A Digenean Metacercaria (Apophallus sp.) and a Myxozoan (Myxobolus sp.) Associated with Vertebral Deformities in Cyprinid Fishes from the Willamette River, Oregon

Abstract

A high prevalence of vertebral deformities has been observed in various fishes, especially cyprinids, from certain regions of the Willamette River for many years. One proposed source of these deformities is exposure to toxicants. Histological evaluation of affected chiselmouth Acrocheilus alutaceus revealed that all lesions associated with vertebrae were associated with metacercariae of digenean trematodes. Approximately half of the northern pikeminnow Ptychocheilus oregonensis had infections in which metacercariae were associated with these lesions. Metacercariae were also associated with vertebral lesions in three of four affected peamouth Mylocheilus caurinus. Many metacercariae that were present within the vertebral bodies were associated with bony dysplasia and bony proliferation in all three species. We also evaluated the association of the metacercariae with the vertebral deformities, using intact fish that had been cleared with trypsin. Fish from the affected regions had a much higher prevalence of metacercariae and deformities and a greater abundance of metacercariae than those in the reference site. Chiselmouths had more deformities and metacercariae than northern pikeminnow. In all fish species, 77% of deformities were directly associated with metacercariae; in chiselmouths, about 95% of the deformities exhibited this relationship. Two types of metacercariae were identified in affected fish: Apophallus sp. (Heterophyidae) and a neascus type (Strigeidida). The Apophallus sp. appeared to be more closely associated with the skeleton deformities. A Myxobolus sp. morphologically similar to M. cyprini was also associated with the vertebral lesions in about 50% of the northern pikeminnow and 5% of the chiselmouths. Intact plasmodia were found in somatic muscle, and lesions containing free spores were often located at bone surfaces. This survey demonstrates that metacercariae (probably Apophallus sp.) and a Myxobolus sp. are major causes of the vertebral deformities seen in cyprinid fishes from certain regions of the Willamette River.

Unilateral perivertebral fibrosis associated with lordosis, kyphosis and scoliosis (LKS) in farmed Chinook salmon in New Zealand

“…data). Infectious agents have been associated with spinal curvature in other fish species (Kent et al 2004, Sarker et al 2015. Farmed Chinook salmon are routinely screened for infectious agents.…”

Patterns of fish deformities and their association with trematode cysts in the Willamette River, Oregon

“…In the Willamette River, Oregon, fish vertebral deformities are unusually high, especially from river mile (RM) 26.5 to RM 55, an area known as Newberg Pool (Ellis et al 1997, Markle et al 2002, Kent et al 2004. Deformities have been found in 12 species and six families with chiselmouth, Acrocheilus alutaceus, showing the highest rates (Markle et al 2002).…”

Record of an Abnormal Schizothoraichthys esocinus (Heckel) from the Himalayan River Chenab Draining Jammu Region of the J&K State, India

“…Fish anomalies have been attributed to physical factors like temperature [1][2][3], fluctuations in one or the other chemical parameters like salinity, low dissolved oxygen, high carbon dioxide [4][5][6][7][8] and water quality degradation by pollutants [9][10][11]. …”