Distribution and abundance of the salmonid parasite Parvicapsula minibicornis (Myxozoa) in the Klamath River basin (Oregon-California, USA)

Abstract

The distribution and abundance of the myxosporean parasite Parvicapsula minibicornis in the Klamath River mirrored that of Ceratomyxa shasta, with which it shares both its vertebrate and invertebrate host. Assay of fish held at sentinel sites and water samples collected from those sites showed that parasite prevalence was highest below Iron Gate dam, which is the barrier to anadromous salmon passage. Above this barrier parasite levels fluctuated, with the parasite detected in the free-flowing river reaches between reservoirs. This was consistent with infection prevalence in the polychaete host, Manayunkia speciosa, which was greater than 1% only in populations tested below Iron Gate dam. Although a low prevalence of infection was detected in juvenile out-migrant fish in the Trinity River, the tributaries tested did not appear to be a significant source of the parasite to the mainstem despite the presence of large numbers of infected adult salmon that migrate and spawn there. Rainbow trout became infected during sentinel exposure, which expands the host range for P. minibicornis and suggests that wild rainbow trout populations are a reservoir for infection, especially above Iron Gate dam. High parasite prevalence in the lower Klamath River is likely a combined effect of high spore input from heavily infected, spawned adult salmon and the proximity to dense populations of polychaetes.KEY WORDS: Distribution · Abundance · Salmonid parasite · Parvicapsula minibicorni · Myxosporea · Klamath River Basin Resale or republication not permitted without written consent of the publisherDis Aquat Org 78: [137][138][139][140][141][142][143][144][145][146] 2007 the estuary, but absent in tributaries with the exception of the headwaters to Klamath Lake in the upper basin (Hendrickson et al. 1989, Stocking et al. 2006. Recent studies have also mapped the distribution of the invertebrate host, Manayunkia speciosa, in the river (Stocking & Bartholomew 2007). However, it is not known if the distribution of P. minibicornis in the KR mirrors either that of C. shasta or its invertebrate host. The exclusion of migrating salmon from the upper portion of the KR system since the completion of Iron Gate dam in the early 1960s may have restricted the parasite to the lower river if its introduction was recent. Distribution may also be affected by the parasite's vertebrate host specificity. P. minibicornis has only been reported from anadromous salmonids, thus their exclusion from above the dams may have resulted in extinction of the parasite above these barriers.The role of Parvicapsula minibicornis as a direct cause of mortality in juvenile Chinook salmon in the KR has not been determined, and there are no data on infection in adult salmon from the Klamath system. This is in contrast to what is known of the effects of P. minibicornis further north in the Fraser River, British Columbia, where certain stocks of sockeye salmon Oncorhynchus nerka have suffered significant prespawn mortality associated with the infection (St. Hilair...

Myxobolus arcticus and Parvicapsula minibicornis infections in sockeye salmon Oncorhynchus nerka following downstream migration in British Columbia

“…In the adult sockeye, severe infection is associated with pathological changes in affected glomeruli and renal tubules (Raverty et al 2000). The parasite has also been reported from adult Pacific salmon in the Columbia and Klamath Rivers (Jones et al 2004, Bartholomew et al 2007, Atkinson et al 2011. Our detection of P. minibicornis confirms an earlier study in which the parasite was reported in juvenile Fraser River sockeye salmon in the Strait of Georgia.…”

Molecular Identification and Real-time Quantitative PCR (qPCR) for Rapid Detection of Thelohanellus kitauei, a Myxozoan Parasite Causing Intestinal Giant Cystic Disease in the Israel Carp

“…Moreover, the number of water-borne parasites in water samples may be considered an indirect indicator of infection risk or intensity, and real-time PCR analysis of water samples may prove useful as a novel method to replace the traditional use of susceptible host fish for both the detection and quantification of specific parasites [15,16,19-21]. In this study, as a preliminary study for pathogen monitoring of environmental water, DNA prepared from spore-suspensions was used in PCR assays.…”

The Effects of Disease-Induced Juvenile Mortality on the Transient and Asymptotic Population Dynamics of Chinook Salmon (Oncorhynchus tshawytscha)

“…An elevated concentration of C. shasta has been documented in a stretch of the Klamath River main stem (Figure 1) [19], [20], [21], referred to herein as the “infectious zone”. Juvenile fall-run Chinook salmon are infected by the parasite while passing through this zone during their spring downstream migration to the ocean.…”

“…The spores of C. shasta that infect juvenile salmon are released from the polychaete Manayunkia speciosa , the secondary host of the parasite [19]. The infectious zone has a much greater density of infected polychaetes than surrounding locations [17], [21] although it is not yet clear why this is the case. It has been suggested that the polychaetes become infected by spores released during the fall and winter from carcasses of adult salmon that were infected while passing through the infectious zone during their upstream spawning migration [17], [19].…”