West Nile Virus

West Nile Virus

• Mosquito borne virus

• Single __

• Endemic in Africa

• First Outbreak in the __

• Zoonotic disease that gets transmitted to humans

The Organism

• Flaviviridae

  • Flavivirus

    • Single stranded RNA virus

• Infects humans, birds, mosquitoes, ___

WNV Emergence in the US

• Possible modes of introduction

  • __

  • Human-transported vertebrate host

    • Legal

    • __

  • Human transported vector

  • Storm-transported vertebrate host (bird)

  • __

Human WNV Activity

• Transmission

• Primary mosquito vector

  • __

• Tick vectors

  • Asia, Russia

  • __

West Nile Transmission

• Overwintering of mosquitoes

• __

• Birds

  • Contact

  • Migratory transport

Human Transmission

• Direct contact

  • __

• Laboratory acquired

• Blood transfusions

  • __

• Organ transplants

• __

• Breast Feeding

Disease in Humans

• Incubation: 2 to 14 days

• Many WNV infections are asymptomatic

• Two forms of disease

• __

  • Most common form

  • Resembles influenze influenza

  • Most infections resolve in 2 to 6 days

  • __

• __

  • Occurs rarely

    • Progression of West Nile Virus

  • Can __

  • Three Syndromes

    • Encephalitis

    • Meningitis

    • Acute flaccid paralysis

Symptoms of WNV

• No Symptoms in Most People. ___ of people will not show any symptoms at all.

• Milder Symptoms in Some People. __ of people who become infected have symptoms such as fever, headache, and body aches, nausea, vomiting, and sometimes swollen lymph glands or a skin rash on the chest, stomach and back.

• Serious Symptoms in Some People. ___ infected with WNV will develop severe illness. Severe symptoms can include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. These symptoms may last several weeks, and neurological effects may be permanent.

Treatment in Humans

• No specific therapy

• Supportive care

• __

  • Interferon

  • Antisense nucleotides

  • IV immunoglobulin

  • Antiviral drugs

Species Affected

• Clinical signs - Horses

  • Many are asymptomatic but if not:

  • Anorexia, Ataxia, Weakness, Teeth grinding (many euthanized)

  • Convulsions, circling, tremors, difficulty swallowing, attitudinal changes

  • Facial edema, colic, urinary dysfunction, Mortality

• Treatment

  • No specific treatment - supportive care

  • Therapy is empiric

Clinical Signs - Ruminants

• Frequently a single animal affected

• Neurological signs

  • Sheep, alpacas, reindeer, white-tailed deer

• __

• Reproductive signs may be seen in sheep

Clinical Signs - Dogs + Cats

• __

  • Rarely

    • Fever, Depression

    • Muscle weakness + spasms

    • Seizures, paralysis

    • Myocarditis

• Suspect WNV in animals exhibiting neurological and cardiac symptoms

Experimental Infection

• Mosquito bite: dogs

  • All dogs showed viremia, no clinical signs

• Mosquito bite: cats

  • __

  • All but one showed mild clinical signs

• Infected prey: cats

  • All cats developed viremia

  • __

• Conclusion

  • Readily infected, not amplifying hosts

Clinical Signs - Wildlife

• Birds

  • __

• Bats, chipmunks, skunks, and domestic rabbits

  • __

• Gray Squirrels

  • Lethargy, paw biting, vocalization, ataxia, circling, encephalitis, myocarditis

Vaccination

• Several commercial vaccines available for horses

  • Consult the label for instructions

  • Usually __

  • Annual revaccination

• __