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Michigan. DNR. West Nile Virus in Wildlife. Thomas M. Cooley Rose Lake Wildlife Disease Lab Michigan Department of Natural Resources. Michigan. DNR. West Nile Virus: Reservoir Hosts. Isolated from numerous wild birds. Wetland and terrestrial species. Birds are primary amplifier hosts.

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Michigan

DNR

West Nile Virus in Wildlife

Thomas M. CooleyRose Lake Wildlife Disease LabMichigan Department of Natural Resources


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Michigan

DNR

West Nile Virus: Reservoir Hosts

Isolated from numerous wild birds.

Wetland and terrestrial species.

Birds are primary amplifier hosts.

Reservoir status not known.

Migratory birds have a role in the distribution and

re-introduction of virus into northern latitudes.

Role of mammals is not known, but they appear to be dead end hosts.


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Michigan

DNR

194 Avian Species -

130 native/wild, 64 captive/exotic

(38 Antibody positive)

In the United States:USGS Data

28 Mammalian Species –

8 wild, 20 captive

(7 Antibody positive)

2 Reptilian Species –

2 captive

(1 Antibody positive)


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Michigan

DNR

Corvid Avian Species

American Crow

Blue Jay

Common Raven

In Michigan:


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Michigan

DNR

Non-Corvid WildAvian Species

Great Horned Owl

Red-tailed Hawk

Northern Goshawk

Sharp-shinned Hawk

Cedar Waxwing

Ruffed Grouse

Canada Goose

House Finch

Bald Eagle – diagnosed in Wisconsin

In Michigan:

Photo Credit: Dave Kenyon DNR


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Michigan

DNR

Mammalian Species

Eastern Fox Squirrel

In Michigan:


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Michigan

DNR

Naturally occurring -

Transmission via mosquito bite.

Transmission Routes:

In captivity (research) –

Transmission via fecal or oral secretions.

Transmission via the eating of infected prey.

It has not been proven that these 2 types of transmission occur naturally.


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Michigan

DNR

Clinical Signs:

Depression, anorexia (weight loss), dehydration,

ataxia (loss of coordination), disorientation,

inability to fly or use their legs,

head tremors, eye twitching,

apparent blindness, seizures/convulsions, abnormal head posture, circling,

weakness, and death.


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Michigan

DNR

Great Horned Owl

diagnosed with WNV

in 2002



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Michigan

DNR

Post Mortem Examination

Many organs are affected by the virus but in most cases appear grossly normal.

The heart and kidney are collected for testing.


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Michigan

DNR

Corvid avian species necropsies are performed at MSU’s Diagnostic Center for Population and Animal Health (DCPAH)

Post Mortem Diagnosis

Non-Corvid avian species and mammalian species necropsies are performed at the DNR’s Rose Lake Wildlife Disease Lab

Testing is performed at MSU’s DCPAH


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Michigan

DNR

Gross lesions in birds are rare.

Brain showing

petechial hemorrhages.

Gross Lesions

Heart with tan areas of myocardial necrosis and myocarditis.

Enlarged spleen.

Intestine with pseudomembranous or necrotizing enteritis.


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Michigan

DNR

Impact on Wildlife:

Reports of lower numbers of various avian and mammalian species have occurred but there is no evidence that this is or is not due to WNV.

Appears avian populations may be impacted in isolated areas of the state, but not statewide.


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Michigan

DNR

Impact on Wildlife:


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Michigan

DNR

Impact on Wildlife:

WNV may cause chronic infection in birds that reappears during times of stress.

Birds may die of secondary organ damage in months or years following the initial infection.


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WN

?

Michigan

DNR

WNV may spread to the subtropics where species are stressed by habitat destruction and where year-round mosquito transmission would be possible.

Impact on Wildlife:

Endangered & threatened species may be impacted where the death of even a few individuals could be significant.


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Michigan

DNR

Monitoring Impact on Wildlife:

Testing of birds and mammals with

central nervous system signs.

Testing until at least 2 positives per species are found in the state.


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Michigan

DNR

Monitoring Impact on Wildlife:

Web-based submission of data and posting of results.

Tables & graphs:

Summaries of dead bird and mammal reports.

Summaries of test results.



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