Shrimp Bacterial Infections in Latin America

2014

A new emerging shrimp disease known as acute hepatopancreatic necrosis syndrome (AHPNS) has been reported to cause significant losses among shrimp farms in China (2009), Vietnam (2010), and Malaysia (2011). Recently, it has been reported to affect shrimp (Penaeusmonodon and P. vannamei) in the eastern Gulf of Thailand (2012). The disease is characterized by mass mortalities (reaching up to 100% in some cases) during the first 20-30 days post-stocking in grow-out ponds. The apparent spread of AHPNS throughout the region suggests that infectious or at least biological agent may be involved. Shrimp suffering from AHPNS show significant atrophy of hepatopancreas (HP), pale to white HP due to pigment loss in the connective tissue capsule and guts with discontinuous or no contents. The purpose of this study was to identify if bacteria could be the cause of AHPNS. DNA samples were prepared either directly from hepatopancreatic tissue or from culturable bacteria isolated from hepatopancreas of the diseased shrimp as templates to specifically amplify 770 bp fragment of 16S rRNA gene for bacterial classification. Nucleotide sequences obtained from the direct DNA extraction of the hepatopancreas revealed majority of Vibrio species, including V. parahaemolyticus, V. harveyi, V. vulnificus, and V. chaqassi. Similarly, the consensus sequences obtained from nine culturable bacterial isolates were identified as V. parahaemolyticus. The healthy shrimps challenged with the selected Vibrio isolate at a dose of 10 3 CFU per shrimp showed high mortality within 6 h after injection, however AHPNS histopathologywas not observed.

Applied and Environmental Microbiology, 2014

Moribund shrimp affected by acute hepatopancreatic necrosis disease (AHPND) from farms in northwestern Mexico were sampled for bacteriological and histological analysis. Bacterial isolates were molecularly identified as Vibrio parahaemolyticus by the presence of the tlh gene. The tdh-negative, trh-negative, and tlh-positive V. parahaemolyticus strains were further characterized by repetitive extragenic palindromic element-PCR (rep-PCR), and primers AP1, AP2, AP3, and AP and an ems2 IQ2000 detection kit (GeneReach, Taiwan) were used in the diagnostic tests for AHPND. The V. parahaemolyticus strains were used in immersion challenges with shrimp, and farmed and challenged shrimp presented the same clinical and pathological symptoms: lethargy, empty gut, pale and aqueous hepatopancreas, and expanded chromatophores. Using histological analysis and bacterial density count, three stages of AHNPD (initial, acute, and terminal) were identified in the affected shrimp. The pathognomonic lesions indicating severe desquamation of tubular epithelial cells of the hepatopancreas were observed in both challenged and pond-infected shrimp. The results showed that different V. parahaemolyticus strains have different virulences; some of the less virulent strains do not induce 100% mortality, and mortality rates also rise more slowly than they do for the more virulent strains. The virulence of V. parahaemolyticus strains was dose dependent, where the threshold infective density was 10 4 CFU ml ؊1 ; below that density, no mortality was observed. The AP3 primer set had the best sensitivity and specificity. Field and experimental results showed that the V. parahaemolyticus strain that causes AHPND acts as a primary pathogen for shrimp in Mexico compared with the V. parahaemolyticus strains reported to date.

2004

Diseases of Aquatic Organisms, 2013

A new emerging disease in shrimp, first reported in 2009, was initially named early mortality syndrome (EMS). In 2011, a more descriptive name for the acute phase of the disease was proposed as acute hepatopancreatic necrosis syndrome (AHPNS). Affecting both Pacific white shrimp Penaeus vannamei and black tiger shrimp P. monodon, the disease has caused significant losses in Southeast Asian shrimp farms. AHPNS was first classified as idiopathic because no specific causative agent had been identified. However, in early 2013, the Aquaculture Pathology Laboratory at the University of Arizona was able to isolate the causative agent of AHPNS in pure culture. Immersion challenge tests were employed for infectivity studies, which induced 100% mortality with typical AHPNS pathology to experimental shrimp exposed to the pathogenic agent. Subsequent histological analyses showed that AHPNS lesions were experimentally induced in the laboratory and were identical to those found in AHPNS-infected shrimp samples collected from the endemic areas. Bacterial isolation from the experimentally infected shrimp enabled recovery of the same bacterial colony type found in field samples. In 3 separate immersion tests, using the recovered isolate from the AHPNS-positive shrimp, the same AHPNS pathology was reproduced in experimental shrimp with consistent results. Hence, AHPNS has a bacterial etiology and Koch's Postulates have been satisfied in laboratory challenge studies with the isolate, which has been identified as a member of the Vibrio harveyi clade, most closely related to V. parahemolyticus.

Aquaculture, 2014

The Thai Department of Fisheries (DOF), 2013 estimated that outbreaks of acute early mortality (often called early mortality syndrome or EMS) in cultivated shrimp were responsible for a 33% drop in shrimp production during the first quarter of 2013. Similar early mortality in Vietnam was ascribed to specific isolates of Vibrio parahaemolyticus that caused acute hepatopancreatic necrosis disease (AHPND) but the status of EMS/AHPND in Thailand was unclear. Here we describe the isolation and characterization of bacteria isolated from the hepatopancreas (HP) of shrimp collected from an early mortality outbreak farm in Thailand. Four independent bacterial isolates were identified as V. parahaemolyticus by BLAST analysis and by gene-specific marker detection of a lecithin dependent hemolysin (LDH) considered to be specific for the species. Immersion challenges with 3 of these and a reference isolate, obtained from China in 2010, using a previously published laboratory infection model caused very high mortality accompanied by characteristic AHPND histopathology in the shrimp HP. Tests with one of these isolates (5HP) revealed that rate of mortality was dose dependent. Using the same challenge protocol, the 4th isolate (2HP) also caused high mortality, but it was not accompanied by AHPND histopathology. Instead, it caused a different histopathology of the HP including collapsed epithelia and unique vacuolization of embryonic cells (E-cells). These results revealed the possibility of diversity in isolates of V. parahaemolyticus that may cause early mortality in shrimp cultivation ponds. Genomic and episomic DNA of these isolates and isolates of V. parahaemolyticus that cause no disease need to be compared to better understand the molecular basis of bacterial virulence in AHPND.

Aquaculture, 2019

Acute hepatopancreatic necrosis disease (AHPND) first emerged as a new shrimp disease in 2009 that heavily affected shrimp industry leading to global economic losses. The etiological agent was previously identified as Vibrio parahaemolyticus that carries a plasmid containing toxins (PirA and PirB). However, recent researches revealed that V. parahaemolyticus is not the only bacterial species capable of causing AHPND, thus this study screened on bacterial strains with AHPND toxins from Penaeus vannamei shrimps in Malaysia. Out of the 86 isolated total strains, 12 AHPND positive strains were arbitrarily selected and were evaluated in in vivo assay using Artemia franciscana as a model organism. All the 12 AHPND positive strains with PirA and PirB genes demonstrated significant mortalities (P < 0.05) of A. franciscana compared to the negative control. The 12 AHPND positive strains were identified using molecular methods of 16S rRNA, RctB and RpoD region amplifications to belonged to the Harveyi clade and were closely related to V. parahaemolyticus and Vibrio harveyi. Further test showed that the yellow colony V. harveyi strain BpShHep24 was found to be more virulent than the green colony V. parahaemolyticus strain BpShHep31 in shrimp P. vannamei challenge test. Histological

Journal of the World Aquaculture Society, 2010

Vibriosis is one of the most widespread infectious diseases of cultured shrimp in Mexico; as a result, the Research Centre for Food and Development (CIAD, for the Spanish wording) offers a diagnostic service to the shrimp farmers where they bring samples of diseased shrimp as judged by themselves.

AHPND is like a big trouble for shrimp culture which is mostly caused by certain Vibrio parahaemolyticus strains; possessing a plasmid with a gene that encodes for Pir A and Pir B toxins. Many shrimp species like Penaeus monodon and Litopenaeus vannamei are affected by AHPND. After stocking 30-35 days PL being affected by this disease can cause 100% mortality. This disease causes huge economic losses of about billions of dollars annually to aquaculture industry. This disease mainly targets hepatopancreas and gut. Proper management and preventions are main and other than that diagnosis and treatment methods are necessary to control further outbreaks.

Biology, 2019

Acute hepatopancreatic necrosis disease (AHPND) has recently emerged as a serious disease of cultured shrimp. A total of 19 lactic acid bacteria (LAB) strains isolated from shrimp samples were characterized based on morphological characteristics, biochemical tests, sequencing analysis, and their ability to antagonize Vibrio parahaemolyticus, which causes AHPND in whiteleg shrimp. Results from the agar well diffusion method indicated that 3 out of 19 isolated LAB strains showed the highest antagonizing ability against AHPND V. parahaemolyticus strain with an inhibition zone diameter ranging from 18 to 20 mm. Experiments where shrimps were given feed supplemented with these LAB strains and challenged with AHPND strain showed high survival rates (approximately 80.0%), which were not significantly different as compared to those recorded in the negative control treatment (86.6%), but significantly different to those recorded in the positive control treatment (40.6%) after 16 days of the ...

Aquaculture is the fastest growing food sector globally and is established itself as high protein resource to fulfill the food demand since the natural resources exhibits over exploitation. But, presently, the biggest problem faced by the aquaculture industry worldwide is diseases caused due to various biological and non-biological agents. Among the groups of microorganisms that cause serious losses in shrimp culture, the best known are bacteria because of the devastating economic effects they have on affected farms. Bacterial diseases, mainly due to Vibrio, have been reported in penaeid shrimp culture systems implicating at least 14 species and they are Vibrio harveyi, V.