Nicholas Gudkovs - Academia.edu (original) (raw)

Papers by Nicholas Gudkovs

J Tissue Cult Meth, 2004

Two cell lines have been established from juvenile pilchards (Sardinops sagax neopilchardus) caug... more Two cell lines have been established from juvenile pilchards (Sardinops sagax neopilchardus) caught in waters off the Victorian coast of Australia. Following establishment of primary cultures derived from different pilchard tissues, using various cell culture media, a pilchard liver (PL) cell line and a pilchard heart (PH) cell line have been maintained in Eagle's minimal essential medium supplemented with 10% foetal bovine serum for over four years. The cell lines have been cryopreserved in liquid nitrogen and can be recovered from storage with

Diseases of aquatic organisms, Jan 23, 2006

The species Aeromonas salmonicida includes a quite complex group of pathogens that cause a variet... more The species Aeromonas salmonicida includes a quite complex group of pathogens that cause a variety of diseases in fishes. Best studied strains of this species are those of the subspecies salmonicida also referred to as 'typical' A. salmonicida, which cause furunculosis in salmonids. Less completely understood are bacteria assigned to other subspecies, e.g. achromogenes and masoucida, or those that cannot be assigned to a recognized subspecies. These strains are referred to collectively as 'atypical' A. salmonicida and cause diseases distinct from furunculosis, primarily affecting non-salmonids. In the course of a study to investigate the suitability of the gene product of tapA as a subunit vaccine, we discovered several atypical strains of A. salmonicida in which the tapA gene was interrupted by an insertion sequence (IS). Subsequent Southern blot analyses indicated that nearly all atypical strains (27 of 29) examined carry many copies of this IS, which we named ISAs...

A longitudinal study of white spot syndrome virus (WSSV) infection and disease was conducted from... more A longitudinal study of white spot syndrome virus (WSSV) infection and disease was conducted from January to August 2007 in a cluster of 12 small-holder shrimp (Penaeus monodon) ponds near Mallampudi in the Krishna District of Andhra Pradesh, India. Seven of the ponds had been sampled during the previous crop ; five adjacent ponds had not been sampled previously. Samples of mud were collected from the bottom of each pond at the commencement of the study. At intervals of approximately 10 days, farmed shrimp were sampled from the ponds and wild shrimp, crabs and plankton were sampled from inside ponds and from canals outside each pond. Of the 375 samples collected, 216 (57.6%) were WSSV-positive by Taqman PCR. The overall prevalence of WSSV infection varied significantly amongst sample types and was higher in farmed shrimp (76.0%) than for any other sample category (56% for crabs and plankton, 47% for wild shrimp, 25% for sediment). A wave of WSSV infection in plankton and wild crustaceans occurred across the study site, commencing at day 10, intensifying at day 20, subsiding at days 30 and 40, and passing by day 50. By day 60, only 2 ponds remained operational. WSSV-infection in plankton and wild crustacean samples collected from inside and outside these ponds again increased with a second peak at day 70. The pattern of WSSV infection in farmed shrimp appeared to follow the first wave of infection in plankton and wild crustaceans, with heavy viral genetic loads detected in most samples collected from days 30 to 80, including the final samples collected from 11 of the 12 ponds. Genotype analysis using the ORF94 variable number tandem repeat (VNTR) marker identified a very wide range of concurrently circulating WSSV genotypes (TRS1-TRS33) with multiple genotypes commonly detected in individual samples of all categories. Genotype TRS18, which had been associated with disease outbreaks in the previous crop, was not detected commonly in plankton or wild crustaceans. Although TRS18 was the most commonly detected genotype in farmed shrimp samples, it did not appear to be the cause of white spot disease outbreaks. There were several examples of simultaneous heavy infections with the same genotype in shrimp from several ponds but there was no clear pattern of association of a single WSSV genotype or a constellation of genotypes with disease outbreaks or pond abandonment. Crown

A longitudinal study was conducted from January to August 2007 in a cluster of 61 small-holder sh... more A longitudinal study was conducted from January to August 2007 in a cluster of 61 small-holder shrimp (Penaeus monodon) ponds at Mallampudi (16°25′29″ N, 81°19′13 ″ E) in the Krishna District of Andhra Pradesh, India. Exhaustive PCR testing of postlarvae collected from ponds at the time of seeding detected no evidence of white spot syndrome virus (WSSV) infection. However, during grow-out, disease outbreaks occurred in 42 of the ponds (68.9%) in which the mean and median crop durations were 42.8 days and 40.5 days, respectively. Only three of the 61 ponds (4.9%) were harvested after more than 120 days of culture. Of 41 ponds sampled at harvest, 35 (85.4%) were WSSV-positive by PCR, including 27 of 28 (96.4%) disease outbreak ponds, of 17 which were graded as heavy or moderate infections. Eight of 13 (61.5%) normal harvest ponds sampled were WSSV-positive at the time of harvest, of which seven (53.8%) were graded as light or very light infections. WSSV genotype analysis was conducted on samples from 35 ponds using the ORF94 variable number tandem repeat (VNTR) marker. In total, 20 different genotypes from TRS1-TRS25 (1 to 25 repeats) were detected. Multiple TRS genotypes were detected in 27 of the 35 ponds sampled (77.1%) and 73 of the 146 individual shrimp sampled (50.0%). The most evident temporal and spatial associations of WSSV genotypes with disease outbreaks were the dominance of genotype TRS18 in seven ponds located on the eastern side and genotype TRS8 in eleven ponds in the central region of the study area. The study indicated a high risk of exposure to WSSV infection during grow-out and that multiple WSSV genotypes were circulating simultaneously in the farming area. The spatial and temporal pattern of WSSV genotype distribution suggested transmission of infection within two clusters of ponds.

Diseases of aquatic organisms, Jan 16, 2014

The white spot syndrome virus (WSSV) genome contains 3 variable number tandem repeat (VNTR) regio... more The white spot syndrome virus (WSSV) genome contains 3 variable number tandem repeat (VNTR) regions, located in open reading frame (ORF) 75, ORF94 and ORF125, which have been employed for molecular epizootiological studies. A previous report suggested that the ORF 94 VNTR is highly unstable, varying in the number of tandem repeats during single passages from shrimp to other crustaceans. As such rapid variations would have profound implications for the interpretation of molecular epizootiological data, we re-examined the stability of the ORF94 VNTR. Two WSSV isolates with different ORF94 VNTR genotypes (TRS5 and TRS7) were obtained from disease outbreaks in farmed black tiger shrimp Penaeus monodon in Indonesia. High titre stocks of each virus were produced by injection in specific pathogen-free (SPF) Pacific white shrimp Litopenaeus vannamei with filtered infected tissue extracts, and the genotypes were confirmed. Each stock (macerated tissue) was then used to feed SPF Pacific white...

Journal of Fish Diseases, 1993

Severe mortalities of up to 60% have oeeurred in Australian and South African farmed rainbow trou... more Severe mortalities of up to 60% have oeeurred in Australian and South African farmed rainbow trout, Oncorhynehus mykiss (Walbaum), infected with Gram-positive eocci. Infected fish develop septieaemia and characteristic exophthalmos. Strains colleeted from outbreaks of disease appear to have attributes of the genus Enterococcus although no Lancefield group D antigen could be detected. All strains grew at 10°C but not at 45°C, grew in 6-5% NaCI, were bile-aesculin positive and hydrolysed L-pyrrolidonyl-/3naphthylamide. Isolates from both eountries have similar phenetic characteristics and whole cell protein profiles.

Journal of Fish Diseases, 1994

A virulent strain of Aeromonas hydrophila associated with epizootic ulcerative syndrome (EUS) was... more A virulent strain of Aeromonas hydrophila associated with epizootic ulcerative syndrome (EUS) was used to produce monoclonal antibodies that identified virulent strains of A. hydrophila. Antibodies from a clone, designated as F26P5C8, were found to identify the A. hydrophila serotype I isolates associated with EUS fish, and which were found to be virulent after subsequent inoculation studies. Immunodiagnosis of a large number of A. hydrophila from Australia and Japan showed some additional isolates to be identified by F26P5C8, but the status of their virulence is presently unknown.

INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY, 2003

Diseases of Aquatic Organisms, 2008

Diseases of Aquatic Organisms, 2000

During routine sampling and testing, as part of a systematic surveillance program (the Tasmanian ... more During routine sampling and testing, as part of a systematic surveillance program (the Tasmanian Salmonid Health Surveillance Program), an aquatic birnavirus was isolated from 'pinhead' (fish exhibiting deficient acclimatisation on transfer to saltwater) Atlantic salmon Salmo salar, approximately 18 mo old, farmed in net-pens located in Macquarie Harbour on the west coast of Tasmania, Australia. The isolate grows readily in a range of fish cell lines including CHSE-214, RTG-2 and BF-2 and is neutralised by a pan-specific rabbit antiserum raised against infectious pancreatic necrosis virus (IPNV) Ab strain and by a commercial pan-specific IPNV-neutralising monoclonal antibody. Presence of the virus was not associated with gross clinical signs. Histopathological examination revealed a range of lesions particularly in pancreatic tissue. The virus was localised in pancreas sections by immunoperoxidase staining using the polyclonal antiserum and by electron microscopy. Examination by electron microscopy demonstrated that the virus isolated in cell culture (1) belongs to the family Birnaviridae, genus Aquabirnaviridae; (2) was ultrastructurally and antigenically similar to virus identified in the index fish; (3) is related to IPNV. Western blot analysis using the polyclonal rabbit antiserum confirmed the cross-reactions between various aquatic birnavirus isolates. In addition, PCR analysis of isolated viral nucleic acid from the index case indicated that the virus is more closely related to IPNV fr21 and N1 isolates than to other birnavirus isolates available for comparison. Sampling of other fish species within Macquarie Harbour has demonstrated that the virus is present in several other species of fish including farmed rainbow trout Oncorhynchus mykiss, wild flounder Rhombosolea tapirina, cod Pseudophycis sp., spiked dogfish Squalus megalops and ling Genypterus blacodes.

Diseases of Aquatic Organisms, 2002

In an effort to develop a rapid diagnostic test for the fish pathogen Aeromonas salmonicida, the ... more In an effort to develop a rapid diagnostic test for the fish pathogen Aeromonas salmonicida, the performance of 2 polymerase chain reaction (PCR) primer sets (AP and PAAS) targeting the fish pathogen A. salmonicida and 1 PCR primer set (MIY) targeting A. salmonicida subsp. salmonicida were evaluated. Initially, the PCR assays were used to screen purified DNA extracted from 308 A. salmonicida isolates. The AP and PAAS PCR tests were demonstrated to be 100% specific for the species A. salmonicida and did not cross-react with any of the non-target organisms (bacterial species other than A. salmonicida) used in this study. The combined sensitivity of the AP and PAAS tests was 99.4% and offered the best coverage in terms of identifying the target organism. The MIY PCR appeared to be 100% sensitive and specific for A. salmonicida subsp. salmonicida. Studies with tissues, spiked with known quantities of bacteria, were conducted to determine the lower detection limit of the PCR tests, and then the ability of these PCR tests to detect A. salmonicida in experimentally infected salmonids was assessed.

Methods in Cell Science, 2004

Aquaculture, 2011

A longitudinal study was conducted from January to August 2005 in small-holder black tiger shrimp... more A longitudinal study was conducted from January to August 2005 in small-holder black tiger shrimp (Penaeus monodon) ponds in the West Godavari District of Andhra Pradesh, India (16°25′ N, 81°19′ E). The study involved 457 ponds owned by low-income farmers participating in a better management practice (BMP) programme. Disease outbreaks occurred in 16.6% of ponds. There was significant spatial clustering of disease outbreaks with 31 (40.8%) of the 76 recorded disease outbreaks occurring in a single village block. Bivariate analysis indicated a 1.6-fold higher likelihood of disease outbreaks from nursery-stocked ponds but this was not significant in multivariate analysis due to the confounding effect of pond location. There was evidence of increasing prevalence of WSSV infection during grow-out. WSSV was detected in 5.9% of 119 batches of postlarvae tested at stocking, 38.2% of 34 juvenile batches collected at the time of transfer to grow-out ponds, and 47.0% of 336 pond stock tested at normal harvest or crop failure. WSSV was detected in 43 of 59 (72.9%) disease outbreak ponds tested and 115 of 277 (41.5%) non-outbreak ponds tested. Heavy WSSV infection was detected at harvest in 116 of the 336 (34.5%) of the ponds tested, including 78 ponds for which no outbreak was recorded. Duration of crop was recorded for 431 ponds with a mean of 117.0 days and a range of 20 to 176 days. Median duration was significantly shorter for disease outbreak ponds (68.5 days) compared to nonoutbreak ponds (119.0 days). Duration of crop also varied according to WSSV detection levels at harvest, with median duration for ponds classified as heavy WSSV infection (108.5 days) significantly shorter than for ponds classified as either light WSSV infection (116.0 days) or WSSV-negative (116.5 days). The study indicated a high risk of WSSV infection during grow-out but a relatively low incidence of disease despite a high prevalence of heavy WSSV infection in non-outbreak ponds.

Diseases of Aquatic Organisms, May 1, 2009