Jyotirmaya Mohanty’s research while affiliated with Central Institute of Freshwater Aquaculture and other places

Tilapia parvovirus (TiPV) is an emerging viral pathogen and responsible for severe economic loss in tilapia culture production. Lethargic, cutaneous haemorrhages; ocular lesions; discolouration of gill and cloudy eye and exophthalmia are common symptoms of TiPV. The TiPV-suspected tilapia fish were collected from grow-out ponds situated in different parts of Tamil Nadu, India, and screened for TiPV by PCR. The results showed the presence of TiPV in disease-suspected fish which was further confirmed by PCR using different primer sets specific to different genomic regions of TiPV. Sequence analysis of 534 bp of genomic region of TiPV showed 100% similarity with the sequence of TiPV strain of Thailand and India. TiPV was found in different organs including eggs of infected fish and showed the possibility of systemic infection and vertical transmission. Snakehead kidney (CSK), snubnose pompano fin (SPF) and tilapia heart (TH) cell lines showed susceptibility to TiPV. The viral replication in cell lines was confirmed by PCR, TiPV-specific cytopathic effect of Cowdry A inclusion bodies with clear halo surrounding them and infectivity experiment. The disease was reproduced in normal fish by intramuscular route using viral inoculum from TiPV-infected fish or virus multiplied in susceptible cell lines to satisfy Koch’s postulates.

Aim: The present study evaluates the immunomodulatory potentials of β-glucan and chitosan administered orally for 15 days to the freshwater prawn, Macrobrachium rosenbergii juveniles. Methodology: Two diets were formulated supplementing 1.5 g kg-1 and 20 g kg-1 of β-glucan (diet G) and chitosan (diet C), respectively, with a control diet (diet B). The prawns were fed twice daily at 5% biomass. At the end of the feeding trials, mRNA expression profiles of immune-related genes lipopolysaccharide- and β-1,3-glucan binding protein (LGBP) and chitinase 3 were analyzed in qPCR. Corresponding LGBP protein and chitinases/CBP (chitinase 1, chitinase 1C and obstructor E, a chitin-binding protein) protein levels were also estimated by ELISA. Results: Supplementation of the immunostimulants (diets G and C) significantly enhanced the mRNA expression of both LGBP and chitinase 3 in the hepatopancreas. The protein expression of LGBP and chitinases/CBP was also significantly increased in the serum and hepatopancreas samples of both treatment groups. Interpretation: The short-term supplementation of β-glucan and chitosan in diets demonstrated beneficial effects in M. rosenbergii by enhancing the expression of important immune molecules like LGBP and chitinases, indicating their potential applications during the period of biotic stress. Key words: β-glucan, Chitinase, Hepatopancreas, Immunostimulants, LGBP, Macrobrachium rosenbergii

Heat stress is a major problem in aquaculture species, causing changes in physiology such as decreased feed intake, growth rate, reproduction, and internal cellular damage, thereby affecting fish’s health. The effects of an acute heat stress simulating a daily rise and fall in temperature on summer days were evaluated in the liver proteome of rohu (Labeo rohita) fingerlings in the present study. The fish maintained at 30 °C were gradually exposed to a higher temperature of 36 °C at an increment rate of 1 °C per 1.5 h, and after 3 h at that temperature, it was gradually reduced to 30 °C. The liver tissue samples were collected at 5 am, 5 pm, and 5 am the next day from the exposed and control fish. Protein samples were prepared from the liver tissues, and the extracted proteins were compared using 2-dimensional (2D) gel electrophoresis (2DGE) and mass spectrometry (MS) using a MALDI-TOF/TOF mass spectrometer. A total of 44 differentially expressed protein spots were visualized in 2D gel analysis from heat stress exposed fish at three time points, out of which 21 proteins including one hypothetical protein could be identified by MS. The abundance of five selected differentially expressed proteins (DEPs) was validated using qPCR. The majority of DEPs were found to be involved primarily in lipid, protein and energy metabolism, immune system regulation, cytoskeletal stability, and ROS management. The findings of this study would help in the development of strategies to mitigate heat stress in L. rohita.

Diseases are the major bottleneck for the successful development of the aquaculture industry. Carassius auratus (goldfish) is one of the major cultured and traded ornamental fish worldwide. Goldfish are frequently encountered with different disease conditions. Cyprinid herpes virus 2 (CyHV-2) is one of the most dreadful diseases of goldfish and its related species. CyHV-2 belongs to the genus Cyprinivirus under the family Alloherpesviridae. The virus consists of an icosahedral capsid of diameter 110-120 nm surrounded by an outer lipid envelope and gives a spherical appearance of 170-200 nm in diameter. The latency of the virus for a long period poses a greater threat of spreading. The immune reaction of the host against the virus is well studied and all are documented in the review. To date, no effective treatment or management strategy is available against the disease. Several trials have been made to develop effective vaccines against the virus. This review compiled and analyzed all the information available and how to move forward for effective management of the virus. Highlights  Carassius auratus (goldfish) is one of the major cultured and traded ornamental fish worldwide.  Cyprinid herpesvirus 2 (CyHV-2) is a major viral pathogen of goldfish and other cyprinids.  Mortality with overt clinical signs can reach up to 100% during heavy infection.  Several promising management tools viz. vaccines, antioxidants and other natural compounds showed encouraging results in laboratory conditions.

Nile tilapia with clinical signs of haemorrhages on the lower jaw, abdominal region and fin bases, discoloration of gill and cloudy eye were obtained from grow-out ponds situated in different parts of India and screened for tilapia lake virus (TiLV) and tilapia parvovirus (TiPV) by RT-PCR and PCR, respectively. The results showed the infection caused by TiPV in tilapia collected from ponds. It was further confirmed by the primers specific to TiPV designed by different workers. Sequence analysis of 534 bp of genomic region of TiPV showed 100% similarity with the sequence of TiPV strain of Thailand. TiPV was found in different organs including eggs of infected fish and showed the possibility of systemic infection and vertical transmission. Snakehead kidney, snubnose pompano fin and tilapia heart cell lines were shown susceptibility to TiPV. The viral replication in cell lines was confirmed by PCR, TiPV specific cytopathic effect of Cowdry A inclusion bodies with clear halo surrounding them and infectivity experiment. The disease was reproduced in normal fish by IM route using viral inoculum from TiPV-infected fish or virus multiplied in susceptible cell lines to satisfy Koch’s postulates. The present report on the occurrence of TiPV in tilapia is the first time in India after China and Thailand.

The present study evaluated the effectiveness of dietary levamisole in the modulation of innate immunity and reducing the percent mortality against nitrite stress or Aeromonas hydrophila infection in giant freshwater prawn, Macrobrachium rosenbergii. Haemolymph agglutinin and total protein levels, lysozyme activity, phenoloxidase (PO) activity, total and differential haemocyte counts, induced nitrite stress and mortality (%) against Aeromonas hydrophila challenge were measured in sub-adult M. rosenbergii fed with diets containing levamisole at 0, 125, 250 and 500 mg/kg feed for 7 or 14 days. M. rosenbergii fed with a diet containing 250 mg levamisole/kg feed for 14 days showed significant (P<0.05) increase in haemagglutination titre, PO activity, undifferentiated haemocyte count, resistance to nitrite stress and survival against A. hydrophila challenge. On the contrary, graded levels of levamisole feeding for 7 days failed to modulate most of the immune parameters or reduce the percent mortality against A. hydrophila challenge or nitrite stress. It is therefore concluded that administration of levamisole in the diet at 250 mg/kg feed for 14 days in sub-adult M. rosenbergii could enhance the immune ability and increase its resistance to A. hydrophila infection and nitrite stress.

Giant freshwater prawn, Macrobrachium rosenbergii is an important freshwater crustacean widely cultured in several countries including India. Of late, its production has come down due to slow growth rate and disease occurrences. The ICAR-Central Institute of Freshwater Aquaculture (ICAR-CIFA), Bhubaneswar in collaboration with the WorldFish, Malaysia has initiated a selective breeding programme for growth improvement of this species. In the present study, two groups of families (I. six numbers of families for growth and II. six numbers of families for disease resistance) were selected for experimentation from the families produced in the fourth generation of selection programme. Each group consisted of two extreme sub-groups of three families in each with higher and lower growth (based on weight) under group I and, susceptible and resistant families (based on larval survival following challenge with Vibrio harveyi) under group II. RAPD- PCR was used to evaluate the genetic variations between and within groups separately. Twelve selected decamer primers were used to amplify DNA fragments of three individuals of each family and data were analyzed by POPGENE version 1.31 software. In group I, a total of 102 bands were scored by the primers out of which 41 bands (40.19%) found to be polymorphic. Genetic diversity within the group varied from 0.0272  0.0965 to 0.0463  0.1316. UPGMA dendrogram of this group based on Nei’s genetic distance showed that families 5 (low growth family 2) and 6 (low growth family 3) are distantly related to high growth families. In the second group of disease resistance, 35 bands (36.46%) were found to be polymorphic out of 96 bands scored. Genetic diversity varied between 0.0301 ± 0.0957 to 0.0438 ± 0.1381 within this group. UPGMA dendrogram showed that families 1 (susceptible group 1) and 2 (susceptible group 2) are distantly related to three resistant families. Thus, the present results showed the existence of genetic variations in both growth and disease resistance traits that could be utilized in the selective breeding programme in M. rosenbergii.