“A mysterious brain disease is killing birds in the southeastern United States and scientists...

““A mysterious brain disease is killing birds A mysterious brain disease is killing birds in the southeastern United States and in the southeastern United States and scientists can't find the cause.” - CNN scientists can't find the cause.” - CNN

Website Website

http://www.nwhc.usgs.gov/publications/fact_sheets/pdfs/avm091002.pdf

Title

ASSESSMENT OF THE POTENTIAL FOR ASSESSMENT OF THE POTENTIAL FOR AN AVIAN VACUOLAR MYELINOPATHY AN AVIAN VACUOLAR MYELINOPATHY

OCCURRENCE IN NEW HANOVER OCCURRENCE IN NEW HANOVER COUNTY PONDSCOUNTY PONDS

Overview1. Introduction

1. Avian Vacuolar Myelinopathy

2. Avian Wildlife

3. Invasive Aquatic Weeds

4. Cyanobacteria

2. Methods

1. Pond locations

2. Pond Areas

3. Sampling Techniques

4. Avian Wildlife Surveys

3. Results

1. Pond locations

2. Pond Areas

3. Aquatic Vegetation

4. Avian Wildlife

4. Discussion

AVIAN

= BIRDS

VACUOLAR

= ACCENTUATION OF CELLULAR SWELLING

MYELINOPATHY

= DISEASE OF MYELIN (A FATTY NERVE COATING)

1. Introduction1. Avian Vacuolar Myelinopathy1.1

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.

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.

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


http://www.aphis.usda.gov/vs/ceah/cei/taf/emergingdiseasenotice_files/avm_0101.htm

AVM has been documented in 11 lakes across 5 states since its discovery


AVM has been documented in 8 species of birds:

1. Bald Eagle, Haliaeetus leucocephalus (~ 100)

2. American coot, Fulica americana (1,000s)

3. Ring-necked duck, Aythya collaris

4. Mallard duck, Anas platyrhynchos

5. Bufflehead, Bucephala albeola

6. Canada goose, Branta canadensis

7. Great Horned Owl, Bubo virginianus (2)

8. Killdeer, Charadrius vociferous (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.


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


Study: Attempts to transmit AVM to mallard ducks by 4 methods of exposure

Results:

1. direct exposure to affected birds = negative

2. ingestion of water = negative

3. ingestion of aquatic plants = negative

4. 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.


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.


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

1. Pseudanabaena catenata

2. 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.


Study: Surveys of AVM positive and negative ponds for aquatic vegetation and cyanobacteria

Results:

• Three types of invasive aquatic plants dominated AVM positive ponds

1. Hydrilla (Hydrilla verticillata)

2. Brazilian elodea (Egeria densa)

3. 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.



"Percentage of coverage of suspect Stigonematales species on three invasive aquatic plants in reservoirs where AVM has not been documented."



"Percentage of coverage of suspect Stigonematales species on three invasive aquatic plants in confirmed AVM reservoirs."


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



Conclusions provide the basis for this study:

“We hypothesize that three elements are needed to produce AVM:

1. an abundance of preferred aquatic vegetation (e.g. hydrilla)

2. an abundance of the suspect Stigonematalan species growing on available substrate

3. and herbivores waterfowl.”


1. Introduction2. Avian Wildlife, Bald Eagle1.2

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)

1. Introduction2. Avian Wildlife, Bald Eagle1.2

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

1. Introduction2. Avian Wildlife, American coot1.2

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

1. Introduction3. Invasive Aquatic Weeds1.3

Negative Impacts:

1. Navigation

2. Water quality

3. Hydropower

4. Irrigation

5. Fisheries

6. Recreation

7. Native vegetation

8. Wildlife

9. Ability to “harbor the vector of human and animal diseases” (Kay, 1992)

1. Introduction3. Invasive Aquatic Weeds1.3

1. Introduction3. Invasive Aquatic Weeds, Hydrilla1.3

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/hydrilla2002.html


Extremely adaptive

Rooted to bottom by rhizomes in up to 30 ft of water

Leaves grow in whorls of 3-8 with serrated edge


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


Management

1. Physical

• drawdown

2. Mechanical

• tools, rakes

3. Biological

• Grass carp (Ctenopharyngodon idella)

4. Chemical

• herbicides

1. Introduction3. Invasive Aquatic Weeds, Brazilian elodea1.3

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

1. Introduction3. Invasive Aquatic Weeds, Eurasian watermilfoil1.3

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

1. Introduction4. Cyanobacteria1.4

“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

1. Introduction4. Cyanobacteria1.4

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


2. 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

2. Methods2. Pond Areas2.2

ArcView GIS software used to calculate pond areas


ArcView GIS software used to calculate pond areas


2. 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

3. 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)

3. Results4. Avian Wildlife3.4

17 of 56 sites contained various species of birds

1. American coot (Fulica americana)

2. Canada goose (Branta canadensis)

3. Snow goose (Chen caerulescens)

4. Mallard duck (Anas platyrhynchos)

5. Great blue heron (Ardea herodias)

6. White ibis (Eudocimus albus)

7. Great egret (Ardea alba)

8. Mute swan (Cygnus olor)

9. Redhead (Aythya valisineria)

10. Turkey vulture (Cathartes aura)

11. Assorted diving ducks, gulls, and domestic waterfowl

3. Results4. Avian Wildlife3.4

American coots on Greenfield Lake, 1/25/06

SiteDate Surveyed

Description Coordinates Area (acres)

Area (hectares)

Vegetation Avian Wildlife

111/17/200501/25/2006

Greenfield Lake 34°12'37.78"N 77°56'14.15"W 87.24 35.30 emergent, green algae

AC, CG, MD, BH, GE, RH, TV, DD, Various ducks, gulls, and domestic waterfowl

2 10/14/2005Randall Pkwy Reservoir

34°13'48.13"N 77°53'51.35"W 22.94 9.28 emergentBH, CG, DD, Various ducks

3 10/19/2005 NP 34° 7'3.09"N 77°55'17.03"W 14.03 5.68 no access none

4 10/19/2005 Silver Lake 34° 8'34.50"N 77°54'56.31"W 10.68 4.32 emergent, green algae CG

5 10/19/2005 NP? 34° 5'30.36"N 77°55'6.76"W 9.40 3.81 no access no access

6 11/3/2005 Airlie Lake 34°12'57.56"N 77°49'40.20"W 8.21 3.32 Ceratophyllum (coontail) CG, WI, MD, BH, GE, S

7 11/3/2005 NP 34°13'53.42"N 77°50'51.51"W 7.85 3.18 green algae none

8 11/3/2005 RP 34°17'25.28"N 77°49'55.81"W 7.79 3.15 none none

9 11/9/2005 NP? 34°16'48.36"N 77°45'59.53"W 7.05 2.86 none CG, WI, MD, DD

10 10/14/2005 CP 34°11'27.22"N 77°54'40.58"W 4.65 1.88 green algae DD

11 11/3/2005 RP 34°15'2.44"N 77°49'25.94"W 3.35 1.36 emergent, green algae none

12 11/17/2005 RP 34°18'11.42"N 77°52'51.56"W 3.16 1.28 none CG

13 10/19/2005 CP 34° 6'12.59"N 77°54'39.40"W 3.16 1.28 none none

14 10/19/2005 RP 34° 9'40.77"N 77°52'46.67"W 2.91 1.18 water lily (unknown species), green algae none

15 11/17/2005 RP 34°17'58.48"N 77°52'37.06"W 2.69 1.09 none none

16 11/17/2005 RP 34°18'8.18"N 77°53'2.84"W 2.68 1.09 none CG

Table 1: Results of ponds surveyed greater than 1 hectare

SiteDate Surveyed


Area (hectares)


17 11/3/2005 RP 34°17'16.78"N 77°50'18.58"W 2.45 0.99 none none

18 10/14/2005 RP 34°10'38.70"N 77°53'49.29"W 2.44 0.99 none none

19 11/9/2005 NP? 34°17'44.15"N 77°48'18.90"W 2.42 0.98 none none

20 10/19/2005 CP 34° 6'5.30"N 77°54'57.38"W 2.40 0.97 none none

21 11/3/2005 RP 34°11'36.70"N 77°52'43.06"W 2.35 0.95 none MD

22 11/3/2005 CP 34°16'14.56"N 77°49'58.65"W 2.09 0.84 none MD

23 11/17/2005 RP 34°18'9.35"N 77°52'39.90"W 2.04 0.83 none none

24 10/19/2005 CP 34° 5'46.42"N 77°54'57.91"W 1.86 0.75 none none

25 10/19/2005 RP 34° 7'15.10"N 77°53'9.81"W 1.73 0.70 green algae none

26 10/14/2005 RP 34°10'16.13"N 77°54'56.41"W 1.55 0.63 green algae none

27 10/19/2005 RP 34° 4'14.70"N 77°53'45.53"W 1.45 0.59 water lilly (unknown species) none

28 10/14/2005 RP 34°12'0.91"N 77°55'44.29"W 1.33 0.54 emergent MD


30 10/19/2005 RP 34° 7'37.52"N 77°53'11.95"W 1.23 0.50 none CG

31 11/3/2005 RP 34°16'26.53"N 77°49'24.46"W 1.21 0.49 none none

32 10/14/2005 CP 34°11'48.71"N 77°54'26.88"W 1.19 0.48 emergent DD

33 11/3/2005 RP 34°16'34.20"N 77°49'35.26"W 1.16 0.47 none none

34 10/19/2005 RP 34° 9'5.51"N 77°52'30.93"W 1.09 0.44 emergent BH

35 11/3/2005 CP 34°16'12.09"N 77°49'33.57"W 1.01 0.41 none none

Table 2: Results of ponds surveyed between 1 and 0.4 hectares

SiteDate Surveyed


Area (hectares)


36 10/19/2005 RP 34° 9'2.83"N 77°52'34.89"W 0.95 0.39 emergent, green algae none

37 10/14/2005 RP 34° 9'38.06"N 77°53'57.51"W 0.95 0.39 green algae none

38 10/14/2005 RP 34°11'58.74"N 77°55'35.60"W 0.95 0.39 emergent none

39 10/19/2005 RP 34° 9'50.25"N 77°51'43.29"W 0.95 0.38 none none

40 10/14/2005 RP 34° 9'40.62"N 77°54'8.01"W 0.87 0.35water lily (unknown species), green algae

BH, SG

41 11/3/2005 RP 34°15'6.94"N 77°49'24.65"W 0.81 0.33 none none


43 11/3/2005 CP 34°11'37.46"N 77°53'5.34"W 0.72 0.29 green algae none

44 11/3/2005 RP 34°11'50.44"N 77°50'23.89"W 0.68 0.28 none none

45 11/9/2005 NP? 34°17'42.67"N 77°48'10.29"W 0.67 0.27 none none

46 10/19/2005 RP 34° 5'47.89"N 77°55'15.13"W 0.65 0.26 none none

47 11/9/2005 RP 34°17'41.62"N 77°48'14.91"W 0.31 0.13 none none

48 10/14/2005 CP 34°14'59.41"N 77°52'53.94"W unavailable unavailable no access CG, DD

49 10/14/2005 CP 34°15'0.22"N 77°53'5.27"W unavailable unavailable no access none

50 10/14/2005 RP 34° 9'19.91"N 77°54'5.05"W unavailable unavailable none CG

51 10/14/2005 RP 34° 9'40.07"N 77°53'53.50"W unavailable unavailable emergent none

52 10/19/2005 RP 34° 6'32.55"N 77°54'49.19"W unavailable unavailable emergent, green algae MD, DD

53 10/19/2005 RP 34° 6'20.71"N 77°54'35.22"W unavailable unavailable none none

54 11/3/2005 CP 34°14'25.65"N 77°49'54.41"W unavailable unavailable none CG, S

55 11/3/2005 CP 34°14'40.09"N 77°50'3.77"W unavailable unavailable none none

56 11/9/2005 RP 34°18'13.47"N 77°46'30.53"W unavailable unavailable none none

Table 3: Results of ponds surveyed less than 0.4 hectares or unavailable

4. Discussion4

NONE of the 56 ponds surveyed will currently produce an AVM occurrence based on Dr. Wilde’s hypothesis

The Suspect bacteria has been documented on several native species:

1. Coontail (Ceratophyllum demersum)

2. Illinois pondweed

3. Bladderwort

4. Lemon bacopa (Bacopa caroliniana)

5. Fragrant water lily (Nymphaea odorata)

6. Watershield (Bransenia shreberi)

4. Discussion4

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

1. Airlie Lake

• 3.32 ha

• Significant population of water birds

• Infestation of coontail

4. Discussion4

2. Sites 14, 27, and 40

• Contained various species of water lilies

• All less than 1.18 ha

• Lack susceptible

birds

4. Discussion4

3. 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

4. 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

4. Discussion4

Birds at Greenfield Lake

4. Discussion4

Green algae at Greenfield Lake

4. Discussion4

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.

4. Discussion4

Current research:

1. Suspect bacteria has been cultured and fed directly to American coots

• Did not produce AVM lesions

• May require environmental triggers to produce toxicity

2. 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

3. Methods are being developed for extracting the toxins produced by the bacteria

4. Discussion4

Future research:

1. Continue to focus on suspect Stig. species and isolation of it’s toxic metabolites

2. Determine the environmental factors responsible for controlling it’s production

3. Accurate database of sites infested with aquatic vegetation capable of supporting bacteria

4. Continue to focus on how AVM is spread

5. Increase public awareness to reduce number of undiagnosed cases of AVM.

4. Discussion4

Contacts:

AVM

1. USGS National Wildlife Health Center at (608) 270-2400, http://www.nwhc.usgs.gov/disease_information/avian_vacuolar_myelinopathy/index.jsp

2. Southeastern Cooperative Wildlife Disease Study at (706) 542-1741, http://www.uga.edu/scwds/index.htm

3. U.S. Fish and Wildlife Service at (919) 856-4520, http://nc-es.fws.gov/ecotox/avm.html

4. South Carolina Algal Ecology Lab, http://links.baruch.sc.edu/scael/research/avm/avm.html

5. NC Wildlife Resources Commission at (919) 707-0050, http://www.ncwildlife.org/

Invasive Weeds

1. NC Aquatic Weed Control Program at (919) 733-4064, http://www.ncwater.org/Education_and_Technical_Assistance/Aquatic_Weed_Control/

2. New Hanover County Cooperative Extension at (910) 452-6393, http://newhanover.ces.ncsu.edu/

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