Disease (class 14)
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What increases the spread of disease-causing species?
Human activities, can lead to outbreaks
Interactions with humans and domestic animals exposes wildlife to…
diseases they have not previously encountered
Name an animal that was lost due to canines, human viruses, and diseases
the black-footed ferret in 1987
What disease killed millions of bats in North America? How was it introduced?
White nose syndrome (powdery white funguses on snout- causes irritation and early waking causing starvation) - possibly introduced by cave explorers or bat researchers in 2006
What are the 3 implications of epidemiology that have practical implications for limiting disease in captive breeding and management of rare species?
• High rate of contact between host and parasite encourages spread of disease • Indirect effects of habitat destruction increase susceptibility to disease • Species in conservation programs may contract diseases from related species, even humans
4 ways to reduce spread of disease:
• inspection and quarantine at borders (domestic and wild species, clothing used by researchers) • limit interaction between endangered species, humans, domestic species and closely related species • endangered species should be monitored for disease outbreajs • healthy living conditions for wild and captive populations
What is an implication of invasive species and disease spread for human health? (and an example)
As humans move into wild areas through development and habitat fragmentation, there is greater potential for disease movement. Example: killer bees and fire ants
Define zoonotic disease:
spread from wildlife to humans
Give an example of zoonotic disease
Lyme disease, rocky mountain spotted fever spread by infected ticks. West Nile virus by mosquitos (also Ebola, HIV, bubonic plague, mad cow, bird flu)
When was West Nile virus first detected in North America? In BC?
1999 and 2009
How has climate change changed the transfer of disease?
It has allowed many disease-carrying insects and associated diseases to expand their ranges to higher elevations and farther from the equator
What can help to reduce disease? (2 words)
species diversity
What is the dilution effect?
greater species diversity reduces disease by diluting the number of suitable host species or by constraining the size of host populations through predation and competition
Give an example of the dilution effect
Lyme disease has been linked to the local abundance of host rodent species and the overall LOSS of diversity
Explain “traditional” vs “dilution effect” perspectives of biodiversity
Traditional: biodiversity amplifies disease risk Dilution effect: biodiversity dilutes disease risk • when compared to no forest and zero biodiversity
Explain the life cycle of an infected tick
1) larval ticks go into rodents 2) grow into nymphs to go into larger animals 3) grow into full adults to infect deer and humans
Human disease risk is related to the number of infected ticks in an area- how can we change this?
By changing the number of infected ticks in an area by: -changing the total tick density or the prevalence of infected ticks
Host species vary in their ability to…: (2 points)
1) provide blood meals to ticks and thus affect tick density 2) infect ticks with B. burgdorferi (host competency) and thus affect the prevalence of tick infection
The density and prevalence of rick infection is related to what?
Which hosts are in a given area
How do deer and opossums vary in their method of hosting ticks?
• deer provide blood meals to ticks, so high deer density increases tick densities • opossums groom and eat their ticks, so they decrease total tick density (both are poor reservoir hosts compared to mice)
What is meant when a host species has “high reservoir competence”?
this describes their ability to transmit B. burgdorferi to ticks (mice are most competent at this)
Disease risk can be diluted by…?
Biodiveristy
If 2 areas have the same tick density, but area 1 has higher host biodiversity, which would create a higher disease risk for humans?
Area 2- because ticks are feeding on other hosts in Area 1