Detection, Isolation, and Experimental Transmission ofMikrocytos mackini,a Microcell Parasite of Pacific OystersCrassostrea gigas(Thunberg)

Hervio, Dominique; Bower, Susan M.; Meyer, Gary R.

doi:10.1006/jipa.1996.0011

Cited by 44 publications

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“…In the population examined by histology and PCR, the estimated prevalence by PCR (11.6%) is closer to the histology initial rapid screening examination prevalence (7.3%) than the more detailed histological examination result (20%), suggesting that PCR may give false negative results when few organisms are present. However, our pri- (Hervio et al 1996, Bower et al 1997.In addition, the fact that we found significant infections in Kumamoto oysters but no infections in the known susceptible and closely related Pacific oysters in Humboldt Bay suggests that Kumamoto oysters may be more susceptible to infection by Mikrocytos mackini than Pacific oysters. A low digestive gland condition of the Kumamoto oysters sampled in winter from the west coast of North America is a typical finding, as was shown in the evaluation of the initial positive sample from this report.…”

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confidence: 54%

Section: Resultsmentioning

confidence: 94%

“…A low digestive gland condition of the Kumamoto oysters sampled in winter from the west coast of North America is a typical finding, as was shown in the evaluation of the initial positive sample from this report. This indicator of poor feed availability, which leads to poor body condition, along with occasional bacterial abscesses, further suggests that the oysters may be more susceptible to any infection during winter, and particularly to infection by M. mackini, which requires cold winter temperatures for infection and replication (Hervio et al 1996).As a result of the February 2011 finding of Mikrocytos mackini, the California Department of Fish and Game undertook certain legislatively mandated proscriptive actions because of the lack of prior knowledge of this oyster pathogen in California. These actions included an immediate holding action on movement of Kumamoto oyster stocks.…”

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Denman Island disease (causative agent Mikrocytos mackini) in a new host, Kumamoto oysters Crassostrea sikamea

Elston¹,

Moore²,

Abbott³

2012

Dis. Aquat. Org.

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Mikrocytos mackini, causative agent of Denman Island disease in Pacific oystersCrassostrea gigas and other oyster species, was found in 2011 in a previously unreported host, the Kumamoto oyster C. sikamea, in Humboldt Bay, California, USA. The detection was also the first reported finding of M. mackini in California. Prevalence was estimated as high as approximately 27% from pooled samples analyzed by PCR. Higher prevalence appeared related to longer residence time in the bay and somewhat colder than typical winter seawater temperatures. No M. mackini was detected in Humboldt Bay juvenile Kumamoto oysters or Pacific oyster brood or seed stock in 2011 or 2012. KEY WORDS: Mikrocytos mackini · Denman Island disease · Kumamoto oyster · Crassostrea sikamea Resale or republication not permitted without written consent of the publisherDis Aquat Org 102: [65][66][67][68][69][70][71] 2012 shellfish farms, consisting of independent sampling conducted by US Department of Agriculture accredited veterinarians. As a result of such routine surveillance in 2011, Mikrocytos mackini infections were discovered in a previously unrecognized host species, Kumamoto oysters Crassostrea sikamea in Hum boldt Bay, California, a location previously unknown to harbor the disease agent. MATERIALS AND METHODS Sample collectionKumamoto and Pacific brood and seed stock oysters were initially sampled (n = 600) from the northern arm of Humboldt Bay, in February 2011 as part of annual routine brood stock disease sur veillance (Table 1). Samples are collected by an independent veterinarian accredited by the US Department of Agriculture, Animal and Plant Health In spection Service. Following the detection of Mikrocytos mackini from the February sampled group, additional Kumamoto and Pacific oyster brood and seed stock were sampled from March to May 2011 by producer collections from Humboldt Bay (n = 600, Table 1). Except as noted in Table 1, brood stock was held on long lines and seed stock was held in floating up weller systems (FLUPSY). In addition to results of testing on samples collected in 2011, we also report results from samples collected by an accredited veterinarian for disease surveillance in 2012 (n = 600, see Table 1). Histological testingAll oysters were processed for histological examination using routine methods. A transverse section of oysters was made in the dorsal region through the digestive gland, gills and connective tissue, including the labial palps in some cases. This was placed in a histological cassette and fixed in seawater formalin (10% v/v). Histological preparations were processed routinely for paraffin embedment and sections were stained with hematoxylin and eosin. In addition to the examination of tissue for hemocytosis and infectious agents, the height of the epithelium of the digestive gland tubules was rated on a basis of 1 to 4 (low to high), with ratings of 3 and 4 considered to be in the normal active feeding range and ratings of 1 or 2 indicating low height of digestive gland epithelium resulting ...

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confidence: 94%

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Denman Island disease (causative agent Mikrocytos mackini) in a new host, Kumamoto oysters Crassostrea sikamea

Elston¹,

Moore²,

Abbott³

2012

Dis. Aquat. Org.

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“…Second, that M. mackini has not been reported in Asia does not necessarily imply its absence. Detection is very difficult, as explained earlier for Mikrocytos in general, and the temperature dependence of M. mackini infections (Hervio et al 1996, Bower et al 1997) means that it could persist at sub-clinical levels in regions with warmer water temperatures than those found in its known range. Last, the recent first report of Mikrocytos sp.…”

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confidence: 99%

“…Mortality rates in Pacific oysters Crassostrea gigas typically range up to about 30% (Quayle 1982), and non-lethal cases of the disease render oysters unmarketable . Long term annual survey data collected from Denman Island, British Columbia, Canada between 1960 and1994 found that the prevalence of disease (characterized by typical green lesions) among Pacific oysters varied from 11 to 48% (Hervio et al 1996). The known geographic range of M. mackini is restricted to British Columbia (BC) and adjacent areas in Washington State, USA, on the Pacific northwest coast of North America .…”

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Sequence homogeneity of internal transcribed spacer rDNA in Mikrocytos mackini and detection of Mikrocytos sp. in a new location

Abbott

Gilmore²,

Lowe³

et al. 2011

Dis. Aquat. Org.

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Mikrocytos mackini is a microcell parasite of Pacific oysters only known to occur on the Pacific coast of North America. It is the only described species in the genus, although a genetically divergent Mikrocytos sp. organism has been reported once in both the Atlantic Ocean and China. We developed methods for sequencing the internal transcribed spacer (ITS) of rDNA for the purpose of characterizing extant diversity within M. mackini throughout its known geographic range, and surveying for other evidence of Mikrocytos sp. organisms. Our specific aims were to examine relatedness of M. mackini among sites to make inferences about its recent evolutionary history, and to provide baseline data for future development of a species-specific molecular detection method. We found a total lack of genetic variation within M. mackini across the complete ITS1-5.8S-ITS2 array in over 70 samples collected throughout its range. We hypothesize that this could be a result of a founder effect if the parasite had been introduced into its known range alongside its host, which was imported from Asia beginning around 1914 to about 1961. We detected a single divergent sequence at a short stretch of 18S that was identical to the Mikrocytos sp. detected elsewhere, which adds to the recent and growing body of evidence that Mikrocytos is much more broadly distributed than the limited range of M. mackini suggests. A 1903 bp section of rDNA from Mikrocytos sp. was generated that contained regions of high divergence from M. mackini (in ITS1 and ITS2) that could be exploited for molecular diagnostics.

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Canada's Approach to Aquatic Animal Biosecurity: Experience and Evolution

McGladdery¹,

Zurbrigg²

2005

Aquaculture Biosecurity

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Detection, Isolation, and Experimental Transmission ofMikrocytos mackini,a Microcell Parasite of Pacific OystersCrassostrea gigas(Thunberg)

Cited by 44 publications

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Denman Island disease (causative agent Mikrocytos mackini) in a new host, Kumamoto oysters Crassostrea sikamea

Denman Island disease (causative agent Mikrocytos mackini) in a new host, Kumamoto oysters Crassostrea sikamea

Sequence homogeneity of internal transcribed spacer rDNA in Mikrocytos mackini and detection of Mikrocytos sp. in a new location

Canada's Approach to Aquatic Animal Biosecurity: Experience and Evolution

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