Tetracapsuloides bryosalmonae abundance in river water

Abstract

Tetracapsuloides bryosalmonae is a myxozoan parasite of freshwater bryozoans and salmonids, causing proliferative kidney disease in the latter. To date, detection of the parasite has required collection of hosts and subsequent molecular or histological examination. The release of infectious spores from both hosts offers an opportunity to detect the parasite in water samples. We developed a novel SYBR ® Green quantitative real-time PCR (qPCR) assay for T. bryosalmonae in water samples which provides an estimation of bryozoan malacospore numbers and tested the assay in 3 rivers in southern England (UK) over a period of 5 wk. The assay proved to be both highly sensitive and specific to the parasite, detecting low levels of spores throughout the study period. Larger-volume samples afforded greater detection likelihood, but did not increase the number of spores detected, possibly as a result of low and patchy spore distributions and lack of within-site replication of large-volume samples. Based on point-measurements, temperature was positively associated with the likelihood of detecting spores, possibly reflecting the temperature dependence of spore shedding from bryozoan hosts. The presence of T. bryosalmonae in water samples was predominantly influenced by spatial (sites within rivers, amongst rivers) and temporal (sampling dates) factors, while the latter also influenced quantification cycle (C q ) values and spore abundance. Environmental monitoring for infectious stages can complement traditional methods, providing faster and easier detection and avoiding potentially prolonged searching, collecting and destructive sampling of invertebrate and vertebrate hosts.

Improved Conventional PCR Assay for Detecting Tetracapsuloides bryosalmonae DNA in Fish Tissues

“…; Fontes et al. ; Hutchins et al., in press), and other sequence‐based (El‐Matbouli and Soliman ) assays exist for detecting T. bryosalmonae DNA. All of these assays, with the exception of that of Hutchins et al.…”

“…Furthermore, only one of the assays located in the PKX5f‐6r region of the gene (Fontes et al. ) defines absolute limits of detection and quantification and explicitly demonstrates repeatability as part of the published results (Jacobson and Wright ). Lastly, there are only three unique conventional PCR assays published prior to the work presented here (Saulnier and De Kinkelin ; Kent et al.…”

Recombinase polymerase amplification assay combined with a lateral flow dipstick for rapid detection of Tetracapsuloides bryosalmonae, the causative agent of proliferative kidney disease in salmonids

“…Tetracapsuloides bryosalmonae was detected in wild fish species throughout Europe [ 16 , 18 – 21 , 43 , 55 ]. Generally, most of the microbial detection methods are based on PCR and real-time PCRs.…”

“…In addition, specific monoclonal antibodies were used for the detection of T. bryosalmonae in the infected fish kidney [ 32 – 34 ]. Subsequently, DNA-based detection assays, such as in situ hybridization, polymerase chain reaction (PCR), real-time PCR and loop-mediated isothermal amplification assays, were developed for specific and sensitive detection of T. bryosalmonae [ 35 – 43 ]. Despite its advantages, PCR has intrinsic disadvantages, such as time-consuming, expensive instruments, and complicated procedures for the detection of amplified products [ 44 , 45 ].…”

Comparative transcriptomics and host-specific parasite gene expression profiles inform on drivers of proliferative kidney disease

“…For gene expression analysis, uninfected and overtly infected bryozoans from the Furtbach River, Switzerland, were used. Bryozoan collections were cultured in a laboratory mesocosm, as described previously 62 , with successfully attaching bryozoan branches constituting a single colony. All bryozoan cultures were maintained for 1-3 weeks to allow colonies to develop transparency, enabling the detection of overt infections using a stereomicroscope.…”