EMERGING INFECTIOUS DISEASES

Lecture 11

Emerging Diseases in Fish and Wildlife:

Introduction and Importance to Agriculture

Cindy P. Driscoll

West Nile Virus
Avian Vacuolar Myelinopathy
Pfiesteria / Harmful Algal Blooms
Chronic Wasting Disease

Wildlife Investigations

State/Federal Gov., Universities, Private Groups

• Departments of Natural Resources, Agriculture, Health, Environment

• Regional Diagnostic Labs / SCWDS / UGA - Athens, GA

• USDOI / NWHC - Madison, WI

• USDA / Wildlife Services - All 50 states

• CDC - Ft. Collins, CO/Atlanta, GA

• Universities

Wildlife Investigations

State/Federal Laws Must be Followed

• Recreational hunting, scientific collecting permits

• Migratory bird regulations

• Threatened and Endangered (T&E) laws

West Nile Virus

WNV Investigation

Time-line

§ August 1999 - Birds found dead at the Bronx Zoo, NYC

§ September 1999 - Crows found dead, NYC

§ September 1999 - Human deaths, SLE ? --> WNLV

§ October 1999 - Spread to adjoining states, NJ, CT

§ October 1999 - First and only positive crow case in MD

§ June 2000 - Positive crows NY

WNV Investigation

Maryland Investigation

§ September 1999 - MD interagency working group formed

§ October 1999 - Began carcass, blood, mosquito collections

§ December 1999 - State officials closed investigation

§ Winter 1999-2000 - DNR continued serosurvey sampling

§ Result - One positive bird (crow)

WNV

Clinical Information

§ Etiology: Flavivirus

§ Common Names: Nile Fever

§ Hosts: Birds, horses, humans

§ Signs: Fever, encephalitis, found dead

§ Transmission: Mosquitoes

§ Gross Pathology: Meningeal congestion, petechiation; pinpoint white cardiac lesions; splenomegaly; GIT petechiations

WNV

§ Transmission: Mosquitoes

§ Diagnosis: Identification of virus

§ Control: Mosquito control, personal protection

§ Human Health: Flu-like symptoms, encephalitis, death

West Nile and St. Louis Encephalitis
Virus Transmission Cycles

WNV Investigation

MD Wildlife Hotline Calls/ Responses

§ 600 Total bird calls from Sept. - Dec. 1999 (all species)

§ 197 Calls were regarding crows

§ 116 Birds (all species) were collected/sent to NWHC

§ 200 Avian blood samples sent to NWHC

WNV Investigation

Delaware Training Workshop

§ Equipment and supplies delivered

§ 10 US FWS / DNREC staff trained /20 birds sampled

§ 1999 - 200 waterfowl sampled /submitted to NWHC

WNV Investigation

Baseline Data Collected

§ NWHC accession number

§ FWHP accession number

§ Weight

§ BCI - (Body Condition Index)

§ Species

§ Sex

§ Freshness Index

§ Capture Method

§ Thorough Exam

§ Location

WNV Investigation

2000 WNV Investigation

§ Hotline enhancement / training workshops

§ Carcass collection --> MD DHMH

§ Blood collection --> NWHC

§ Mosquito control increased

§ Sentinel birds scheduled around MD

§ MD DHMH lab enhancement

WNV Investigation

2000 WNV Investigation

§ Training workshops to include:

• bird carcass I.D. & collection / blood collection

• hotline calls / notification of biologist on duty

• data collection / regular summary analyses

• public health/ safety concerns

WNV Investigation

CDC / NWHC 2000 WNV Investigation

§ Funding increased to states:

• bird carcass collection / blood collection funded

• hotline calls analyzed by MD DHMH epidemiologist

• data collection / regular summary analyses

• mosquito control increased

• public awareness increased

Avian Vacuolar Myelinopathy

AVM Investigation

Clinical Information

§ Etiology: Unknown

§ Common names: Coot and Eagle Brain Lesion Syndrome (CEBLS)

§ Species Affected: Bald Eagle, American Coot (possibly mallard, wigeon, ring-necked ducks)

§ Signs: Neurological - inability to swim/ fly/ walk, crash landings, swim with one leg extended or listing to one side

AVM Investigation

Clinical Information

§ Gross lesions: Vacuolar myelinopathy; separation of myelin layers surrounding nerves

§ Transmission: Unknown

§ Control: Unknown

§ Importance: If unknown etiology is it - Contagious? Zoonotic? Contaminating the environment?

Avian Vacuolar Myelinopathy (AVM) Emerging
Neurologic Disease Syndrome in Eagles, Coots, & Waterfowl

AVM Investigation

Maryland Field Investigation

§ Oct. 1999 - sampled for WNV, collected coots -->SCWDS

§ Nov. 1999 - subsequent investigation mounted - sampled 75 coots both Eastern / Western shores of the Chesapeake Bay--> SCWDS

§ Samples sent to SCWDS

§ MD samples - all negative

Pfiesteria piscicida / HAB’s

HAB’s

Variety of Harmful Algal Blooms (HAB’S) Exist:

§ Gymnodinium breve - responsible for marine mammal die-offs 1980 - 1990’s

§ Ciguatera - responsible for Hawaiian Monk Seal Die-off early 1990’s

§ Pfiesteria piscicida- responsible for deaths of Atlantic menhaden in NC - 1990’s

HAB’s

§ Most Affect Wildlife Via Release of Toxin

§ Brevitoxin

§ Ciguatera toxin

§ Pfiesteria toxin - yet to be identified

Pfiesteria Investigation

Time-line

§ 1980’s - Ulcerative mycosis identified in North Carolina Menhaden

§ 1990’s - Pfiesteria associated with NC fish kills; increased press coverage

§ 1996 Fall - Lesioned fish of multiple species in MD/ Pocomoke River

§ 1997 Spring - Lesioned fish of multiple species in MD/ Pocomoke River

§ August - Menhaden mortality - 10,000 menhaden in MD/ Pocomoke River

§ Sept.- Menhaden morbidity - MD/ King’s Creek, Chicamacomico River

§ 1998 Summer - Menhaden morbidity / no mortality events

§ 1999 Summer - Menhaden morbidity / no mortality events

Pfiesteria Investigation

§ Clinical Information

§ Etiology: Pfiesteria/ Aphanomyces / Kudoa ?

§ Signs: Focal or multifocal deep ulcerations; erratic swimming behavior

§ Transmission: Unknown

§ Pathology: Necrotic, fungal, bacterial, parasitic

§ Control: ? Nutrient flow control ?

§ Human Health: Possible Estuarine Associated Syndrome

Pfiesteria Investigation

§ Clinical Information

§ Diagnosis: Histology / PCR of tissues; microbiology; SEM to I.D. Pfiesteria or other HAB

§ Pathology: Necrotic, fungal, bacterial, parasitic

§ Control: ? Nutrient flow control ?

§ Human Health: Possible Estuarine Associated Syndrome

Field Sampling
Aug. 1997
Pocomoke River

Mixed Infection

1999 Pathology Findings To Date

Results - early 1999:

Sporozoan parasites in muscle tissues of YOY fish

• Two forms of sporozoans present

• Little inflammation

• Species - Kudoa

1999 Affected
Menhaden

Kudoa - Healed Ulcer

Field Sampling
Sept. 1999 Middle River

Field Investigations
1999 Middle River

Mixed Infection

Menhaden Pathology Studies

Summary of MD Findings

§ Menhaden early summer: raised lesions - parasitic

§ Menhaden mid summer: no external lesions

§ Menhaden late summer: ulcerative lesions - fungal, bacterial, parasitic

§ No link yet established between parasites, fungus bacteria and Pfiesteria

Menhaden Pathology Studies

Summary of Recent Research Findings

§ NC studies duplicated at Virginia institutions

§ Fish in culture developed lesions / died when exposed to Pfiesteria piscicida

§ USGS duplicated lesions with Aphanopmyces experimental infections

§ No further cases of human exposure

Chronic Wasting Disease

CWD

Time-line

§ 1960’s - First observed in captive mule deer in Colorado

§ 1978 - Diagnosed as spongiform encephalopathy in Colorado

§ 1980’s-1990’s - Diagnosed in captive deer /elk Co and WY; game ranches in western states and Canada

CWD - Mule Deer

CWD

Clinical Information

§ Etiology: Unknown; possibly a prion

§ Common names: CWD, Wasting Disease

§ Species Affected: Mule deer, elk

§ Range: CO, WY, MT, NE, OK, SD, Saskatchewan

§ Signs: Loss of body condition, emaciation, salivation, increased thirst/ urination, stumbling, tremors, depression, death

CWD

Clinical Information

• Diagnosis: Microscopic examination / IHC of brain tissues

• Pathology: Spongiform encephalopathy

• Transmission: Unknown; possibly contaminated feed; feeding stations and/or animal-to-animal contact

• Control: Quarantine/ test translocated cervids

• Human Health: Not known to be transmissible to humans

• Considerations: Similar to Scrapie, BSE, Creutzfeldt-Jacob Dz

CWD - Spongiform Encephalopathy

Other Cervids???

CWD

Implications

§ Research into prevalence on game farms nationwide

§ Further research into human health links

§ Transmission studies ongoing

§ Source of disease unknown, but scrapie infected pens housed subsequently affected mule deer and elk

Emerging Wildlife Disease

Implications

§ Domestic animal - wildlife transmission ?

§ Animal - Human transmission ?

§ Cooperation and collaboration with state wildlife /agriculture / health agencies, universities, zoos and professional groups essential

Emerging Wildlife Disease

Acknowledgements

• MD DNR, MD DHMH, MDA, UM

• USGS / NWHC

• SCWDS

• CSU

• NCSU

Sample Questions:

1. Avian Vacuolar Myelinopathy is a disease of birds that is caused by:

a. Herpes virus

b. Flexibacter bacteria

c. Unknown cause

2. The life cycle of West Nile Virus involves:

a. mosquito - bird transmission with other animals as dead end hosts

b. snail - bird transmission with other animals as dead end hosts

c. mosquito - snail - bird transmission with other animals as dead end hosts

3. Pfiesteria is a "Harmful Algal Bloom - HAB" that has been assoicated with which clinical signs:

a. fish with ulcerative lesions

b. deer with sloughing hooves

c. amphibian deformities

4. The disease described in lecture concerning mule deer and elk has the

following clinical signs:

a. chronic debilitation and wasting

b. acute gastrointestinal distress

c. none of the above