- And today we have Maggie Batton,
who is a graduate student
with the Rubenstein School of Environment
and Natural Resources within the University of Vermont.
Maggie is also a biological science technician
with USDA APHIS Wildlife Services Program.
Maggie's talk today will be
Evaluating ONRAB Vaccine Bait Fate
and the Use of Bait Stations
in the Oral Rabies Vaccination Program
in Burlington, Vermont.
- [Maggie] Thank you for being here.
My name is Maggie Batton.
My co-presenters are James Murdoch
from the University of Vermont,
Richard Chipman from the United States'
Department of agriculture,
National Rabies Management Program.
Amy Gilbert from the USDA National Wildlife Research Center,
Shiloh Johnson also from the USDA NWRC and Fred Pogmore
from the USDA Wildlife Services.
And today I'm going to be discussing my research,
looking into improving the success
of rabies vaccination strategies in wildlife
across the greater Burlington area.
So you've most likely heard of rabies before,
but you might not be aware
of how dangerous this virus actually is.
It is a fatal zoonotic disease
that's spread through the bite or scratch
of an infected animal.
So if somebody is exposed to this virus,
it needs to be quickly treated because if it's not,
then it is fatal in both wildlife and in people.
So this makes it one of the world's most deadly diseases,
and it's also a major global public health concern.
And because of this,
there is a global initiative
to eliminate dog mediated rabies virus by 2030,
because this is the most common source
of exposure in the world.
So we have eliminated the canine variant from North America,
but we still have the highest diversity
of carnivores rabies vector species.
Different strains tend to dominate specific regions
of the US, but within the Eastern United States,
the raccoon variant is a major source of exposure.
And although very few people actually die
from rabies in the US,
about 55,000 people are exposed to this virus every year,
which requires an extremely expensive treatment.
So the USDA National Rabies Management Program was created
to manage rabies virus in the US and they've developed
a plan to manage the raccoon variant in the Eastern US
over the next 30 years.
And they have two main goals for managing raccoon rabies.
The first is to stop the spread of rabies virus outside
of areas enzoonotic to the disease
and to vaccinate a sufficient percentage
of target populations,
which is thought to be about 70% to create herd immunity.
And they do this
through a program known as Oral Rabies Vaccination,
which involves distributing baits on a landscape
that contain liquid vaccines that are covered
in an attractant.
So the idea is that the animal will bite into the bait,
exposing themselves to the vaccine,
which will in turn activate
a rabies virus neutralizing antibody response.
So these baits are currently being distributed
over a range of landscapes.
And there are a few different methods
that are used to most effectively deploy these baits,
which is dependent on the landscape that's being targeted.
Fixed wing aircraft is the most efficient
and commonly used method across the entire baiting zone,
but it can't really be used in densely populated areas
or where there are a lot of buildings.
So in more suburban and urban areas,
we have a few other baiting methods that are used.
So helicopters are typically used
in more suburban environments.
Hand baiting is often used in urban areas
and then bait stations are less frequently used,
but can be used in both urban and suburban settings.
So using these methods,
the USDA is able to distribute over 9.5 million baits,
and this is over 18 states.
So this is a very large program.
There are many considerations
that need to be taken into account
when planning for ORV.
Bait density is a really critical factor because it needs
to reflect the target species population densities
in the areas that we're targeting.
But there are several factors that limit the ability
to bait at this density in real time,
such as increased amounts of sidewalks and roads
or open water.
So the NRMP developed an algorithm
to estimate how much of an area is actually unbaitable.
And this is referred to as the off-time calculator,
which adjusts the target number of baits on a landscape.
So areas with high amounts of pavement usually end up
with less baits.
So ORV has been shown to be really successful
in more rural settings,
but the ORV percentage is much lower
in many urban environments.
And there's a lot of questions about why this is,
but baiting in urban areas does come with many challenges.
For one, there's an abundance of alternative food sources,
there's a chance of non-target bait competitors.
And there are some hand baiting limitations
because it does mostly occur on roads,
sidewalks, and trails,
so we might not be accessing some of the suitable habitat.
And although there have been studies looking
into these potential factors,
we haven't found the solution to this problem yet.
So this map shows the current ORV operations in Vermont,
anything that shaded orange or tan received baits mostly
by aircraft in August of every year,
but in our more urban areas,
we do use hand baiting to distribute these baits.
So this is a zoomed in view of our operations
in the greater Burlington area and the gridded areas
where we hand bait and the area shaded orange
around that is where we've recently began to use helicopters
to deploy these baits
and between aerial helicopter and hand baiting,
Vermont receives over 428,000 vaccine baits.
So ORV has been successful in rural areas of Vermont,
but seroprevalence is consistently low in Burlington
for some unknown reasons.
And this is reflected on this graph,
which shows a percentage of target animals
with a positive RVNA response after hand baiting
in Burlington over several years.
Hand baiting has been the only ground baiting strategy
that's ever been used in Vermont.
And we have tried refining this hand baiting strategy
to get a more even bait distribution across the area,
but it's still largely restricted to roads
and we haven't seen a positive increase
in our RVNA as of yet.
Burlington has also been a study area
for multiple rabies resource projects over the years
to try and better understand the factors that are relating
to these low seroconversion rates.
But despite these studies,
there's still a lot of questions left unanswered.
So this is where my study comes in.
I have two objectives and I'll walk you
through each individually.
So the goal of objective one is to improve the effectiveness
of current ORV strategies in urban environments
by understanding the factors that are driving bait survival
on the landscape.
And I'm going to be using camera traps
to monitor ONRAB vaccine bait.
And I'll be mimicking our current hand baiting strategy
to try and identify what's actually happening
to these baits once they're on the landscape.
So my study area is separated
into three categories being high, medium,
and low human development,
to be able to observe any differences in bait up take
across these categories.
So this is what the current bait distribution looks like
in Burlington within the hand baiting zone.
The area is split into one kilometer squared cells,
and each of these cells receive a specific number of baits.
So using this data,
I was able to select a subset of 100 locations
for my camera sites.
So the cameras are split up between each development type.
So we have 40 cameras in my high development areas,
40 cameras in the medium development.
And then I have 20 cameras
in the low development helicopter zone.
So the objectives are to monitor the fate
of ONRAB vaccine bait using camera traps in real time,
as a USDA is conducting hand baiting operations in the area.
And then I will be summarizing the fates of the baits
from the camera data that was collected
and modeling the probability of bait uptake
as a function of several site level
and landscape level characteristics.
So my cameras are out for a maximum of four weeks
from the date of the bait was deployed.
And I had weekly site checks to record the status
of the bait as one of four options being present and whole,
it could be partially chewed, but viable.
It could be fully chewed and non-viable,
or it could be taken from the camera site.
And by the conclusion of the study,
65% of the bait had been taken,
25% were chewed and non-viable
and 10% were still present and viable at the camera site.
The camera data also revealed
that only 14% of the baits had been taken
from target animals.
The top cause of bait loss in this study
was actually lawnmowers,
which took 28% of the baits across the entire study.
Following the lawnmower were squirrels which took 14%.
And then the raccoon, which was our main target animal,
well, had only taken 8% of these vaccines.
When looking at the cause of bait loss
in the different levels of development,
you can see that across all three categories,
non-target species are the number one cause of bait loss.
The low development area does have the highest rate
of bait uptake by target animals,
which was found to be at 30% of baits in that area.
But the high development category was found
to have the lowest rate of bait uptake
by target species at just 7.5%.
And then the average persistent time
of baits also vary depending on the development type.
So in the highly developed areas,
the average number of days that these baits were left
on the landscape was four,
in moderately developed areas these baits average
about seven days on the landscape,
and then in the low development zone,
they were on the landscape for an average of two days.
So the camera data revealed a pretty clear pattern,
but there may be other factors that are contributing
to the cause of bait loss.
So I'm going to be using a modeling approach
to gain insight into how different site level
and landscape level factors influences probability
of bait uptake by target species over time.
Some of the hypotheses we believe may be contributing
to bait loss are the chance of bait counter,
food abundance, bait competitors, and habitat configuration.
And looking into these hypotheses may help
to reveal the factors that most influence bait uptake.
And then we can predict the rates of uptake across a range
of values over time.
Okay, so I'm gonna move on to objective two.
And the goal of this objective is to assess
the effectiveness of adding bait stations
to hand baited areas
at improving seroprevalence conversion rates
in urban environments.
Specifically, I'll be quantifying the effect
of adding bait stations to hand baited areas
by comparing the results with hand baited only areas.
And the reason why we're using bait stations in conjunction
with hand baiting is because they do provide many benefits.
As I mentioned before,
we've never used them in Burlington before,
but you can be very strategic about their placement.
So you can put them in areas with high wildlife corridors
or near a resource.
So for example,
I put this bait station this summer next to a compost pile
in somebody's backyard.
They also give you a chance to distribute baits away
from roads and more urban settings.
And studies have also shown that there's a lower chance
of non-target bait competitors taking baits
from these stations.
So my study has two treatments.
The first being bait stations added
to hand baited cells
where off-time is greater than 50%.
The second is bait stations added to hand baited cells
where off-time is between 30 and 50%.
And then I have a control group,
which is my hand baited cells only.
So I have a total of 16 treatment cells
and four control cells.
And two bait stations were added
to each of the treatment cells to increase the bait density,
to absolute density and to provide an additional opportunity
for these target animals to encounter the bait.
So unique molecular biomarkers have been placed
in all of the bait in this study to identify
where the animals ingested the bait.
So all of the hand baiting baits have one biomarker
and all of the bait station bait have another biomarker.
And this biomarker is identifiable in the blood serum
of the animals that ingest this bait.
So the reason why we're using these biomarkers
is because we conduct trapping sessions
that occurred before and after ORV takes place
in July and October.
And during these trapping sessions,
we collect biological data from target species
and then the blood serum from all the captured animals
will be analyzed for evidence of RVNA response,
as well as evidence of that biomarker.
So I did just include my first field season,
where I distributed bait stations
during the hand baiting operations.
And by the conclusion of the baiting period,
93% of the baits had been taken from the bait stations.
In addition, we wrapped up our pre and post bait trapping,
where we had a total of 1200 trap locations
across the whole study area.
And we had a record number of captures
in both July and October.
So in our July trapping session,
we collected data
from gray foxes, red foxes, raccoons, and skunks.
And after 10 days of trapping,
we had captured a total of 489 unique target animals.
In October, we collected data from the same species
and by the end of that trapping period,
we had processed 470 animals.
So the data that's collected from this study will be used
to develop a model of a raccoon being vaccinated
as of a function of variables that fall
within one of two categories,
being those related to baits
and those related to land cover.
So each animal that's captured in the post-baiting period
will have one of these four outcomes,
and then I'll be developing
a multinomial logistic regression model
that will predict the probability of each of these outcomes.
So this study will identify
the what and the why our seroconversion rates
are lower in Burlington,
and then hopefully be able to inform the NRMP
on the best ORV strategy to maximize the probability
of bait consumption by target species,
and then be able to apply this to other urban areas.
Understanding why the RVNA responses are much lower
in urban settings,
and then being able to successfully increase the rate
of consumption in target species is crucial
to managing raccoon rabies
because about 13% of the area focused
on targeting raccoon rabies elimination,
are always within these urban environments.
I also just wanna take a moment to acknowledge
those who have participated in this study.
This has been a huge collaborative project
between the USDA National Rabies Management Program,
USDA National Wildlife Research Center,
the USDA Vermont Wildlife Services Operational Program,
and the UVM Rubenstein School.
Here's a list of my references.
And thank you.
- Wonderful, thank you Maggie.
And we have a few minutes to take any questions.
- [James] Maybe I'll jump in there.
Hi, this is James Murdoch,
Maggie, of course,
we work closely together on this great presentation.
Again, really appreciate it,
I had some Zoom headaches joining the meeting.
So I missed the first bit,
but I am aware of the presentation.
So with the bait stations, I mean, what would prevent
a little raccoon from reaching into the bait station
and basically consuming all of the baits that are in there.
And is that also maybe bias or does that create any problems
in terms of your analysis?
If you get one greedy raccoon that eats them all.
- Yeah, that's definitely a possibility
and something that we've discussed,
but we will hopefully be able to see that if we can catch
the animals that did eat, take baits in the bait stations,
we should be able to see,
it has like a level of how much
of the biomarker is in there I believe,
so, hopefully we'll be able to identify
if there's one raccoon that took a bunch,
we won't be able to say how many they actually took,
but it might give us some insight into.
You know why we don't really see that so many baits
were taken, but not actually seeing that similar results
in the biomarker results.
- Right. - Yeah.
- [James] Interesting, well,
let me ask you one follow up question,
sorry, just getting back to the main problem here
which is just low vaccination,
low bait uptake in the urban environment of Burlington.
Is that problem common to other urban areas
that are sort of along this leading edge of rabies
or is it something that's just particular to Burlington?
- I know Burlington is kind of an anomaly
and has a little bit more unique situation than other areas,
but I know that, or I believe that some will be able
to apply this to some of the other urban areas
to try to increase their serology as well.
But I do know that Burlington is particularly unique.
- In so many ways. - Yeah.
(both laughs)
- [James] Thank you.
- [Suzanne] Hi Maggie, this is Suzanne Gifford,
ecologist and wildlife biologists
with the Green Mountain and Finger Lakes National Forest.
Two questions, one.
Why are the higher elevation areas excluded
from your orange bait area?
Is it just because of species ranges
and two, as time allows,
will you please tell us on how you capture
and draw blood from a skunk?
- Sure. Yeah.
So, the National Rabies Management Program
is pretty strategic about where they put their baits
when flying and the species that ranges,
they do take into account the elevation
and do eliminate the,
like we don't bait over those
because the species' home ranges
and the second question about trapping.
So basically we just put out a set number
of the Tomahawk (indistinct) traps across the area
that we're trying to capture these animals.
And we do that like the afternoon before that we hope
to capture them.
And then you come back,
check the trap in the morning,
and then you would bring that animal to,
if you caught an animal,
you bring it to a central processing site to get processed.
And then it's released just a few hours
after that once it recovers.
- [Suzanne] So specific describes, actually I'm asking,
how do you avoid getting sprayed?
(Maggie laughs)
- There is a couple of different strategies.
I personally think that making them aware
of your presence and this sounds kind of weird and crazy,
but like singing to them or like talking like you would
to an animal, like a dog or something.
And just letting them know
that you're not a threat really helps,
people still get post sprayed,
but I knock on wood,
I've never gotten sprayed and that seems to help me.
And then we put a burlaps, like burlap over them
because I think being covered
in their darkness makes them feel safer.
And then usually once you have them covered,
there isn't really a threat of them spraying,
but it happens frequently to people.
- [Suzanne] Interesting, thank you.
I appreciate that. - Yeah.
- Hope we have one more question.
The 28% whacked by lawn mowers,
were many or most of those destroyed where they were placed
and did they end up somewhere else somehow?
- Yeah, most of those ones were thrown,
like were actually were placed there
so they didn't just get moved.
And then people just weren't aware
that there was a bait there.
So cause you try
to get a pretty even bait distribution across the area.
So I think that might have something
to do with why they're getting thrown on lawn sometimes,
or sometimes you want to throw them
in a tall grassy area and then you think
that they're not gonna get,
there's not going to be a lawnmower there
and then somebody does end up coming
to mow that area within the next couple of days.
So, yeah, I don't know if that answers your question a bit.
- Thank you for your presentation.
- Thanks, thank you so much.