Spore ornamentation of Haplosporidium hinei n. sp. (Haplosporidia) in pearl oysters Pinctada maxi... more Spore ornamentation of Haplosporidium hinei n. sp. (Haplosporidia) in pearl oysters Pinctada maxima (Jameson, 1901)
In October 2001, a new intracellular parasite was detected in Western Australian pearl oysters, P... more In October 2001, a new intracellular parasite was detected in Western Australian pearl oysters, Pinctada maxima. This ciliated parasite had not previously been seen in the area despite surveillance over preceding years. A study was performed to identify its characteristics and distribution. The information provided by this study could thereby assist the Pearl Producers Association and Government bodies in determining the industry’s response to infections. The morphology of the intracellular ciliate of pearl oysters was investigated using light microscopy, revealing organisms that were approximately 5 x 11 μm in size, with 9 rows of cilia and a lobulated nucleus. The ciliates were located within the apical portion of the cytoplasm of digestive epithelial cells of the digestive gland. Investigations into the ultrastructure of the ciliate using transmission electron microscopy (TEM) supported the findings made using histology. On initial morphological examination, a similarity between ...
Encephalomyocarditis virus (EMCV) infection was detected by real-time reverse transcription PCR (... more Encephalomyocarditis virus (EMCV) infection was detected by real-time reverse transcription PCR (qRT-PCR) in four adult alpacas (Vicugna pacos) from two properties on the Far North Coast of New South Wales (NSW) in April and May 2018 and in two adult alpacas from a third property on the Central Coast of NSW in October 2018. Viral RNA was detected in a range of samples, including blood, fresh body organs and mucosal swabs. EMCV was isolated from the blood and body organs of five of these alpacas. These animals displayed a range of clinical signs, including inappetence, colic, recumbency and death. Necropsy findings included multifocal to coalescing areas of myocardial pallor, pulmonary congestion and oedema, hepatic congestion and serosal effusion. Histopathological changes comprised acute, multifocal myocardial degeneration and necrosis, with mild, neutrophilic and lymphocytic inflammation (5/5 hearts) and mild, perivascular neutrophilic meningoencephalitis (1/3 brains). This is the first report of disease due to EMCV in alpacas under farm conditions, and it identifies EMCV infection as a differential diagnosis for acute disease and death in this camelid species. In addition to the samples traditionally preferred for EMCV isolation (fresh heart, brain and spleen), blood samples are also appropriate for EMCV detection by qRT-PCR assay.
Winter mortality (WM) is a poorly studied disease affecting Sydney rock oysters Saccostrea glomer... more Winter mortality (WM) is a poorly studied disease affecting Sydney rock oysters Saccostrea glomerata in estuaries in New South Wales, Australia, where it can cause significant losses. WM is more severe in oysters cultured deeper in the water column and appears linked to higher salinities. Current dogma is that WM is caused by the microcell parasite Bonamia roughleyi, but evidence linking clinical signs and histopathology to molecular data identifying bonamiasis is lacking. We conducted a longitudinal study between February and November 2010 in 2 estuaries where WM has occurred (Georges and Shoalhaven Rivers). Results from molecular testing of experimental oysters for Bonamia spp. were compared to clinical disease signs and histopathology. Available environmental data from the study sites were also collated and compared. Oyster condition declined over the study period, coinciding with decreasing water temperatures, and was inversely correlated with the presence of histological lesions. While mortalities occurred in both estuaries, only oysters from the Georges River study site showed gross clinical signs and histological changes characteristic of WM (lesions were prevalent and intralesional microcell-like structures were sometimes noted). PCR testing for Bonamia spp. revealed the presence of an organism belonging to the B. exitiosa−B. roughleyi clade in some samples; however, the very low prevalence of this organism relative to histological changes and the lack of reactivity of affected oysters in subsequent in situ hybridisation experiments led us to conclude that this Bonamia sp. is not responsible for WM. Another aetiological agent and a confluence of environmental factors are a more likely explanation for the disease.
The Canadian veterinary journal. La revue vétérinaire canadienne, 2010
C ongenital defects result from errors during fetal development, and can be caused by genetic def... more C ongenital defects result from errors during fetal development, and can be caused by genetic defects, infectious agents, or environmental factors (1). Conjoined or fused twins arise from incomplete division of a single embryo during the primitive streak stage. The components of the fetuses are, therefore, monozygotic (2) (Table 1). The defects present in conjoined twins may range from minor duplications to near complete separation and can be broadly classified in terms of the general location of the failure of complete separation. For example, fusion located in the cranial region is termed dipygus; however, there are more specific terms such as, thoracopagus, craniopagus, or abdominopagus (1). This case report describes monocephalic twin fetuses with failure of separation at the level of the thorax or thoracopagus. Cross-bred, fetal, twin lambs, both male, from northeastern New South Wales, Australia, were submitted for necropsy to the Regional Veterinary Laboratory following an unsuccessful assisted delivery by the owner. The ewe had died during parturition and the owner had experienced difficulty in removing the fetuses from the ewe. The lambs were markedly autolyzed and there was a traumatic opening of the abdominal cavity extending from the prepuce to the midline of both bodies. The combined weight of the lambs was 5.1 kg. Grossly, there was a single head, an apparent duplication of the thorax, and 8 limbs-4 brachial (tetrabrachius) and 4 pelvic (tetrascelus) (Figure 1). The crown-to-rump lengths of the 2 fused bodies were 36 cm and 35 cm, respectively; however, curvature rendered accurate measurement difficult (Figure 2). There was bifurcation of the cervical spine at the level of C4 that extended caudally to include 2 distinct tails. There was marked scoliosis of the entire vertebral columns. Rostral to C4, there was a single, normal appearing, cervical spinal cord. The thoraces were fused (thoracopagus), but there were 2 sternums and 2 complete sets of ribs encasing a single heart and lower respiratory system. The heart was 6 cm from base to apex and 5 cm in greatest diameter with an irregular and small atrioventricular valve. The abdomen
Between November 2010 and January 2011, triploid Crassostrea gigas (Pacific oysters) cultivated i... more Between November 2010 and January 2011, triploid Crassostrea gigas (Pacific oysters) cultivated in the Georges River, New South Wales, experienced >95% mortality. Mortalities also occurred in wild diploid C. gigas in the Georges River and shortly thereafter in the adjacent Parramatta River estuary upstream from Sydney Harbour. Neighbouring Saccostrea glomerata (Sydney rock oysters) did not experience mortalities in either estuary. Surviving oysters were collected to investigate the cause of mortalities. Histologically all oysters displayed significant pathology, and molecular testing revealed a high prevalence of ostreid herpesvirus-1 (OsHV-1). Quantitative PCR indicated that many C. gigas were carrying a high viral load at the time of sampling, while the load in S. glomerata was significantly lower (p < 0.001). Subsequent in situ hybridisation experiments confirmed the presence of a herpesvirus in C. gigas but not S. glomerata tissues, suggesting that S. glomerata is not susceptible to infection with OsHV-1. Naïve sentinel triploid C. gigas placed in the Georges River estuary in January 2011 quickly became infected and experienced nearly 100% mortality within 2 wk of exposure, indicating the persistence of the virus in the environment. Phylogenetic analysis of sequences derived from the C2/C6 region of the virus revealed that the Australian strain of OsHV-1 belongs to the microvariant (µ-var) cluster, which has been associated with severe mortalities in C. gigas in other countries since 2008. Environmental data revealed that the Woolooware Bay outbreaks occurred during a time of considerable environmental disturbance, with increased water temperatures, heavy rainfall, a toxic phytoplankton bloom and the presence of a pathogenic Vibrio sp. all potentially contributing to oyster stress. This is the first confirmed report of OsHV-1 µ-var related C. gigas mortalities in Australia.
A Minchinia sp. (Haplosporidia: Haplosporidiidae) parasite was identified infecting rock oysters ... more A Minchinia sp. (Haplosporidia: Haplosporidiidae) parasite was identified infecting rock oysters and morphologically described by Hine and Thorne (2002) using light microscopy and transmission electron microscopy (TEM). The parasite was associated with up to 80% mortality in the host species and it is suspected that the parasite would be a major impediment to the development of a tropical rock oyster aquaculture industry in northern Western Australia. However, attempts to identify the parasite following the development of a specific probe for Haplosporidium nelsoni were unsuccessful. The SSU region of the parasite's rRNA gene was later characterized in our laboratory and an in situ hybridization assay for the parasite was developed. This study names the parasite as Minchinia occulta n sp. and morphologically describes the parasite using histology, scanning electron microscopy and transmission electron microscopy. The non-spore stages were unusual in that they consisted primarily of uninucleate stages reminiscent of Bonamia spp. The parasite's spores were ovoid to circular shaped and measured 4.5 microm-5.0 microm x 3.5-4.1 microm in size. The nucleus of the sporoplasm measured 1.5-2.3 microm and was centrally located. The spores were covered in a branching network of microtubule-like structures that may degrade as the spore matures.
An infection of pearl oysters, Pinctada maxima, attributed to a Haplosporidium sp. by Hine and Th... more An infection of pearl oysters, Pinctada maxima, attributed to a Haplosporidium sp. by Hine and Thorne (1998) has been detected on 3 occasions and is considered to represent a serious concern to the pearling industry in Australia. The spore ornamentation of the parasite was determined by scanning electron microscopy and transmission electron microscopy. Spores of the parasite were pleomorphic, or elongated 3.5-4 microm x 2.5-3.0 microm in size. Two filaments were wound around the spore and originated from 2 'knob-like' posterior thickenings. Both filaments passed up one side of the spore together until just below the operculum whereupon each split and passed obliquely under the lip of the opercula lid. Each filament wrapped around the spore 4 times. The posterior thickenings seem to appear late in the development of the spore and were composed of spore wall material. A second set of branching tubular filaments composed of a different material was observed on the spore body although not on mature spores possessing a 'knob-like' posterior thickening. The ornamentation on the spores of the pearl oyster parasite was unique amongst described haplosporidian species where spore ornamentation is known. The parasite is named in this manuscript as Haplosporidium hinei n. sp.
The pathology associated with an intracellular ciliate infection in the digestive gland of pearl ... more The pathology associated with an intracellular ciliate infection in the digestive gland of pearl oysters Pinctada maxima (Jameson, 1901) is described. Histopathological and transmission electron microscopic examination were used to characterise the organism and its location within host cells. The parasite is tear-drop shaped measuring 5.53 lm (range of 2.73-7.47 lm, n = 9) in width and 11.15 lm (range of 9.02-16.2 lm) in length with a centrally located lobulated nucleus and a large nucleus:cytoplasmic ratio.
A haplosporidian parasite was identiWed in rock oysters (Saccostrea cuccullata Born, 1778) from t... more A haplosporidian parasite was identiWed in rock oysters (Saccostrea cuccullata Born, 1778) from the Montebello Islands (latitude ¡20.4ЈS longitude 115.53ЈE) oV the northern coast of Western Australia by histopathological examination, PCR ampliWcation and DNA sequencing of a segment of the SSU region of the parasite's rRNA gene. An oligonucleotide probe was constructed from the parasite's SSU rRNA gene in order to conWrm its presence by in situ hybridisation. The parasite was disseminated throughout the gonad follicles of the host and to a lesser extent in the gills. The only parasite life stages thus far observed in this study were a uninucleate naked cell assumed to be a precursor to multinucleate plasmodial stages and a binucleate plasmodial stage. Whilst no parasite spores were detected in aVected rock oysters, a phylogenetic analysis of the SSU region of the parasite's rRNA gene indicates the parasite belongs to the genus Minchinia. A PCR and in situ hybridisation assay for the Minchinia sp. was used to identify haplosporidians described by Hine and Thorne [Hine, P.M.., Thorne, T., 2002. Haplosporidium sp. (Haplosporidia: Haplosporidiidae) associated with mortalities among rock oysters Saccostrea cuccullata in north Western Australia. Dis. Aquat. Organ. 51, 123-13], in archived rock oyster tissues from the same coastline. Crown
Haplosporidian parasites infect various invertebrate hosts including some commercially important ... more Haplosporidian parasites infect various invertebrate hosts including some commercially important shellfish. Haplosporidium nelsoni (along with Perkinsus marinus) has severely affected Eastern oyster production on the eastern seaboard of the United States and flat oyster production in Europe has been severely impacted by Bonamia ostreae. These parasites are also often present at a very low prevalence and there are a variety of morphologically similar species that can be difficult to differentiate during cytological or histological diagnosis hence the need to develop specific tests. Recently, a Minchinia sp. was described affecting rock oysters (Saccostrea cuccullata) in north Western Australia.
Objective To determine if juvenile pearl oysters (Pinctada maxima) infected with Haplosporidium h... more Objective To determine if juvenile pearl oysters (Pinctada maxima) infected with Haplosporidium hinei are also infected with another haplosporidian parasite, Minchinia occulta.
Winter mortality (WM) is a poorly studied disease affecting Sydney rock oysters Saccostrea glomer... more Winter mortality (WM) is a poorly studied disease affecting Sydney rock oysters Saccostrea glomerata in estuaries in New South Wales, Australia, where it can cause significant losses. WM is more severe in oysters cultured deeper in the water column and appears linked to higher salinities. Current dogma is that WM is caused by the microcell parasite Bonamia roughleyi, but evidence linking clinical signs and histopathology to molecular data identifying bonamiasis is lacking. We conducted a longitudinal study between February and November 2010 in 2 estuaries where WM has occurred (Georges and Shoalhaven Rivers). Results from molecular testing of experimental oysters for Bonamia spp. were compared to clinical disease signs and histopathology. Available environmental data from the study sites were also collated and compared. Oyster condition declined over the study period, coinciding with decreasing water temperatures, and was inversely correlated with the presence of histological lesions. While mortalities occurred in both estuaries, only oysters from the Georges River study site showed gross clinical signs and histological changes characteristic of WM (lesions were prevalent and intralesional microcell-like structures were sometimes noted). PCR testing for Bonamia spp. revealed the presence of an organism belonging to the B. exitiosa−B. roughleyi clade in some samples; however, the very low prevalence of this organism relative to histological changes and the lack of reactivity of affected oysters in subsequent in situ hybridisation experiments led us to conclude that this Bonamia sp. is not responsible for WM. Another aetiological agent and a confluence of environmental factors are a more likely explanation for the disease.
Spore ornamentation of Haplosporidium hinei n. sp. (Haplosporidia) in pearl oysters Pinctada maxi... more Spore ornamentation of Haplosporidium hinei n. sp. (Haplosporidia) in pearl oysters Pinctada maxima (Jameson, 1901)
In October 2001, a new intracellular parasite was detected in Western Australian pearl oysters, P... more In October 2001, a new intracellular parasite was detected in Western Australian pearl oysters, Pinctada maxima. This ciliated parasite had not previously been seen in the area despite surveillance over preceding years. A study was performed to identify its characteristics and distribution. The information provided by this study could thereby assist the Pearl Producers Association and Government bodies in determining the industry’s response to infections. The morphology of the intracellular ciliate of pearl oysters was investigated using light microscopy, revealing organisms that were approximately 5 x 11 μm in size, with 9 rows of cilia and a lobulated nucleus. The ciliates were located within the apical portion of the cytoplasm of digestive epithelial cells of the digestive gland. Investigations into the ultrastructure of the ciliate using transmission electron microscopy (TEM) supported the findings made using histology. On initial morphological examination, a similarity between ...
Encephalomyocarditis virus (EMCV) infection was detected by real-time reverse transcription PCR (... more Encephalomyocarditis virus (EMCV) infection was detected by real-time reverse transcription PCR (qRT-PCR) in four adult alpacas (Vicugna pacos) from two properties on the Far North Coast of New South Wales (NSW) in April and May 2018 and in two adult alpacas from a third property on the Central Coast of NSW in October 2018. Viral RNA was detected in a range of samples, including blood, fresh body organs and mucosal swabs. EMCV was isolated from the blood and body organs of five of these alpacas. These animals displayed a range of clinical signs, including inappetence, colic, recumbency and death. Necropsy findings included multifocal to coalescing areas of myocardial pallor, pulmonary congestion and oedema, hepatic congestion and serosal effusion. Histopathological changes comprised acute, multifocal myocardial degeneration and necrosis, with mild, neutrophilic and lymphocytic inflammation (5/5 hearts) and mild, perivascular neutrophilic meningoencephalitis (1/3 brains). This is the first report of disease due to EMCV in alpacas under farm conditions, and it identifies EMCV infection as a differential diagnosis for acute disease and death in this camelid species. In addition to the samples traditionally preferred for EMCV isolation (fresh heart, brain and spleen), blood samples are also appropriate for EMCV detection by qRT-PCR assay.
Winter mortality (WM) is a poorly studied disease affecting Sydney rock oysters Saccostrea glomer... more Winter mortality (WM) is a poorly studied disease affecting Sydney rock oysters Saccostrea glomerata in estuaries in New South Wales, Australia, where it can cause significant losses. WM is more severe in oysters cultured deeper in the water column and appears linked to higher salinities. Current dogma is that WM is caused by the microcell parasite Bonamia roughleyi, but evidence linking clinical signs and histopathology to molecular data identifying bonamiasis is lacking. We conducted a longitudinal study between February and November 2010 in 2 estuaries where WM has occurred (Georges and Shoalhaven Rivers). Results from molecular testing of experimental oysters for Bonamia spp. were compared to clinical disease signs and histopathology. Available environmental data from the study sites were also collated and compared. Oyster condition declined over the study period, coinciding with decreasing water temperatures, and was inversely correlated with the presence of histological lesions. While mortalities occurred in both estuaries, only oysters from the Georges River study site showed gross clinical signs and histological changes characteristic of WM (lesions were prevalent and intralesional microcell-like structures were sometimes noted). PCR testing for Bonamia spp. revealed the presence of an organism belonging to the B. exitiosa−B. roughleyi clade in some samples; however, the very low prevalence of this organism relative to histological changes and the lack of reactivity of affected oysters in subsequent in situ hybridisation experiments led us to conclude that this Bonamia sp. is not responsible for WM. Another aetiological agent and a confluence of environmental factors are a more likely explanation for the disease.
The Canadian veterinary journal. La revue vétérinaire canadienne, 2010
C ongenital defects result from errors during fetal development, and can be caused by genetic def... more C ongenital defects result from errors during fetal development, and can be caused by genetic defects, infectious agents, or environmental factors (1). Conjoined or fused twins arise from incomplete division of a single embryo during the primitive streak stage. The components of the fetuses are, therefore, monozygotic (2) (Table 1). The defects present in conjoined twins may range from minor duplications to near complete separation and can be broadly classified in terms of the general location of the failure of complete separation. For example, fusion located in the cranial region is termed dipygus; however, there are more specific terms such as, thoracopagus, craniopagus, or abdominopagus (1). This case report describes monocephalic twin fetuses with failure of separation at the level of the thorax or thoracopagus. Cross-bred, fetal, twin lambs, both male, from northeastern New South Wales, Australia, were submitted for necropsy to the Regional Veterinary Laboratory following an unsuccessful assisted delivery by the owner. The ewe had died during parturition and the owner had experienced difficulty in removing the fetuses from the ewe. The lambs were markedly autolyzed and there was a traumatic opening of the abdominal cavity extending from the prepuce to the midline of both bodies. The combined weight of the lambs was 5.1 kg. Grossly, there was a single head, an apparent duplication of the thorax, and 8 limbs-4 brachial (tetrabrachius) and 4 pelvic (tetrascelus) (Figure 1). The crown-to-rump lengths of the 2 fused bodies were 36 cm and 35 cm, respectively; however, curvature rendered accurate measurement difficult (Figure 2). There was bifurcation of the cervical spine at the level of C4 that extended caudally to include 2 distinct tails. There was marked scoliosis of the entire vertebral columns. Rostral to C4, there was a single, normal appearing, cervical spinal cord. The thoraces were fused (thoracopagus), but there were 2 sternums and 2 complete sets of ribs encasing a single heart and lower respiratory system. The heart was 6 cm from base to apex and 5 cm in greatest diameter with an irregular and small atrioventricular valve. The abdomen
Between November 2010 and January 2011, triploid Crassostrea gigas (Pacific oysters) cultivated i... more Between November 2010 and January 2011, triploid Crassostrea gigas (Pacific oysters) cultivated in the Georges River, New South Wales, experienced >95% mortality. Mortalities also occurred in wild diploid C. gigas in the Georges River and shortly thereafter in the adjacent Parramatta River estuary upstream from Sydney Harbour. Neighbouring Saccostrea glomerata (Sydney rock oysters) did not experience mortalities in either estuary. Surviving oysters were collected to investigate the cause of mortalities. Histologically all oysters displayed significant pathology, and molecular testing revealed a high prevalence of ostreid herpesvirus-1 (OsHV-1). Quantitative PCR indicated that many C. gigas were carrying a high viral load at the time of sampling, while the load in S. glomerata was significantly lower (p < 0.001). Subsequent in situ hybridisation experiments confirmed the presence of a herpesvirus in C. gigas but not S. glomerata tissues, suggesting that S. glomerata is not susceptible to infection with OsHV-1. Naïve sentinel triploid C. gigas placed in the Georges River estuary in January 2011 quickly became infected and experienced nearly 100% mortality within 2 wk of exposure, indicating the persistence of the virus in the environment. Phylogenetic analysis of sequences derived from the C2/C6 region of the virus revealed that the Australian strain of OsHV-1 belongs to the microvariant (µ-var) cluster, which has been associated with severe mortalities in C. gigas in other countries since 2008. Environmental data revealed that the Woolooware Bay outbreaks occurred during a time of considerable environmental disturbance, with increased water temperatures, heavy rainfall, a toxic phytoplankton bloom and the presence of a pathogenic Vibrio sp. all potentially contributing to oyster stress. This is the first confirmed report of OsHV-1 µ-var related C. gigas mortalities in Australia.
A Minchinia sp. (Haplosporidia: Haplosporidiidae) parasite was identified infecting rock oysters ... more A Minchinia sp. (Haplosporidia: Haplosporidiidae) parasite was identified infecting rock oysters and morphologically described by Hine and Thorne (2002) using light microscopy and transmission electron microscopy (TEM). The parasite was associated with up to 80% mortality in the host species and it is suspected that the parasite would be a major impediment to the development of a tropical rock oyster aquaculture industry in northern Western Australia. However, attempts to identify the parasite following the development of a specific probe for Haplosporidium nelsoni were unsuccessful. The SSU region of the parasite's rRNA gene was later characterized in our laboratory and an in situ hybridization assay for the parasite was developed. This study names the parasite as Minchinia occulta n sp. and morphologically describes the parasite using histology, scanning electron microscopy and transmission electron microscopy. The non-spore stages were unusual in that they consisted primarily of uninucleate stages reminiscent of Bonamia spp. The parasite's spores were ovoid to circular shaped and measured 4.5 microm-5.0 microm x 3.5-4.1 microm in size. The nucleus of the sporoplasm measured 1.5-2.3 microm and was centrally located. The spores were covered in a branching network of microtubule-like structures that may degrade as the spore matures.
An infection of pearl oysters, Pinctada maxima, attributed to a Haplosporidium sp. by Hine and Th... more An infection of pearl oysters, Pinctada maxima, attributed to a Haplosporidium sp. by Hine and Thorne (1998) has been detected on 3 occasions and is considered to represent a serious concern to the pearling industry in Australia. The spore ornamentation of the parasite was determined by scanning electron microscopy and transmission electron microscopy. Spores of the parasite were pleomorphic, or elongated 3.5-4 microm x 2.5-3.0 microm in size. Two filaments were wound around the spore and originated from 2 'knob-like' posterior thickenings. Both filaments passed up one side of the spore together until just below the operculum whereupon each split and passed obliquely under the lip of the opercula lid. Each filament wrapped around the spore 4 times. The posterior thickenings seem to appear late in the development of the spore and were composed of spore wall material. A second set of branching tubular filaments composed of a different material was observed on the spore body although not on mature spores possessing a 'knob-like' posterior thickening. The ornamentation on the spores of the pearl oyster parasite was unique amongst described haplosporidian species where spore ornamentation is known. The parasite is named in this manuscript as Haplosporidium hinei n. sp.
The pathology associated with an intracellular ciliate infection in the digestive gland of pearl ... more The pathology associated with an intracellular ciliate infection in the digestive gland of pearl oysters Pinctada maxima (Jameson, 1901) is described. Histopathological and transmission electron microscopic examination were used to characterise the organism and its location within host cells. The parasite is tear-drop shaped measuring 5.53 lm (range of 2.73-7.47 lm, n = 9) in width and 11.15 lm (range of 9.02-16.2 lm) in length with a centrally located lobulated nucleus and a large nucleus:cytoplasmic ratio.
A haplosporidian parasite was identiWed in rock oysters (Saccostrea cuccullata Born, 1778) from t... more A haplosporidian parasite was identiWed in rock oysters (Saccostrea cuccullata Born, 1778) from the Montebello Islands (latitude ¡20.4ЈS longitude 115.53ЈE) oV the northern coast of Western Australia by histopathological examination, PCR ampliWcation and DNA sequencing of a segment of the SSU region of the parasite's rRNA gene. An oligonucleotide probe was constructed from the parasite's SSU rRNA gene in order to conWrm its presence by in situ hybridisation. The parasite was disseminated throughout the gonad follicles of the host and to a lesser extent in the gills. The only parasite life stages thus far observed in this study were a uninucleate naked cell assumed to be a precursor to multinucleate plasmodial stages and a binucleate plasmodial stage. Whilst no parasite spores were detected in aVected rock oysters, a phylogenetic analysis of the SSU region of the parasite's rRNA gene indicates the parasite belongs to the genus Minchinia. A PCR and in situ hybridisation assay for the Minchinia sp. was used to identify haplosporidians described by Hine and Thorne [Hine, P.M.., Thorne, T., 2002. Haplosporidium sp. (Haplosporidia: Haplosporidiidae) associated with mortalities among rock oysters Saccostrea cuccullata in north Western Australia. Dis. Aquat. Organ. 51, 123-13], in archived rock oyster tissues from the same coastline. Crown
Haplosporidian parasites infect various invertebrate hosts including some commercially important ... more Haplosporidian parasites infect various invertebrate hosts including some commercially important shellfish. Haplosporidium nelsoni (along with Perkinsus marinus) has severely affected Eastern oyster production on the eastern seaboard of the United States and flat oyster production in Europe has been severely impacted by Bonamia ostreae. These parasites are also often present at a very low prevalence and there are a variety of morphologically similar species that can be difficult to differentiate during cytological or histological diagnosis hence the need to develop specific tests. Recently, a Minchinia sp. was described affecting rock oysters (Saccostrea cuccullata) in north Western Australia.
Objective To determine if juvenile pearl oysters (Pinctada maxima) infected with Haplosporidium h... more Objective To determine if juvenile pearl oysters (Pinctada maxima) infected with Haplosporidium hinei are also infected with another haplosporidian parasite, Minchinia occulta.
Winter mortality (WM) is a poorly studied disease affecting Sydney rock oysters Saccostrea glomer... more Winter mortality (WM) is a poorly studied disease affecting Sydney rock oysters Saccostrea glomerata in estuaries in New South Wales, Australia, where it can cause significant losses. WM is more severe in oysters cultured deeper in the water column and appears linked to higher salinities. Current dogma is that WM is caused by the microcell parasite Bonamia roughleyi, but evidence linking clinical signs and histopathology to molecular data identifying bonamiasis is lacking. We conducted a longitudinal study between February and November 2010 in 2 estuaries where WM has occurred (Georges and Shoalhaven Rivers). Results from molecular testing of experimental oysters for Bonamia spp. were compared to clinical disease signs and histopathology. Available environmental data from the study sites were also collated and compared. Oyster condition declined over the study period, coinciding with decreasing water temperatures, and was inversely correlated with the presence of histological lesions. While mortalities occurred in both estuaries, only oysters from the Georges River study site showed gross clinical signs and histological changes characteristic of WM (lesions were prevalent and intralesional microcell-like structures were sometimes noted). PCR testing for Bonamia spp. revealed the presence of an organism belonging to the B. exitiosa−B. roughleyi clade in some samples; however, the very low prevalence of this organism relative to histological changes and the lack of reactivity of affected oysters in subsequent in situ hybridisation experiments led us to conclude that this Bonamia sp. is not responsible for WM. Another aetiological agent and a confluence of environmental factors are a more likely explanation for the disease.
Uploads
Papers by Z. Spiers