Investigating the fungus that causes WNS in bats

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1 Investigating the fungus that causes WNS in bats
An “itchy” situation Investigating the fungus that causes WNS in bats

2 How many mammal species can you name?
Before we get to the meat of my talk, I would like to start with a couple of questions. I think it is important because it establishes a foundation for the relative importance of the topic I am discussing here today. If I asked you to write out all of the mammal species you could think of and just to get your brain rolling late into this Friday afternoon, I have added this picture that shows some of the different mammal orders. You might be surprised to know that there are over 5400 different species of mammals around the world.

3 Rodents ~2500 ~70% It is also interesting to note that Rodents and bats account for nearly 70% of the mammal species found around the world. There are approximately 2500 species of rodent and 1000 species of Bats Bats ~1000

4 ~500 mammal species in North America
~200 rodents ~45 bats Given the size of North America, it isn’t particularly diverse in terms of mammals, but of the nearly 500 found in the United States, almost half of them are rodents or bats.

5 Bats of North America 4 different Families Mormoopidae Phyllostomidae
Vespertilionidae (32 species) Molossidae

6 Objectives Describe the life history of bats
Describe the life history of bats, predominantly focusing on species here in the United States that have been most affected by WNS.

7 Objectives Describe the life history of bats
In order to understand the epidemiology and impacts WNS poses on North American bat populations

8 Objectives Describe the life history of bats
In order to understand the epidemiology and impacts WNS poses on North American bat populations Introduce the current plan of action

9 Life History Only mammal capable of true flight Nocturnal
Most are insectivorous Bat belong to the order Chiroptera…which means hand wing. They are the only mammals capable of true flight. While they eat everything from fruit to pollen and nectar or frogs fish and lizards or even blood….most bats are insectivorous. A single little brown bat can eat over 500 mosquitos in a single hour….and a pregnant female can eat its body weight in insects every night. (the colony under Austin bridge…..30,000 pounds per night)

10 Life History Generally social Long-lived
They are generally considered social animals, often roosting together in colonies that range from the tens to millions.

11 Life History Roosting in caves, mines, abandoned buildings, houses
Hibernate in fall/winter They are generally considered social animals, often roosting together in colonies that range from the tens to millions.

12 Life History Mate in fall/winter
Usually 1 young per year in the spring First of all, the pattern I am depicting here is a form of delayed reproduction that is found in most temperate bats including big brown bats. What you will notice is that mating occurs when males and females are at the same basal hormonal levels. In this graph, the blue bats represent bouts of mating upon arousal. In addition, what I want you to notice is that females are storing sperm most likely from several copulations, during the several months of the mating season until ovulation occurs in the spring.

13 White-nose Syndrome Emergent disease caused by the fungus Pseudogymnoascus destructans About the time I was finishing graduate school there was an emergent disease spreading through North American bat populations. This disease, better known as white nose syndrome is caused by the fungus P. destructans. As you cans see here, it was named for the distinctive white fungal growth visible on the muzzles, ears, and wings of those infected.

14 Bat’s are at risk WNS combines some of the worst possible epidemiological characteristics: highly virulent pathogen density- and frequency-dependent transmission long-term persistence in hibernacula susceptibility of multiple hosts WNS combines some of the worst possible epidemiological characteristics……. Environmental reservoir…….It can live in the cave without a host for a long time….but needs the host in order to grow! Given their life history, I think it is easy to understand why bats are particularly susceptible.

15 First detected in Schoharie County New York, 2006
It appears to have been introduced from Europe. Persistent high prevalence and pathogen load with absence of population declines in European bats are in sharp contrast to the situation in the Nearctic

16

17 August 2016

18 Hibernacula seasonal range
WNS Cold loving fungus 5° 15° 20° 10° Optimal growth Marginal growth Upper limit The fungus that causes white nose thrives in cold conditions typical of the caves where bats are overwintering. Hibernacula seasonally range from 2 degrees C to 14 degrees C which permits year round growth and reservoir maintenance of the fungus. Given these criteria there are predictive models that show potential spread of the disease. Hibernacula seasonal range

19 This is the latest model tracking potential spread of the disease
This is the latest model tracking potential spread of the disease. The black dots are where the disease has been confirmed, and the red shading is the predicted spread of the disease.

20 Distinct cutaneous infection
Fungal hyphae replace hair follicles and associated sebaceous and sweat glands Breaches basement membrane to invade regional tissue Erodes epidermis of ears and wings WNS causes cellular changes that affect the function of the skin on a bat's face and wing and tail membranes; research suggests that this may affect the bats in two deadly ways. Theory #1: Hunger Initial research indicated that the fungus may irritate the bat's skin, rousing the animal from torpor. As much energy as 30 days of hibernation is consumed each time the bat wakes up. In order to redress this energy need, the bat moves towards the entrance of the cave to look for food, but they find that it is still winter and there is no food, and no warmth. The bat dies of starvation and cold. But new research has demonstrated that it may be thirst and not hunger that is causing infected bats to wake up and move towards the entrance of their hibernaculum. Though the white muzzle of infected bats is the most obvious sign of the disease, it's actually the wings that appear to be particularly susceptible to the invasive fungus. Scientists believe that the way P. destructans invades bats' wing skin is unlike any known skin fungal pathogen in land mammals. The fungus digests, erodes and invades the skin by sending its tentacles through dead surface skin and into living dermis tissue - dissolving that tissue and using the liquid to feed itself. But this does more than limit a bats ability to fly. Apart from enabling bats to perform amazing aerial feats, the bat's wings are also involved in many roles of homeostasis, such as regulating body temperature, blood pressure, water balance and blood and gas circulation and exchange. P. destructans interferes with the physiological functions performed by the bat's skin causing a “catastrophic disruption” in these functions.  Healthy wing membranes are critical in maintaining water balance in bats. During hibernation, bats are susceptible to dehydration due to their large lungs and exposed wing membranes; evaporative water loss from the skin can result in as much as 99% of total water loss in healthy hibernating bats. Bats counter this dehydration by selecting more humid roosting spots, licking condensation off of fur and taking short flights to drink water (rehydration is hypothesized to be one reason behind the arousals in hibernating bats). But in infected bats, the fungus digests the delicate wing tissues, possibly causing unsustainable dehydration and triggering frequent arousals. And when the bats wake up to look for water, they are instead faced with a cold winter and limited resources, resulting in the premature depletion of fat stores. Bats have been observed leaving hibernacula affected by WNS and drinking from water surfaces or even eating snow—anecdotal evidence to corroborate the “dehydration hypothesis”.​ The fungus that causes white nose thrives in cold conditions typical of the caves where bats are overwintering. The fungus colonizes the skin. Generally appearing on the muzzle and ears and spreading to the wings. The fungus has also been known to completely cover the animal, attaching the victim to the cave's surface. 

21 Proposed progression model
Verant et al. 2014

22 Immune response? Contrary to original hypothesis….immune system is active (at least partially) It was long hypothesized that bats have a depressed or weakened immune response during hibernation. Contrary to previous hypotheses a recent study has shown that little brown bats infected with WNS during hibernation still have an actively fighting immune system (at least partially). Researchers found a strong immune response appropriate for a fungal infection. However, part of the immune response was missing…..the part that recruits neutrophils. You can almost think of it like pulling the fire alarm, but the fire department never shows up….. There is probably a lot of itching, maybe pain…..which certainly contributes to the frequent arousal suspected from the disease…..Remember, these frequent arousals would use vital fat reserves…which could be one of the main causes of death for hibernating bats. ……Using the fire alarm analogy again….even if the fire alarm is going off but nobody is coming and you still can’t go back to sleep because of the noise. It could be that the immune system is repressed from hibernating or that the fungus is preventing the neutrophil response. Suspected to be the fungus though because hibernating bats have neutrophil response to other infections.

23 WNS Mass mortality (damaged tissue and zero fat reserves)
The degree of mortality, is unprecedented. Mortality rate in many hibernacula where the fungus is present can reach over 90% Little brown bat was once the most abundant predator in North America.

24 Potential Impacts Considerable and abrupt reductions in predation pressure on insect populations Increased numbers of insect pests resulting in damage to forests and agriculture (estimated yearly cost $3-50 billion) Higher loads of environmental pesticides Potential public health risks associated with zoonotic disease or chemical contact As the major contributor of nutrients into many cave systems, mainly in the form of guano, bats are also an integral part of cave and karst ecosystems. The loss of bats could also, therefore, disrupt cave ecosystems and put many rare and unique cave fauna in jeopardy. Little brown bat once the most abundant bat in North America is threatened with extinction. In March 2007, New York biologists were surveying a cave near Albany when they came upon an eerie sight. "There are dead bats everywhere," they reported. In 2008, a 2006 photograph taken by a spelunker clearly showed a white-nose-afflicted bat in Howe Caverns, NY. This became the first evidence of WNS in the US. By the time the fungus was officially identified as a new species of cold-loving fungus in 2009, and named Geomyces destructans, WNS had plowed through northeastern caves and had spread as far south as Virginia. Since its deadly appearance, just 5 years ago, WNS has caused losses of up to 100% in some NE bat hibernacula (a place where bats gather to hibernate, e.g., caves and mines) and it is not uncommon to have losses of up to 60-70% in once healthy populations. Scientists have entered caves that once housed thousands of bats to discover only sick individuals unlikely to recover. In an old graphite mine near Lake George, N.Y., where the bats once hung by the thousands in grape-like bunches, the number of bats plunged from 185,000 to 2,000 in three years. About 90 percent of affected populations along the East Coast have died. "Our bats are almost gone" reports Al Hicks, who was the first scientists to encounter WNS. And after only 5 years of WNS' appearance in Howe Caverns, one NY state biologist predicts that “Losing bats altogether from New York in the foreseeable future is a very real possibility

25 Current Action Plan White-nose syndrome national plan Action plans
1. Communication and outreach 2. Data and technical information management 3. Diagnostics 4. Disease management 5. Epidemiological and ecological research 6. Disease surveillance 7. Conservation and recovery

26 Promising Treatment VOC’s produced by the bacterium Rhodococcus sp. inhibits fungus that causes WNS This has shown a lot of promise, but it shouldn’t be considered a magic bullet. It does not cure WNS, but it limits or delays its growth and development. Researchers are in the early stages of looking for ways to apply this to the cave environment, but the cave system is a delicate ecosystem and they want to ensure it is not jeopardized. Dishes a, b, and c have different amount of the bacteria (1g, 0.5, and 0.25), and d is the unexposed control…..image taken 21 days post-inoculation

27 Current Action Plan White-nose syndrome national plan Action plans
1. Communication and outreach 2. Data and technical information management 3. Diagnostics 4. Disease management 5. Epidemiological and ecological research 6. Disease surveillance 7. Conservation and recovery I don’t have time to discuss the details of all of the action plans, but instead can briefly elaborate on a couple of areas that overlap with the research questions I am addressing.

28 Background White-nose syndrome national plan Action plans
4. Disease management Goal 3: Reduce inter-/intra-specific transmission and disease spread. Actions: (1) Investigate bat-to-bat transmission of WNS. (b) Develop techniques for identifying infected animals. I realizes this is a broad topic and would be a long term project, And I RECOGNIZED THIS WAS GOING TO TAKE A MULTI-STEP APPROACH. SO, I BEGAN LOOKING FOR WAYS THAT MY PROJECT COULD OVERLAP WITH FUNDING OPPORTUNITIES. The USFWS had a direct request to develop techniques for identifying infected animals, and the first step of my research project meant being able to detect the disease at the earliest stages possible so I could then monitor changes over time.

29 Disease may be present before outward visual signs
I saw WNS as an opportunity to address that need. Currently, there are 3 ways the fungus can be diagnosed. Obviously there is visual observation, but it means the fungus has to be well established. It has been shown that the disease may be present well before outward visual signs can be detected. Ultraviolet light has shown promise in detecting the disease before outward visual signs, but the only firm diagnostic tool is by microscopic histologic examination of tissue. The problem with histologic examination is that it requires euthanasia, which is obviously detrimental to the bat. Ultraviolet light is a good technique but requires handling of the bat which adds undo stress during a time when the bat may already be stressed and most certainly needs to conserve energy.

30 Development of a non-invasive techniques that could be used to monitor bat health
In the case of WNS….it is clear that there needs to be non-invasive techniques for the detection of the fungus (hopefully early in the process).

31 Infrared Thermography
Applications Veterinary medicine before after Measuring stress levels of zoo animals…….non-invasive way to gain insight into animal health. Limits handling, anesthetics, etc. Stess and physiology etc. Temperature changes are always the foremost indicators of a simultaneous structural change; generally speaking, nature attempts to keep core temperatures stable so if the temperature is changing, something is definitely happening. When a temperature change affects the animal you care for, you understand the need to find the source of the problem quickly and start the appropriate treatment as soon as possible. Temperature change is where veterinary infrared thermography plays an important role. Measuring surface body temperatures with a veterinary infrared thermography camera (IRT) is a much more sophisticated version of the mud patterns used by the ancient Greeks. It shows us where to investigate further to find the underlying problem. Once treatment has been instituted, it shows us how effective the treatment is. And additionally, veterinary infrared thermography helps us monitor the animal athlete's body to see how well it is adapting to any training it is undergoing.

32 Infrared Thermography
Applications Zoos Physiology of birds and mammals before after Measuring stress levels of zoo animals…….non-invasive way to gain insight into animal health. Limits handling, anesthetics, etc. Stess and physiology etc. Temperature changes are always the foremost indicators of a simultaneous structural change; generally speaking, nature attempts to keep core temperatures stable so if the temperature is changing, something is definitely happening. When a temperature change affects the animal you care for, you understand the need to find the source of the problem quickly and start the appropriate treatment as soon as possible. Temperature change is where veterinary infrared thermography plays an important role. Measuring surface body temperatures with a veterinary infrared thermography camera (IRT) is a much more sophisticated version of the mud patterns used by the ancient Greeks. It shows us where to investigate further to find the underlying problem. Once treatment has been instituted, it shows us how effective the treatment is. And additionally, veterinary infrared thermography helps us monitor the animal athlete's body to see how well it is adapting to any training it is undergoing.

33 Infrared Thermography
Applications To detect disease and infection in wildlife Measuring stress levels, physiology, etc. Temperature changes are always the foremost indicators of a simultaneous structural change; generally speaking, nature attempts to keep core temperatures stable so if the temperature is changing, something is definitely happening. When a temperature change affects the animal you care for, you understand the need to find the source of the problem quickly and start the appropriate treatment as soon as possible. Temperature change is where veterinary infrared thermography plays an important role. Measuring surface body temperatures with a veterinary infrared thermography camera (IRT) is a much more sophisticated version of the mud patterns used by the ancient Greeks. It shows us where to investigate further to find the underlying problem. Once treatment has been instituted, it shows us how effective the treatment is. And additionally, veterinary infrared thermography helps us monitor the animal athlete's body to see how well it is adapting to any training it is undergoing. Technique has been successfully used for progression of rabies in Eptesicus (Ellison et al. 2013)

34 Stress Homeostasis Health?
A separate research questions came about because I had read an article that SUGGESTED TOXIN EXPOSURE MAY INCREASE SUSCEPTIBLITY OF BATS TO WNS. I was curious how animals deal with or maybe even overcome various environmental stressors. Health?

35 ~4,500,000 barrels Agricultural pesticides are being applied at an alarming rate…………..While this may be good for crop production, there are certainly risks…..especially in regards to our water supply.

36 Hey, These Bugs Taste Terrible!!!
Investigating toxin exposure in small mammals As I mentioned, bats live a relatively long time compared to other small mammals. If they are exposed to toxins, and that biomagnifies in their system, then does that put them at increased risk when exposed to other stressors like WNS. I have initially been collecting tissue samples and sending them off for broad spectrum analysis. If the bats have measureable amounts of toxin in their system would that correlate in any way with fungal load.

37 Study Site I was made aware of an antebellum property in SE Arkansas owned by UAM that had a large population of Raf’s.

38 DDE at 14,545 ppb in the fur DDT at 3929 ppb in the fur

39 Surveillance I think its obvious that the spread of WNS is unfortunate, but I looked at it as an opportunity to address my research question. HOW DO VARIOUS………?

40 QUESTIONS?