Chronic Pathology and Longevity of Drepanocephalus spathans Infections in Juvenile Channel Catfish

Abstract

Drepanocephalus spathans (Digenea: Echinostomatidae) is a common parasite of the double-crested cormorant Phalacrocorax auritus. The cercariae of D. spathans have been shown infective to juvenile Channel Catfish Ictalurus punctatus. The developing metacercariae concentrate in the cranial regions, often occluding blood vessels at the base of the branchial arch, occasionally resulting in death. The purpose of this study was to determine how long metacercariae of D. spathans persist in experimentally challenged Channel Catfish. Two separate infectivity trials were conducted. In both trials, metacercariae persisted at least 49 d postinfection, although prevalence and intensity of infection decreased over time. In the first trial, juvenile catfish (1-3 g) were exposed over three consecutive days to 100, 100, and 80 cercariae/fish/d, respectively. Fish were sampled 7 d after the final exposure, and metacercariae were observed in 83.3% (five of six) of challenged fish. At 21 d postexposure, metacercariae were present in only 50% of exposed fish (three of six). No metacercaria were observed in fish sampled at 35 d, however, metacercariae were present in one of six (16.7%) fish sampled 49 and 70 d postexposure, respectively. A second challenge consisted of a 24-h pooled exposure of 500 cercariae per fish. Again, metacercariae were present in most (six of seven; 85.7%) fish at 7 d postexposure. At 21 d postexposure, metacercariae were only evident in one of seven (14.3%) sampled fish. No metacercariae were present in any fish at 35 d postchallenge, yet one of seven (14.3%) fish was positive at 49 d postchallenge. The second study was terminated at 63 d postchallenge, as all fish sampled (n = 14) were negative for metacercariae. These data suggest that cercariae of D. spathans are infective to juvenile Channel Catfish, although the infection appears short lived as metacercariae rarely persisted longer than 2 months.

Biomphalaria straminea (Mollusca: Planorbidae) as an intermediate host of Drepanocephalus spp. (Trematoda: Echinostomatidae) in Brazil: a morphological and molecular study

“…reticulata, Australoheros facetus (Jenyns, 1842)] from the Pampulha Reservoir (HAP, unpublished data). In the current study, several fish died during experimental laboratory challenges following exposure to these parasites and the potential pathogenic effects of D. spathans (now D. auritus) have been well documented by Griffin et al (2012Griffin et al ( , 2014. This would suggest these parasites could have deleterious effects on the fitness of the fish community in this region.…”

“…cercaria from a previous study (Griffin et al 2014), were fixed in 95 % ethanol and used for molecular identification. Genomic DNA (gDNA) was isolated from pools of five cercariae using the DNeasy Blood and Tissue Kit (QIAGEN, Venlo, Netherlands).…”

“…Sequences for both morphotypes, as well as sequences from the archived Drepanocephalus sp. isolate from North America (Griffin et al 2014), were submitted to GenBank under accessions KP053255-KP053256, KP053259-KP053264, and KR259644.…”

Encapsulation of Bolbophorus damnificus (Digenea: Bolbophoridae) Metacercariae in Juvenile Channel Catfish, Ictalurus punctatus, Is Linked to Delayed‐onset Mortality

“…A magnetic stir bar was added to the flask, and cercariae were gently stirred. While stirring, 10 aliquots of 100 μL were collected and placed as separate droplets on a plastic petri dish, similar to the methods used in previous studies (Yost ; Griffin et al , ; Rosser et al ; Alberson et al ). Cercariae in each droplet were counted using a Nikon SMZ‐U stereoscopic microscope (Nikon Instruments, Melville, NY, USA).…”

“…Bolbophorus damnificus (Digenea: Bolbophoridae) sequentially infects the American white pelican, Pelecanus erythrorhynchos ; the planorbid snails, Planorbella trivolvis and Biomphalaria havanensis ; and multiple fish hosts including channel and hybrid, I. punctatus × Ictalurus furcatus , catfish (Overstreet et al ; Griffin et al ; Rosser et al ). In US catfish aquaculture, outbreaks of B. damnificus have been linked to mortality, poor production efficiency, and increased incidence of bacterial infections (Wise et al ).…”