Mosquitoes, West Nile Virus and What You Can Do to Help the Fight

1
Mosquitoes, West Nile Virus and What You Can Do
to Help the Fight

• Kelly V. Tindall
• Extension Entomologist
• Twin Falls County

2

• Mosquito Biology
• Ecology of West Nile
• Mosquito Control

3
Mosquito Life Cycle
Adults emerge
Eggs (100-250/egg laying event)
10 times a year
Pupae
Overwinter all stages (species dependent) Egg to
Adult some species 4-5 days Adults As many as 2
weeks
Larvae
4
Mosquito Facts

• Only females bite (bloodmeal)
• Males feed on nectar
• 200 species in the US
• 43 species are WNV vectors
• As many as 51 species in ID
• Of the 20 most common in ID 10 are WNV vectors

5
Mosquito Breeding Habits
6
Mosquito Feeding Behavior
Species A
Species B
Species C
Birds
Mammals
Mammals Birds
7
Spread of West Nile Virus
Human Cases
1st - Uganda (1937)
Algeria (94)
Romania (96-97)
Czech Republic (97)
Horse Cases
Congo (98)
Morocco (1996)
US (1999-01)
Mexico (2003)
US, Canada Russia (99)
Italy (1998)
France (2000)
Israel (2000)
8
How is West Nile Spread?

• Birds
• 300 species can be infected
• Some species resistant
• Some susceptible
• Bird Migration
• American Robin is prime candidate
• Infected birds enter a new area
• Mosquitoes bite infected birds and acquire the
  virus

9
West Nile Virus Ecology
Incidental Infections
Robin More tolerant Virus continues to
replicate
Mammals Dead-end Hosts (virus doesnt
replicate) Varying levels of susceptibility
No symptoms - death
Magpie Susceptible Virus continues to
replicate until death occurs
10
West Nile Virus Ecology

• Primary vectors
• Primarily bird feeders, rarely mammals
• Infect bird population
• Multiple species
• 1 Northern House Mosquito

• Bridge vectors
• Opportunistic feeders
• Both birds and mammals
• Multiple species
• Western Encephalitis Mos.
• Inland Flood Water Mos.

11
Reported US Human West Nile Cases 1999-2005
www.cdc.gov
12
Reported US Human West Nile Cases 1999-2005
www.cdc.gov
13
Reported US Human West Nile Cases 1999-2005
www.cdc.gov
14
Reported US Human West Nile Cases 1999-2005
www.cdc.gov
15
Top 10 Causes of Death (US-2003)Total Deaths
2,448,288
28
23
6.4
0.0108
5.2
4.5
3
2.7
2.6
1.7
1.4
US National Center for Health Statistics, Health,
Unites States, 2005.
16
Management Techniques

• Integrated Pest Management (IPM)
• Management of pests that incorporates many
  practices for environmentally friendly and
  economically feasible control of pests
• Physical/Mechanical barriers, squashing
• Cultural proper irrigation, personal behavior
• Biological adults birds larvae fish
• Chemical larvicides vs adulticides, deterrents

17
Natural Control (Abiotic)

• Temperature
• Hard winters ? populations
• High temps increase insect development
• Rainfall
• More breeding sites
• Too dry, less breeding sites
• Sunny versus shady
• Mosquitoes prefer shaded areas
• Wind
• Increases migration potential

18
Mechanical/Physical Control
Window screens mechanical barrier
Mosquito netting
Proper care of bird baths
Manually killing
19
Cultural ControlAround the House
20
Cultural ControlAround the House
21
Cultural ControlBehavior Adaptation the 4 Ds

• Avoid DUSK / DAWN activities
• Most active time for most mosquitoes
• DRESS light-colored, loose-fitting long sleeves
  pants
• For extra protection spray thin clothing with
  repellent
• Use repellent with DEET
• Follow label instructions, and always wear
  repellent when outdoors
• Natural repellents are available lemon and
  eucalyptus oils
• DRAIN standing water in your backyard
  neighborhood
• Reduces breeding sites
• Potential water sources bird baths, old tires,
  flowerpots, and clogged rain gutters

Adapted from TX State Health Department
22
Tips for Around the House
23
Biological Control for Adults
24
Biological Control for Larvae
25
Chemical Control
26
Non-Control
27
Environmental ImpactsToxic Levels for Various
Animals
Chronic effects are denoted as mg/kg/day Acute
toxic effects are denoted as mg/kg
http//npic.orst.edu/
28
Additional Concerns

• Illegal residues on crops
• Not labeled for certain crops
• Organic farmers
• Individuals that have immune deficiencies/
  chemical sensitivity issues

29
Species of Mosquitoes from TFC
8 Samples collected since 8-28 to 9-7 from
various locations in TFC
30
For More Information

• www.cdc.gov
• http//www.dshs.state.tx.us/idcu/disease/arboviral
  /westNile/information/special/
• http//en.wikipedia.org/wiki/West_Nile_virus
• As with all web search, .gov, .edu and .org
  websites are more reliable than .com addresses