West Nile fever is an infection by the West Nile virus, which is typically spread by mosquitoes. It causes disease in humans, horses, and several species of birds
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West nile fever
1. West Nile Fever
MD. Abdul Karim Mia
MS in Microbiology
ID: 192-033-061
Department of Microbiology
Primeasia University
Department of Microbiology, Primeasia University
2. West Nile fever
West Nile fever is an infection by the West Nile virus, which
is typically spread by mosquitoes. It causes disease in
humans, horses, and several species of birds. In about 80%
of infections people have few or no symptoms. About 20% of
people develop a fever, headache, vomiting, or a rash. In less
than 1% of people, encephalitis or meningitis occurs, with
associated neck stiffness, confusion, or seizures. Recovery
may take weeks to months. The risk of death among those in
whom the nervous system is affected is about 10%.
Department of Microbiology, Primeasia University
3. West Nile virus (WNV)
Flaviviridae
Flavivirus
Single stranded RNA virus
2 genetic lineages
Linage 1
3 clades (1a, 1b, 1c)
Infects humans, birds, mosquitoes, horses,
and other mammals
Department of Microbiology, Primeasia University
4. History
1937: West Nile District, Uganda
First isolated
1950: Egypt
Ecology studied
Additional outbreaks
1951-54, 1957, Israel
1962, 2000: France
1973-74: South Africa
1996: Romania, 1998: Italy
Department of Microbiology, Primeasia University
5. Transmission
Primary mosquito vector
Culex spp.
Tick vectors
Asia, Russia
Role in transmission not clear
Overwintering of mosquitoes
Transovarial transmission
Birds
Contact
Migratory transport
Department of Microbiology, Primeasia University
6. Human Transmission
Direct contact
Infected birds, tissues
Laboratory acquired
Blood transfusions
Screening implemented in 2003
Organ transplants
Transplacental transmission
Breast feeding
Department of Microbiology, Primeasia University
8. Horses Black Bear Bats
Goats Wolf Llama
Sheep Alpaca Cattle
Dog Mountain Goat Seal
Rabbit Alligator Cat
Chipmunk Gray Squirrels Deer
Skunk
Crocodile
Species Affected By West Nile Virus
Department of Microbiology, Primeasia University
10. Diagnosis In Human
Serology
Serum or CSF
IgM capture ELISA
Cross reactions possible
Plaque neutralization test
Detection of virus, antigen, or nucleic acids
RT-PCR
Immunohistochemistry
Department of Microbiology, Primeasia University
11. Treatment
No specific therapy
Supportive care
Therapies in clinical trials
Interferon
Antisense nucleotides
IV immunoglobulin
Antiviral drugs
Department of Microbiology, Primeasia University
12. Vaccination
Several commercial vaccines available for horses
Consult label for instructions
Usually 2 doses, 3 to 6 weeks apart
Annual revaccination
Vaccines sometimes used off-label to protect birds
Prevention and Control
Mosquito Management
Surveillance
Source reduction
Personal protection
Biological control
Larvicide & Adulticide
Department of Microbiology, Primeasia University
13. Surveillance
Dead bird testing
Sentinel chicken flocks
Mosquito collection
Test for pathogens
Account for species
Larval and adult mosquitoes
Map habitats
Record keeping
Mosquito Management
Source Reduction
Eliminating larval habitats
Tires, bird baths, containers,
rain gutters, unused swimming
pools
Making habitats unsuitable for
larval development
Public education
Marsh water management
Drain, fish access, gated
Personal Protection
Reduce time outdoors
Especially evening hours
Long pants and sleeves
Use mosquito repellent
35% DEET
Do not use DEET on
animals
Keep window screens
intact
Use yellow “bug” light
bulbs in outdoor light
fixtures
Department of Microbiology, Primeasia University
14. Biological Control
Utilizes predators, both natural and
introduced, to eat larvae and
pupae
Mosquito fish
Gambusia affinis, G.
holbrooki most
common
Fundulus spp.,
Rivulus spp., killifish
Other agents have been used but
are not readily available
Fungus, protozoa, nematodes
Copepods
Larvicides
Use when source reduction
and biological control not
feasible
More effective and target-
specific
Less controversial than
adulticides
Applied to smaller
geographic areas
Larvae concentrate in
specific locations
Adulticides
When other control
measures unsuccessful
Least efficient
Proper type and time of
application helps efficacy
Ultra Low Volume foggers
1 ounce per acre
Small droplets contact and
kill adults
Mosquito Management
Department of Microbiology, Primeasia University