Article

Identification of Fusarium solani as a causal agent of black spot disease (BSD) of Pacific white shrimp, Litopenaeus vannamei

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Abstract

In Nov 2020, mass mortality of cultured Pacific white shrimp (Litopenaeus vannamei) occurred due to black spot disease (BSD) in some shrimp farms in China. To investigate the disease cause, a potential pathogenic fungus was isolated from melanized lesions of L. vannamei suffering from the BSD syndrome. The fungal isolate was then identified as Fusarium solani based on TEF1α and ITS-gene sequences. The isolate of fungus was used in infection studies. This study used Koch postulates confirmed that the studied agent was causing BSD symptoms in the white leg shrimp, which were significantly symptoms relieved after molting. Results showed that an identical fungus was re-isolated from black lesions after the artificial infection period. Virulence test revealed that F. solani could cause 88.66% mortality within 30 dpi at a dose of 1.015 × 10⁶ CFU/mL, and the LC50 of F. solani at 30 dpi is 3.37 × 10⁴ CFU/mL. The accumulative mortalities also displayed concentration dependence. The histopathological characterization displayed that responses of L. vannamei against F. solani are haemocytic infiltration, encapsulation, melanization, etc. in the black spot lesions. Furthermore, severe infection of F. solani in L. vannamei causes molting failure, and further contributes to the mortality of the diseased individuals. The findings of our study would be useful to provide a theoretical basis for early prevention and control of BSD.

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... The colonial appearance colour difference might occur as a result of isolating media (GYA) components that probably affected the colour development. Additionally, the colonial development colour characteristics of the three obtained isolates act in the same manner as those earlier reported by Yao et al. (2022). Although they isolated F. solani, accused in BGD, they described its colonial colour development as pink colonies with black to brown centres, and some colonies were dark pinkish and changed to white at the periphery. ...
... These results, together with those obtained from morphological characterization, showed high discriminatory power to identify and differentiate the divergence similarities between Fusarium species. Similarly, Yao et al. (2022) clarified the usefulness of sequence alignment and phylogenetic identification in the discrimination of intraspecies similarities between F. solani and related species. ...
... That might explain why the cumulative mortality pattern occurred 7 days post-injection for both groups (A and B), and that was evident in their replicates as well. Additionally, the mycotoxin produced by injected Fusarium elements might contribute to the moulting failure and result in increasing the damage to the host (Moret and Moreau 2012;Yao et al. 2022). Supportively obtained results showed that control groups and their replicates exhibited successful moulting with no evidence of mortality. ...
... The colonial appearance colour difference might occur as a result of isolating media (GYA) components that probably affected the colour development. Additionally, the colonial development colour characteristics of the three obtained isolates act in the same manner as those earlier reported by Yao et al. (2022). Although they isolated F. solani, accused in BGD, they described its colonial colour development as pink colonies with black to brown centres, and some colonies were dark pinkish and changed to white at the periphery. ...
... These results, together with those obtained from morphological characterization, showed high discriminatory power to identify and differentiate the divergence similarities between Fusarium species. Similarly, Yao et al. (2022) clarified the usefulness of sequence alignment and phylogenetic identification in the discrimination of intraspecies similarities between F. solani and related species. ...
... That might explain why the cumulative mortality pattern occurred 7 days post-injection for both groups (A and B), and that was evident in their replicates as well. Additionally, the mycotoxin produced by injected Fusarium elements might contribute to the moulting failure and result in increasing the damage to the host (Moret and Moreau 2012;Yao et al. 2022). Supportively obtained results showed that control groups and their replicates exhibited successful moulting with no evidence of mortality. ...
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The Egyptian aquaculture sector is still struggling to establish L. vannamei culture. In an effort to stimulate shrimp production with minimal environmental impact and less water loss, biofloc technology (BFT) has been employed. Chronic mortality was recently observed in L. vannamei which was raised in the BFT system. Examining samples of moribund shrimp revealed sporadic melanization on the musculature and gills, suggesting the potential existence of black gill disease. The present work was carried out to isolate and identify potentially implicated fungus species based on mycological properties of interest. To isolate and serve as initial identification tools, wet mount preparations and colonial features, along with slide culture techniques, were used. PCR assays, gene sequencing, and phylogenetic analyses were used in the molecular identification process to clarify the confirmation of the fungal isolates that were acquired. The pathogenicity tests were designed to fulfil Koch’s postulates in addition to clarifying the infectivity of isolated fungus. Moreover, histopathological examination was employed to notice tissues’ alterations associated with experimentally infected shrimp. The results revealed the isolation of three fungal isolates, namely, BNS 1117, BNS 2117, and BNS 3117, that were confirmatively identified as Fusarium verticillioides, and their selected sequences were submitted to Genbank. Moreover, experimental infection using F. verticillioides selected isolate (BNS 31,117) at both high (5 × 10⁵ CFU/mL, group A) and low (3 × 10⁵ CFU/mL, group B) doses of its conidial suspensions experienced cumulative mortality of 72.2% and 21.1%, respectively. Besides, the selected isolate was re-isolated from the experimentally infected shrimp in a pure form, which satisfied Koch’s postulates. Histopathological alterations demonstrated several degrees of either degenerative, oedema, or proliferative changes in the hepatopancreas, musculatures, and gills, respectively. This study sets a new record for F. verticillioides to be included in Fusarium species linked to shrimp mortality.
... Shrimp have simple body structures and a primeval immune structure because they do not create antibodies and are deficient in the functionality of adaptive immune structure (Farag et al. 2021;Lim et al. 2023;Raza et al. 2022). Among these infections, black spot disease (BSD) promoted by Fusarium spp. is a main matter in shrimp-producing sectors (Yao et al. 2022). ...
... belonged to the family Nectriaceae are prevalent fungi frequently found in freshwater, soil, plants, and brackish water. Fusarium solani was recognized as the main causative organism (Ramesh et al. 2021), resulting in molting miscarriage and quick beginning of BSD occurrences among individuals (Yao et al. 2022). The pathogen affected multi-culture sites of shrimp counting Pacific white shrimp in China (Yao et al. 2022) and P. japonicus in Japan (Tsuchiya et al. 2023). ...
... Fusarium solani was recognized as the main causative organism (Ramesh et al. 2021), resulting in molting miscarriage and quick beginning of BSD occurrences among individuals (Yao et al. 2022). The pathogen affected multi-culture sites of shrimp counting Pacific white shrimp in China (Yao et al. 2022) and P. japonicus in Japan (Tsuchiya et al. 2023). Shrimps could protect themselves from pathogens via using innate immune responses such as their, mucous layers, shells, and epithelium. ...
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Shrimp aquaculture is one of the fastest-growing food production sectors in the world, due to its economic importance and ability to meet the protein needs of a growing population. However, bacterial and fungal infection has caused significant problems in the shrimp sector which instigated enormous economic loss for the main producer countries. Probiotic feed additives can enhance the gut health benefits and immune status of shrimp, thus boosting the growth, production efficacy, and disease resistance. Thereafter, the effects of different levels of dietary probiotic, Pediococcus acidilactici (PA), on growth performance, feed consumption, immunological response, antioxidant activities, and disease resistance in Litopenaeus vannamei juveniles against the pathogen, Fusarium solani, were investigated in this study. In 12 hapas (4 treatments × 3 replicates), 240 L. vannamei juveniles (4.0 ± 0.03 g) were randomly allocated into four treatments (T0 = 0 g PA/kg as control, T1 = 2.0 g PA/kg, T2 = 2.5 g PA/kg, and T3 = 3.0 g PA/kg of diet). The results provided that all PA-supplemented groups had considerably higher growth performance (final body weight, weight gains, and percentages), the final number, shrimp biomass (m³), survival rate, and feed intake (p < 0.05) than the control, with T3 being much higher. Regarding the body chemical composition, protein percentage was increased significantly in T3, while lipid was decreased significantly by dietary PA inclusion (p < 0.05). Feed conversion ratio (FCR, ↓) and nonspecific immune responses (↑), beneficial bacteria were improved significantly by dietary PA supplementation (p < 0.05). When challenged with the fungus F. solani, shrimp treated with dietary PA had significantly (p < 0.05) decreased fatality rates. Overall, the current investigation discovered that high doses of dietary PA increased growth status, feed utilization, gut microbiota, and health status of L. vannamei and disease resistance against F. solani.
... Shrimp have simple body structures and a primeval immune structure because they do not create antibodies and are deficient in the functionality of adaptive immune structure (Farag et al. 2021;Lim et al. 2023;Raza et al. 2022). Among these infections, black spot disease (BSD) promoted by Fusarium spp. is a main matter in shrimp-producing sectors (Yao et al. 2022). ...
... belonged to the family Nectriaceae are prevalent fungi frequently found in freshwater, soil, plants, and brackish water. Fusarium solani was recognized as the main causative organism (Ramesh et al. 2021), resulting in molting miscarriage and quick beginning of BSD occurrences among individuals (Yao et al. 2022). The pathogen affected multi-culture sites of shrimp counting Pacific white shrimp in China (Yao et al. 2022) and P. japonicus in Japan (Tsuchiya et al. 2023). ...
... Fusarium solani was recognized as the main causative organism (Ramesh et al. 2021), resulting in molting miscarriage and quick beginning of BSD occurrences among individuals (Yao et al. 2022). The pathogen affected multi-culture sites of shrimp counting Pacific white shrimp in China (Yao et al. 2022) and P. japonicus in Japan (Tsuchiya et al. 2023). Shrimps could protect themselves from pathogens via using innate immune responses such as their, mucous layers, shells, and epithelium. ...
Article
Full-text available
... Recently, numerous diseases have emerged in cultured L. vannamei due to further intensification and environmental water deterioration [5,6], resulting in a significant impact on the global shrimp farming business. Among these diseases, black spot disease (BSD) caused by Fusarium spp., is considered a major issue in shrimp-producing sectors [7]. Fusarium spp. ...
... The fungi have caused several diseases in plants and animals, resulting in decreased crop yields, lethal mycotoxins, and disease emergence [10,11]. L. vannamei is highly susceptible to BSD, with most naturally infected shrimp exhibiting black gill symptoms and serious tissue damage with high mortality [7]. F. solani was identified as the main causative organism [12], causing molting failure and rapid onset of BSD outbreaks among individuals [7]. ...
... L. vannamei is highly susceptible to BSD, with most naturally infected shrimp exhibiting black gill symptoms and serious tissue damage with high mortality [7]. F. solani was identified as the main causative organism [12], causing molting failure and rapid onset of BSD outbreaks among individuals [7]. The pathogen affects a wide range of cultured shrimp, including Penaeus semisulcatus in Israel [13], Penaeus. ...
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The potential effects of dietary supplementation with β-1,3 glucan and fructooligosaccharides (β-1,3 GF) on antioxidant activities, immunological response, and growth performance of Pacific white shrimp (Litopenaeus vannamei) was investigated. Four diets (iso-energetic and iso-nitrogenous) with different levels of β-1,3 GF (0, 0.5, 1.0, and 1.5 g kg−1 ) were fed to healthy shrimp juveniles weighing 3±0.5 g for 75 days. Shrimps were randomly distributed into 12 net enclosures at a density of 30 shrimp/net and the experiment was performed in triplicates. The results revealed that long‐term supplementation with 1.5 g kg−1 β-1,3 GF significantly improved shrimp weight gain (WG), feed conversion ratio (FCR), and digestive enzyme profiles compared to the control diet group. However, there were no substantial variations in the contents of moisture, crude protein, total lipids, and ash in the muscles of shrimp fed on different diets. Surprisingly, all antioxidants (superoxide dismutase, catalase, glutathione peroxidase) and immune biomarkers (lysozyme, total hemocyte count phenol oxidase, and respiratory burst) activities were significantly elevated with increasing levels of β-1,3 GF in shrimp diet and the highest values were recorded in the 1.5 g kg−1 diet groups. Moreover, dietary treated groups with different doses of β-1,3- GF showed a lower cumulative mortality rate (20-43.3%) than those fed a normal basal diet (86.7%). Overall, this study recommended an appropriate incorporation level of β-1,3 GF that could enhance growth performance and improve antioxidant activities, non-specific immunity, and disease resistance of L. vannamei , with an optimal level of 1.5 g kg-1.
... Recently, numerous diseases have emerged in cultured L. vannamei due to further intensification and environmental water deterioration [5,6], resulting in a significant impact on the global shrimp farming business. Among these diseases, black spot disease (BSD) caused by Fusarium spp., is considered a major issue in shrimp-producing sectors [7]. Fusarium spp. ...
... The fungi have caused several diseases in plants and animals, resulting in decreased crop yields, lethal mycotoxins, and disease emergence [10,11]. L. vannamei is highly susceptible to BSD, with most naturally infected shrimp exhibiting black gill symptoms and serious tissue damage with high mortality [7]. F. solani was identified as the main causative organism [12], causing molting failure and rapid onset of BSD outbreaks among individuals [7]. ...
... L. vannamei is highly susceptible to BSD, with most naturally infected shrimp exhibiting black gill symptoms and serious tissue damage with high mortality [7]. F. solani was identified as the main causative organism [12], causing molting failure and rapid onset of BSD outbreaks among individuals [7]. The pathogen affects a wide range of cultured shrimp, including Penaeus semisulcatus in Israel [13], Penaeus. ...
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Citation: Eissa, E.-S.H.; Ahmed, R.A.; Abd Elghany, N.A.; Elfeky, A.; Saadony, S.; Ahmed, N.H.; Sakr, S.E.-S.; Dayrit, G.B.; Tolenada, C.P.S.; Atienza, A.A.C.; et al. Potential Symbiotic Effects of β-1,3 Glucan, and Fructooligosaccharides on the Growth Performance, Immune Response, Redox Status, and Resistance of Pacific White Shrimp, Litopenaeus vannamei to Fusarium solani Infection. Fishes 2023, 8, 105.
... More specifically, whiteleg shrimp, Litopenaeus vannamei, largely contributes to the crustacean production Mansour et al. 2022b). Unfortunately, the high demand for shrimp forces farmers to intensify their production, resulting in high mass mortality (Abidin et al. 2022;Huang et al. 2022), whereas intensive farming systems induce stressful features and low water quality that coincide with immunosuppression and increase the susceptibility to infection (Mansour et al. 2022c;Yao et al. 2022). ...
... In the current investigation, black gill symptoms were markedly shown on infected shrimps. Several recent studies revealed that F. solani is the main causative agents for black gill disease in L. vannamei (Pazir et al. 2022;Yao et al. 2022). The disease sign developed initially by yellowish gills to brownish, and then became black after disease progression (Velmurugan and Ayyaru 2014). ...
... In addition, black gill disease may cause adhesion of new exoskeletons at lesion sites. Similarly, Yao et al. (2022) stated that L. vannamei infected with F. solani showed a high mortality rate. Crustaceans' exoskeletons, or cuticles, are thought to be an effective line of defense that incorporates physical, biochemical, and physiological features (Moret and Moreau 2012). ...
Article
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A total of 250 whiteleg shrimp juveniles, Litopenaeus vannamei, clinically infected with black gill melanization were subjected to mycological examination to isolate the main causative agents. The results showed the dominance of Fusarium solani at a 66% incidence rate compared to 34% of F. oxysporum in the examined shrimp. The in vitro antifungal activity of Origanum vulgare and orange peel essential oils (EOs) against F. solani was determined in comparison with Biotronic® Top3 (commercial antimicrobial). In addition, four groups in triplicates of L. vannamei (20.01 ± 3.02 g) were used to investigate the in vivo immunostimulant, antioxidant, gill histopathological changes, and antifungal effects of dietary O. vulgare and orange peel EOs for 28 day against the F. solani infection. The first group was a negative control that fed a basal diet, and the second group was a positive control that fed a basal diet and was artificially infected with 0.1 mL of 5.0 × 10⁶ conidia/mL of F. solani. The third and fourth groups were fed diets supplemented with O. vulgare and orange peel EOs (1 mL/kg diet), respectively, and infected with F. solani (0.1 mL of 5.0 × 10⁶ conidia/mL). The in vitro antifungal activity revealed a very strong inhibition effect of O. vulgare and orange peel EOs on F. solani (˃50%) compared to 31–50% inhibition induced by Biotronic® Top3. In addition, the in vivo feeding experiment showed that the positive control had lower cellular (hemocyte count, phagocytosis activity, and index) and humoral)phenoloxidase and lysozyme activities) immune responses than other treatments. Also, superoxide dismutase activity was significantly decreased in F. solani-infected shrimp. The histopathological investigation of infected shrimp showed dense aggregation of black melanin pigment in gill filaments and variable lesions of necrosis, edema, and congestion. Dietary both EOs significantly alleviated the immune suppression and histopathological effects of F. solani, especially O. vulgare EOs. The mortality rate was decreased to 16.66 and 30.00% with O. vulgare and orange peel EOs, respectively, compared to 70% in the positive control. In conclusion, O. vulgare and orange peel EOs can be used as antifungal and immunostimulant supplementation in L. vannamei diets against F. solani infection.
... 20 white-leg shrimps with an average weight of 7.5±2 g (8.5±0.5 cm) were collected from a commercial shrimp farm (Phong Dien, Thua Thien Hue Province) and transported to the Laboratory of Fish Pathology, Faculty of Fisheries, University of Agriculture and Forestry, Hue University, Hue city, Vietnam. Among these, 5 shrimp showed characteristic signs of black spot in gills, as described by Yao et al (2022), and 5 exhibited typical signs of AHPND infection, as described by Lightner et al (2012). The causative agent of black gill diseases or AHPND in white leg shrimp have been identified as F. solani or V. parahaemolyticus respectively, according to the study of Phuong et al (2023). ...
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C-type lectin (CTL) plays an important role in the innate immune responses of white-leg shrimp (Litopenaeus vannamei). The upregulation of CTL gene expression occurs when shrimp is infected with bacterial and viral pathogens. The aim of this study was to evaluate the expression of LvCTL3 gene encoding CTL in white-leg shrimp infected with acute hepatopancreatic necrosis disease (AHPND) and black gill disease from Thua Thien Hue Province, Vietnam. Real-time PCR with specific primers targeting LvCTL3 and a reference gene (actin) was used to analyze gene expression in various tissues. The results revealed an increasing trend in the expression of LvCTL3 in tissues such as the intestine, stomach, and hemocytes following AHPND and fungal (black gill disease) infection. Additionally, a strong expression pattern of LvCTL3 was observed in the hepatopancreatics of both AHPND-infected shrimps and black gill diseased shrimps. This finding highlights the significant role of the LvCTL3 gene in the shrimp defense system, as the upregulation of the CTL-encoding gene in key body parts during disease infection suggests its involvement in protection against invading pathogens.
... In this sense, since in the final host Scaphanocephalus acts as an endoparasite, in fish where it produces pigmented dermatopathies, presented as focal circular spots or papules, it would act more as an ectoparasite or cutaneous endoparasite. Black spot disease caused by Scaphanocephalus has been found in invertebrates such as Penaeus vannamei (Boone, 1931) [15], marine fish such as Bolbometopon muricatum (Valenciennes, 1840), one of the largest parrot fish [16], and even in freshwater fish such as Esox lucius (Linnaeus, 1758) [17]. Up to now, only three species of this genus have been described, including S. australis (Johnston, 1917), S. adamsi (Iwata, 1997) and S. expansus (Creplin, 1842). ...
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Global change produces substantial modification to the distribution and rhythm of infection of diseases in fish, favouring the introduction of new pathogens. Recently, the presence of black spot disease, associated with a digenean fluke of the genus Scaphanocephalus, has been observed in specimens of Xyrichthys novacula on the island of Ibiza (Balearic Islands). The aim of the present study was to evaluate the antioxidant and immune response in both the skin mucus and spleen of X. novacula depending on the degree of infection by Scaphanocephalus sp. The specimens were captured in a control area, without the presence of the parasite, and in an affected area, classifying the fish as low infection (1–15 spots) and high infection (>15 spots). As the degree of infection increased, a decrease in the body condition index was observed. The activity of the antioxidant enzymes in the mucus—catalase, superoxide dismutase and glutathione peroxidase—increased progressively with the degree of infection. This activation of antioxidant defences was not enough to prevent an increase in malondialdehyde levels, an indicator of oxidative damage, in the group with the highest infection. Similarly, an increase in immunological parameters—lysozyme, alkaline phosphatase, myeloperoxidase and immunoglobulins—was observed in mucus as infection increased. Regarding the spleen, only an increase in lysozyme activity and alkaline phosphatase in fish with a greater severity of infection was observed. In conclusion, as the severity of Scaphanocephalus sp. infection increased, it induced an immune and oxidative stress response in skin mucus, leading to a decrease in overall body condition. The potential health effects that the ectoparasite may have on X. novacula populations will require follow-up studies.
... This disease was first reported in the kuruma prawn, Marsupenaeus japonicus, by Ishikawa (1968) and was caused by a fungal infection. Hatai and Egusa (1978) identified the causal agent of BSD as Fusarium solani, which was then regarded as one of the most severe infections of M. japonicus in Japan (Khoa et al. 2005;Yao et al. 2022). Fusarium species are ubiquitous fungal agents affecting plants, soil, freshwater, and brackish water (Lightner 1996;Palmero et al. 2009). ...
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This study investigated the impacts of water application of a commercial Bacillus species probiotics, SANOLIFE®PRO-W (containing Bacillus subtilis and B. licheniformis), on water quality, digestive enzymes, growth performance, antioxidants, innate immunity, body composition, and resistance of whiteleg shrimp against Fusarium solani infection. A total of 240 animals (2.00 ± 0.07 g) were stocked into twelve 1-m³ concrete ponds and divided into four triplicate treatments. For 56 days, the rearing water was supplemented with Bacillus species probiotic at 0, 0.01, 0.02, and 0.03 g/m³ and defined as control, T1, T2, and T3 groups, respectively. Results revealed that Bacillus species probiotics increased dissolved oxygen and decreased total ammonia, nitrite, and unionized ammonia in the rearing ponds. However, adding probiotic Bacillus to rearing water significantly increased the digestive enzyme (chymotrypsin, trypsin, protease, lipase, and amylase) and growth performance parameters compared to the control. On the other hand, the antioxidant levels of superoxide dismutase, catalase, and glutathione peroxidase were increased significantly, while the malondialdehyde concentrations were decreased significantly compared to the control. Furthermore, Bacillus probiotics boosted the innate immunity of shrimp manifested by increased activities of lysozyme, prophenoloxidase, respiratory burst, and the total hemocyte count compared with the control treatment. Of interest, shrimp mortalities decreased after F. solani infection to 35% in the T3 group compared to 100% in the control group. In conclusion, water application of Bacillus species probiotics, especially at 0.02 and 0.03 g/m³, improved the water quality, welfare, and resistance of whiteleg shrimp to F. solani infection.
... Outbreaks of disease that cause significant morbidity and/or mortalities due to high-density farming and environmental changes in an aquaculture operation are always a major concern (Ramirez-Paredes et al., 2021; Yao et al., 2022). This case report specifically confirmed via PCR, histopathology, ISH, and TEM outbreaks of disease causing by CMNV in local semi-intensive farms in Dongying City and Weifang City, China. ...
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Penaeid shrimp including Litopenaeus setiferus (white shrimp), Farfantepenaeus aztecus (brown shrimp), and Farfantepenaeus duorarum (pink shrimp) support one of the most valuable commercial fisheries in the U.S. Southeast Atlantic. Since the late 1990s, the fishery, especially in coastal Georgia and South Carolina, has experienced a significant decline. A contributing factor to this decline has been hypothesized to be a severe outbreak of shrimp black gill caused by a ciliate parasite. DNAsequence-based analysis of the gill parasite small subunit rRNA gene identifies the proposed causative agent as being closely related to the apostome ciliate Hyalophysa chattoni; however, morphological characteristics of the ciliate observed by electron microscopy are inconsistent with this identification. Although studies are ongoing to identify this ciliate, it was possible to develop a diagnostic polymerase chain reaction-based assay targeting the small subunit rRNA gene and use it to investigate the seasonal and geographic distribution of the parasite in wild shrimp populations. Next-generation sequencing of the gill microbiome confirmed that when black gill is at its peak, microeukaryotic communities were dominated by apostome-related ciliates, but over the year highly diverse communities of gill associates, including other potential ciliate, fungal, euglenozoid, and amoeboid parasites are commonly detected. Improved molecular diagnostics and the ability to explore the diversity of potential parasites in shrimp provide important new insights into the relationship between the shrimp fishery and black gill.
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In the Southeast United States, an unidentified parasite is infecting shrimp and presenting new challenges for an already struggling industry. Emerging research in Georgia is investigating the resulting condition, known as Black Gill, to better understand this newest threat to the state’s most valuable commercial fishery. Researchers, shrimpers, extension agents, and fishery managers are working collaboratively to gather baseline data on where, when, and how frequently Black Gill is occurring, as well as partnering to determine its epidemiology, dispersal, and possible intervention strategies.
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The exoskeleton or cuticle of arthropods is an important feature that contributes to their great success in colonising numerous habitats on earth. It has numerous functions among which to provide protection against parasites. Whereas often regarded as a simple physical barrier to the outside world, the immune protection of the cuticle is slightly more complex than that. Here, we provide an overview of the cuticle defensive traits against parasites and examine their variation as a response to parasitism. It appears that the cuticle is an efficient line of defense, which includes physical, biochemical and physiological defensive components that are potentially subject to genetic and plastic variation in response to parasitism. It also appears that the cuticle defense systems are relatively understudied despite it may determine for large part the success of parasitic attacks.
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Litopenaeus vannamei (pacific white shrimp) is the most cultured shrimp species which is also susceptible to microbial diseases like other shrimps. In the present study, the fungi, Aspergillus awamori KM434331 caused black gill disease to pacific white shrimp. It was first reported from L. vannamei in shrimp grow out pond located at Vellapallam, Nagapattinam District, Tamil Nadu, India. A. awamori KM434331 was isolated from affected gill of shrimp. Further, its morphological, cultural and phylogenetic characteristics were identified. The histopathological depiction is inflammatory response of L. vannamei against A. awamori KM434331 are haemocytic infiltration, encapsulation, melanization and collagen-like fibre deposition in the gill. In addition to that, Aspergillus awamori KM434331 cause dysfunction of gills that leads to chronic mortality in the grow-out pond of shrimps.
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Results of experiments on the effect of temperature on the survival of conidia of BG-Fusarium in sterile sea water and sterile distilled water suggested that the organism can survive in each water for prolonged of time. The survival rate was about 80% even after 140 days in each water at 10 to 30°C. Conidia of BG-Fusarium in sterile sea water, however, failed to survive 140 and 105 days when they were held at 5°C and 37°C, respectively. On the contrary those in sterile distilled water failed to survive 70 and 21 days when they were held at 5°C and 37°C, respectively.The BG-Fusarium grew well on Sabouraud dextrose agar containing 0 to 0.5% NaCl, and did up to 10% NaCl, but failed to grow at 12% NaCl. It grew in Sabouraud dextrose broth at the pH range from 4 to 11.All the BG-Fusarium strains and F. solani F-21 (plant pathogen) were resistant to cycloheximide. Two strains, F-22 and F-23 of F. solani, however, were susceptibile to the antibiotic. Malachite green completely inhibited mycelial growth at 6.3 ppm. Sodium dichloroisocyanurate was found to kill the conidia of BG-Fusarium at a concentration of 6.2 ppm as active ingredient.
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Penaeus monodon (black tiger shrimp) is one of the most cultured shrimp species in India due to its susceptibility toward microbial diseases and consequently affects the total growth and production. The present study deals about first time report of phytopathogenic fungi Gilbertella persicaria infection on P. monodon which retains cotton like appearance on the whole body. The histopathological investigations suggested that the G. persicaria causes respiratory dysfunction of the gills, absences of storage vacuoles in hepatopancreases, degeneration of basement membrane, degeneration of epithelial cell in muscle of shrimp through hemocytic encapsulation and melanization which lead to chronic mortalities in the pond.
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Author Summary The melanization reaction is a major immune response in Arthropods and involves the rapid synthesis of a black pigment, melanin, at the site of infection and injury. Melanization requires the activation of proPhenoloxidase, an enzyme that catalyzes the oxidation of phenols to quinones, which polymerize to melanin. The Drosophila genome contains three genes encoding prophenoloxidases (PPO). In this paper, we have generated flies carrying deletions in the PPO1 and PPO2 genes. By analyzing these mutations alone and in combination, we clarify the functions of both prophenoloxidases in humoral melanization. We report that PPO2 composes most of the crystals found in crystal cells, a specific hemocyte cell type. Although PPO1 and PPO2 both contribute to phenoloxidase activity in the insect blood, these PPOs are not fully redundant. Our study shows that PPO1 is involved in the rapid delivery of phenoloxidase activity when required, while PPO2 provides a storage form that can be deployed in a second phase. Some controversy exists in the Drosophila field about the importance of melanization in the Drosophila host defense. Our study demonstrates the important role of PPO1 and PPO2 in the survival to infection with both Gram-positive bacteria and fungi, underlining the importance of melanization in insect immunity.
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Research on an innate immune system of penaeid shrimp is greatly motivated by economical requirements, because their culture is limited by the development of infectious diseases. As invertebrates, shrimp's natural immunity acts as a fast and efficient defence mechanism against the pathogens. Their immune system involve hemocytes (for encapsulation, nodule formation and phagocytosis), several plasma components (antimicrobial peptides, histones, lysosomal enzymes, lipopolysaccharide, beta-1,3-glucan binding proteins, and recognition molecules), and multimeric systems (clotting protein cascade, prophenoloxidase system). When these defense mechanisms fail to protect the shrimp against bacteria, viruses, fungi, protozoa and their products, disease develops and a negative impact takes place in the shrimp culture system. Studying the shrimp immune system is attractive for the advancement of a basic knowledge on invertebrate and vertebrate general immunity, because it offers various possible alternatives for disease management in shrimp aquaculture. The aim of this document is to present the general status of the shrimp defense system, to help in the development of strategies that favour the control and prevention of disease.
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Noble crayfish (Astacus astacus) stocks on the Estonian Island of Saaremaa are productive and have long been void of major disease outbreaks. Since the early 1990's, a disease causing cuticle melanisation was observed in some populations. The frequency of infected specimens is high, and can reach 60% of the crayfish in the River Kuke. Lhe disease is assumed to be burn spot disease, but it has not been formally diagnosed. Symptoms are atypical for burn spot disease, at least when compared to symptoms seen in Finland. Microbes were isolated from ten noble crayfish collected from the River Kuke that exhibited disease symptoms. Samples were collected from melanised spots on the abdominal cuticle and walking legs, and a variety of fungi and oomycetes were isolated including; Saprolegnia parasitica, Saprolegnia australis, Mucor hiemalis and Mucor racemosus. A combination of several of these pathogens may cause the atypical symptoms of burn spot disease seen in Estonia, or the isolated Saaremaa crayfish populations may just express disease symptoms differently.
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CITATION: Li, G., Xie, G., Wang, H., Wan, X., Li, X., Shi, C., Wang, Z., Gong, M., Li, T., Wang, P., Zhang, Q., & Huang, J. (2021). Characterization of a novel shrimp pathogen, Vibrio brasiliensis, isolated from Pacific white shrimp, Penaeus vannamei. Journal of Fish Diseases, 44(10), 1543–1552. https://doi.org/10.1111/jfd.13475. ABSTRACT: A novel pathogenic strain Vibrio 20190611023 was isolated from the hepatopancreas of moribund cultured Penaeus vannamei suffering from black gill disease. This strain was identified as V. brasiliensis based on the phylogenetic analyses of 16S rDNA gene and five other housekeeping genes (i.e., gapA, ftsZ, mreB, topA and gyrB). Some biochemical features of this strain were determined with an API 20NE system, and its haemolytic activity was determined using a sheep blood agar plate. The pathogenicity of this isolate 20190611023 was confirmed by the experimental challenge tests and histopathological examinations. P. vannamei were challenged via reverse gavage with different doses of bacterial suspensions. The calculated median lethal dose (LD50) was (3.16 ± 1.78) × 10⁵ CFU/g (body weight). Moreover, antibiotic susceptibility tests were performed, the results of which showed that the strain 20190611023 was sensitive to chloramphenicol, compound sulphamethoxazole, ciprofloxacin, doxycycline and oxacillin, but resistant to erythromycin, kanamycin, gentamicin, cefoperazone, ceftriaxone, cefamezin and piperacillin. To our knowledge, this is the first report for demonstrating V. brasiliensis as a shrimp pathogen, which expands the host range of V. brasiliensis infection. The present study highlights that more attention should be paid to this novel pathogen in intensive shrimp aquaculture.
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Cultured fisheries of developing countries are continously challenged by a number of pathogenic microbes. Among microbial diseases, fungal and fungal like pathogen outbreaks lead to negative social and economic impacts on stakeholders. The cultured fisheries of Kashmir valley are also facing challenge from fungal pathogens , leading to tremendous socioeconomic lossess to the fish farmer community hence, yearns to boost the sector with efficient management strategy. Our study was aimed at investigating the diversity of fungal communities infecting cultured rainbow trout and carp fish species. We employed classical microbiology, macro and micro morphological characteristics, and molecular analysis (multilocus typing) for fungal identification. Also histopathological approach was used to examine the pathogenicity patterns of diverse fungal groups. The study revealed that the infection in fish was predisposed to both superficial as well as visceral organs. However, skin, gills and head were predominantly infected compared to internal organs. The microbiological investigation of infected fish by culture dependent approach helped us to obtain the total of 250 fungal isolates. Out of these isolates, 21 different species were identified belonging to three diverse fungal groups which mostly included 14 species among Ascomycetes, 03 species of Oomycetes and 04 species of Zygomycetes. The majority of fungi which were infectious to cultured fish of valley are biotrophic or opportunistic soil fungi, and some of them being exclusive pathogens of fish.
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The fungal genus Fusarium is one of the most important groups of plant-pathogenic fungi and affects a huge diversity of crops in all climatic zones across the globe. In addition, it is also a human pathogen and produces several extremely important mycotoxins in food products that have deleterious effects on livestock and humans. These fungi have been plagued over the past century by different perspectives of what constitutes the genus Fusarium and how many species occur within the genus. Currently, there are conflicting views on the generic boundaries and what defines a species that impact disease diagnosis, management, and biosecurity legislation. An approach to defining and identifying Fusarium that places the needs of the community of users (especially, in this case, phytopathologists) to the forefront is presented in this review. Expected final online publication date for the Annual Review of Phytopathology Volume 57 is August 26, 2019. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Aquaculture remains the world's fastest-growing sector producing food of animal origin. Unlike in terrestrial animal agriculture, in aquaculture both farmed and wild aquatic animals in the same water column experience the same virus challenges. Additionally, the burgeoning international aquaculture expansion and expanding global trade in live aquatic animals and their products have been accompanied by long distance geographical redistribution of aquatic animal species and their viruses. The outcome is a continuous emergence of viral diseases in aquaculture, which may be driven by virus factors, animal host factors, environmental factors, and/or anthropogenic factors. Examples of emerging viruses in aquaculture include viral haemorrhagic septicaemia virus, infectious haematopoietic necrosis virus, infectious salmon anaemia virus, piscine orthoreovirus, Tilapia lake virus, Covert mortality nodavirus, Shrimp hemocyte iridescent virus, and Abalone herpesvirus.
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Diseases have caused tremendous economic losses and become the major problem threatening the sustainable development of shrimp aquaculture. The knowledge of host defense mechanisms against invading pathogens is essential for the implementation of efficient strategies to prevent disease outbreaks. Like other invertebrates, shrimp rely on the innate immune system to defend themselves against a range of microbes by recognizing and destroying them through cellular and humoral immune responses. Detection of microbial pathogens triggers the signal transduction pathways including the NF-κB signaling, Toll and Imd pathways, resulting in the activation of genes involved in host defense responses. In this review, we update the discovery of components of the Toll and Imd pathways in shrimp and their participation in the regulation of shrimp antimicrobial peptide (AMP) synthesis. We also focus on a recent progress on the two most powerful and the best-studied shrimp humoral responses: antimicrobial peptides (AMPs) and melanization. Shrimp AMPs are mainly cationic peptides with sequence diversity which endues them the broad range of activities against microorganisms. Melanization, regulated by the prophenoloxidase activating cascade, also plays a crucial role in killing and sequestration of invading pathogens. The progress and emerging research on mechanisms and functional characterization of components of these two indispensable humoral responses in shrimp immunity will be summarized and discussed. Interestingly, the pattern recognition receptor (PRR) crosstalk is evidenced between the proPO activating cascade and the AMP synthesis pathways in shrimp, which enables the innate immune system to build up efficient immune responses.
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Among the food safety issues, the occurrence of fungal species able to produce toxic metabolites on the agro-food products has acquired a general attention. These compounds, the mycotoxins, generally provided of low molecular weight, are the result of the secondary metabolism of the toxigenic fungi. They may have toxic activity toward the plants, but mostly represent a serious risk for human and animal health worldwide, since they can be accumulated on many final crop products and they have a broad range of toxic biological activities. In particular, mainly cereals are the most sensitive crops to the colonization of toxigenic fungal species which accumulate in the grains the related mycotoxins both in the field, until the harvest stage, and in the storage. According to a Food and Agriculture Organization study, approximately 25 % of the global food and feed output is contaminated by mycotoxins. Therefore, since a large proportion of the world’s population consumes, as a staple food, the cereals, the consumption of mycotoxin-contaminated cereals is a main issue for health risk worldwide. Furthermore, mycotoxin contamination can have a huge economic and social impact, especially when mycotoxin occurrence on the food commodities is over the regulation limits established by different national and transnational institutions, implying that contaminated products must be discarded. Finally, the climate change due to the global warming can alter stages and rates of toxigenic fungi development and modify host-resistance and host-pathogen interactions, influencing deeply also the conditions for mycotoxin production that vary for each individual pathogen. New combinations of mycotoxins/host plants/geographical areas are arising to the attention of the scientific community and require new diagnostic tools and deeper knowledge of both biology and genetics of toxigenic fungi. Moreover, to spread awareness and knowledge at international level on both the hazard that mycotoxins represent for consumers and costs for stakeholders is of key importance for developing all possible measures aimed to control such dangerous contaminants worldwide.
Article
White shrimp (Litopenaeus setiferus) fisheries-independent and fisheries-dependent landings can be highly variable and may be related to environmental factors that influence growth, mortality, and survival. We used linear regression analysis to look for potential relationships between environmental and white shrimp catch-per-unit-effort (CPUE) data collected from the Ashepoo-Combahee-Edisto (ACE) Basin National Estuarine Research Reserve (NERR) for four critical months in the shrimp life cycle. This analysis used data from white shrimp fisheries-independent CPUE (2002 to 2014) and water quality and meteorological variables for August (juvenile), December (sub-adult), March (adult), and April (spawning adult). The results showed that shrimp CPUE was mainly correlated with water temperature, salinity, and dissolved oxygen concentration collected through the ACE Basin NERR’s System-Wide Monitoring Program (SWMP), but offshore wind, precipitation, and intra-annual CPUEs also partially explained the variability in monthly CPUEs. Black gill prevalence was correlated with water temperature and salinity. Additionally, our analysis found that winter water temperatures of ≤11 °C were correlated with reduced shrimp abundance the following spring. Ultimately, managers would like to successfully predict white shrimp stock abundance throughout fishing seasons based on environmental conditions. This study is a first step in identifying the environmental variables that may be useful in predicting white shrimp CPUE in the South Atlantic Bight. The techniques employed here can serve as a basis for predicting and managing other wild annual fisheries stocks.
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Many fungal pathogens gain entrance into their hosts by direct penetration of the cuticle. Thus, the plant cuticle is the first barrier to be overcome by many plant-pathogenic fungi.
Article
A major structural component of the cuticle of plants is cutin. Analysis of the function of cutin in vivo has been limited because no mutants with specific defects in cutin have been characterized. Therefore, transgenic Arabidopsis plants were generated that express and secrete a cutinase from Fusarium solani f sp pisi. Arabidopsis plants expressing the cutinase in the extracellular space showed an altered ultrastructure of the cuticle and an enhanced permeability of the cuticle to solutes. In addition, pollen could germinate on fully differentiated leaves of cutinase-expressing plants but not on control leaves. These differences coincided with strong postgenital organ fusions. The junctions of the fusions contained pectic polysaccharides. As fused organs grew apart from each other, organ deformations and protrusions of epidermal cells developed at positions with high mechanical stress. These results demonstrate that an intact cutin layer not only is important for plant–environment interactions but also prevents fusions between different plant organs and is therefore necessary for normal epidermal differentiation and organ formation.
Article
Anatomical and histological studies were made on the distributions of Fusarium solani in kuruma shrimp, Penaeus japonicus, which were naturally and experimentally infected with the fungus. Hyphae and tissue destruction due to fungal infection were observed in the gills of all the naturally and experimentally infected shrimps examined. They were also frequently obseved in the maxillipeds, pereiopods, thoracic body wall, thoracic central nerve and occasionally in the ventral thoracic artery. Hyphae were seldom or never observed in the other organs examined. The gill conditions of the dead or moribund shrimps could be classified into the following two types. 1) Entirely blackened gill. This condition was observed mainly in the shrimps which died within a short period after infection. All the gills were severely infected with the fungus and blackened. The gill tissues were degenerated and the hemal channels were obstructed with hemocytes, hyphae and tissue debris. Failure of gas exchange in the gills was thought to be the main cause of death in this condition. 2) Partially blackened gill. This condition was observed in the shrimps which died long after infection. Most of the gills were partially affected with the fungus and blackened. Destruction of the gill filaments was rather rare, but the fungus penetrated into the thoracic body wall which collapsed. The hyphae infected further the thoracic central nerve and ventral thoracic artery. In this condition, in addition to respiratory failure damage of the central nerve and the ventral thoracic artery was thought to be responsible to death.
Article
Nine strains of fungi in the genus Fusarium were isolated from the lesions with black gills of cultured kuruma prawn Penaeus japonicus in Japan between 2000 and 2003. All strains showed same morphological characters. Two strains selected at random showed pathogenicity to kuruma prawns by intramuscular injection. From the precise morphological features of a representative isolate, it was identified as a member of the Fusarium solani complex. Phylogenetic analyses based on the sequences of its internal transcribed spacer region, including 5.8S ribosomal DNA and a partial 28S ribosomal DNA region, showed that all five strains tested were monophyletic.The present strains and the phytopathogenic Fusarium solani were clearly distinguished by the morphological and phylogenetical characteristics.
Article
The goal of this synthesis is to highlight some of the major findings of the New England Lobster Research Initiative (NELRI), provide a context for these findings based on previous research, discuss the potential impacts of this important emerging disease on the dwindling lobster populations in southern New England (SNE), and provide suggestions on avenues for future research. Most of the research funded in this initiative focused on epizootic shell disease (ESD), the emerging syndrome severely impacting lobster populations primarily in coastal waters in Rhode Island, southern Massachusetts, and eastern Long Island Sound (ELIS), but some new information about other forms of shell disease in lobsters is included. We also discuss how these novel findings on lobster shell disease should be used to inform management of lobster populations.
Article
A member of the imperfect fungi was isolated on a soytone-dextrose agar medium with chloramphenicol and cycloheximide from gill lesions of Penaeus japonicus BATE infected with black gill disease. Intramusculaly inoculation of conidia of the fungus caused invariably black gill disease in prawns, and the fungus could be isolated from gill lesions of artificially-infected prawns. The gills of healthy prawns were alway free of the fungus. Therefore the fungus was regarded as the pathogenic agent of black gill disease. The fungus produces mainly 4-celled, canoe-shaped macroconidia and 1-celled microconidia. Usually the mycelium is hyaline, but it characteristically produces a brown pigment when grown on the above-mentioned medium, salt Sabouraud's medium, and a salt potato-dextrose agar medium. On the basis of morphological criteria, this fungus fits best in the genus Fusarium.
Article
A new nodavirus (named covert mortality nodavirus, CMNV) is associated with covert mortality disease of shrimp which caused serious loss in China since 2009. Histopathological examination of shrimp suffering the disease revealed coagulative necrosis of striated muscle similar to typical histopathology features of infectious myonecrosis virus (IMNV), Penaeus vannamei nodavirus (PvNV) and Macrobrachium rosenbergii nodavirus (MrNV). However, shrimp suffering this disease tested negative for IMNV, MrNV and PvNV by RT-PCR. Additionally, eosinophilic inclusions were found in epithelium of the tubules in hepatopancreas and lymphoid organ, and mass karyopyknotic nuclei existed in muscle and lymphoid organ. The tubular epithelium of hepatopancreas show significant atrophy. A cDNA library was constructed from total RNA of infected shrimp. Sequencing and alignment analysis showed that one clone with an 1185 bp insert (designated CMNV-7) shares 54%, 53% and 39% identities with the amino acid sequences of RNA-dependent RNA polymerase from flock house virus, black beetle virus, and MrNV. The results of fluorescence in situ hybridization (FISH) showed that the hepatopancreas, striated muscle, and lymphoid organ were positively reacting tissues. The average size of negative stained virus particles was 32 nm. In addition, a nested RT-PCR assay was developed for CMNV and the RT-PCR detection results revealed that Fenneropenaeus chinensis, Litopenaeus vannamei and Marsupenaeus japonicus suffering from this disease were CMNV positive. Full-text can be download at: http://vir.sgmjournals.org/cgi/reprint/95/Pt_12/2700.pdf?ijkey=g4Azj7ImUqbxM34&keytype=ref
Article
Melanization is a rapid defense mechanism in invertebrates. The substrate specificity of phenoloxidases (POs) and the role of melanization reaction products were investigated in the black tiger shrimp, Penaeus monodon. Two PmPOs (PmproPO1 and PmproPO2) were found to display a substrate specificity towards monophenols and diphenols, and exhibit relatively weak activity against 5,6-dihydroxyindole (DHI). Systemic infection of the PmproPO1/2 co-silenced shrimp with the fungus, Fusarium solani, led to a significantly increased mortality, suggesting an important role of PmproPOs in shrimp's defense against fungal infection. Using L-DOPA, dopamine or DHI as a substrate, the melanization reaction products exhibited in vitro antimicrobial activities towards Gram-negative bacteria (Vibrio harveyi and V. parahaemolyticus) and Gram-positive bacteria (Bacillus subtilis), whereas the lower effect was detected against the fungus (F. solani). SEM analysis revealed the morphological changes and damage of cell membranes of V. harveyi and F. solani after treatment with shrimp melanization reaction products. Together, these findings demonstrate the crucial functions of the proPO system and the importance of melanization reaction products in the shrimp's immune defense.
Article
Sea urchin, Strongylocentrotus intermedius, transplanted from Japan in 1989, has been widely cultured along the coasts of Liaoning and Shandong Provinces and has become the dominant and most economically important maricultured species in North China. However, a lesion syndrome symptom of S. intermedius broke out frequently these years, showing lethargy in activities, blackish peristomial membrane and body well lesions, and brought about high mortality eventually. Six representative prominent bacterial strains were isolated from diseased sea urchin from September 2009 to January 2010. By means of API 20NE and 16S rRNA gene sequences analysis, isolates were identified as Shewanella aquimarina, Pseudoalteromonas tetraodonis, Vibrio shilonii, V. harveyi, V. fortis and V. splendidus. Bacterial challenge tests showed that their representative isolates were virulent to S. intermedius with LD50 values ranging from 9.2 × 104 to 3.4 × 106 CFU/g body weight, among which S. aquimarina , V. fortis and P. tetraodonis were highly virulent, and the other three isolates showed moderate virulence. The results indicated that a variety of bacteria including Shewanella, Pseudoalteromonas and Vibrio were involved in the mortality of S. intermedius, and the six isolates were opportunistic pathogens of sea urchins. All isolates reported herein were sensitive to ampicillin, enrofloxacin, ofloxacin, doxycycline and florfenicol.
Article
Cuticular lesions from twenty-four market sized lobsters (Homarus americanus) with winter im- poundment shell disease were examined. Histological de- scriptions of cuticular lesions were correlated with the substage of molt for each lobster, because cuticle com- ponents and inflammatory mechanisms vary in each. A lesion severity grading system was developed and applied to four specific substages of the five-stage (A-E) molting cycle. Lesions present in substage Cd, in which the mem- branous layer is deposited, and Do (passive premolt) were divided into five grades, ranging from mild erosions (Grade I) to severe ulceration (Grade V) of the cuticle. Cuticular lesions from lobsters in C4/Do were compared with cuticular lesions from lobsters in substages Cz/C3. Defensive mechanisms exhibited by animals in all sub- stages were epicuticle deposition, melanization, inflam- matory cell infiltration, and pseudomembrane formation. In addition, animals in C4 and Do showed proliferation ofthe membranous layer in affected foci. The lesion grad- ing scheme presented in this paper can be used to describe and compare both inter- and intraspecies crustacean shell lesions.
Article
Black burn spot exoskeletal lesions of bacterial aetiology are a frequent feature of crustaceans in intensive culture. The appearance under the scanning electron microscope of such lesions associated with Aeromonas hydrophila on Macrobrachium rosenbergii is described. The effect of oxolinic acid treatment on these lesions is discussed.
Article
A fungus of the genus Fusarium was associated with black spot cuticular lesions on Macrobrachium rosenbergii (De Man) and appeared opportunistic rather than invasive. Attempts to transmit the fungus to non-affected prawns were negative. Comparisons are made with other Fusarium sp. isolated from crustaceans.
Article
Burn spot disease has been causing epidemics both in the Estonian mainland and in Saaremaa Island in the threatened noble crayfish (Astacus astacus) stocks. To study the cause of the disease, we isolated several Fusarium spp. from Estonian noble crayfish (Astacus astacus) populations suffering from burn spot disease syndrome. We first identified fungi directly from melanised cuticle by their ITS sequences. Then we isolated Fusarium spp. from melanised spots of crayfish showing burn spot disease symptoms, such as melanisation and shell erosion, from two different crayfish populations and watercourses in Estonia. The isolates were then identified based on ITS and EF1α-gene sequences. Isolates of Fusarium spp. taken from two separate Estonian noble crayfish populations were used in infection studies. Koch postulates confirmed that the studied agent was causing burn spot disease symptoms including shell erosion in the noble crayfish, which were significantly more severe after molts. After the infection period, an identical Fusarium spp. was re-isolated from carapace lesions and was thus shown to be the disease agent causing burn spot disease syndrome and shell erosion in noble crayfish. Based on GenBank database searches, the isolates causing burn spot disease symptoms were identified as Fusarium avenaceum in mainland Estonia and F. solani in Saaremaa crayfish.
Article
Several immune-related molecules in penaeid shrimps have been discovered, most of these via the analysis of expressed sequence tag libraries, microarray studies and proteomic approaches. These immune molecules include antimicrobial peptides, serine proteinases and inhibitors, phenoloxidases, oxidative enzymes, clottable protein, pattern recognition proteins, lectins, Toll receptors, and other humoral factors that might participate in the innate immune system of shrimps. These molecules have mainly been found in the hemolymph and hemocytes, which are the main sites where immune reactions take place, while some are found in other immune organ/tissues, such as the lymphoid organs, gills and intestines. Although the participation of some of these immune molecules in the shrimp innate immune defense against invading pathogens has been demonstrated, the functions of many molecules remain unclear. This review summarizes the current status of our knowledge concerning the discovery and functional characterization of the immune molecules in penaeid shrimps.