10 - Non-zoonotic disease (bats) Flashcards
Bats make up what % of all mammalian species? Order?
20%
Chiroptera
Smallest bat? Largest bat?
Smallest = kitti’s hog-nosed bat (bumblebee bat; 2g)
Largest = giant golden crowed flying fox (5’6” wingspan, fruit bat)
Suborders of chiroptera
- megachiroptera (flying foxes): fruit eating
- microchiroptera: echolocating
What do most bats eat?
70% are insectivores
Most of rest are fruit eaters
How many bat species in Canada
19-21
How many species of bats in US/Canada? What are the endangered spp? How many rely on hibernation?
45 species
Gray bat, big-eared bat, indiana bat, etc endangered
25% rely on hibernation
Bat lifespan and birth rate
> 20 year lifespan
Slow birth rate (=population recovery very slow)
Bat that pollinates agave plan
Mexican long-tongued bat
Nectar eater
Get tequila from distillation of juices from agave
Association between long-nosed bats and agave
Bat-plant association is so strong, the disappearance of one would threaten the survival of the other
Indirect effects of bats on one health
- pest control (echolocators)
- pollination
What is durian
One of the most important fruits of SE asia
Export value: 254 million USD
Pollinated primarily by bats
How do bats affect corn crops?
Important for predation of insects
Structures are inserted into corn fields and a net is put over corn plots in the evening and taken down during the day
Found that bat prey (insects) had a large impact on corn (more larva, damaged kernels)
How many insects are consumed by a colony of big brown bats in a year? How many by a little brown bat in a night?
1.5 million insects a year
4-8 g of insects each night
Value of bats per acre? To the US agriculture industry per year?
$12-$173/acre value in pest suppression
~22.9 billion/year value to US ag industry
Includes reduced cost of pesticide applications that are not needed
What is white-nosed syndrome? Caused by…
Emerging infectious disease
Affects hibernating cave-dwelling bats throughout NA
Caused by fungus (Pseudogymnoascus destructans)
Where did WNS emerge in NA?
New York state in 2006
Winter of 2006-07: ~10,000 bats dead and dying in four caves
Slides 25, 26
Spread in NA
Mortality with WNS? Spread in NA?
> 6 million bats in NA dead (likely higher)
Spread to 43 US states and 10 provinces
Different ways bats are affected by WNS
- 12 bat species get skin lesions (white fungus on muzzle and/or wings)
- 9 species DNA (pathogen identified by DNA tests, mortality less likely to be discovered)
Three species that have declined >90% bc of WNS
Northern long-eared bat
Little brown bat (Myotis lucifigus)
Tricolored bat
Signs of WNS
- white fungus on bats body
- flying outside during day in very cold temperatures (animals are starving; fungus uses up energy reserves)
- bats clustered near the entrance of hibernacula
- dead or dying bats on the ground, on buildings, trees during winter months
P. destructans infection? Temperature growth range? Bat body temp?
Fungal infectious of skin (bat wing) (not systemic)
Growth range: 4-20C
Optimal growth 12-16C
Active bats: 37-40C body temp
Hibernating bats: 1-16C (in optimal range)
Why is WNS only found in hibernating bats (not migrating)
Hibernating bats body temps drop into optimal growth range (12-16C) for P. destructans
How does bat hibernation work in infected vs uninfected bats?
Torpor (decreased physical activity / decreased physiological activity)
Uninfected bats: bouts of torpor last from days-> weeks (brief <3h arousals)
Infected bats: increased arousal episodes, increased fat depletion
Why was P. destructans being the cause of WNS initially controversial?
- fungal infections in mammals typically a response to immune dysfunction
- P destructans present in bat pops in EU with no evident bat mortality
How did they prove WNS was caused by P destructans?
Exposure of healthy little brown bats to pure cultures of P destructans causes WNS
Live P destructans was subsequently cultured from diseased bats
Koch’s postulates
= P destructans is primary pathogen
2 hypotheses of EU vs NA WNS
- WNS historically present in Europe
- european bats adapted to the disease
- accidentally transported to NA (tourist cave) - P. destructans variant in NA?
P destructans global origin? How
Western EU
EU and NA strains both cause disease when experimentally inoculated in North American bat (same pathogen)
Slides 45, 47
Look
Colony numbers of the little brown bat are declining, however…
- 12 banded bats with WNS survived over multiple years
- 14/20 recaptured bats had healed wing damage
What is happening in persisting bat populations?
- over winter mortality declining (~80% -> ~50%)
- 2x increase in torpor bout length (increase in body fat)
Treatments for WNS
- vaccine in development
- antifungal experiments
How can temperature affect P. destructans growth
- grows more slowly at temperatures lower than optimal range (colder hibernacula: 3-6C)
- low humidity associated w reduced growth
How can we cool bat hibernacula
One-time engineering of entrances (sealing main entrance, side entrances used by bats)
- cools on average 2.1C
- populations increased over time
- cool warm sties that were not being used by bats
How do wind turbines affect bats? Fatalities?
Tree-dwelling, migratory bat species are susceptible to wind turbines
600,000-900,000 annual bat fatalities
Wind turbine collision is linked to…
blade movement
How are hoary bats at risk bc of wind turbines
- 2.5 million of them in Canada
- estimated 2.3% mortality annually for next 15 years
- migratory (US and Canada wind turbines)
- 11.5% decline in 15 years
Direct means of bat deaths by wind turbines
- collision with blades
- barotrauma (drop in air pressure at the turbines, bats become disoriented)
Conclusion on barotrauma from a recent paper…
Barotrauma not the cause of bat fatalities
Pressure changes that occur in proximity to moving blades affect is low
Five hypotheses of why bats are attracted to wind turbines
- attracted to the noise
- increased prey availability
- wind turbines as roost sites
- rendezvous point to mating aggregations
- olfaction
Slide 66**
Most likely hypothesis on why bats are attracted to turbines
Wind turbines as potential roost sites (migratory bats attracted to tall structures)
How can we mitigate bat mortality
- most fatalities occur in low-wind conditions (less activity in high)
- raising “cut in” speed (wind speed at which turbines produce electricity/ blade movement occurs)
- mortality reductions of >44%
Bat fatality reduction when turbines not operating with mean wind speeds of…
reduced 82 to 85% if not operating with mean wind speeds of less than 6 m/sec
