Disease Surveillance Flashcards
Recognise the goals for, and purpose of, wildlife disease surveillance schemes
Conservation: • They can impact population numbers • They may lead to extinction risk • A key factor of translocations • There are emerging threats • Illegal trade / persecution
Ecosystem health:
• Climate change is exacerbating problems
• Chemical contamination
Wild animal welfare:
• Anthropogenic causes?
• Large numbers affected
Human health
• Wildlife can be a source of human infection
• E.g. West Nile Virus carried by mosquitoes
Protecting domestic animals
• Wildlife can be a source of domestic animal infection
• E.g. foot and mouth from buffalo to cattle
• Effects trade
Critically evaluate the methods of detecting diseased wild animals
- Routine submission to laboratories
- Examinations of dead animals
- Detection dependent on volunteers – issues
- Bias (convenience sampling is not random) - motivation, human-animal distribution, small population size, size of species, behaviour, disease progression, vast majority not found
Critically evaluate the information that can be gathered from wildlife disease surveillance
Detect new entities, monitor endemic disease spatially and temporally, confirming presence or absence, early detection of pathogens, find results of an intervention
HOWEVER: Cannot infer disease impact, difficult to determine prevalence or incidence
BUT: Improving technology
Critically appraise a plan for a new, or revised, wildlife disease surveillance scheme
AN IDEAL SCHEME:
• investigate all Classes of animals
• clinical and post-mortem investigations
• species standard protocols for analyses
• database
• team of trained professionals
• extensive service laboratories
• mobile reactive investigation team
• links with research on ecology of disease
CONCLUSIONS
• Non-random, convenience, biased samples require careful interpretation
• Surveillance provides information on new disease entities and temporal and spatial changes in existing diseases
Assess the potential benefits and limitations of citizen science reporting networks for wildlife disease surveillance and give examples of how these methods can be optimised.
Benefits to public:
• Science education
• Engagement with nature
• Optimise habitat management for disease prevention
Benefits to science:
• Ability to undertake large-scale surveillance
Opportunistic schemes:
Ad hoc reports of morbidity and mortality & Ad hoc post-mortem examinations
• Variable temporal and geographical observer effort
• Relative over-reporting of charismatic species
• Detection bias – body size, colour/cryptic, habitat type
• Bias towards incidents of “unknown” cause
• Reporting after the event – reduced chance of obtaining meaningful information/ samples
• Unknown impact of disease on wildlife populations
• Limited conclusions
Minimise through expert verification of data
Describe the meaning of the term ‘emerging infectious disease’ (EID), being classified as disease caused by a novel pathogen, or a known pathogen in a new host, location or at increasing occurrence.
Emerging infectious diseases (EIDs) - ‘diseases caused by novel pathogens or known pathogens affecting new host populations, with increased incidence or extended geographic range’
They represent a threat to geographically restricted and critically endangered species as well as common and widely distributes species
Recognise that EIDs have the potential to cause rapid declines of common wildlife species over a wide geographical area within a short time frame and be able to illustrate this understanding with specific wild bird examples.
Garden bird disease
• Parasitic – Trichomonas gallinae (canker)
• Viral – Avian poxvirus
• Bacterial – Salmonella Typhimurium
Explain how the population impact of an EID might be quantified in principle, for example through integrated analysis of long-term population monitoring datasets and disease surveillance.
> Opportunistic surveillance:
• Ad hoc reporting
• Maximum potential observer coverage
• Ability to detect novel incidents
> Systematic surveillance: • BTO Garden BirdWatch • Weekly monitoring year-round • Species distribution & abundance • Observation of sick/ dead birds
> PM examinations: • Scanning (or general) surveillance rather than targeted • Infectious & non-infectious disease • Standardised examination protocols • Case definitions • Incident definitions • Passive reporting method
Define diagnostic test characteristics (sensitivity and specificity)
Sensitivity:
• Ability of a test to correctly detect diseased individuals
• Proportion of diseased individuals that test positive
• “If an animal has the disease, what is the probability that it will test positive?”
Specificity:
• Ability of a test to correctly detect non-diseased individuals
• Proportion of non-diseased individuals that test negative
• “If an animal does not have the disease, what is the probability that it will test negative?”
Explain the effect of imperfect tests on prevalence estimations
sensitivity and specificity need to be incorporated into the calculation
Overestimation and underestimation
Explain the effect of prevalence on test accuracy
Changes in prevalence influence the extent of overestimation due to imperfect reference standard classification
Diagnostic accuracy is affected by the disease prevalence. With the same sensitivity and specificity, the diagnostic accuracy of a particular test increases as the disease prevalence decreases.
Explain how different diagnostic tests can be combined to improve accuracy
Can:
Interpret in parallel: animal considered to have the disease if any of the tests are positive
- Disease is less likely to be missed but false positives are more likely
- Se increases
- Sp decreases
- PPV decreases
- NPV increases
Interpret in series: animal considered to have disease if all tests are positive
- Disease is more likely to be missed but false positives are less likely - Se decreases - Sp increases - PPV increases - NPV decreases
Amphibians can suffer from the same range of types of infectious diseases as other taxa:
Diseases caused by viral, bacterial, fungal, protozoan, metazoan pathogens.
Key pathogens of amphibians include:
Batrachochytrium spp. chytrid fungi, ranaviruses, Pseudocapillaroides xenopi, Ribeiroia ondatrae, SPI
Ranaviral disease can cause:
Explosive outbreaks of fatal disease characterised by internal haemorrhaging of adult or larval amphibians or can cause longer-term lower incidence outbreaks characterised by skin ulceration and limb necrosis.
only asscoiated with pop declines in 2 cases (uk and spain)
climate change likely to exacrebate outbreaks
Batrachochytrium dendrobatidis, Batrachochytrium salamandrivorans and ranaviruses are the only pathogens known to:
Cause long-term amphibian population declines; B. dendrobatidis is by far the most important infectious cause of amphibian declines globally
How to diagnose chytridiomycosis and B. dendrobatidis infection (and being able to differentiate between the two).
A diagnosis of chytridiomycosis rather than solely Bd presence includes consideration of whether clinical signs are present. Laboratory examination of carcasses is recommended where skin swabs from the ventral abdomen, thighs, and digits, alongside skin samples of the ventral abdomen are collected to carry out a duplex real-time PCR test (qPCR) that can detect and differentiate both Bd ad Bsal.
Dissecting toe tips and multiple small rectangles from the ventral abdomen of each carcass and staining allows for histological examination. Identification of sporangia within the tissues under a microscope can diagnose chytridiomycosis rather than simply identifying a Bd infection as a qPCR resembles. Histology also shows inactive infections if empty sporangia are observed, which can aid understanding of disease transmission in terms of spatio-temporal patterns. Classifying the severity of chytridiomycosis via histology allows one to determine whether it was the cause of mortality rather than toxins or other environmental pressures.
true diagnosis of chytridiomycosis disease requires histopathologic examination of tissues
The ecology of B. dendrobatidis and the drivers of B. dendrobatidis emergence
non-hyphal parasitic chytrid fungus
Two hypotheses:
1. Endemic disease. Emerged due to global changes (UV-B, climate, pollution) increasing virulence or decreasing host immunity
- Panzootic. Emerging due to anthropogenic introduction
Bd infection confirmed in:
• Pet trade (e.g. dendrobatid frogs)
• Food trade e.g. bullfrog farms in Uruguay & Brazil (> 1 million p.a. enter USA)
• Lab animal trade (Xenopus spp.)
• Zoo animal trade
• Introduced species e.g. bullfrogs, alpine newts
• Food trade (> 1 million bullfrogs p.a. USA)
• US official trade > 5 million live amphibians imported p.a. (majority wild caught)
• > 2500 tons of frog legs exported annually from China
Bsal is spread through the amphibian trade
Thermal Preference for bd and bsal
- B. dendrobatidis - 17-25 oC
* B. salamandrivorans - 10-20 oC
Host Range for bd and bsal
- B. dendrobatidis - possibly all amphibia
* B. salamandrivorans - newts and salamanders (& some anurans)
Distribution for bd and bsal
- B. dendrobatidis global - wherever there are amphibians
- B. salamandrivorans - SE Asia, Belgium, The Netherlands, Germany & Spain (so far)
- B. dendrobatidis - transmission only via motile zoospores
- B. salamandrivorans - motile zoospores and encysted spores
How batrachochytrids and ranaviruses are recognised as causal agents in the global amphibian decline.
They are not always conservation threats
Environment and host range can limit or exacerbate pathogen impact
Apply and demonstrate safety procedures when handling large dangerous carnivores
• Human safety comes first. Always.
• There may be times when you can’t intervene in a carnivore anaesthetic event because of human safety (i.e. induction or recovery)
• Every institution/group will have different rules
do you need a gun team member present, etc.?
– ‘shoot to kill policy’
– Other considerations for human safety…
– Risk Assessments
– Be familiar with institutional policy
Describe, identify and explain relevant equipment and anesthetic drugs commonly used for large carnivore anesthesia
• Ketamine: disassociative (2 – 5mg/kg)
– May precipitate seizures
• Medetomidine (or Xylazine): alpha-2 agonist (0.02 – 0.07mg/kg)
– Causes peripheral vasoconstriction and hypertension, reflex bradycardia
– Poor muscle relaxation
– Reverse with Atipamezole at 5X medetomidine dose
• Telazol/Zoletil (tiletamine-zolazepam): combo (4 – 8mg/kg)
– Prolonged recovery
- Midazolam: benzodiazepine, anxiolytic, muscle relaxation
- Opioid: analgesia, may cause respiratory depression
- Isoflurane gas maintenance
have an overview of spatial analysis techniques
spatial analysis: any of the formal techniques which studies entities using their geographical properties
Database > Visualization > Exploration > Modelling
understand specific characteristics of spatial data relevant to epidemiological analysis
Describing, analysing, and explaining patterns of attribute data across a map
feature data vs attribute data
vector map vs raster map
be able to describe methods used in visual analysis of spatial data
Vector maps: points to represent features
Raster maps: continuous surface of squares which each have a value
Kernel smoothing: uses point locations to produce a raster map showing weighted estimate of the density of points at any location on the map
be able to describe selected methods used for investigation of the presence of spatial clustering
Exploration involves identifying disease clusters – regions of higher risk
A cluster is an unexpected aggregation, real or perceived, of health events that are grouped together in space, or in time and space
Cluster analysis: Uses a range of cluster detection tests to determine whether the cluster is a chance occurrence or is significant.
• Global
• Local
- Non-focused, focused, space-time
Spatial scan statistic: Location, size and time of cluster
Moran’s I test: Determines whether areas of a similar attribute are grouped together
Explain how squirrelpox virus invaded as a consequence of a translocation and lead to an outbreak of infectious disease
1876 grey squirrels > South-East England because people liked the look of them
1900-1930 > epidemic disease in red squirrels as the greys were carriers and took resources
1970-now > resource competition, behavioural interactions
Critically appraise how squirrelpox viral disease was detected and how a wildlife disease surveillance scheme demonstrated temporal and spatial changes in the disease
Keymer in 1960s-1980s > investigated outbreaks with a convenience sample, evidence for greys being a reservoir • Serological survey (antibody to SQPV) • Koch’s postulates • Spatial epidemiology of SQPV disease • Model impact of SQPVdisease • (surveillance)
Critically evaluate the method through which the impact of squirrelpox virus on red squirrel populations was determined
- Manipulation of populations required?
* Scotland / England comparison provides very good circumstantial evidence
Understand the mechanics of strandings assessment and investigation in the UK
• Stranding report- what next? • Species ID • Sex ID • Carcass condition • Nutritional condition • External marks - natural? (rakemarks etc) - disease related? (tattoo lesions etc) - anthropogenic? (net marks etc) • Accessibility for recovery - safe to recover?
Understand the necropsy methodology employed in the UK and the criteria for diagnosis of a variety of drivers of mortality
- Sex identification
- Decomposition condition
- Nutritional condition
- External lesions
- Morphometric measurements
- Blubber thickness measurements
- Skin and blubber removal
- Flensing and rib removal
- Thoracic and peritoneal cavity; microbiology, virology, serology
- Necropsy process - lesions
- Necropsy process - brain removal and sampling
- Ear extraction and fixation
Understand the anthropogenic and non-anthropogenic threats that UK cetaceans face
Anthropogenic: • Bycatch • Entanglement • Ship strike • Pollutant exposure (chemical, acoustic and physical)
Non-anthropogenic:
• Inter/intraspecific aggression
• Infectious disease related mortality
Understand the criteria for diagnosing bycatch and associated pathology relative to fishery type
Bycatch:
- thin and linear cutaneous lesions
- Subcutaneous bruising
- Jaw fractures
- Stomach often full
- Aspiration pneumonia/foreign bodies
- No other lesions to explain death
Understand the range of chemical pollutants that marine mammals are exposed to and the dynamics of exposure pathways in different species
PCBs, DDTs, dieldrin, dioxins, etc.
• synthesized from mid-1940s for industrial and agricultural uses
• highly lipophilic
• environmentally persistent
• bioaccumulate in food chain
• banned in developed countries
• highest global exposure occurs in marine mammals
• range of toxicities in experimental animals
Heavy metals(Hg, Cd, Pb - most toxic)
• v. high dietary exposure in marine top predators (bioaccumulation)
• little evidence of toxicity in marine mammals
• in vivo detoxification mechanisms (e.g. Hg, Cd) in cetaceans/seals
Hydrocarbons esp. polycyclic aromatic hydrocarbons (PAHs)
• some PAHs carcinogenic (e.g. benzo[a]pyrene)
Polybrominated compounds(e.g. flame retardants)
Butyltins(e.g. TBT in anti-fouling paints)
Understand the range of potential toxic effects caused by chemical pollutant exposure (including polychlorinated biphenyls, PCBs)
– immunosuppression (e.g. increased infectious disease susceptibility)
– reproductive impairment (e.g. reduced female fecundity)
Understand the challenges associated with sampling and treating marine mammals
Constraints • Limited proximity • Stress of handling • Disturbance of rookery/haulout • Aquatic environment • Blubber layer • Dive reflex/thermoregulation • May need to intervene with treatment same time as sampling for diagnosis
Symptomatic treatment • Precautionary principle • Few pharmacokinetic studies • Effects of administration may outweigh effects of the drug • Stress of approach, handling • Impact of multiple dart needles • Injection volume • Repeated dosing hard on wild animals • Monitoring effect hard on wild animals
Understand marine mammal adaptations to aquatic life and diving
Respiratory system: larynx and blowhole
Haemoglobin rich muscles (dark red colour)
Communication - melon
Give examples of how health assessments of marine mammals can contribute to policy
- Health data are generated, published, provided to managers, shared through data sharing portals
- Date informs managers and policy makers to inform action to conserve marine mammal populations
• Laws to protect marine mammals - Protected areas - Species specific laws (Marine Mammal Protection Act, ESA etc) - Disease/lesion specific actions –> Fishery gear modifications –> Cat litter disposal
Understand the most important health issues for conservation of marine mammals
Increasing noise:
• Shipping traffic, sonar, oil and gas exploration
Changing water temperatures:
• Increased pathogen survival and transmission
• Increasing HABs
• Change in prey distribution
Increasing coastal urbanization:
• Run-off transfer terrestrial pathogens and contaminants to the marine environment
• Eutrophication - Increasing HABs
• Increasing density of domestic animals and humans enhance disease transmission
Be aware of the role of animal health practitioners in marine mammal management and policy
• Health assessment
o Epidemiologists, biologists (natural history, molecular),dog trainers, veterinarians, radiologists, dentists, engineers, statisticians
• Necropsy,
o Pathologists, knife sharpeners, physiologists, immunologists, microbiologists
• Data analysis
o Biostatisticians, modelers, epidemiologists
• Amplifying the issue
o Scientists, writers, journalists, film makers
• Agency decisions
o Government staff, lawyers, NGO lobbyists
Understand the most important issues to address when first finding and handling a stranded dolphin
- Ensure blow hole and eyes are clear of mud/water
- Put animal in ventral recumbency
- Dig holes in sand for pectoral flippers
- Wet skin, cover with light cloth (or umbrella!) to protect from sun
- If in water, don’t be deeper than human waist
Understand the risks and challenges of dolphin rehabilitation
Expensive – transportation and dedicated facilities
Be aware of the risks to humans when rescuing live stranded dolphins
water
caudal to dorsal fin is considered danger zone
Describe the different types of approaches that can be used for sampling
marine mammals
- Photographs (ID, lesions, photo-grammetry)
- Skin (DNA for genetics, immunohistochemistry for stress markers, biopsy of lesions, proteinomics)
- Blubber/muscle (Fat soluble contaminants, hormones, fatty acids (diet))
- Faeces (Hormones, biotoxins, pathogens)
- Urine (Leptospirosis)
- Saliva (Hormones, nutritional status, pathogens)
- Blow - Vapor or gas (hormones, pathogens, nutritional status, toxin exposure)
- Bood (Hematology, serum chemistry, hormones, immune function)
Describe the different types of approaches that can be used for anaesthetising
marine mammals
- Subcutaneous (pinnipeds - tent skin and insert needle, cetaceans - insert beneath blubber but limited space for fluid administration)
- Intramuscular (needle length > blubber thickens, remote darts, pinnipeds - gluteals, cetaceans - upper body cranial to fin)
- Intravenous
Describe the different types of approaches that can be used for treating
marine mammals
Symptomatic treatment • Precautionary principle • Few pharmacokinetic studies • Effects of administration may outweigh effects of the drug - Stress of approach, handling - Impact of multiple dart needles - Injection volume • Repeated dosing hard on wild animals • Monitoring effect hard on wild animals
Antibiotic therapy
• Antibiotic resistance increasing in bacteria from wild animals
• Antibiotic resistance ubiquitous
• Bacterial species causing infections often mixed, un-speciated
• Long acting broad spectrum preparations useful for field use
• Rehabilitation can facilitate exchange of antibiotic resistant genes
Infectious agent therapy
Vaccination
• Morbillivirus vaccination of wild Hawaiian monk seals
• Recombinant poxvirus vaccine designed for ferrets
• Serial testing in surrogate captive species
• Modelling numbers of vaccinated animals required to prevent epidemic (86% of population for herd immunity)
• Prophylactic vaccination more effective
Formulate and communicate plans for the anaesthetic induction of large carnivores
• Manual capture and restraint:
– Obviously, only appropriate for small species
• Trained behaviour:
– Hand injection via trained behaviour
- Dart gun, blow pipe, syringe pole…
- Gas induction; less than ideal, only in small animals
- Other?
- Debrief team before starting procedure
- Administer drugs (dart or hand injection)
- Wait 10 – 15 minutes without stimulating animal
- Check depth of anaesthesia BEFORE opening enclosure
- Do not touch animal until you’re certain it’s safely immobilized
- Work quickly, quietly and efficiently, everyone should know their task in advance
- Have an escape route and an emergency plan BEFORE you get started
• Animal in lateral recumbency with head/neck extended
– vs. ruminants (sternal recumbency with head pointeddown)
– Cover eyes, consider ear plugs, minimize stimulation andnoise
Formulate and communicate plans for the anaesthetic maintenance of large carnivores
• Ideally, intubated with supplemental isoflurane and oxygen as needed
• Ideally, IV catheter placed and fluids running
- IV access in the event of an emergency
- Nasal insufflation (or mask) supplemental oxygen if not intubated
- Monitoring consistently throughout until procedure is complete
- Record findings on anaesthetic sheet
- Monitor for trends!
Formulate and communicate plans for the anaesthetic monitoring of large carnivores
- Response to stimuli
- Palpebral reflex, jaw tone, corneal reflex, globe position, ear twitch, toe pinch
- Airway
- Breathing
- Circulation
- Measure a TPR: Temperature, Pulse, Respiration
Performed AT LEAST every 5 minutes and recorded on anaesthetic record:
• Mucous membrane colour and capillary refill time (CRT), pulse rate and quality
• Rectal/Esophageal Temperature
• Heart Rate (and rhythm)
• Respiratory Rate and Depth
• Pulse oximetry: haemoglobin saturation of oxygen
• Blood pressure
• Capnography
• Anaesthetic depth
• EKG: heart rate and rhythm
• Blood Gas Analysis
Formulate and communicate plans for the anaesthetic recovery of large carnivores
• Is the environment safe and tidy?
• Have you removed all of your equipment, trash, sharps,
- darts, etc.?
• Are all personnel out of the way and the area secured?
• Make sure animal is stable, extubate, remove iv
- catheters, machines, etc. (consider positioning)
- Administer reversal agent
- Leave and secure area immediately
- Monitor animal breathing from behind secure barrier
Formulate and communicate plans for the preparation of anaesthesia of large carnivores
Preparation
• Fasted overnight, vomiting is common upon anaesthetic induction
• Animal must be separated from others and in a secure, safe location, ideally a small den
Plan
• Risk vs. Benefit analysis; why are we doing this procedure?
- Anaesthesia carries with it the risk of death!
• Who is in charge? Veterinarian
• Exactly what you’re going to do
- Priority of tasks/samples, etc.
• Exactly how you are going to do it
- Step by step
- Everyone has specific tasks
- Have equipment organized, checklists in place
- Work quickly, quietly, efficiently
