Diseases of Wildlife Flashcards
What is a risk assessment
Calculate quantitatively or qualitatively
prob hazard occurs
magnitude of harm
- concequences of affected species, ecosystem and economy
- probability of trasfer
- exposure of suseptible species
Defining impact of disease on:
Biodiversity
Agriculture
Public Health
mechanisms of disease emergence
Loss/changes of biodiversity
contact with new hosts
expansion of vectors
alteration to environmental phases of lifecycles
host compromise
How does ecosystem health drive disease?
Land use
climate change
shifts in:
- host/resovior/ vector (distribution, resiliance & interactions)
- Pathogen survival/transfer/amplification/pollution
Habitat fragmentation
– Land use- agriculture, industry, residential
– Climate change
* Altitude restriction, loss of marginal corridors
* Also favours parasites
Habitat degradation
– Logging, altered burning regimes, feral species, altered hydrology
– Invasive species- plants, invertebrates, vertebrates
– Generalist species dominate over specialists
– Predators, large vertebrates often first affected due to large ranges
Favours small, aggressive, generalists
Impacts host resilience
Favours parasites and vectors
Degredation/alteration to vertical strata and horizontal:
Vertical strata:
– Canopy and hollows (refuge from predators, nest sites,
accessible palatable foliage for herbivores)
– Understory/shrub level (invertebrates, refuge, nesting
sites)
– Ground cover and litter (invertebrates and refuges)
– Below ground biomass (bulbs, rhizomes, fungi,
invertebrates)
Horizontal:
– Continuity of home ranges
– Scope for dispersal/ foraging
Features of urban environment that damage environment
– Year-round fruits and flowers, garbage
* Removes advantage of survival strategies developed for harsh conditions
* Permits accelerated breeding of some species
– Scarcity of specialist nesting sites (esp hollows for psittacines)
– Removal of understory/ shrubs (lack of refuge and nesting sites for small passerines etc, and
medium sized mammals)
– Diminished invertebrate diversity (loss of leaf litter, native flora)
* What is there is more exposed
– Hostile environment for all but smallest ground dwellers
* Med sized- Predation (pets, aggressive spp, cars), simplification of habitat
* Larger sized- Fragmentation (fences, roads)-limitations on foraging and dispersal
aggressive, mobile generalists
What problems do native species cause?
Currawongs feast on chicks of other spp
Grasses encourage galahs who take over nest hollows
Fire removes understory allowing aggresive social species to dominate
How do flying fox diseases emerge?
What are examples of flying fox diseases?
Flying fox viruses
Hendravirus
Menanglevirus- NSW
Nipahvirus- Malaysia
Lyssaviruses
Why do these diseases emerge?
– Habitat destruction and encroaching domestic animals >
increased contact with new hosts
How do wildlife diseases spread?
Movement of animals by humans
Wildlife trade
Bushmeat
Bird markets
Wildlife farms
Why are bird markets bad for spreading disease?
High turnover
Listed species
Mixed species
High density
Stressed
Close contact with humans
What species does white nose syndrome effect?
bats in eastern canada –> nearly wiped them out –> fungus –> wakes them up from hibernation
What is translocation and what are the pros and cons?
Re-stocking with captive-bred or free-ranging animals
Pros:
– For hunting
– Following captive breeding of endangered species
To establish new populations of endangered species
To remove an endangered population from a threat
To relieve overpopulation pressure
To improve genetic diversity of isolated populations
– Also includes corridor construction
– Same thinking for migration/ any movement
Cons:
Expression of disease due to stress of shipment
Expression of disease due to change of environment
Failure to remove cause of initial local extinction
Exposure of valuable naïve animals to a diseased recipient
population
Introduction of disease
– to con-specifics
– to other vulnerable species
Increased shedding of potential pathogens due to shipment
Normally think of infectious disease but need to consider
others (eg trauma, hypo/ hyperthermia etc)
How are environmental reservoirs expanding?
Parasites:
- extended breeding seasons
- faster development
Changes to host densities
and mobility
– avian cholera
– duck plague
Changes to spore production and dispersal
– anthrax
Changes to water quality
– botulism
– blue-green algae
Host compromise/ environmental change:
Bushfire
- removes cover for vertebrate
- clears land favouring fire-resistant grasses
- vines allow wicking for fire into canopies
Drought/heat
- degrades habitat
- overgrazing
- reduces niche advantages, allows invasion of generalists
- limits access to habitat
- energetic/nutritional pressures
- people and animal movement
- amplification and movement of vectors/resoiviors
- animals in care (mixing, biosecurity)
- disease risk with captive breeding and translocation
Why is disease important in ecosystem health?
Many potential pathogens:
are beneficial to host immune system maturation and digestive/
metabolic function
allow predators and scavengers to access prey
maintain selective pressure for host viability and general
resistance to disease
maintain population numbers at a sustainable level
– High host densities result in increased transmission and reduced
resources, expression of disease, and reduction in host density
– This can either increase or decrease boom-bust oscillations
Host/path co evolution
new path cause mortailies in anive host pop
pathogen becomes extinct if sufficent hosts eliminated or immune
if sufficient suseptible hosts survive, host and path co-evolve (state of equilibrium)
Typically, diseased individuals or populations will possess
traits that are not desirable in this equilibrium. eg,
diminished host response (inherent or imposed), altered
social behaviours, etc.
