West Nile Virus; Avian Implications

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West Nile Virus Avian Implications

• By Jason Chudy and
• Beth Laskowski
• September 27,2002

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West Nile Virus Background

• Flavivirus commonly found in Africa, West Asia,
  and the Middle East
• Other flavivirus diseases include Yellow Fever
  and St. Louis Encephalitis
• Infects humans, birds, mosquitoes, horses and
  some other mammals
• Prior to 1999 it had not been previously
  documented in the Western Hemisphere

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West Nile Virus Background (cont.)

• Causes two primary disease forms
• West Nile Fever
• West Nile encephalitis, West Nile meningitis, or
  West Nile meningoencephalitis
• WNV can be transmitted year round
• Thought to over-winter in the adult Culex species
  of mosquito
• Permanently established in the Western Hemisphere

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West Nile Virus Disease Forms

• West Nile Fever
• Mild disease
• Flu like symptoms
• Lasts only a few days
• No apparent long-term health effects

• West Nile Encephalitis / meningitis /
  meningoencephalitis
• More severe disease
• Causes inflammation of the brain, tissues
  surrounding the brain an spinal cord, or both
• fatal

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Back to the skeeters

• Population control of mosquitoes could decrease
  frequency of infection and rate of spread.
• Culex has minimal requirements for reproduction
  and thrives in urban areas.
• Culex can complete reproduction in a week.
• Other species carry the disease
• Aedes albopictus, A cinereus, A. vexans,
  Anopheles barberi, A. punctipennis, A.
  quadrimaculatus, A. coquillettidia A.perturbans,
  Culex pipiens, C. restuans, C. nigripalpus,
  C. quinquefasciatus, C. salinaris, Culiseta
  melanura, Ochlerotatus atlanticus, O. atropalpus,
  O. Canadensis, O. cantator, O. japonicus,
  O. sollicitans, O. taeniorynchus, O. tormentor,
  O. trivittatus, Orthropodomyia signiferus
  Psorophora columbiae, P. ferox, Uranotaenia
  sapphirina

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Skeeters continued

• Why do we see cases in the winter?
• Confused mosquito?
• Dormancy in bird (ie chickens dont get sick)
• Mammalian vector (isolated WNV in mouths of mice)
• We are now seeing a species of mosquito that is a
  day feeder
• Have to watch our pets during the day now as well!

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WNV in Bird Populations

• Birds are far more likely than people and other
  mammals to become infected and sickened by the
  WNV
• By Sept 5 2002, WNV had been detected and
  confirmed WNV in at least 3,243 dead crows and in
  2,232 other dead birds
• Migratory birds are likely a key means by which
  the virus is transported to new areas

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WNV in Bird Populations cont.

• In some species, most notably the Corvids, the
  virus causes disease that is often fatal in
  infected birds.
• It has been shown to be near 100 fatal in crows.
• Bird species may seroconvert and carry the virus
  without becoming sick
• WNV has also been confirmed as the cause of death
  of a privately owned Macaw

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WNV Bird Cases in Michigan
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Native North American Species Found Positive for
WNV

• At least 111 different native North American bird
  species have tested positive in surveillance
  efforts
• Some species affected
• Crow
• Mallard, wood ducks
• Bald, golden eagles
• Canada goose
• Barred, great horned, short eared, and snowy owls
• Pigeon
• American robin
• Broad-winged, coopers, red-shouldered,
  red-tailed, and sharp-shined hawks
• Wild turkey
• Flamingo

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WNV in Raptors and Owls

• According to the USGS National Wildlife Health
  Center, there have been daily reports of raptor
  and owl morbidity and mortality due to WNV since
  August 10 (complete diagnostic work up and
  confirmed diagnoses are still pending)
• Most of the raptor and owl cases seem to be
  centered around the Midwest with the following
  states reporting deaths
• Ohio, Iowa, Indiana, Michigan, Illinois,
  Wisconsin, Minnesota, Pennsylvania, Kentucky,
  Maryland and Virginia

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WNV in Raptors and Owls cont.

• Probable cause of death of two flamingos and two
  snowy owls at the Detroit Zoo as well as the two
  snowy owls at Lansings Potter Park Zoo

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Symptoms of WNV in Raptors

• WNV presents as three phases
• Phase 1 depression, anorexia, weight loss,
  sleeping, pinching off blood feathers, and
  elevated WBC count
• Phase 2 the above plus head tremors, green
  urates (liver necrosis), mental dullness, central
  blindness, lack of awareness of surroundings,
  ataxia, weakness in legs
• Phase 3 more severe tremors, seizures

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West Nile Virus
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Differential Diagnosis

• Eastern equine encephalomyelitis
• Avian influenza
• Newcastle disease
• West Nile Virus

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Pathogenesis

• WNV specificity for macrophages and nervous
  tissue responsible for progression of disease.
• Nerve cell bodies and dendrites of Purkinje cells
  of the cerebellum most common site.
• Dysfunction of neurons and macrophages results in
  typical calvarial hemorrhage and neurological
  symptoms.

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Necropsy lesions

• Calvarial hemorrhage
• Severe necrotic myocarditis
• Splenomegaly
• Meningeal hemorrhage and cerebral edema
• Intestinal hemorrhage
• Meningitis composed primarily of lymphocytes, and
  plasma cells. Heterophils were also seen on
  occasion. Perivascular cuffing
• Splenic abnormalities seen as a decrease in
  lymphocytes, fibrin deposition, and coagulative
  necrosis, thrombosis, infearction
• Hepatitis was seen in many of the birds
• Pretty much every tissue has some kind of lesion
  with WNV (renal, lungs, ovaries

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Gross pathology of WNV infection in birds
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Ultrasound findings
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Histological findings

• Meningitis primarily lymphocytes and plasma
  cells. Heterophils were also seen on occasion.
• Perivascular cuffing
• Spleen decrease in lymphocytes, fibrin
  deposition, coagulative necrosis, thrombosis,
  infarction
• Hepatitis
• Pretty much every tissue has some kind of lesion
  with WNV (renal, lungs, ovaries)

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Histopathology and IHC of WNV Infection in Birds
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Treatment Options??

• There is no prescribed treatment
• Supportive care can be provided and recovery does
  seem to be possible in these species
• Best prognosis if intervention is done prior to
  phase 2
• Intervention at phase 3 will probably not alter
  disease course

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Prevention of WNV in Birds

• Protect the animals from mosquito bites
• Mosquito netting, indoor housing
• Horse vaccine ?
• 2 doses, 3-4 weeks apart w/out side effects
• Efficacy ?
• Experimental results showed some protection with
  WNV challenge
• 5/11 vaccinated American crows survived challenge
• 0/9 unvaccinated crows survived

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Surveillance

• Hotline to call if dead birds found.
• Web-based reporting
• Necropsy headed up by our own Jon Patterson.
• Only birds in counties that have never had a
  positive test for WNV will be tested.
• Mosquito surveillance

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Can it get any worse?

• 1st canine case demonstrated in Illinois.
• 3 squirrels, a wolf and llama also died from the
  virus.
• 4 organ transplant recipients contracted the
  disease
• Warning on front of Lansing State Journal about
  blood transfusions.

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Al Quida Mosquito?

• The New York 99 strain is very similar to the
  strain isolated in a goose from Israel 1998.
• Bioport was investigated by Congress because they
  we deemed untrustworthy.
• Bioports operating plans were discovered by
  American forces at a Afghanistan encampment.
• Saudi Arabian owned Bioport found to have direct
  links to Osama bin Laden

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Husseins new army?

• Hussein official/Iraqi defector warned the US of
  the threat of an altered West Nile virus 2 months
  before the first case in the summer of 1999.

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In the News

• I think we have to ask ourselves Is it a
  coincidence that we are seeing such an increase
  in West Nile virus, or is that something that is
  being tested as a biological weapon against us?
• -Senator Patrick Leahy, chairman of the Senate
  Judiciary Committee on a recent radio broadcast
  in Vermont.

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Bush Sends Troops To West Nile

• -the Onion

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Questions?

• "There's an old saying in TennesseeI know it's
  in Texas, probably in Tennessee...that says Fool
  me once, shame onshame on you. Fool me...you
  can't get fooled again." President Bush
  Nashville, TN, Sept. 17, 2002.