A mysterious brain disease is killing birds in the southeastern United States and scientists can't f

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A mysterious brain disease is killing birds in
the southeastern United States and scientists
can't find the cause. - CNN Website
http//www.nwhc.usgs.gov/publications/fact_sheets/
pdfs/avm091002.pdf
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Title
ASSESSMENT OF THE POTENTIAL FOR AN AVIAN VACUOLAR
MYELINOPATHY OCCURRENCE IN NEW HANOVER COUNTY
PONDS
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Overview

• Introduction
• Avian Vacuolar Myelinopathy
• Avian Wildlife
• Invasive Aquatic Weeds
• Cyanobacteria
• Methods
• Pond locations
• Pond Areas
• Sampling Techniques
• Avian Wildlife Surveys
• Results
• Pond locations
• Pond Areas
• Aquatic Vegetation
• Avian Wildlife
• Discussion

AVIAN BIRDS VACUOLAR ACCENTUATION OF
CELLULAR SWELLING MYELINOPATHY DISEASE
OF MYELIN (A FATTY NERVE COATING)
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Introduction1. Avian Vacuolar Myelinopathy
1.1

• First discovered at DeGray Lake, Arkansas
• 1994-1995, 29 bald eagles died
• 1996-1997, 26 bald eagles died
• American coots also discovered
• dead during the two winters.
• Affected birds appeared intoxicated,
• demonstrating a lack of coordination while
• flying, swimming, and walking.

THOMAS, N. J., C. U. MYETEYER, AND L. SILEO.
1998. Epizootic vacuolar myelinopathy of the
central nervous system of bald eagles (Haliaeetus
leucocephalus) and American coots (Fulica
Americana). Veterinary Pathology 35 479-487.
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Introduction1. Avian Vacuolar Myelinopathy
1.1
Examination of affected birds revealed
vacuolation of the white matter of the central
nervous system Substances known to cause
similar lesions in animals have not been
identified in cases of AVM
THOMAS, N. J., C. U. MYETEYER, AND L. SILEO.
1998. Epizootic vacuolar myelinopathy of the
central nervous system of bald eagles (Haliaeetus
leucocephalus) and American coots (Fulica
Americana). Veterinary Pathology 35 479-487.
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Introduction1. Avian Vacuolar Myelinopathy
1.1
http//www.aphis.usda.gov/vs/ceah/cei/taf/emerging
diseasenotice_files/avm_0101.htm
AVM has been documented in 11 lakes across 5
states since its discovery
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Introduction1. Avian Vacuolar Myelinopathy
1.1

• AVM has been documented in 8 species of birds
• Bald Eagle, Haliaeetus leucocephalus ( 100)
• American coot, Fulica americana (1,000s)
• Ring-necked duck, Aythya collaris
• Mallard duck, Anas platyrhynchos
• Bufflehead, Bucephala albeola
• Canada goose, Branta canadensis
• Great Horned Owl, Bubo virginianus (2)
• Killdeer, Charadrius vociferous (1)

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Introduction1. Avian Vacuolar Myelinopathy
1.1

• Study Healthy coots and mallards were released
  on an AVM positive lake (Lake Surf, NC)
• Results
• the birds were diagnosed with AVM within 5 days
  of release
• only the birds released during November developed
  AVM
• Significance
• causative agent is site specific
• contraction of AVM is seasonal, causative agent
  may only be present at lethal levels
  during the winter months
• source of disease is most likely a naturally
  occurring chemical toxin

ROCKE, T. E., N. J. THOMAS, T. AUGSPURGER, AND K.
MILLER. 2002. Epizootiologic studies of avian
vacuolar myelinopathy in waterbirds. Journal of
Wildlife Diseases 38 678-684.
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Introduction1. Avian Vacuolar Myelinopathy
1.1

• Study Tissues of American coots confirmed AVM
  positive fed to red-tailed hawks, Buteo
  jamaicensis
• Results
• all five hawks developed microscopic lesions
  associated with AVM despite lack of neurological
  dysfunction
• Significance
• AVM can be spread by ingestion of affected birds
• confirmed method of exposure to bald eagles and
  suggests susceptibility of other birds of prey

FISHER, J. R., L. A. LEWIS-WEIS, AND C. M. TATE.
2003. Experimental vacuolar myelinopathy in
red-tailed hawks. Journal of Wildlife Diseases
39 400-406
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Introduction1. Avian Vacuolar Myelinopathy
1.1

• Study Attempts to transmit AVM to mallard
  ducks by 4 methods of exposure
• Results
• direct exposure to affected birds negative
• ingestion of water negative
• ingestion of aquatic plants negative
• ingestion of sediment negative
• Significance
• samples either did not contain causative agent or
  it was not in a high enough concentration to
  induce AVM
• affected birds may be present for some time after
  the agent is no longer active

LARSON, R. S., F. B. NUTTER, T. AUGSPURGER, T. E.
ROCKE, N. J. THOMAS, AND M. K. STOSKOPF. 2003.
Failure to transmit avian vacuolar myelinopathy
to mallard ducks. Journal of Wildlife Diseases
39 707-711.
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Introduction1. Avian Vacuolar Myelinopathy
1.1

• Study Attempts to transmit AVM to domestic
  chicken and swine by ingestion of affected birds
  and plant material
• Results
• swine did not develop AVM
• chicken developed AVM from both feeding trials
• Significance
• mammals may not be susceptible
• causative agent is most likely associated with
  the plant material collected from the AVM
  positive site

LEWIS-WEIS, L. A., R. W. GERHOLD, AND J. R.
FISHER. 2004. Attempts to reproduce vacuolar
myelinopathy in domestic swine and chickens.
Journal of Wildlife Diseases 40 476-484.
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Introduction1. Avian Vacuolar Myelinopathy
1.1

• Study Establishing a link between aquatic
  plant material and AVM in Mallards
• Results
• two types of cyanobacteria discovered associated
  with the plant material collected during an
  outbreak
• Pseudanabaena catenata
• an unknown species of Stigonematales
• Six of Nine ducks fed the plant material
  developed AVM
• Significance
• established cause-effect link between AVM and
  aquatic vegetation
• both species of bacteria are capable of producing
  harmful toxins

BIRRENKOTT, A. H., S. B. WILDE, J. J. HAINS, J.
R. FISHER, T. M. MURPHY, C. P. HOPE, P. G.
PARNELL, AND W. W. BOWERMAN. 2004. Establishing a
food chain link between aquatic plant material
and avian vacuolar myelinopathy in mallards (Anas
platyrhynchos). Journal of Wildlife Diseases 40
485-492.
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Introduction1. Avian Vacuolar Myelinopathy
1.1

• Study Surveys of AVM positive and negative ponds
  for aquatic vegetation and cyanobacteria
• Results
• Three types of invasive aquatic plants dominated
  AVM positive ponds
• Hydrilla (Hydrilla verticillata)
• Brazilian elodea (Egeria densa)
• Eurasian watermilfoil (Myriophyllum spicatum)
• Unknown species of Stigonematales rare in AVM
  negative ponds
• Stig. species dominated up to 95 of invasive
  weeds in AVM positive ponds

WILDE, S. B., T. M. MURPHY, C. P. HOPE, S. K.
HABRUN, J. KEMPTON, A. BIRRENKOTT, F. WILEY, W.
W. BOWERMAN, AND A. J. LEWITUS. 2005. Avian
vacuolar myelinopathy linked to exotic aquatic
plants and a novel cyanobacterial species.
Environmental Toxicology 20 348-353.
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Introduction1. Avian Vacuolar Myelinopathy
1.1
"Percentage of coverage of suspect Stigonematales
species on three invasive aquatic plants in
reservoirs where AVM has not been documented."
WILDE, S. B., T. M. MURPHY, C. P. HOPE, S. K.
HABRUN, J. KEMPTON, A. BIRRENKOTT, F. WILEY, W.
W. BOWERMAN, AND A. J. LEWITUS. 2005. Avian
vacuolar myelinopathy linked to exotic aquatic
plants and a novel cyanobacterial species.
Environmental Toxicology 20 348-353.
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Introduction1. Avian Vacuolar Myelinopathy
1.1
"Percentage of coverage of suspect Stigonematales
species on three invasive aquatic plants in
confirmed AVM reservoirs."
WILDE, S. B., T. M. MURPHY, C. P. HOPE, S. K.
HABRUN, J. KEMPTON, A. BIRRENKOTT, F. WILEY, W.
W. BOWERMAN, AND A. J. LEWITUS. 2005. Avian
vacuolar myelinopathy linked to exotic aquatic
plants and a novel cyanobacterial species.
Environmental Toxicology 20 348-353.
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Introduction1. Avian Vacuolar Myelinopathy
1.1

• Study Mallard ducks released onto a small pond
  (1.6 ha) with a dense infestation of hydrilla
  and 50 to 95 coverage of the unknown
  Stigonematalan species
• Results
• 15 of the 20 ducks released on the pond developed
  AVM within 6 weeks
• Significance
• AVM had only been documented on ponds greater
  than 450 ha
• The unknown Stigonematales species has been
  documented at ALL locations that have had cases
  of AVM

WILDE, S. B., T. M. MURPHY, C. P. HOPE, S. K.
HABRUN, J. KEMPTON, A. BIRRENKOTT, F. WILEY, W.
W. BOWERMAN, AND A. J. LEWITUS. 2005. Avian
vacuolar myelinopathy linked to exotic aquatic
plants and a novel cyanobacterial species.
Environmental Toxicology 20 348-353.
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Introduction1. Avian Vacuolar Myelinopathy
1.1

• Conclusions provide the basis for this study
• We hypothesize that three elements are needed
  to produce AVM
• an abundance of preferred aquatic vegetation
  (e.g. hydrilla)
• an abundance of the suspect Stigonematalan
  species growing on available substrate
• and herbivores waterfowl.

WILDE, S. B., T. M. MURPHY, C. P. HOPE, S. K.
HABRUN, J. KEMPTON, A. BIRRENKOTT, F. WILEY, W.
W. BOWERMAN, AND A. J. LEWITUS. 2005. Avian
vacuolar myelinopathy linked to exotic aquatic
plants and a novel cyanobacterial species.
Environmental Toxicology 20 348-353.
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Introduction2. Avian Wildlife, Bald Eagle
1.2

Populations declined from hunting, use of DDT,
and loss of habitat Endangered Species Act in
1973 helped increase nesting sites
Growth rates of North Carolina bald eagle
populations as a result of the North Carolina
Bald Eagle Project. From (Bald eagle fact sheet,
2005)
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Introduction2. Avian Wildlife, Bald Eagle
1.2

• Susceptibility to AVM
• Opportunistic feeders mostly fish but also
  other vertebrates including waterfowl whether
  alive or dead. AVM outbreaks killing many coots
  can provide a significant source of food.
• Nests located within ½ mile from water
• Mature eagles return to site of birth to breed
• Populations increase approximately 8.5 per year.
  However, AVM can set back populations by
  decades.
• An estimated 30 to 65 of population was killed
  during DeGray Lake outbreak
• Approximately 100 killed by AVM to date

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Introduction2. Avian Wildlife, American coot
1.2
Migratory, fresh water birds Osprey and Eagle
are main predators
Omnivorous consume small animals and insects.
Primary diet consists of submerged aquatic
vegetation which they dive for in shallow water.
Demonstrate a preference for hydrilla Thousands
killed by AVM to date

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Introduction3. Invasive Aquatic Weeds
1.3

• Negative Impacts
• Navigation
• Water quality
• Hydropower
• Irrigation
• Fisheries
• Recreation
• Native vegetation
• Wildlife

9. Ability to harbor the vector of human and
animal diseases (Kay, 1992)
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Introduction3. Invasive Aquatic Weeds
1.3

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Introduction3. Invasive Aquatic Weeds, Hydrilla
1.3
Introduced to US as an aquarium plant Found
growing wild in Florida in 1960 and spread
throughout US NC hydrilla first discovered in
Raleigh in 1980

2002 North Carolina hydrilla infestations
http//www.weedscience.ncsu.edu/aquaticweeds/hydri
lla2002.html
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Introduction3. Invasive Aquatic Weeds, Hydrilla
1.3
Extremely adaptive Rooted to bottom by rhizomes
in up to 30 ft of water Leaves grow in whorls of
3-8 with serrated edge
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Introduction3. Invasive Aquatic Weeds, Hydrilla
1.3

• Reproduction
• Fragmentation broken stem fragments can survive
  for days before rooting to bottom
• Tubers and turions specialized structures
  capable of producing new plants when released
• Seeds contributes little due to successful
  vegetative means

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Introduction3. Invasive Aquatic Weeds, Hydrilla
1.3

• Management
• Physical
• drawdown
• Mechanical
• tools, rakes
• Biological
• Grass carp (Ctenopharyngodon idella)
• Chemical
• herbicides

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Introduction3. Invasive Aquatic Weeds,
Brazilian elodea
1.3
Introduced to US as an aquarium plant,
Anacharis in late 1800s Similar to Hydrilla but
lacks special structures (tubers,
turions) Reproduces primarily through
fragmentation Managed primarily by grass carp

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Introduction3. Invasive Aquatic Weeds, Eurasian
watermilfoil
1.3

Introduced to US as an aquarium plant, first
discovered in D.C. in 1940s Leaves thin and
feather-like Reproduces primarily through
fragmentation, without turions First discovered
in NC in 1965 on Currituck Sound. Spread from 40
to 32,000 ha in 9 years. Less desirable food
source for grass carp
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Introduction4. Cyanobacteria
1.4

• Blue-green algae
• Similar to Plants
• contain chlorophyll and release oxygen during
  photosynthesis
• Similar to Bacteria
• lack a nucleus and chloroplasts

• Produce wide range of toxins sometimes released
  during blooms

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Introduction4. Cyanobacteria
1.4

Suspect cyanobacteria responsible for causing AVM
is a filamentous form found attached to submerged
aquatic vegetation New species of
Stigonematales Large colonies can be seen on the
underside of leaves
WILDE, S. B., T. M. MURPHY, C. P. HOPE, S. K.
HABRUN, J. KEMPTON, A. BIRRENKOTT, F. WILEY, W.
W. BOWERMAN, AND A. J. LEWITUS. 2005. Avian
vacuolar myelinopathy linked to exotic aquatic
plants and a novel cyanobacterial species.
Environmental Toxicology 20 348-353.
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Methods
2

• Google Earth used to locate 56 ponds based on
  size and accessibility
• Ponds surveyed for presence of submerged aquatic
  vegetation
• Hydrilla
• Brazilian elodea
• Eurasian watermilfoil
• Ponds surveyed for presence of susceptible avian
  wildlife

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Methods2. Pond Areas
2.2
ArcView GIS software used to calculate pond areas
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Methods2. Pond Areas
2.2
ArcView GIS software used to calculate pond areas
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Methods2. Pond Areas
2.2
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Methods3. Sampling Techniques/4. Avian
Wildlife Surveys
2.3/2.4

• Sampling Techniques
• Visual inspection and sampling tool used from
  shore to retrieve submerged vegetation
• Suspect samples taken to UNCW for positive
  identification

• Avian Wildlife Surveys
• Species of waterfowl and birds of prey identified
  at each site

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Results1. Pond Locations / 2. Pond Areas / 3.
Vegetation
3.1/3.2/3.3

• Pond Locations
• 56 Natural ponds, Commercial and Residential
  Retention ponds surveyed throughout New Hanover
  County

• Pond Areas
• 35.3 ha to 0.13 ha

• Aquatic Vegetation
• NO pond contained the invasive species of
  interest hydrilla, Brazilian elodea, or
  Eurasian watermilfoil
• One site (Airlie Lake) had infestation of
  coontail (Ceratophyllum)

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Results4. Avian Wildlife
3.4

• 17 of 56 sites contained various species of birds
• American coot (Fulica americana)
• Canada goose (Branta canadensis)
• Snow goose (Chen caerulescens)
• Mallard duck (Anas platyrhynchos)
• Great blue heron (Ardea herodias)
• White ibis (Eudocimus albus)
• Great egret (Ardea alba)
• Mute swan (Cygnus olor)
• Redhead (Aythya valisineria)
• Turkey vulture (Cathartes aura)
• Assorted diving ducks, gulls, and domestic
  waterfowl

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Results4. Avian Wildlife
3.4
American coots on Greenfield Lake, 1/25/06
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Table 1 Results of ponds surveyed greater than
1 hectare
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Table 2 Results of ponds surveyed between 1 and
0.4 hectares
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Table 3 Results of ponds surveyed less than 0.4
hectares or unavailable
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Discussion
4

• NONE of the 56 ponds surveyed will currently
  produce an AVM occurrence based on Dr. Wildes
  hypothesis
• The Suspect bacteria has been documented on
  several native species
• Coontail (Ceratophyllum demersum)
• Illinois pondweed
• Bladderwort
• Lemon bacopa (Bacopa caroliniana)
• Fragrant water lily (Nymphaea odorata)
• Watershield (Bransenia shreberi)

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Discussion
4
Therefore the potential exists for a future
occurrence of AVM at several sites

• Airlie Lake
• 3.32 ha
• Significant population of water birds
• Infestation of coontail

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Discussion
4

• Sites 14, 27, and 40
• Contained various species of water lilies
• All less than 1.18 ha
• Lack susceptible
• birds

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Discussion
4

• Greenfield Lake
• 35.3
• Highest number of susceptible birds including
  American coot
• Significant infestation of preferred vegetation
  could harbor the suspect Stigonematalan species
  in large enough numbers to produce AVM
• Sites 2, 4, and 9
• 9.28 ha to 2.86 ha
• several species of susceptible birds including
  mallard ducks and Canada geese
• An infestation of vegetation could support the
  bacteria and produce an AVM occurrence

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Discussion
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Birds at Greenfield Lake
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Discussion
4
Green algae at Greenfield Lake
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Discussion
4
The 56 ponds surveyed represent an estimated 1/5
of the total ponds in New Hanover County. Many
ponds too small for consideration or not
accessible due to location. A more thorough
survey should include ALL ponds greater than
perhaps 1 ha.
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Discussion
4

• Current research
• Suspect bacteria has been cultured and fed
  directly to American coots
• Did not produce AVM lesions
• May require environmental triggers to produce
  toxicity
• Grass carp fed hydrilla material with associated
  Stig. Bacteria
• Developed lesions similar to those seen in birds
• Carp then fed to mallard ducks
• Ducks developed AVM lesions
• Methods are being developed for extracting the
  toxins produced by the bacteria

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Discussion
4

• Future research
• Continue to focus on suspect Stig. species and
  isolation of its toxic metabolites
• Determine the environmental factors responsible
  for controlling its production
• Accurate database of sites infested with aquatic
  vegetation capable of supporting bacteria
• Continue to focus on how AVM is spread
• Increase public awareness to reduce number of
  undiagnosed cases of AVM.

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Discussion
4

• Contacts
• AVM
• USGS National Wildlife Health Center at (608)
  270-2400, http//www.nwhc.usgs.gov/disease_inform
  ation/avian_vacuolar_myelinopathy/index.jsp
• Southeastern Cooperative Wildlife Disease Study
  at [phone], http//www.uga.edu/scwds/index.
  htm
• U.S. Fish and Wildlife Service at [phone],
  http//nc-es.fws.gov/ecotox/avm.html
• South Carolina Algal Ecology Lab,
  http//links.baruch.sc.edu/scael/research/avm/avm.
  html
• NC Wildlife Resources Commission at (919)
  707-0050, http//www.ncwildlife.org/
• Invasive Weeds
• NC Aquatic Weed Control Program at (919)
  733-4064, http//www.ncwater.org/Education_and_Tec
  hnical_Assistance/Aquatic_Weed_Control/
• New Hanover County Cooperative Extension at (910)
  452-6393, http//newhanover.ces.ncsu.edu/

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Questions?