Hermanus, South Africa
Hermanus, South Africa

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Boonzaaier M.K.,Stellenbosch University | Neethling S.,Stellenbosch University | Neethling S.,University of South Africa | Mouton A.,Amanzi Biosecurity | Simon C.A.,Stellenbosch University
African Journal of Marine Science | Year: 2014

Although there has been an increase in our understanding of the shell-boring polydorids that infest abalone Haliotis midae in South Africa, abalone from a limited number of farms, and wild populations from east of Cape Agulhas only, have been examined. To gain further knowledge and a more complete understanding of the local distribution of polydorids, we examined up to 30 abalone from each of 14 farms in the Northern, Western and Eastern Cape provinces, and five wild sites in the Western Cape, west of Cape Agulhas. Farm and wild communities were significantly different from each other (ANOSIM, r = 0.632, p < 0.002) and Bray–Curtis cluster analysis showed that most farms clustered separately from wild sites. Boccardia proboscidea was present on all but one of the infested farms, whereas some were also infested by Dipolydora capensis. By contrast, D. capensis was present at all wild sites sampled, whereas B. proboscidea was absent from these sites. Polydora hoplura, a common shell-boring pest, was present at only two farms and two wild sites. There appeared to be some exchange of polydorids among farms and between farms and wild abalone. The farm on the East Coast did not cluster with any other sites, indicating a unique composition of polydorids on that coast. No new, potentially problematic, species was encountered, although four species showed an increase in their known distribution. © 2014, Copyright © NISC (Pty) Ltd.


Macey B.M.,Nutreco Aquaculture Research Center | Christison K.W.,Nutreco Aquaculture Research Center | Christison K.W.,University of the Western Cape | Mouton A.,Amanzi Biosecurity
Aquaculture | Year: 2011

A recent outbreak of mycosis has been discovered in abalone culture facilities in South Africa. Infected abalone are characterised by multifocal areas of necrosis of the epithelium, underlying muscle fibres and connective tissues of the foot, epipodium and mantle. The lesions are typically 2-3. mm in diameter and contain numerous hyphae. Affected aquaculture facilities have suffered significant production losses, with up to 90% mortality among spat and up to 30% mortality among older animals. The pathogen has been identified as Halioticida noduliformans Muraosa, Morimoto, Sano, Nishimura and Hatai, 2009 from the morphological characteristics, the physiological characteristics that were investigated and molecular analysis of the large subunit ribosomal RNA (LSU rRNA) gene. Although the optimum temperature for growth of the fungus was 20-25°C, it grew at a wide range of temperatures (10-25°C). No growth occurred at 5 and 30°C. The fungus grew well in peptone yeast glucose saline (PYGS) agar containing 50-100% seawater, with optimum growth occurring in full strength seawater (~. 35. ppt salinity). No vegetative growth was observed on PYG agar without seawater or supplemented exclusively with varying concentrations (0-5%) of NaCl. The isolate grew at a wide range of pH (4.0-10.0) with the optimum pH value of 7.0-8.0. The disease was reproduced in juvenile abalone (30-50. mm shell length) by artificial infection and the fungus was re-isolated from moribund abalone, demonstrating that the isolated H. noduliformans fungus is the cause of abalone tubercle mycosis disease that has been occurring in South Africa since 2006. © 2011 Elsevier B.V.


Mouton A.,Amanzi Biosecurity | Mouton A.,University of Pretoria | Gummow B.,James Cook University | Gummow B.,University of Pretoria
Aquaculture | Year: 2011

Abalone have been cultured in South Africa for seventeen years. The growing industry has led to increased intensification. Farms are concentrated in certain areas, notably Hermanus on the South coast, and may be close to wild abalone populations and processing facilities. These factors contribute to increased risk of disease emergence. Data on parasite prevalence generated from the abalone health management program between 2000 and 2004 was analysed for trends. Abalone were sampled systematically from participating farms and subjected to gross and histological examination. Data on age, size, gonad development, diet and type of system were recorded. This paper presents the most significant results for gut protozoa, digestive gland protozoa and rickettsia like prokaryotes, which are all gut associated. Prevalence was found to increase with increasing age and size. Higher parasite prevalences were found on the West coast than on the South coast, and outside Hermanus compared to within Hermanus, suggesting that concentration of farms is not leading to increased prevalence. Gut associated parasites were significantly more prevalent in animals fed on kelp than artificial feed. It was found that animals younger than 24. months are more at risk of infection when fed kelp than older animals. The results indicate that separation of age groups, removal of poor performers and use of artificial feed, especially in younger animals, are likely to reduce risk of infection with gut associated parasites. © 2011 Elsevier B.V.


Horwitz R.,University of Cape Town | Mouton A.,Amanzi Biosecurity | Coyne V.E.,University of Cape Town
Aquaculture | Year: 2016

A Rickettsiales-like prokaryote was observed in digestive gland epithelium of farmed South African abalone Haliotis midae sampled for routine surveillance. Histological examination showed basophilic inclusions typical of rickettsial infections in shellfish (Mouton, 2000). This study aimed to identify the Rickettsiales-like prokaryote (RLP) colonising H. midae. Total genomic DNA was extracted from infected digestive gland sampled from cultured H. midae. PCR performed with ". Candidatus Xenohaliotis californiensis" specific primers RA 5-1 and RA 3-6 did not yield positive results, indicating that the H. midae RLP is not the withering syndrome agent. The 16S rRNA gene sequence of the intracellular bacterium was determined following nested PCR using universal eubacterial primers fD1/Rp2 and the broad spectrum primers EHR16SD/EHR16SR which are specific for members of the Anaplasmataceae family within the Rickettsiales order. Phylogenetic and evolutionary distance analysis showed that the H. midae RLP is a unique member of the α-proteobacteria. The identity and location of the histologically observed intracellular bacterium was confirmed by in situ hybridization performed on sequential sections of infected H. midae digestive gland using a combination of three digoxigenin-labelled probes specific to various regions of the 16S rRNA gene of the RLP. Statement of relevanceThe manuscript shows that farmed abalone, showing no disease symptoms, can remain healthy despite the presence of intracellular bacteria colonising their digestive glands. The study shows that Rickettsiales-like prokaryotes detected in farmed abalone are not necessarily ". Candidatus Xenohaliotis californiensis", the causative agent of withering syndrome. © 2015 Elsevier B.V.

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