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Hepatopancreatic microsporidiosis, the shrimp disease caused by Enterocytozoon hepatopenaei (EHP) infection, has been widely spread in farmed Litopenaeus vannamei in Thailand. The symptoms include decreased feeding, muscle waste, slow growth, and chronic mortality. Since 5-aminolaevulinic acid (5-ALA), a non-protein amino acid, has been known to enhance ATP production in the cell through the increased formation of hemoproteins in the electron transport complex of mitochondria, it was hypothesized that providing 5-ALA to EHP-infected shrimp might reduce the mortality caused by the infection. Naturally EHP-infected L. vannamei were randomly sampled from a commercial shrimp pond that showed signs of hepatopancreatic microsporidiosis. The shrimp samples were reared under 30-ppt seawater in 40-L plastic tanks, divided into four groups; each receiving commercial pellets supplemented with different doses of 5-ALA: 0 (control), 15, 30, and 60 ppm. After 21 days of the experiment, it was found that the shrimp receiving 5-ALA at 60 ppm survived at a rate significantly (p < 0.05) higher than that of other groups, and had a significant increase in biomass, compared with that of the control group. Histology of the hepatopancreas of the 60-ppm group revealed significantly (p < 0.01) less percentage of atrophic tubules and larger areas of the vacuoles of the B-cells, suggesting improved hepatopancreatic functions. The levels of the EHP load in the hepatopancreas as revealed by semi-quantitative PCR were increasing in a dose-related manner of 5-ALA supplement. Histology of the hepatopancreas also revealed the presence of EHP. The ATP levels in the hepatopancreas of the 30- and 60-ppm groups were significantly (p < 0.01) higher than that of the control group. Further tests are required in commercial farms to find out if the 5-ALA supplement is beneficial to tackle the problem of hepatopancreatic microsporidiosis at the industrial level. [Display omitted] • Supplementation of 5-ALA in feed to EHP-infected L. vannamei reduced the mortality and increased the biomass of the affected shrimp. • The supplementation decreased the percentage of atrophic hepatopancreatic tubules and increased the areas of the B-cell vacuoles. • The supplement increased ATP levels in the shrimp hepatopancreas. • However, the supplement also increased the EHP load in the hepatopancreas. [ABSTRACT FROM AUTHOR]

Enterocytozoon hepatopenaei (EHP), a microsporidian parasite, has emerged as a serious pathogen reported to be associated with retarded growth in cultured shrimp in many of the shrimp growing countries in Asia. As a part of ongoing disease surveillance among the farmed shrimp, we have investigated Penaeus (Litopenaeus) vannamei cultured in the south-east coast of India for EHP infection using light and scanning electron microscopy, histopathology, polymerase chain reaction (PCR) and in situ hybridisation. Squash preparation of hepatopancreas and white faecal strings showed large number of microsporidian spores. Spores under scanning electron microscope appeared oval and measured 1.7 × 1.0 μm. Histology of infected animals showed severe degeneration of hepatopancreatic tubules. Basophilic inclusions resembling the developmental stages of EHP were found in the epithelial cells and large number of spore aggregations was observed in the tubular lumen. Enlargement of haemal sinuses and encapsulation of hepatopancreatic tubules were also observed in some cases. DNA extracted from hepatopancreas was subjected to PCR amplification using primers targeting microsporidian ssu rRNA gene. The PCR yielded an expected product of ~ 951 bp and the sequences showed 100% identity with the EHP reported from Vietnam, Thailand and China. Further screening of field samples was carried out using nested PCR employing EHP-specific primers. Of the 137 juvenile P. vannamei samples tested, 10 were found to be positive in the first step and 77 in the nested PCR. Overall prevalence of EHP was estimated to be 63.5%. However, only first step PCR-positive samples showed discernible number of spores in the hepatopancreas under a light microscope. Post-larvae of P. vannamei collected from a hatchery were found to be PCR negative for EHP. In situ hybridisation using EHP-specific DIG-labelled probe showed positive signals in infected hepatopancreatic tissue. Animals collected from white faeces syndrome (WFS)-affected pond showed higher prevalence of EHP (96.4%) compared to those from the unaffected pond (39.7%). On the contrary, slow growing animals showed low prevalence (58.5%) compared to normally growing animals (80.8%). Although EHP could be detected from slow-growing as well as WFS-affected animals, the present study could not conclusively elucidate the association of EHP with these clinical signs through experimental infection trials. This report forms the first record of the emergence of EHP infection in cultured SPF P. vannamei in India. Statement of relevance E. hepatopenaei (EHP), a microsporidian parasite, is an emerging pathogen having serious economic consequences to cultured shrimp in Asia. This report forms the first record of the emergence of the parasite in farmed P. vannamei from India, and presents a comprehensive account of the pathogen and its impact on the host. [ABSTRACT FROM AUTHOR]

Abstract: The problem of growth retardation in cultured black tiger shrimp, Penaeus monodon was observed at one commercial shrimp farm in East Africa in mid 2004. The mean body weight of the shrimp at the sixth month in affected ponds was only 19±4 g, which was 30% less than the expected size of normal shrimp grown within the same period at this farm. A preliminary examination for pathogenic bacteria, parasites and viruses revealed mild bacterial infections in a few specimens but all were negative for 7 known pathogenic shrimp viruses, either by assays using polymerase chain reaction (PCR) technology or by histological examination. A subsequent examination of a second lot of samples prepared for transmission electron microscopy (TEM) revealed the presence of previously undescribed lesions in the lymphoid organ and gills. In semithin sections stained with toluidine blue, these were apparent as large cytoplasmic inclusions that were not visible in normal tissue sections stained with hematoxylin and eosin. By TEM, the cytoplasmic inclusions contained large numbers of non-enveloped, icosahedral virions of approximately 25 nm diameter. Given the unique nature of the lesions and the negative results with molecular tests for known shrimp viruses, it is possible that the particles seen constitute a new viral pathogen of shrimp. The retarded growth problem in East Africa resembles a similar problem called monodon slow growth syndrome (MSGS) that has been problematic with P. monodon in Thailand since 2001. Whether the slow growth in Africa and Thailand are due to the same or related pathogens or some other factor(s) remains to be explored. [Copyright &y& Elsevier]

Macrobrachium rosenbergii , the giant freshwater prawn, is an economically crucial freshwater shrimp that has been severely affected by slowing growth in recent years. In Gaoyou County, Jiangsu Province, China, Enterobacter cloacae infection frequently occurs in M. rosenbergii hatcheries, and E. cloacae has been detected with high prevalence in slow-growing prawns. In this study, the growth of prawns was found to be significantly reduced after E. cloacae infection. In addition, under co-culture of healthy and slow-growing prawns, slow-growing prawns were infectious and able to cause the slow growth of healthy prawns. The expression of growth-related genes after E. cloacae infection was analyzed, and differential expression of growth-related genes between slow-growing and healthy prawns was investigated. The results showed that the expression of CHIT3 , Cat , JHEH , EcR , and RXR was downregulated after E. cloacae infection and that of EcR was upregulated after E. cloacae infection. Similarly, the expression of CHIT3 , Cat , JHEH , EcR , and RXR was downregulated in slow-growing prawns compared to that in healthy prawns, and that of EcR was upregulated in slow-growing prawns compared to that in healthy prawns. The present results reveal a high prevalence of E. cloacae in slow-growing M. rosenbergii and suggest that this pathogen is the probable cause of the slow growth in M. rosenbergii. • High prevalence of E. cloacae was detected in M. rosenbergii with slow growth. • The growth of M. rosenbergii was reduced significantly after E. cloacae infection. • E. cloacae infection induced differential expression of growth-related genes compared to healthy M. rosenbergii. [ABSTRACT FROM AUTHOR]