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Viral nervous necrosis (VNN), or viral encephalopathy and retinopathy caused by nervous necrosis virus (NNV), is an acute viral disease of fish, resulting in high mortality globally in cultured marine fish. The pathogen, Betanodavirus belonging to the family Nodaviridae, has been widely documented in both farmed and wild fish, besides in invertebrate species across the habitat barriers. However, cichlid fish, in particular Etroplus species, have a low susceptibility or resistance to this disease. The present study was undertaken to check the susceptibility of a brackishwater cichlid, orange chromide (Etroplus maculatus) through intramuscular injection and immersion challenge by NNV (RGNNV genotype). Intramuscular injection (10 μl) with NNV (105 viral particles ml−1) resulted in cumulative mortality of 50% at 15 days of post-infection (dpi), while immersion challenge in NNV spiked sea water (105 TCID50 ml−1) resulting in a mortality of 25% at 19 dpi. Unlike many marine fish which showed 100% mortality within 3–5 days, E. maculatus challenged through both the routes exhibited severe clinical symptoms for 2–3 weeks followed by a recovery stage and moderate level of mortality. Reverse transcription polymerase chain reaction (RT-PCR) tests on live fish sampled during the course of the experiment and the dead fish exhibiting symptoms in both challenge groups tested NNV-positive. Histological examination of fish in challenged groups showed VNN-specific lesions characterized by vacuolations in the brain and eye with more severe lesions in the injected group than the immersion group. In survived fish, no clinical sign was observed, but NNV could be detected by RT-PCR with moderate to severe vacuolations in the brain and eyes until 30 dpi. Despite the virus entering the body and triggering typical symptoms of VNN, the fish appeared to exhibit moderate resistance with a survival of 50–75%. The results indicate that E. maculatus could serve as a brackishwater fish model to study host-pathogen interaction and development of resistance for potential application in NNV-vaccine studies.

Enterocytozoon hepatopenaei (EHP), is an emerging microsporidian pathogen responsible for hepatopancreatic microsporidiasis (HPM) in shrimps and is associated with severe growth retardation. The disease causes economic losses in shrimp aquaculture. In this study, EHP spore germination was induced and demonstrated with a scanning electron microscope (SEM). The ions (cations and anions) generated by high-energy electrons during frozen water radiolysis in the SEM specimen chamber induce EHP spore germination. This study is the first to demonstrate the induction of a microsporidian spore germination by ions generated under SEM. This study will enhance our understanding of EHP biology, life cycle and lead to the development of prophylactics and therapeutics for EHP control. Also, this method will help standardize the study of germination in other microsporidians.

Viral encephalopathy and retinopathy otherwise known as viral nervous necrosis (VNN) is a neuropathological condition affecting more than 50 fish species worldwide, mostly marine. Different PCR protocols with specific primers were reported from many countries for confirmation of VNN in fishes. In the present study, two pairs of primers were designed and evaluated for the diagnosis of clinical and subclinical cases of infections from field. These primers designated as BARL-F1/BARL-R1 amplified a 902 bp product in the variable region (T4) of the coat protein gene by first step PCR. Nested PCR primers BARL-F2/BARL-R2 amplified a fragment of 313 bp. The results were comparable with other commonly used primer sets such as F2/R3 and RG668f/RG919r primers. These new primers could detect betanodavirus in standard reference samples containing low, moderate and high viral load. Known positive and negative control samples of fish also revealed a predictive value of 100 % by RT-PCR diagnosis.

Jagadeesan, V.; Ezhil Praveena, P.; Otta, S.K., and Jithendran, K.P., 2019. Classical runt deformity syndrome cases in farmed Penaeus vannamei along the east coast of India. In: Jithendran...

A probable vertical mode of piscine nodavirus transmission is reported in the present investigation based on a case of nodavirus associated larval mortalities in hatchery produced Asian sea bass. Polyclonal rabbit anti-SJNNV antibodies (SGWak97) detected the viral antigens in the tissue sections from the eggs and the larvae at different time intervals from − 1 to 42 days post hatch (dph). Immunopositive ovarian connective tissue associated with the oocytes along with the progressive localization of the viral antigens in the brain, spinal cord, liver, stomach and dermal musculature during the larval development indicates a probable vertical transmission of nodavirus in the Asian sea bass. The surviving larger larvae, from the batch suffering mass mortalities, produced very intense immunofluorescent positivity in the liver, stomach and dermal musculature. Results of this investigation demonstrating a possibility of vertical transmission of the nodavirus emphasize the need for screening of eggs and larvae for evolving suitable preventive and prophylactic health management strategies.

White tail disease is a recently reported disease of giant freshwater prawn, Macrobrachium rosenbergii associated with M. rosenbergii nodavirus (MrNV). The present study is the first report on RT-PCR and sequence analysis of MrNV of an Indian isolate confirming the nodavirus infection in M. rosenbergii from India. Total RNA was extracted and the cDNA was synthesized from the infected post larvae collected from a hatchery located in Chennai, India. An 850-bp amplified product could be obtained by RT-PCR. The nucleotide sequence analysis of this 850-bp segment showed 98% nucleotide and 99% amino acid sequence identity with the reported sequence of an MrNV isolate from the West Indies.

Histopathology of Y-organ (moulting gland) in Indian white shrimp Fenneropenaeus indicus was studied after challenging the shrimp with virulent white spot syndrome virus (WSSV). Histopathological investigation on the Y-organ collected from moribund shrimps revealed the presence of intranuclear basophilic inclusions, characteristic of WSSV. More than 70% of the Y-organ cells were infected, suggesting the degenerated state of the organ. The cellular integrity of the Y-organ was completely destroyed by the WSSV. Further, Y-organ tissue samples collected from all the 16 experimental shrimp were positive by one-step polymerase chain reaction (PCR), confirming severe WSSV infection. The infected Y-organ in F. indicus with majority of the organ cells observed in the lysed condition suggests a physiological dysfunction of the organ. In uninfected and healthy controls, the lobulated Y-organ showed closely packed normal cells with prominent nuclei and sparse cytoplasm. Physiological implication of a degenerated Y-organ in the moulting and reproduction of the penaeid shrimp is discussed.

A systematic survey was conducted during two spells of 5 years each (1986-1990 and 1993-1997) to study the prevalence of parasitoses with particular reference to gastrointestinal (GI) nematodes and flukes in dairy animals (crossbred and native cattle, and buffaloes) belonging to 12 villages in the Kangra valley (Himachal Pradesh). Flukes (Fasciola, amphistomes and Dicrocoelium) and strongyles were the most important parasitic infections. Fasciola was endemic throughout the year, with a higher percentage infection in buffaloes than in cattle. Other fluke and nematode infections showed a seasonal pattern in prevalence, with a small peak in March April followed by a high peak in July September. The faecal egg counts (eggs per gram, epg) of flukes (Fasciola/amphistomes) ranged from 50 to 300 in cattle and 50 to 400 in buffaloes, with high loads during the rainy and post-rainy seasons. The GI nematode egg counts (excluding Toxocara) revealed a similar trend, with the overall monthly mean epg ranging from 85 to 1720 in cattle and 90 to 1625 in buffaloes, with a high peak during the months of July to September. On coproculture of positive samples, the nematode infections in order of prevalence were: Strongyloides, Trichostrongylus, Haemonchus, Oesophagostomum, Bunostomum and Mecistocirrus. The prevalence of most of the parasites was lower during the second 5-year period.