IntroductionSea lice are parasitic copepods that harm salmon health, reduce farm productivity, and create ecological and economic challenges for aquaculture.MethodsA stochastic, state-based, time-dependent epidemiological model was developed to characterize the dynamics of adult female sea lice (Lepeophtheirus salmonis) infestation in Atlantic salmon farms in New Brunswick, Canada. The model integrated covariates associated with farming practices and environmental conditions (stocking week, farming cycle week as proxy of fish age, sea lice treatments, seaway distance to neighboring farms as a proxy for waterborne transmission, and sea surface temperature). Data from 57 farming sites were used for model training and validation. An initial exploratory analysis assessed the relationship between treatment timing and recovery from infestation. Treatment effects were incorporated into weekly transitions between infestation states, accounting for severity and time-varying environmental factors.ResultsResults suggest that spring and summer stocking increases exposure to external infestation pressure and raises the probability of high lice concentrations. Further, reduced winter treatments are associated with elevated infestation levels. Treatment effectiveness appeared to be compromised by continued waterborne transmission from nearby farms.DiscussionThe model achieved an overall likelihood of 59%, reaching up to 74% during the first 10 weeks following stocking. Limitations included the use of proxy connectivity measures, i.e. seaway distance, rather than hydrodynamic connectivity, and the absence of data on fish size, salinity, and other farming practices such as fish density. Additionally, we were unable to include information from all farms in the study area, potentially underestimating transmission risk. Addressing these gaps and integrating hydrodynamic connectivity and fish growth models could improve predictive performance.

Effective surveillance of viral disease in fish populations is critical for disease control and the sustainable development of global aquaculture. Here, we evaluated the application and performance of pooled serum samples using an indirect ELISA based on recombinant segment 4 protein to assess farm-level immunity in tilapia infected with Tilapia lake virus (TiLV). The TiLV-S4 ELISA was developed using a recombinant nucleoprotein (segment 4) antigen, optimized through checkerboard titration, and validated for repeatability and reproducibility, with intra- and inter-assay coefficients of variation below 10%. A pooling strategy was used to combine multiple serum samples before testing for the presence of TiLV-specific antibodies using an enzyme-linked immunosorbent assay (ELISA). Our results showed that pooling five serum samples was effective for detecting TiLV-specific antibodies, particularly when multiple seropositive individuals were presented in the pool, supporting its application for population-level surveillance. However, ELISA sensitivity may be reduced when only one seropositive sample is included in the pool, due to the dilution effects. Despite this limitation, pooled testing yielded a high proportion of positive results, suggesting similar detection performance in many cases. Overall, the pooling strategy provides a cost-effective and time-efficient approach for large-scale monitoring of immune status in tilapia populations.

Real-time PCR (qPCR) testing is an essential component of early detection surveillance systems for Piscirickettsia salmonis infection in Atlantic salmon farms in Chile. Currently, all 11 laboratories in the authorised diagnostic laboratory network use assays based on published protocols. Compared with other P. salmonis qPCR assays, these assays have the advantage of targeting two different genes, that is, the 16S ribosomal gene and the internal transcribed spacer (ITS), potentially allowing for higher diagnostic accuracy. However, variation and lack of harmonisation of qPCR testing systems (e.g., primers/probe, RNA/DNA as target, extraction methods, etc.) may contribute to among-laboratory variation in qPCR results and an increased frequency of false-negative and false-positive results. The purpose of the ring trial reported herein was to compare qPCR results from 11 laboratories in Chile routinely testing Atlantic salmon for P. salmonis as part of a national control program. The panel of 14 samples included duplicates of three concentrations of P. salmonis in a homogenised head kidney, LF89 and EM90 bacteria and two negative controls (blank and a suspension of Flavobacterium psychrophilum). The sample order was randomised across labs, samples were tested blinded and analysed without knowledge of the source lab. Of the laboratories, 8 (72.7%) had at least one incorrect result out of 14 tested samples. Low-concentration samples (Ct of about 30) were more often incorrectly classified by reverse transcription-qPCR (RT-qPCR) (3/6 labs) than by qPCR (0/5). Six (54.5%) labs had at least one false-positive result indicating that cross-contamination was likely during sample processing. Affected laboratories are advised to conduct internal investigations to confirm the causes of false-positive results and recommendations for design and implementation of future ring trials are discussed.

Chronic subclinical infection with the aetiological agent of bacterial kidney disease (BKD), Renibacterium salmoninarum, presents challenges for the clinical management of disease in farmed salmonids and for prevalence estimation. Harvested salmon sampled at processing plants provide the opportunity to describe subclinical outcomes of BKD using gross necropsy observations and diagnostic test results in farmed Atlantic salmon (Salmo salar L.) populations that are apparently healthy (i.e. alive at harvest) but naturally exposed to R. salmoninarum infection. Sampling of farmed salmon (Population A, n = 124 and Population B, n = 160) was performed immediately post-slaughter as fish were being processed at a plant in New Brunswick, Canada. Populations were selected based on planned harvests from sites with histories of recent exposure events related to clinical BKD as evidenced by the site veterinarian's diagnosis of mortality attributable to BKD: One site (Pop A) had recently increasing mortalities attributed to BKD, and the other site (Pop B) had ongoing low-level mortalities with BKD pathology. As expected with the different exposure histories, Pop A had a higher percentage (57.2%) of R. salmoninarum culture-positive kidney samples compared with similar fish samples in Pop B (17.5%). Diagnosis of R. salmoninarum by gross granulomatous lesions in internal visceral organs, bacterial culture and identification by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) using different swab transport methods, and molecular detection methods (quantitative PCR, qPCR) were compared. Agreement of culture-positive percentages at the sample level was moderate (kappa: 0.61-0.75) among specimens collected using different kidney sampling methods in Pop A and Pop B. The highest proportion of R. salmoninarum-positive cultures occurred when kidney tissues were transported to the laboratory and inoculated directly onto agar using a swab (94% of cultures from Pop A and 82% from Pop B when fish were positive by any culture method). Fish with cumulative lesion scores (severity of granulomatous lesions in 3 different visceral organs) of >4 were all culture positive, and when compared with non-lesioned fish, had substantially higher odds of being culture positive: Pop A: odds ratio (OR) = 73, 95% confidence interval (CI) (7.91, 680.8); Pop B: OR = 66, 95% CI (6.12, 720.7). Our study found that onsite postmortem examinations with severity scores of gross granulomatous lesions were predictive of positive culture results for R. salmoninarum, and they were a useful proxy for assessing prevalence in apparently healthy populations with subclinical infection.

This study aimed to generate data on performance characteristics for 2 real-time TaqMan PCR assays (CSIRO and WOAH WSSV qPCRs) for the purposes of (1) detection of white spot syndrome virus (WSSV) in clinically diseased prawns and (2) detection of WSSV in apparently healthy prawns. Analytical sensitivity of both assays was 2 to 20 genome copies per reaction, and analytical specificity was 100% after testing nucleic acid from 9 heterologous prawn pathogens and 4 prawn species. Results obtained after testing more than 20 000 samples in up to 559 runs with the CSIRO WSSV qPCR and up to 293 runs with the WOAH WSSV qPCR demonstrated satisfactory repeatability for both assays. Both assays demonstrated median diagnostic sensitivity (DSe) 100% (95% CI: 94.9-100%) when testing clinically diseased prawns. When 1591 test results from apparently healthy prawns were analysed by Bayesian latent class analysis, median DSe and diagnostic specificity (DSp) were 82.9% (95% probability interval [PI]: 75.0-90.2%) and 99.7% (95% PI: 98.6-99.99%) for the CSIRO WSSV qPCR and 76.8% (95% PI: 68.9-84.9%) and 99.7% (95% PI: 98.7-99.99%) for the WOAH WSSV qPCR. When both assays were interpreted in parallel, median DSe increased to 98.3 (95% PI: 91.6-99.99%), and median DSp decreased slightly to 99.4% (95% PI: 97.9-99.99%). Routine testing of quantified positive controls by laboratories in the Australian laboratory network demonstrated satisfactory reproducibility of the CSIRO WSSV qPCR assay. Both assays demonstrated comparable performance characteristics, and the results contribute to the validation data required in the WOAH validation pathway for the purposes of detection of WSSV in clinically diseased and apparently healthy prawns.

Our objectives were to evaluate the diagnostic accuracy of a rapid and novel immunochromatography-based mastitis kit that includes 3 independent tests to detect coliforms (Escherichia coli or Klebsiella pneumoniae), Streptococcus spp., and Staphylococcus aureus. The kit was developed to facilitate diagnostic-based mastitis treatment. Validation of the kit was based on 154 aseptically collected mastitis samples from 2 clinical herds (clinical population) and 120 milk samples from 3 nonclinical herds (nonclinical population) without clinical cases at the time of enrollment. One herd sampled at different times was common to both populations. A 3-test in 2-population Bayesian latent class model with uniform priors for all test parameters except specificity of culture, which was modeled informatively, was used to estimate sensitivity (Se) and specificity (Sp) of the test kit, culture, and PCR at the cow level. The mastitis test kit's 96.9% Sp for Streptococcus spp. had a low false positive percentage (3.1%), which, together with the kit's rapid turnaround time for results, makes it a suitable initial screening test that producers can use to identify clinical cows to treat based on Streptococcus spp. mastitis in kit-positive results. Due to the 60.4% kit Se, producers should follow up on Streptococcus spp. kit-negative cows using a confirmatory test such as PCR (Sp of 98.4%) or culture (Sp of 99.6%). In contrast, aerobic culture had Se of 76.5% and Sp of 99.6% for Streptococcus spp. Similarly, the Sp of the kit (98.2%) and culture (99.8%) for Staph. aureus were particularly high, and even though the kit's Se (61.0%) was lower than culture (88.4%; posterior probability of difference 98%), the kit could be beneficial before use of a confirmatory test for kit-negative samples due to its ease and rapid turnaround time. Mostly, quantitative real-time (q)PCR outperformed the kit's Se (37.7%) and Sp (92.9%) for coliforms, as well as the kit's Se (60.4%) for Streptococcus spp. However, qPCR may require more technical skills and turnaround time for final results. Use of the on-farm mastitis test kit evaluated in the present study could enhance sustainable antimicrobial drug use by rapidly identifying Streptococcus mastitis for targeted treatment. Furthermore, the kit may be used in a Staph. aureus outbreak where cows can be rapidly screened to identify cases for segregation or culling during an outbreak and kit-negative cows further confirmed by milk culture or qPCR. However, the cost-effectiveness of such an approach has not been investigated.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) allows rapid and reliable identification of microorganisms. The accuracy of bacterial identification using MALDI-TOF MS depends on main spectral profiles (MSPs) provided in a quality-assured commercial reference library, which requires ongoing improvement. This study aimed to develop and validate an in-house MALDI-TOF MS MSP to rapidly identify Yersinia ruckeri isolated from Atlantic salmon (Salmo salar). The novel MSP was prepared using an isolate of Y. ruckeri recovered from Atlantic salmon and confirmed by 16S rRNA gene sequencing. Subsequently, a validation set which comprises 29 isolates of Y. ruckeri were examined from three fishes: Atlantic salmon (Salmo salar) (n = 26), American eel (Anguilla rostrata) (n = 1), and Atlantic cod (Gadus morhua) (n = 2). These isolates were randomly selected from the Atlantic Veterinary College, Aquatic Diagnostic Services Bacteriology Laboratory's culture collection to validate the novel MSP. Analytical sensitivity of MALDI-TOF MS using the novel MSP to identify the validation set was 86.2%. Repeatability was assessed by acquiring spectra from 30 different spots of a randomly-selected isolate of Y. ruckeri, and analyzed spectra from each spot were compared against the novel MSP. The coefficient of variation was 3.3%. The novel MSP clustered with Bruker MSPs (n = 3) of Y. ruckeri in the reference library and did not falsely identify any closely related bacteria to Y. ruckeri. This study reports the development of a novel MSP of high analytical sensitivity and specificity for rapid identification of Y. ruckeri using MALDI-TOF MS.

Costs of diagnostic testing including sample collection, sampling frequency and sample size are an important consideration in the evaluation of the economic feasibility of alternative surveillance strategies for detection of infectious diseases in aquatic animals. In Chile, Piscirickettsia salmonis is the primary reason for antibiotic treatments in farmed Atlantic salmon. In 2012, a surveillance and control programme for piscirickettsiosis was established with an overall goal of reducing antibiotic use. The present study estimated the cost-effectiveness of different sampling frequencies and sample sizes to achieve at least 95% confidence of early detection of P. salmonis at the netpen and farm levels using a validated qPCR test. We developed a stochastic model that incorporated variability in test accuracy, within-pen prevalence and sampling costs. Our findings indicated that the current piscirickettsiosis surveillance programme based on risk-based sampling of five moribund or dead fish from 2 to 3 netpens is cost-effective and gives a high probability of detection of P. salmonis in Atlantic salmon farms in Chile at both the netpen and farm levels. Results from this study should incentivize salmon farmers to establish cost-effective strategies for early detection of P. salmonis infection and the application of this approach to other highly infectious diseases.

Infection with Streptococcus agalactiae causes mortality and major economic losses in Nile tilapia (Oreochromis niloticus) farming worldwide. In Brazil, serotype strains Ia, Ib and III have been isolated in streptococcosis outbreaks, but serotype Ib is the most prevalent. Vaccination is considered an effective method to prevent economically-important diseases in aquaculture and has been associated with decreased use of antibiotics and improvements in fish survival. We developed a flexible partial-budget model to undertake an economic appraisal of vaccination against Streptococcus agalactiae in Nile tilapia farmed in net cages in large reservoirs. The model considers the benefits and costs that are likely to be associated with vaccination at the farm-level, in one production cycle. We built three epidemiological scenarios of cumulative mortality attributable to S. agalactiae (5%, 10%, and 20%, per production cycle) in a non-vaccinated farm. For each scenario, we applied a stochastic model to simulate the net return of vaccination, given a combination of values of "vaccine efficacy", "gain in feed conversion ratio", "feed price", "fish market price", and "cost of vaccine dose". In the 20% cumulative mortality scenario, the net return would break-even (benefits >= costs) in at least 97.9% of interactions. Should cumulative mortality be lower than 10%, the profitability of vaccination would be more dependent on better feed conversion ratio. The inputs "feed price" and "cost of vaccine" had minor effects on the output, in all pre-vaccination mortality scenarios. Although our simulations are based on conservative values and consider uncertainty about the modeled parameters, we conclude that vaccination against S. agalactiae is likely to be profitable in Nile tilapia farms, under similar production conditions.

Glanders is a zoonotic contagious disease of equids caused by Burkholderia (B.) mallei. Serodiagnosis of the disease is challenging because of false-positive and false-negative test results. The accuracy of the complement fixation test (CFT) which is prescribed for international trade by the World Organisation for Animal Health (OIE), five ELISAs and a Western blot (WB) were compared for serodiagnosis of glanders using sera from 3,000 glanders-free and 254 glanderous equids. Four ELISA tests are based on recombinant antigens (TssA, TssB, BimA and Hcp1), the IDVet ELISA is based on a semi-purified fraction of B. mallei and WB makes use of a purified LPS-containing B. mallei-antigen. Sensitivity and specificity of tests were estimated using cut-off values recommended by the test developers. The WB and all ELISAs, except BimA, were significantly more specific than the CFT. ELISAs based on TssA, TssB, and BimA antigens had significantly lower sensitivity compared to CFT while the sensitivities of the Hcp1-ELISA, the IDVet-ELISA and the WB did not differ significantly from that of the CFT. Given their comparable sensitivities and specificities, the CFT (98.0%, 96.4%), the WB (96.8%, 99.4%), the Hcp1-ELISA (95.3%, 99.6%) and the IDVet-ELISA (92.5%, 99.5%) should be further developed to meet OIE requirements.

Renibacterium salmoninarum infection causes bacterial kidney disease (BKD) in salmonid freshwater and saltwater life stages, with potentially severe financial loss for the aquaculture industry. Preventing vertical transmission, from infected broodstock to eggs, is key to disease management. As there is no perfect reference standard for detecting R.salmoninarum, we used Bayesian latent class analyses to compare real-time reverse transcriptase PCR (RT-rPCR, mRNA target) and enzyme-linked immunosorbent assay (ELISA; p57 antigen target) diagnostic accuracy for detection in Atlantic salmon broodstock from British Columbia, Canada, and assessed ELISA repeatability. In 2016, 4,544 Atlantic salmon broodstock (no clinical signs of BKD or gross lesions) were sampled for ELISA testing of kidney tissue. Two groups of ELISA positives (n=132) and two groups of a random sample of ELISA negatives (n=137) were then tested with RT-rPCR, and ELISA testing was repeated. ELISA testing of broodstock provided the best diagnostic sensitivity (DSe; less chance of false-negative results). The use of joint RT-rPCR and ELISA testing improved DSe over that from each test alone, if a sample was considered positive when either test result was positive. Using these testing schemes in combination with management practices can decrease the likelihood of vertical transmission from subclinically infected broodstock.

Fish aquaculture is rapidly growing in Brazil. Nile tilapia is the most cultivated species, mainly through an intensive production system carried out in floating cages installed in large reservoirs. However, fish pathogens pose a major challenge to production chain sustainability, and tilapia farmers may have limited knowledge of prevailing health problems and rarely implement effective biosecurity practices to prevent introduction of economically important infectious agents. This study aimed to identify the key disease risks of tilapia farming in a tropical reservoir and characterize the dynamics of the prevalent pathogens, as a basis for development of effective control measures for tilapia health and surveillance programs. From August 2015 to October 2016, a longitudinal study was carried out at the Três Marias reservoir, in the municipality of Morada Nova de Minas in the southeast of Brazil. Daily and monthly data were collected from six out of 32 existing fish farms, including fish samples, mortality counts, and measurements of temperature and water quality parameters. The main bacteria detected were Streptococcus agalactiae, infecting mostly adult tilapia throughout the period, with higher frequency as the average temperature increased, and Francisella noatunensis subsp. orientalis (Fno), infecting mainly younger tilapia, only during the cooler months. Coinfections with multiple pathogens were detected in 33 fish. The detection of Fno in one farm in two consecutive winters, after months of unfavorable water temperature conditions and without evidence of introduction of infected stock, strengthens the case for investigating if this pathogen can survive and remain infective causing new outbreaks. Furthermore, variation in mortality was likely associated with the dynamics of the studied pathogens.

Biosecurity has been identified as a core concept for Asian freshwater aquaculture for purposes of food safety, aquaculture sustainability, and trade. To our knowledge, no published studies have evaluated producers' knowledge of biosecurity and biosecurity practices in Chinese aquaculture. We carried out a questionnaire-based knowledge, attitudes, and practices (KAP) survey of farmers culturing yellow catfish in Guangdong and Zhejiang provinces in China. Yellow catfish is a freshwater fish with high market value, and is mostly cultured in ponds on small-scale farms. The purpose of the survey was to evaluate biosecurity practices currently applied on those freshwater farms. Eighty-seven farmers in Guandong (n= 44) and Zhejang (n= 43) were interviewed, and 50 (57.5%) farmers completed responses to all KAP questions. Demographics of participating farmers and their responses to each question were described. We developed a KAP index to categorize and subcategorize KAP questions, and assigned scores to farmers' original answers to each question. Every farmer was evaluated with both numeric scores for their farm-level biosecurity and with score categories of "Good"(= 75%), "Fair" (50% to 75%), and "Poor"(<50%). Results of this study indicated that: (1) farmers' basic knowledge of pathogens was good, but their understanding of pathogen transmission was limited; (2) overall scores for attitude towards biosecurity were slightly higher than practices scores, although they were still relatively low; and (3) all farmers were classified as poor or fair for their compliance with overall farm-level biosecurity measures. Our findings showed that: farmers' practices were mostly not in compliance with the principles of biosecurity, especially in regards to prevention of pathogen introduction and spread; and the inconsistencies between practices and attitudes indicated that it may be feasible to improve farmer's implementation of aquatic biosecurity at the farm level. Biosecurity concepts evaluated in the study were based on salmonid aquaculture and their relevance to biosecurity measures of catfish aquaculture in China should be explored in future research. We recommend that current farm-level biosecurity practices in finfish aquaculture in China be improved through investment in education and training, in collaboration with academic and industry partners. Statement of relevance: Chinese yellow catfish producers need additional guidance on the importance and implementation of biosecurity principles for pond systems. (C) 2017 Elsevier B.V. All rights reserved.

The Standards for the Reporting of Diagnostic Accuracy (STARD) statement, which was recently updated to the STARD2015 statement, was developed to encourage complete and transparent reporting of test accuracy studies. Although STARD principles apply broadly, the checklist is limited to studies designed to evaluate the accuracy of tests when the disease status is determined from a perfect reference procedure or an imperfect one with known measures of test accuracy. However, a reference standard does not always exist, especially in the case of infectious diseases with a long latent period. In such cases, a valid alternative to classical test evaluation involves the use of latent class models that do not require a priori knowledge of disease status. Latent class models have been successfully implemented in a Bayesian framework for over 20 years. The objective of this work was to identify the STARD items that require modification and develop a modified version of STARD for studies that use Bayesian latent class analysis to estimate diagnostic test accuracy in the absence of a reference standard. Examples and elaborations for each of the modified items are provided. The new guidelines, termed STARD-BLCM (Standards for Reporting of Diagnostic accuracy studies that use Bayesian Latent Class Models), will facilitate improved quality of reporting on the design, conduct and results of diagnostic accuracy studies that use Bayesian latent class models.

Rabies continues to pose a significant threat to human and animal health in regions of Indonesia. Indonesia has an extensive network of veterinary diagnostic laboratories and the 8 National laboratories are equipped to undertake diagnostic testing for rabies using the commercially-procured direct fluorescent antibody test (FAT), which is considered the reference (gold standard) test. However, many of the Indonesian Provincial diagnostic laboratories do not have a fluorescence microscope required to undertake the FAT. Instead, certain Provincial laboratories continue to screen samples using a chemical stain-based test (Seller's stain test, SST). This test has low diagnostic sensitivity, with negative SST-tested samples being forwarded to the nearest National laboratory resulting in significant delays for completion of testing and considerable additional costs. This study sought to develop a cost-effective and diagnostically-accurate immunoperoxidase antigen detection (RIAD) test for rabies that can be readily and quickly performed by the resource-constrained Provincial laboratories. This would reduce the burden on the National laboratories and allow more rapid diagnoses and implementation of post-exposure prophylaxis. The RIAD test was evaluated using brain smears fixed with acetone or formalin and its performance was validated by comparison with established rabies diagnostic tests used in Indonesia, including the SST and FAT. A proficiency testing panel was distributed between Provincial laboratories to assess the reproducibility of the test. The performance of the RIAD test was improved by using acetone fixation of brain smears rather than formalin fixation such that it was of equivalent accuracy to that of the World Organisation for Animal Health (OIE)-recommended FAT, with both tests returning median diagnostic sensitivity and specificity values of 0.989 and 0.993, respectively. The RIAD test and FAT had higher diagnostic sensitivity than the SST (median = 0.562). Proficiency testing using a panel of 6 coded samples distributed to 16 laboratories showed that the RIAD test had good reproducibility with an overall agreement of 97%. This study describes the successful development, characterisation and use of a novel RIAD test and its fitness for purpose as a screening test for use in provincial Indonesian veterinary laboratories.

Heart and skeletal muscle inflammation (HSMI) is an emerging disease of marine-farmed Atlantic Salmon (Salmo salar), first recognized in 1999 in Norway, and later also reported in Scotland and Chile. We undertook a longitudinal study involving health evaluation over an entire marine production cycle on one salmon farm in British Columbia (Canada). In previous production cycles at this farm site and others in the vicinity, cardiac lesions not linked to a specific infectious agent or disease were identified. Histologic assessments of both live and moribund fish samples collected at the farm during the longitudinal study documented at the population level the development, peak, and recovery phases of HSMI. The fish underwent histopathological evaluation of all tissues, Twort's Gram staining, immunohistochemistry, and molecular quantification in heart tissue of 44 agents known or suspected to cause disease in salmon. Our analysis showed evidence of HSMI histopathological lesions over an 11-month timespan, with the prevalence of lesions peaking at 80-100% in sampled fish, despite mild clinical signs with no associated elevation in mortalities reported at the farm level. Diffuse mononuclear inflammation and myodegeneration, consistent with HSMI, was the predominant histologic observation in affected heart and skeletal muscle. Infective agent monitoring identified three agents at high prevalence in salmon heart tissue, including Piscine orthoreovirus (PRV), and parasites Paranucleospora theridion and Kudoa thyrsites. However, PRV alone was statistically correlated with the occurrence and severity of histopathological lesions in the heart. Immunohistochemical staining further localized PRV throughout HSMI development, with the virus found mainly within red blood cells in early cases, moving into the cardiomyocytes within or, more often, on the periphery of the inflammatory reaction during the peak disease, and reducing to low or undetectable levels later in the production cycle. This study represents the first longitudinal assessment of HSMI in a salmon farm in British Columbia, providing new insights on the pathogenesis of the disease.

Event Abstract Back to Event Production and health constraints to sustainable Nile tilapia production by small-holders, using net cages at the Três Marias reservoir, Brazil Geórgia D. Roriz1, Marina C. Delphino1, Ian Gardner2 and Vitor Salvador P. Gonçalves1* 1 University of Brasilia, FAV, Brazil 2 University of Prince Edward Island; Atlantic Veterinary College, Canada Brazil has a huge potential for aquaculture but it is the 17th largest producer according to aquaculture rankings, indicating an underutilization of its resources. The most efficient strategy to ensure a high annual growth rate is the adoption of more competitive and sustainable production systems, such as fish farming in net cages installed within the key reservoirs of the country, and following public policies that regulate the assignment of water from the Union to aquaculture production. The present study aimed to characterize tilapia production patterns in net cages at the Três Marias reservoir, focusing on the production and sanitary aspects. The data were collected through an interview, using a structured questionnaire, during May 2015. The study involved all the 32 fish farmers, who use net cages, in the municipality of Morada Nova de Minas, the most important site for fish production at the Três Marias reservoir. Aquaculture was the sole income-generating activity for only 17% of the farmers in this municipality. Less than half of the farmers had a workforce that comprised their family members only. Irrespective of the type of workforce, having up to three members of staff for the management of animals was the predominant trend (81.3%), and only two farms received regular technical assistance. Tilapia was the only species commercially produced in the municipality of Morada Nova de Minas, and was sold to local slaughterhouses, most of which did not undergo official sanitary inspections (67%). Sanitation practices were adopted by a majority of the farmers, who cleaned their cages and tools, did not share equipment with other farms, and appropriately discarded dead or dying animals in ditches (76%). According to the farmers’ perception, the primary causes of fish mortality in the reservoir were water temperature and water level (72%), fingerling quality (31%), and improper feed management (24%). The concerns most frequently reported by the fish farmers were: difficulty in getting environmental licenses (59%), high cost of animal feed (34%), and low water levels in the reservoir (31%). A follow-up study will be implemented to describe the infection dynamics of main pathogens in this production ecosystem. In conclusion, this emerging production chain is mostly made of small fish farmers with low levels of production technology and limited support of health and extension services. The sustainable development of fish production in public waters needs to be in line with environmental concerns and will depend on identification of cost-effective solutions for the health and production bottlenecks. Acknowledgements This research work was funded by the Brazilian Federal Government Agency – CNPq - through the Program “Science Without Borders” (grant no. 481064/2012-5). The field work was carried out with the support of the local office of CODEVASF, especially Dr. José Jacobina Romaguera Neto and Dr. Antônio Jessey de Abreu Tessitore, whose collaboration was essential to carry out this project. Keywords: Aquaculture, Net cages, public reservoirs, Nile tilapia, sanitary and production practices, Brazil Conference: AquaEpi I - 2016, Oslo, Norway, 20 Sep - 22 Sep, 2016. Presentation Type: Poster Topic: Aquatic Animal Epidemiology Citation: Roriz GD, Delphino MC, Gardner I and Gonçalves VP (2016). Production and health constraints to sustainable Nile tilapia production by small-holders, using net cages at the Três Marias reservoir, Brazil . Front. Vet. Sci. Conference Abstract: AquaEpi I - 2016. doi: 10.3389/conf.FVETS.2016.02.00024 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 20 May 2016; Published Online: 14 Sep 2016. * Correspondence: Prof. Vitor Salvador P Gonçalves, University of Brasilia, FAV, Brasilia, Distrito Federal, Brazil, vitorspg@unb.br Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Geórgia D Roriz Marina C Delphino Ian Gardner Vitor Salvador P Gonçalves Google Geórgia D Roriz Marina C Delphino Ian Gardner Vitor Salvador P Gonçalves Google Scholar Geórgia D Roriz Marina C Delphino Ian Gardner Vitor Salvador P Gonçalves PubMed Geórgia D Roriz Marina C Delphino Ian Gardner Vitor Salvador P Gonçalves Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

The global distribution of bluetongue virus (BTV) has been changing recently, perhaps as a result of climate change. To evaluate the risk of BTV infection and transmission in a BTV-endemic region of California, sentinel dairy cows were evaluated for BTV infection, and populations of Culicoides vectors were collected at different sites using carbon dioxide. A deterministic model was developed to quantify risk and guide future mitigation strategies to reduce BTV infection in California dairy cattle. The greatest risk of BTV transmission was predicted within the warm Central Valley of California that contains the highest density of dairy cattle in the United States. Temperature and parameters associated with Culicoides vectors (transmission probabilities, carrying capacity, and survivorship) had the greatest effect on BTV's basic reproduction number, R-0. Based on these analyses, optimal control strategies for reducing BTV infection risk in dairy cattle will be highly reliant upon early efforts to reduce vector abundance during the months prior to peak transmission.

Event Abstract Back to Event Disease risks of fish farming in public reservoirs: a follow-up study conducted in Três Marias, Brazil Marina K. Delphino1*, Georgia D. Roriz1, Ian Gardner2, Carlos A. Leal3, Henrique C. Figueiredo3, Eduardo Cunha4 and Vitor Salvador P. Gonçalves1 1 University of Brasília, Brazil 2 University of Prince Edward Island, Canada 3 Federal University of Minas Gerais, AQUACEN, National Reference Laboratory for Aquatic Animal Diseases, Brazil 4 Ministry of Agriculture, Livestock and Food Supply, Brazil Background: Fish production in public waters expanded in Brazil over the last decade and is mostly carried out by small-holder fish farmers in large reservoirs. Nile tilapia (Oreochromis niloticus) is the main fish species raised in such environment, but the production and sanitary constraints are not well described, limiting the planning of health and extension services. Objectives: This project comprises a longitudinal study to identify the key disease risks that hamper productivity of fish farming in floating cages in reservoirs and characterize the natural history and dynamics of the prevalent diseases, in order to develop effective surveillance and control measures. Methodology: A one-year follow-up study is on-going at the municipality of Morada Nova de Minas (MNM) at the reservoir of Três Marias, Minas Gerais. The study comprises six out of 32 existing fish farms given the budget and logistic constraints for collecting and sending fish to the laboratory every month. The farms were selected for convenience, representing the common type of fish farmers, based on results of a survey on producers’ perceptions and attitudes towards health risks, carried out in May 2015. The present study started in August 2015 and is expected to end in August 2016. Producers are responsible for daily collection of data on water temperature, mortality, introduction of new stock, harvesting, use of antibiotics and salt, and fish handling frequency. Once a month, the research team collects fish samples and water quality data such as reservoir depth, water pH, water turbidity, dissolved oxygen, water temperature, total dissolved solids and redox potential, using a calibrated Horiba water quality multi-parameter. With respect to the sampling strategy, the population within the farm was considered to be homogenous with regard to the risk of infection. The sample size of 30 fish per farm was chosen to detect at least one positive individual with 95% confidence if a pathogen was present in at least 10% of the population. Sampling was targeted at moribund fish and those with clinical signs of infectious diseases (melanosis, exophthalmia, erratic swimming, skin ulcers, gill pallor and others), which may lead to increased sensitivity of detection. The animals are euthanized and send to the laboratory on ice within 48h when a screening test (bacteriological) is performed immediately upon arrival. Then, kidney, liver and brain samples are collected for bacterial isolation and identification of the isolates by species-specific qPCR. All laboratory testing is being carried out at Aquacen, the national reference laboratory, located at the Federal University of Minas Gerais (UFMG), whereas data analysis is underway at the Veterinary Epidemiology Laboratory of the University of Brasilia (EpiPlan/FAV/UnB). Partial results: From the beginning of the follow-up in August 2015, 11 different bacteria were detected out of the 430 isolates from 1186 individual fish samples. Also, there were co-infection cases in Nile tilapia, including a first report of co-infection by Francisella noatunesis subsp orientalis (FNO) and Streptococcus iniae. Throughout the period, an interesting finding was that FNO was detected only during the colder months (August and September 2015), when average water temperature was about 26°C or less. Not surprisingly, water temperature appears to play a significant role in the development of francisellosis. As the average water temperature increased (28 to 30ºC) over the following months, S. agalactiae was isolated with higher frequency compared to other detected bacterial species. There was a statistical association (P<0.05) between the variables "fish weight" (<100g; from 101 to 450g; > 450g) and "bacteria detected" (S. agalactiae, S. iniae and FNO). These preliminary results are consistent with previous findings, indicating that Streptococcus infection involves mainly adult tilapia whereas FNO infection tends to affect younger (up to 100g) tilapia. Data from this study will be associated with the results of the monitoring of infectious agents carried out at the two hatcheries of the region. The bacteriological monitoring of the hatcheries started in March 2016. Acknowledgements This project is supported by a grant of the program “Science without Borders”, funded by CNPq. Special thanks to the Company for the Development of the San Francisco and Parnaíba rivers (CODEVASF) for the logistical field assistance to the National Reference Laboratory for Aquatic Animal Diseases (AQUACEN/RENAQUA). Keywords: Floating cages, Disease risk, Tilapia, reservoirs, surveillance Conference: AquaEpi I - 2016, Oslo, Norway, 20 Sep - 22 Sep, 2016. Presentation Type: Oral Topic: Aquatic Animal Epidemiology Citation: Delphino MK, Roriz GD, Gardner I, Leal CA, Figueiredo HC, Cunha E and Gonçalves VP (2016). Disease risks of fish farming in public reservoirs: a follow-up study conducted in Três Marias, Brazil. Front. Vet. Sci. Conference Abstract: AquaEpi I - 2016. doi: 10.3389/conf.FVETS.2016.02.00046 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 30 May 2016; Published Online: 14 Sep 2016. * Correspondence: Dr. Marina K Delphino, University of Brasília, Brasilia, Brazil, marinakd@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Marina K Delphino Georgia D Roriz Ian Gardner Carlos A Leal Henrique C Figueiredo Eduardo Cunha Vitor Salvador P Gonçalves Google Marina K Delphino Georgia D Roriz Ian Gardner Carlos A Leal Henrique C Figueiredo Eduardo Cunha Vitor Salvador P Gonçalves Google Scholar Marina K Delphino Georgia D Roriz Ian Gardner Carlos A Leal Henrique C Figueiredo Eduardo Cunha Vitor Salvador P Gonçalves PubMed Marina K Delphino Georgia D Roriz Ian Gardner Carlos A Leal Henrique C Figueiredo Eduardo Cunha Vitor Salvador P Gonçalves Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. 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