West Nile Virus

Question 1

Family

Answer 1

Flaviviridae

Question 2

Vector-borne disease

Answer 2

mosquitoes: Culex pipiens, Culex tarsalis, and Culex quinquefasciatus

Question 3

Reservoir Species

Answer 3

wide variety of bird species
can also be found in people, horses, some carnivores, alligators, bats, rabbits, and squirrels

Question 4

Transmission Cycle

Answer 4

Mosquitoes prefer birds (passerines most)
Infected mosquitoes-> naive birds-> infected birds-> naive mosquitoes
Some species become highly viremic-> improves transfer of virus to mosquitoes

Question 5

Dead end hosts bit by mosquitos

Answer 5

most do not develop enough viremia to infect naive mosquitoes

Question 6

Transmission methods in mammals

Answer 6

transuterine, transmammary, and blood transfusion

Question 7

Pathogenesis

Answer 7

replicates at sight of infection-> lymphoid tissue via bloodstream-> toll-like receptors-> CNS
Directly infects neurons in gray matter, brainstem, and spinal cord
Collateral damage to neighboring cells due to immune response

Question 8

Clinical Signs

Answer 8

Some animals can be asymptomatic or have mild symptoms
Emaciation, sudden death, paresis, ataxia, head tilt, tremors, torticollis

Question 9

Clinical signs mammals

Answer 9

muzzle twitches, muscle spasms

Question 10

Pathologic Legions

Answer 10

Myocarditis
-inflammation of spleen, kidneys, or liver with secondary megaly
-focal areas of necrosis
-multiple organ shutdown may lead quickly to death
-hemorrhages on organ surfaces including brain
-bleeding in the mouth, nares, or cloaca

Question 11

Testing

Answer 11

MRI to look for gross changes, WNV-specific IgM ELISA, plaque reduction neutralization tests comparing titers to cross-reacting agents

Question 12

Treatment

Answer 12

Supportive Care

Question 13

Management

Answer 13

Local control methods: use chickens as sentinels, surveillance for increased death in wild birds, mosquito control (pesticides, removal of still-standing water), equine vaccination