Validity and reliability of State-Trait Anxiety Inventory in Danish women aged 45 years and older with abnormal cervical screening results.

BACKGROUND: State Trait Anxiety Inventory (STAI) scale was developed in the 1980's and has been widely used both in clinical settings and in research. However the Danish version of STAI has not been validated. The aim of this study was to assess the validity and reliability of STAI - state anxiety scale in Danish women aged 45 years and older with abnormal cervical cancer screening results. METHODS: Women ≥45 years referred with an abnormal cervical cytology and healthy volunteers (n = 12) underwent cognitive interview after completing STAI. Further, STAI was sent out in an electronic questionnaire to women (n = 109) seen at the gynecological department with abnormal cervical cancer screening test during 2018. Validity and reliability of STAI was evaluated according to the Consensus-based Standards for the selection of health Measurement Instruments (COSMIN) checklist by examining internal consistency, test-retest reliability, measurement error, floor and ceiling, construct validity and content validity. RESULTS: In the cognitive interviews the content validity was evaluated to be very good. The internal consistency of the scale was excellent with Cronbach's α = 0.93. Test-retest reliability was good with an intra-class correlation coefficient of 0.80 and the systematic difference between test-retest results was negligible. The construct validity was good. CONCLUSION: To our best knowledge, this is the first validation study of the Danish translation of STAI-state anxiety scale. This version of STAI demonstrates an acceptable reliability and validity when used in a gynecological setting.

Connectivity-based risk ranking of infectious salmon anaemia virus (ISAv) outbreaks for targeted surveillance planning in Canada and the USA.

Infectious salmon anaemia (ISA) can be a serious viral disease of farmed Atlantic salmon (Salmo salar). A tool to rank susceptible farms based on the risk of ISA virus (ISAv) infection spread from infectious farms after initial incursion or re-occurrence in an endemic area, can help guide monitoring and surveillance activities. Such a tool could also support the response strategy to contain virus spread, given available resources. We developed a tool to rank ISAv infection risks using seaway distance and hydrodynamic information separately and combined. The models were validated using 2002-2004 ISAv outbreak data for 30 farms (24 in New Brunswick, Canada and 6 in Maine, United States). Time sequence of infection spread was determined from the outbreak data that included monthly infection status of the cages on these farms. The first infected farm was considered as the index site for potential spread of ISAv to all other farms. To assess the risk of ISAv spreading to susceptible farms, the second and subsequent infected farms were identified using the farm status in the given time period and all infected farms from the previous time periods. Using the three models (hydrodynamic only, seaway-distance, and combined hydrodynamic-seaway-distance based models), we ranked susceptible farms within each time interval by adding the transmission risks from surrounding infected farms and sorting them from highest to lowest. To explore the potential efficiency of targeted sampling, we converted rankings to percentiles and assessed the model's predictive performance by comparing farms identified as high risk based on the rank with those that were infected during the next time interval as observed in the outbreak data. The overall predictive ability of the models was compared using area under the ROC curve (AUC). Farms that become infected in the next period were always within the top 65% of the rank predicted by our models. The overall predictive ability of the combined (hydrodynamic-seaway-distance based model) model (AUC = 0.833) was similar to the model that only used seaway distance (AUC = 0.827). Such models can aid in effective surveillance planning by balancing coverage (number of farms included in surveillance) against the desired level of confidence of including all farms that become infected in the next time period. Our results suggest that 100% of the farms that become infected in the next time period could be targeted in a surveillance program, although at a significant cost of including many false positives.

Expert Elicitation Provides a Rapid Alternative to Formal Case-Control Study of an H7N9 Avian Influenza Outbreak in the United States.

An expert elicitation was staged to rapidly decipher plausible routes and risks of pathogen transmission in the 2017 H7N9 avian influenza (AI) outbreak in the four-state region of Tennessee, Alabama, Georgia, and Kentucky. The process included the identification of risk factors found in a preponderance of commercial broiler breeder case farms over matched controls and an opinion-based weighting of risks and mitigations perceived influential to this outbreak. Although the two highly pathogenic AI case farms had general location and company ownership in common, obvious connections were lacking for the remainder of H7N9-infected (all low pathogenicity) commercial farms. Expert elicitation of differences between known cases and controls suggested a key role for environmental rather than lateral (business network) pathways in the distribution of low pathogenicity AI across commercial broiler breeder operations. Factors with greatest strength as predictors of disease, whether or not they were causal, included mesopredator or rodent incursions, enclosure defects, and habitat disturbance that might attract wildlife to the farm (e.g., feed spills and vacating of neighboring properties). Business affiliations that may have facilitated farm-to-farm transfer, in contrast, were limited. Biosecurity standards varied across this study group but were no more or less stringent among cases over controls. However, results from a parallel hypothetical scenario staged to address field data gaps suggest that uniformity and consistency in the implementation of biosecurity practices may impact risk of disease introduction. Importantly, this study was conducted within a few weeks and with little disruption to emergency response activities. As such, the approach offers an alternative model for interim field investigation of new or emerging high-consequence diseases with immediate decision support needs.

A systematic surveillance programme for infectious salmon anaemia virus supports its absence in the Pacific Northwest of the United States.

In response to reported findings of infectious salmon anaemia virus (ISAV) in British Columbia (BC), Canada, in 2011, U.S. national, state and tribal fisheries managers and fish health specialists developed and implemented a collaborative ISAV surveillance plan for the Pacific Northwest region of the United States. Accordingly, over a 3-1/2-year period, 4,962 salmonids were sampled and successfully tested by real-time reverse-transcription PCR. The sample set included multiple tissues from free-ranging Pacific salmonids from coastal regions of Alaska and Washington and farmed Atlantic salmon (Salmo salar L.) from Washington, all representing fish exposed to marine environments. The survey design targeted physiologically compromised or moribund animals more vulnerable to infection as well as species considered susceptible to ISAV. Samples were handled with a documented chain of custody and testing protocols, and criteria for interpretation of test results were defined in advance. All 4,962 completed tests were negative for ISAV RNA. Results of this surveillance effort provide sound evidence to support the absence of ISAV in represented populations of free-ranging and marine-farmed salmonids on the northwest coast of the United States.

Area contact networks and the spatio-temporal spread of infectious salmon anemia virus (ISAV) in Chile.

Area management, the coordination of production and biosecurity practices across neighboring farms, is an important disease control strategy in aquaculture. Area management in aquaculture escalated in prominence in response to outbreaks of infectious salmon anemia (ISA) internationally. Successes in disease control have been attributed to the separation achieved through area-level synchronized stocking, fallowing, movement restrictions, and fomite or pest control. Area management, however, is costly; often demanding extra biosecurity, lengthy or inconveniently timed fallows, and localization of equipment, personnel, and services. Yet, this higher-order organizational structure has received limited epidemiologic attention. Chile's National Fisheries and Aquaculture Service instigated area management practices in response to the 2007 emergence of ISA virus (ISAV). Longitudinal data simultaneously collected allowed retrospective evaluation of the impact of component tenets on virus control. Spatiotemporal analyses identified hydrographic linkages, shared ports, and fish transfers from areas with recent occurrence of ISAV as the strongest predictors of virus spread between areas, though specifics varied by ISAV type (here categorized as HPR0 for the non-virulent genotypes, and HPRv otherwise). Hydrographic linkages were most predictive in the period before implementation of enhanced biosecurity and fallowing regulations, suggesting that viral load can impact spread dynamics. HPR0 arose late in the study period, so few HPRv events were available by which to explore the hypothesis of HPR0 as progenitor of outbreaks. However, spatiotemporal patterns in HPRv occurrence were predictive of subsequent patterns in HPR0 detection, suggesting a parallel, or dependent, means of spread. Better data precision, breadth and consistency, common challenges for retrospective studies, could improve model fit; and, for HPR0, specification of diagnostic test accuracy would improve interpretation.

Enteric outbreak surveillance in British Columbia, 2009-2013.

BACKGROUND: Understanding enteric disease outbreak sources, burden of illness, mode of transmission and use of interventions informs planning, policy development and prevention programs. OBJECTIVE: To describe trends in enteric disease outbreaks investigated in British Columbia (BC) between 2009 and 2013. METHODS: An analysis was conducted of enteric disease outbreaks that had been entered into a national, secure web-enabled outbreak reporting system using the Canadian Network for Public Health Intelligence (CNPHI) and investigated in BC between January 1, 2009 and December 31, 2013. The data included information on pathogen, number of cases, hospitalizations, deaths, setting, mode of transmission, source, factors that contributed to the outbreak and interventions. Residential facility-based viral outbreaks and outbreaks associated with international travel were excluded. RESULTS: There were 104 outbreaks investigated in BC between 2009 and 2013. Ninety-three were reported by BC organizations and 11 were national outbreak investigations reported by the Public Health Agency of Canada (PHAC). There was an average of 21 outbreaks per year. Overall, the annual rate of foodborne outbreaks in BC was 2.8 per one million population. Seventy-nine (76%) outbreaks had a pathogen identified, most commonly norovirus, Salmonella and E. coli. There was a total of 108 hospitalizations (3.8% of all cases) and two deaths (0.1% of all cases); one caused by botulism, the other by E. coli O157. Food service establishments were the most common setting (33.7%), followed by the community (24.0%) and private functions (12.5%). The food types most often reported were fruits and vegetables, meat and seafood. The data showed a pathogen-food source combination between Salmonella and eggs. CONCLUSION: This is the first publication summarizing trends in enteric disease outbreaks in BC including assessing sources, burden and interventions. Ongoing reporting and analysis of outbreak data in BC will allow for improved assessment of trends in sources and pathogens over time and further understanding of the effectiveness of interventions associated with outbreaks.

Vulval cancer and HPV vaccination in recurrent disease.

KEY CLINICAL MESSAGE: A woman diagnosed with a recurrent vulval carcinoma after initial treatment with radiochemotherapy is presented. After three additional relapses she was vaccinated with Gardasil. She has had no relapses in her vulvar area for 39 months and an overall progression-free survival of almost 24 months.

Risk factors perceived predictive of ISA spread in Chile: applications to decision support.

Aquaculture is anticipated to be a critical element in future solutions to global food shortage. However, diseases can impede industry efficiency and sustainability. Consequently, diseases can and have led to dramatic re-structuring in industry or regulatory practices. The emergence of infectious salmon anemia (ISA) in Chile is one such example. As in other countries, many mitigations were instituted universally, and many incurred considerable costs as they introduced a new layer of coordination of farming activities of marine sites within common geographic areas (termed 'neighborhoods' or 'barrios'). The aggregate response led to a strong reduction in ISA incidence and impact. However, the relative value of individual mitigations is less clear, especially where response policies were universally applied and retrospective analyses are missing 'controls' (i.e., areas where a mitigation was not applied). Further, re-focusing policies around disease prevention following resolution of an outbreak is important to renew sustainable production; though, again, field data to guide this shift in purpose are often lacking. Expert panels can offer timely decision support in the absence of empirical data. We convened a panel of fish health experts to weight risk factors predictive of ISA virus (ISAV) introduction or spread between Atlantic salmon barrios in Chile. Barrios, rather than sites, were the unit of interest because many of the new mitigations operate at this level and few available studies examine their efficacy. Panelists identified barrio processing plant biosecurity, fallowing strategies, adult live fish transfers, fish and site density, smolt quality, hydrographic connection with other neighborhoods, presence of sea lice (Caligus rogercresseyi), and harvest vessel biosecurity as factors with the greatest predictive strength for ISAV virulent genotype ('HPR-deleted') occurrence. Fewer factors were considered predictive of ISAV HPR0 genotype ('HPR0') occurrence, with greatest strengths assigned to fish and site density, adult live fish transfers, and smolt facility HPR0 status. Field validation based on ISAV and risk factor occurrence after panel completion generally supports expert estimates, and highlights a few factors (e.g., broodstock HPR0 status) less conclusive in the original study. Results inform legislation, industry best management practices and surveillance design.

Viral hemorrhagic septicemia IVb status in the United States: inferences from surveillance activities and regional context.

The United States (U.S.) response to viral hemorrhagic septicemia virus (VHSV) IVb emergence in the Laurentian Great Lakes (GL) included risk-based surveillance for cost-effective decision support regarding the health of fish populations in open systems. All U.S. VHSV IVb isolations to date derive from free-ranging fish from GL States. Most originate in the region designated by US Geological Survey hydrologic unit code (HUC) 04, with the exception of two detections in neighboring Upper Mississippi (HUC 05) and Ohio (HUC 07) regions. For States outside the GL system, disease probability was assessed using multiple evidence sources. None substantiated VHSV IVb absence using surveillance alone, in part due to the limited temporal relevance of data in open systems. However, Bayesian odds risk-based analysis of surveillance and population context, coupled with exclusions where water temperatures likely preclude viral replication, achieved VHSV IVb freedom assurance for 14 non-GL States by the end of 2012, with partial evidence obtained for another 17 States. The non-GL region (defined as the aggregate of 4-digit HUCs located outside of GL States) met disease freedom targets for 2012 and is projected to maintain this status through 2016 without additional active surveillance. Projections hinge on continued basic biosecurity conditions such as movement restrictions and passive surveillance. Areas with navigable waterway connections to VHSV IVb-affected HUCs (and conducive water temperatures) should receive priority for resources in future surveillance or capacity building efforts. However, 6 years of absence of detections in non-GL States suggests that existing controls limit pathogen spread, and that even spread via natural pathways (e.g., water movement or migratory fish) appears contained to the Great Lakes system. This report exemplifies the cost-effective use of risk-based surveillance in decision support to assess and manage aquatic animal population health in open systems.

Proposed terms and concepts for describing and evaluating animal-health surveillance systems.

The information provided by animal-health surveillance helps to reduce the impact of animal diseases. The widespread movement of animals and their products around the world results in an increasing risk that disease will spread. There is, therefore, a need for exchange between countries of comparable information about disease incidence; the exchange must be based on a common understanding of surveillance approaches and how surveillance systems are designed and implemented. Establishing agreed-upon definitions of surveillance terms would be a first step in achieving this standardisation, and will enhance transparency and confidence. To this end, a workshop was held with the aim of agreeing upon key terms and concepts for animal-health surveillance. In this paper, we describe the methods used at the workshop and summarise the discussions. A complete list of all the proposed definitions including lists of characteristics that can be used to describe surveillance activities and attributes for evaluation of surveillance is available in the workshop report (available at http://www.defra.gov.uk/ahvla-en/disease-control/surveillance/icahs-workshop/). Some important issues were highlighted during these discussions; of particular note was the importance of economic efficiency as an evaluation attribute. Some remaining inconsistencies in the proposed use of terms are highlighted (including the definition of 'risk-based surveillance' and the use of the term 'event-based surveillance').

Integrating expert judgment in veterinary epidemiology: example guidance for disease freedom surveillance.

Expert opinions supplement empirical data in many epidemiologic assessments. For veterinary disease freedom surveillance, where the geographic scope of concern is often broad, populations subject to change, decisions eminent and empirical data, expert opinion can be a critical component of the decision making process. However, opinion is by definition subjective and the manner in which opinion is sought can impact the quality and reliability of estimates. Group interaction can hinder or improve the estimation process, depending on its facilitation. Further, whether and how validation is conducted can limit or increase acceptance of the resulting model. While the utility of expert opinion is widely recognized in many fields, and the impact of its use or misuse implicit, standards for application to veterinary assessments are not readily available. This paper aims to foster discussion on this influential component of epidemiology, with disease freedom application as a focus. Benefits and concerns attributed to expert judgment and guidelines for its structured elicitation are described, borrowing insights from its long history of use in decision science fields and examples from recent veterinary assessments.

Reducing delirium in elderly patients with hip fracture: a multi-factorial intervention study.

BACKGROUND: There is an evident need for improved management of elderly patients with trauma in order to avoid common and troublesome complications such as delirium. The aim of this study was to investigate whether an implementation of a multi-factorial program including intensified pre-hospital and perioperative treatment and care could reduce the incidence of delirium in elderly patients with hip fracture, cognitively intact at admission to the hospital. In addition, we explored the factors that characterize patients who developed delirium. METHODS: A prospective, quasi-experimental design was used. A total of 263 patients with hip fracture (> or = 65 years), cognitively intact at admission, were consecutively included between April 2003 and April 2004. On 1 October 2003, a new program was introduced. All patients were screened for cognitive impairment within 30 min after admission to the emergency department using The Short Portable Mental Status Questionnaire (SPMSQ). To screen for delirium, patients were tested within 4 h of admission and thereafter daily, using the Organic Brain Syndrome scale. RESULTS: The number of patients who developed delirium during hospitalization was 74 (28.1%), with a decrease from 34% (45 of 132) in the control group to 22% (29 of 131) in the intervention group (P=0.031). Patients who developed delirium were statistically older, more often had > 4 prescribed drugs at admission and scored less well in the SPMSQ test. CONCLUSION: The use of a multi-factorial intervention program in elderly hip fracture patients, lucid at admission, reduced the incidence of delirium during hospitalization by 35%.

Combining surveillance and expert evidence of viral hemorrhagic septicemia freedom: a decision science approach.

The ability to combine evidence streams to establish disease freedom or prioritize surveillance is important for the evaluation of emerging diseases, such as viral hemorrhagic septicemia virus (VHSV) IVb in freshwater systems of the United States and Canada. Waterways provide a relatively unconstrained pathway for the spread of VHSV; and structured surveillance for emerging disease in open systems has many challenges. We introduce a decision framework for estimating VHSV infection probability that draws from multiple evidence streams and addresses challenges associated with the assessment of emerging disease. Using this approach, historical and risk-based evidence, whether empirical or expert-derived, supplement surveillance data to estimate disease probability. Surveillance-based estimates of VHSV prevalence were described using beta distributions. Subjective likelihood ratios (LRs), representing contextual risk, were elicited by asking experts to estimate the predicted occurrence of risk factors among VHSV-affected vs. VHSV-unaffected watersheds. We used the odds form of Bayes' theorem to aggregate expert and surveillance evidence to predict the risk-adjusted posterior probability of VHSV-infection for given watersheds. We also used LRs representing contextual risk to quantify the time value of past surveillance data. This evidence aggregation model predicts disease probability from the combined assessment of multiple sources of information. The method also provides a flexible framework for iterative revision of disease freedom status as knowledge and data evolve.

ADHD in adult psychiatry. Minimum rates and clinical presentation in general psychiatry outpatients.

The objective of the study was to determine the prevalence and comorbidity of persisting attention-deficit hyperactivity disorder (ADHD) in adult psychiatric outpatients. Consecutive patients, first visits excluded, at a general psychiatric outpatient clinic were offered a screening for childhood ADHD with the Wender Utah Rating Scale (WURS). One hundred and forty-one patients out of 398 (35%) completed and returned the scale. Patients above or near cut-off for ADHD (n=57) were offered an extensive clinical evaluation with psychiatric as well as neuropsychological examination. The attrition was analysed regarding age, sex and clinical diagnoses. Out of the screened sample, 40% had scores indicating possible childhood ADHD. These 57 patients were invited to the clinical part of the study, but 10 declined assessment, leaving 47 (37 women and 10 men) who were actually examined. Thirty of these (21 women and nine men) met diagnostic criteria for ADHD at the time of examination. Among the patients with ADHD, affective disorders were the most common psychiatric diagnoses. The rate of alcohol and/or substance abuse, as noted in the medical records, was also high in the ADHD group. In the WURS-screened group, 22% (30 patients assessed as part of this study and one person with ADHD previously clinically diagnosed) were shown to have persisting ADHD. Therefore, it is clearly relevant for psychiatrists working in general adult psychiatry to have ADHD in mind as a diagnostic option, either as the patient's main problem or as a functional impairment predisposing for other psychiatric disorders.

Estimating diagnostic test accuracy for infectious salmon anaemia virus in Maine, USA.

Infectious salmon anaemia virus (ISAV) is a pathogen of consequence to farmed Atlantic salmon, Salmo salar L. ISA control centres on active surveillance for early detection by reverse transcription polymerase chain reaction (RT-PCR), indirect fluorescent antibody assay (IFAT) and virus isolation. Because diagnostic test performance varies among populations and laboratories, the Office International des Epizooties (OIE) recommends an evaluation of test accuracy in each region of use. This is complicated in Maine, USA by the co-existence of ISAV genotypes homologous to North American (NA) and European (EU) isolates. While NA ISAV genotypes isolated in Maine are characterized by high morbidity and mortality, the single EU genotype in Maine has not yet been linked to disease or isolated by cell culture. Consequently, distinguishing among genotypes is critical to infection response. Accuracy in NA genotype detection was estimated from ISA surveillance data using latent class models. Results suggested that RT-PCR is an excellent screening test for NA ISAV genotypes in Maine, although probably with reduced specificity in the presence of EU genotypes. IFAT, in contrast, was a poor screening test for detection of ISAV in Maine, although it may be useful in confirmation of NA genotypes during disease outbreaks.

The effects of different bill-trimming methods on the well-being of Pekin ducks.

Pekin ducks are often bill-trimmed to prevent feather pecking and cannibalism, but this practice has been criticized because of the resulting potential for acute and chronic pain. The goal of this experiment was to compare 2 different bill-trimming methods, hot blade trimming with cautery (TRIM) and cautery only (tip-searing; SEAR), on the behavior, bill morphology, and weight gain of Pekin ducks. Ducklings (n = 192, 96 per sex) were trimmed at the hatchery and assigned to 12 floor pens (3.66 x0.91 m) by treatment. Behavior was evaluated by scan sampling, and plumage condition was scored using a 0 to 3 scoring system. Thirty-six ducks were randomly euthanized at 3 and 6 wk of age, and their bills were collected for examination. Following fixation and decalcification, the bills were embedded in paraffin wax and sectioned longitudinally. Alternate sections were stained with hematoxylin and eosin and Masson's trichrome for the connective tissues, and with Bielschowsky's silver impregnation, Bodian's staining, and Holmes' staining for the nerve fibers. Trimmed ducks engaged in fewer bill-related behaviors and rested more than untrimmed ducks (NOTRIM) during the first 2 wk posttrim. Ducks in the SEAR and NOTRIM groups showed similar patterns of weight gain, but those in the TRIM group had a lower rate of gain than ducks in the SEAR group during the first week posttrim and had a lower rate of gain than those in the NOTRIM group for 2 wk posttrim. Feather scores of ducks in the NOTRIM group were significantly worse than those in the TRIM or SEAR group by 18 d, and scores continued to deteriorate at a greater rate than those of trimmed ducks throughout the study. Both trimming methods caused connective tissue proliferation in the bill stumps, but the TRIM method caused thicker scar tissue than the SEAR method. No neuromas were found with either trimming method, but there were more nerve fibers in bill stumps of the SEAR ducks than the TRIM ducks. These results suggest that acute pain is associated with both trimming methods, but that SEAR may be a preferable method, causing less check in weight gain and fewer bill morphological changes while still being effective in minimizing feather pecking damage.

Attempts to improve absolute quantification of cerebral blood flow in dynamic susceptibility contrast magnetic resonance imaging: a simplified T1-weighted steady-state cerebral blood volume approach.

BACKGROUND: Attempts to retrieve absolute values of cerebral blood flow (CBF) by dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) have typically resulted in overestimations. PURPOSE: To improve DSC-MRI CBF estimates by calibrating the DSC-MRI-based cerebral blood volume (CBV) with a corresponding T1-weighted (T1W) steady-state (ss) CBV estimate. MATERIAL AND METHODS: 17 volunteers were investigated by DSC-MRI and 133Xe SPECT. Steady-state CBV calculation, assuming no water exchange, was accomplished using signal values from blood and tissue, before and after contrast agent, obtained by T1W spin-echo imaging. Using steady-state and DSC-MRI CBV estimates, a calibration factor K = CBV(ss)/CBV(DSC) was obtained for each individual. Average whole-brain CBF(DSC) was calculated, and the corrected MRI-based CBF estimate was given by CBF(ss) = K x CBF(DSC). RESULTS: Average whole-brain SPECT CBF was 40.1+/-6.9 ml/min x 100 g, while the corresponding uncorrected DSC-MRI-based value was 69.2+/-13.8 ml/min x 100 g. After correction with the calibration factor, a CBF(ss) of 42.7+/-14.0 ml/min x 100 g was obtained. The linear fit to CBF(ss)-versus-CBF(SPECT) data was close to proportionality (R = 0.52). CONCLUSION: Calibration by steady-state CBV reduced the population average CBF to a reasonable level, and a modest linear correlation with the reference 133Xe SPECT technique was observed. Possible explanations for the limited accuracy are, for example, large-vessel partial-volume effects, low post-contrast signal enhancement in T1W images, and water-exchange effects.

Spatial and non-spatial risk factors associated with cage-level distribution of infectious salmon anaemia at three Atlantic salmon, Salmo salar L., farms in Maine, USA.

The distribution of infectious salmon anaemia (ISA) was examined among 80 cages from three Atlantic salmon grow-out farms in Maine, USA that were stocked with smolts from a single hatchery. Cage-level disease was broadly defined as one or more moribund fish testing positive for infectious salmon anaemia virus (ISAV) by RT-PCR and a second confirmatory test (IFAT, culture or genotype sequence). Spatio-temporal and cage-level risks were explored using logistic regression and survival analysis. Non-spatial risk factors associated with ISA, or shortened survival time to disease, included increased predation, trucking company choice for smolt transfers, a finely-sedimented benthic substrate, and smaller average size of smolts at stocking. Univariable analysis identified the time-dependent spatial factor 'adjacency to newly infected cages' to be predictive of new infection in neighbouring cages 11-12 weeks later. However, none of the spatial factors, or their lags retained relevance in multiple-variable models. The results suggest a diffuse distribution of virus exposure throughout infected sites, with host-susceptibility factors probably influencing disease manifestation in individual cages. The narrow focus of the current study may limit application of the findings to other sites and year-classes. However, these data support the relevance of husbandry efforts to optimize fish health in regions affected by ISAV.

Hydrographics and the timing of infectious salmon anemia outbreaks among Atlantic salmon (Salmo salar L.) farms in the Quoddy region of Maine, USA and New Brunswick, Canada.

Infectious salmon anemia (ISA) has caused severe morbidity and mortality in farmed Atlantic salmon in North America, Norway, Scotland and the Faroe Islands. The Quoddy region of Maine, United States of America (USA), and New Brunswick (NB), Canada is characterized by extensive tidal mixing and close proximity between farms. This region is also prone to recurrent appearances of ISA, though control measures limit disease spread and severity on infected farms. We conducted a retrospective longitudinal analysis of the apparent impact of hydrographics on the incidence and timing of ISA outbreaks on Atlantic salmon (Salmo salar L.) farms in the Quoddy region from May 2002 to August 2004. A time-series cross-sectional regression of 32 farms over 28 months demonstrated a limited, but statistically significant, spatio-temporal clustering of ISA outbreaks linked hydrographically. New outbreaks correlated temporally with those occurring on-site 1 and 3 months prior, and those occurring within one tidal-excursion upstream the same month. Other risk factors included holdover of previous year-class fish, wharf sharing, and possibly harvests of cages infected in previous months. Conclusions suggest that tidal dispersion does play a role in ISAV transmission in the Quoddy region. Dispersal of free virus and/or tidal distribution of lice or other hydrographically influenced vectors or fomites could all contribute to the spatio-temporal patterns described.