Public Health Issues Tires, Mosquitoes and Disease

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Public Health IssuesTires, Mosquitoes and Disease

• Jane A. Rooney, D.V.M.
• State Public Health Veterinarian
• WV Dept. of Health and Human Resources

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Tires and Mosquitoes

• It is well known among mosquito entomologists and
  mosquito abatement personnel that scrap
  automobile and truck tires often support large
  populations of certain mosquito species
• Discarded tires provide an ideal "incubator" for
  mosquito larvae. They are easily filled by rain
  and collect leaf litter. Mosquito larvae feed on
  the microorganisms that grow on decaying leaf
  litter. The dark color of tires makes them good
  heat absorbers which helps to speed up larval
  growth

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Tires can be sliced and stacked upside down to
prevent them from collecting rain water. In this
image, part of the stack tipped over. The sliced
tires were then easily filled by rain. An
entomologist is collecting mosquito larvae from
the water in these tires.
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Tires and Mosquitoes cont.

• In southern U.S. two species predominate in
  tires, Aedes aegypti and Aedes albopictus. These
  two species are known to be the principle vectors
  of Yellow Fever and Dengue, diseases which
  afflict millions of people in the tropics. (A.
  albopictus has also been found in WV)
• In temperate regions of North America, Aedes
  (Ochlerotatus) triseriatus (the native "Eastern
  Treehole Mosquito") and A.(Oc) atropalpus
  predominate in scrap tires
• Both of these species are known to be competent
  vectors of Eastern Equine Encephalitis (EEE) and
  LaCrosse Encephalitis (LAC). Oc. triseriatus is
  also a competent vector for West Nile Virus (WNV)

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Tires and Mosquitoes cont.

• Aedes albopictus (the "Asian Tiger Mosquito")
  merits special consideration. This species was
  accidentally transported from Japan to the
  western hemisphere in the mid-1980's in shipments
  of used tires. It has since become established in
  many states, and had been found in West Virginia
• It reproduces rapidly in a wide variety of
  artificial containers, readily inhabits urban
  areas, and is a competent vector of EEE and LAC
  (also found highly efficient vector of WNV in the
  laboratory)
• It is obvious that eliminating scrap tires will
  eliminate a prolific mosquito habitat and the
  associated disease risks

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LaCrosse Encephalitis Virus
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LaCrosse Ecology

• Vector Aedes (Ochlerotatus) triseriatus or
  Treehole mosquito
• Non-glaciated hardwood forests
• Breeds in
• Basal holes of oaks
• leaves accumulate in standing pools of water
• Containers, including tires, troughs, planters
• Remains close to woodland breeding sites

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LaCrosse Ecology (2)

• Amplifying host chipmunks and squirrels
• Drink from treeholes
• Achieve high levels of viremia allows virus
  transmission to previously uninfected mosquitoes
• Do not become ill they form an immune response
• Have 1-2 litters per year, assuring a steady
  supply of previously uninfected hosts

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LaCrosse Ecology (3)

• Overwintering
• Adults are killed by a hard freeze
• Infected eggs can over-winter
• Amplification females lay many eggs
• Newly-hatched females are capable of transmission
• Venereal transmission
• Males transmit to females
• Females can retain semen to fertilize successive
  clutches of eggs

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Eggs of Aedes mosquito in a glass container
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Aedes mosquito - egg
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siphon
Aedes mosquito larvae - wigglers
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Aedes mosquito pupae - tumblers
trumpet
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LaCrosse Encephalitis

• Most people infected with LaCrosse virus do not
  get sick
• Mild illness
• Headache, fever, nausea, vomiting, drowsiness and
  confusion
• Severe illness may also include seizures or coma
• Rarely fatal (neurological sequelae

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West Nile Virus
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How much activity in 2001?

• 1999 28 counties in 4 states reported
• any WNV activity
• 2000 136 counties in 12 states DC
• reported any WNV activity
• 2001 358 counties in 27 states DC
• reported any WNV activity

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WNV Activity 2001 AnimalsMMWR 2002 51497-501

• Dead birds
• Mosquito pools
• Veterinary
• Captive sentinel animals
• Wild birds (seropositive)

• 7,333
• 919
• 733 (483/Florida)
• 218
• 55

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West Nile Virus Activity 2001Human Cases

• Human Cases 66
• Alabama (2), Connecticut (6), Florida (12),
  Georgia (6), Louisiana (1), Maryland (6),
  Massachusetts (3), New Jersey (12), New York
  (15), and Pennsylvania (3)
• 9 Deaths

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How Much Activity in 2002?Reported to CDC and
Verified as of 10/23/2002
43 States and DC

• Dead Birds
• Mosquito pools
• Veterinary
• Human

• 11,493
• 4,617
• 7061
• (3 canines, 10 other spp., remainder equine)
• 2885 (182 deaths)

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West Virginia West Nile Surveillance 2002

• As of October 4, 2002 The LHDs have reported
  6,575 dead birds to the Infectious Disease
  Epidemiology Program.
• As of October 22, 2002 a total of 901 birds have
  been submitted to the Southeastern Cooperative
  Wildlife Disease Study (SCWDS) at the University
  of Georgia for virus testing.

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West Virginia West Nile Surveillance 2002

• A total of 76 positive dead birds have been
  identified in 44 counties.
• As of October 14, 2002 a total of 708 dead birds
  have tested negative for the virus

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West Virginia West Nile Surveillance 2002

• Three positive horses have been identified in the
  state (Mercer, Cabell and Jefferson counties).
• Two probable human cases with one death (Putnam
  and Wood counties).

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2002 Mosquito Surveillance

• A total of 25 species are shown to be positive
  for the virus in 2002.
• 11 additional species of mosquitoes were positive
  for the virus in previous years (1999- 2001)
• Total number of mosquito species testing positive
  for West Nile Virus 36

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2002 Mosquito Surveillance

• Genera that tested positive included
• Aedes (4 species) , Anopheles (6 species),
  Coquillettidia (1 species), Culex (8 species),
  Culiseta (2 species), Deinocerites (1 species)
  Ochlerotatus (9 species), Orthopodomyia (1
  species), Psorophora (3 species), and Uranotaenia
  (1 species).

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Female Mosquito (Cx. quinquefasciatus) Blood
Feeding on a finger
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2002 Mosquito Surveillance

• Although 36 species were shown to be positive for
  West Nile Virus not all are competent vectors.
• Uranotaenia sapphirina prefers to feed on frogs
  and other cold blooded vertebrates.
• Culiseta melanura prefers to feed on birds, but
  rarely bites man.

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Prevention and control of arboviral diseases
is accomplished most effectively through a
comprehensive, integrated mosquito
management program CDC 2001
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Integrated Pest Management

• Surveillance
• Source Reduction
• Larvaciding
• Adulticiding
• Biological Control
• Public Education

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Surveillance

• Identifies locations where mosquito populations
  may be increasing.
• Allows identification of potential vector
  species.
• Adult surveillance can assist in pinpointing
  larval sites.
• Adult surveillance
• CDC Miniature Light Traps
• Larval Surveillance
• Dippers and turkey basters

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Source Reduction

• The process of removing or modifying larval
  habitats to make them unsuitable for larval
  development.
• Source reduction includes
• Eliminating discarded tires and emptying
  containers which hold water.
• Habitat modification such as re-grading ditches,
  so water drains quickly.
• Naturalistic Control management of wetlands and
  marshes.

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Larvaciding

• Larvaciding is adding a chemical or other product
  to the water source to kill mosquito larvae.
• Chemical Larvicides
• Altosid (Insect Growth Regulator)
• Temephos (Organophosphate)
• Biorational Larvicides
• Bacillus thuringiensis israeliensis
• Bacillus sphaericus

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Adulticiding

• The process of spraying low rates of pesticides
  with special equipment mounted on trucks or small
  aircraft
• Commonly used adulticides
• Malathion (Cythion ULV concentrate)
• Resmethrin (Scourge)

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Biological Control

• Biological Control is the use of a biological
  agent to control mosquito populations.
• Biological Control targets the egg, larva, or
  pupal stage of the mosquito lifecycle.
• Biological Agents that do not work well
• Birds
• Bats

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Biological Control

• Biological Agents that work well
• Mosquito fish (Gambusia)
• Other Biological Agents that have been tested
• Predatory mosquito larvae (Toxorhynchites)
• Copepods (Macrocyclops albidus)
• Parasitic nematodes (Romanomermis)
• Fungi (Laegenidium giganteum)

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Public Education

• Public education is an essential part of any IPM
  program
• Public Education should include
• Educating school children on mosquito awareness
• Informing the public about mosquito control
  around the home
• Personal protective measures

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