidneys (Overstreet and Curran 2004). The snails and up to millions of associated cercariae occur along the shallow sides of fish-ponds where young catfish occur and receive massive infections, often resulting in death (e.g., Terhune et al 2002).…”