Public Health information regardiing mosquitos.

1. By Eric C. Ratcliff

2. Mosquito Biology
63 species in Ohio – several species transmit diseases, but
only a small percentage of any given population is infected
Mosquito bites infected host, then can transmit disease to
another host via injection of its saliva
Can overwinter as eggs, larvae, or fertilized adults
Adults become inactive below 55 degrees F, & freezing kills
the adults
Females lay eggs on water, just above the water line, or in
moist depressions in the soil depending on species
Eggs laid above water line dry out, then develop months
later when water level rises
Need standing, stagnant water to develop - larvae drown or
are washed away in flowing water

3. Mosquito Biology
Complete metamorphosis: eggs hatch into larvae,
larvae pupate, then transform into adults
Adults emerge about 10 days after eggs hatch
Females feed on blood, males feed on plant juices
Adults may fly 10 miles per day assisted by the wind
Lifespan – 1 week to several months depending on
species
Some species are active at night, others during the day
Some species are adapted to human habitations &
urban areas, some to forest & jungle

4. Mosquito Life Cycle

5. Mosquito Stages
Eggs – elongate, usually 1/40” long
Larvae – “wigglers”, move with S-shaped motion, live
submerged in water, breath air through tube which
pierces water surface, feed on organic matter &
microorganisms in water
Pupae – “tumblers”, comma-shaped, non-feeding,
tumble through water when disturbed
Adult – small (3/16” – ½”), slender body, 1 pair wings, 6
pairs of legs, long piercing beak, live out of water

6. Mosquito Eggs

7. Mosquito Larvae (Wigglers)

8. Mosquito Pupa (Tumbler)

9. Adult Mosquitoes
Asian Tiger Mosquito
(Aedes albopictus)
Northern House Mosquito
(Culex pipiens)
Malarial Mosquito
(Anopheles stephensi)

10. Mosquito External Anatomy

11. Mosquito-borne Diseases in Ohio
West Nile virus (WNV), Eastern equine encephalitis
(EEE), St. Louis encephalitis (SLE), & LaCrosse
encephalitis (LAC)
All are viral disease
No vaccines are available
Treatment is symptomatic, i.e. based on symptoms
Severe cases often need to be hospitalized in order to
provide supportive care

12. West Nile Virus (WNV)
Endemic in Clermont County
Most people have no symptoms if infected, a few may
become mildly ill with a slight fever, headache, body
aches, & sometimes skin rash or swollen lymph glands
Symptoms usually occur 5 to 15 days after being bitten
Very few people become severely ill, or die
Severe cases develop encephalitis & may be
permanently impaired
People older than 50 & those immunocompromised
are at greatest risk

13. West Nile Virus Transmission Cycle

14. West Nile Virus Distribution Map

15. Eastern Equine Encephalitis (EEE)
A rare illness in humans, but is frequently fatal (33%),
& causes brain damage in most survivors
Most people infected have no symptoms
Can infect horses, a variety of other mammals, & birds
Is usually rare, but epidemics can reoccur suddenly
without warning
Severe cases begin with sudden onset of headache,
high fever, chills, & vomiting, then may progress into
disorientation, seizures, or coma

16. St. Louis Encephalitis (SLE)
Is usually rare, but epidemics can reoccur suddenly
without warning
Most infected people have no apparent illness
Initial symptoms include fever, headache, nausea,
vomiting, & tiredness
Severe disease occurs more commonly in older adults
Long-term disability or death can occur in rare cases

17. LaCrosse Encephalitis (LAC)
Is considered endemic to Ohio, & occurs year after year
at low levels
Least severe of the three types of mosquito-borne
encephalitis found in Ohio
Occurs most often in children
Initial symptoms include headache, fever, nausea,
vomiting, & tiredness

18. Other Diseases Transmitted by
Mosquitoes Worldwide
Dengue fever
Malaria
Yellow fever
Tularemia
Elephantiasis
Rift Valley fever
Ross River fever
Japanese encephalitis
Western equine encephalitis
Etcetera

19. Travelers, Beware of These Three!
Dengue fever – also known as breakbone fever; over 100
million cases worldwide each year with a 1% mortality rate;
outbreaks have occurred in Texas & Florida recently
Malaria – 21o million cases worldwide in 2010 & caused
660,000 to 1.2 million deaths; 63 outbreaks in the U.S.
between 1957 & 2011; 1500 cases reported every year in U.S.
Yellow fever – known historically as Yellow Jack; on the rise
worldwide with 30,000 deaths per year; once epidemic in
U.S. & caused over 100,000 deaths during the 19th century

20. Dengue Fever
Viral disease – no vaccine available
Incubation period is 3 to 14 days, most often 4 to 7 days
Principal symptoms: severe headache, severe eye pain, joint
pain, muscle/bone pain, rash, mild bleeding
Go immediately to emergency room if these symptoms
appear: severe abdominal pain, persistent vomiting, red
spots or patches on skin, bleeding from nose or gums,
vomiting blood, drowsiness, irritability, difficulty
breathing, & pale , cold, or clammy skin
Treatment is symptomatic – use pain relievers with
acetaminophen
Protect patients from mosquito bites to prevent spread of
disease

21. Dengue Fever Distribution Map

22. Malaria
Caused by a microscopic parasite
Prophylaxis is available
Transmitted only by Anopheles mosquitoes
Incubation period in most cases is 7 to 30 days
Symptoms – high fever, chills, headache, vomiting
Severe malaria – complicated by serious organ failure
Protect patients from mosquito bites to prevent spread
of disease
Curable if diagnosed correctly & treated promptly –
treatment depends on many factors

23. Malaria Distribution Map

24. Yellow Fever
Viral disease – vaccine is available
Incubation period is typically 3 to 6 days
Initial symptoms – sudden onset of fever, severe headache,
body aches, nausea, vomiting, fatigue
15% develop severe disease – high fever, jaundice, bleeding,
multiple organ failure, with a 20% to 50 % mortality rate
Most infected persons have no symptoms, or only mild
illness
Treatment is symptomatic – avoid aspirin or other anti-
inflammatory drugs
Protect patients from mosquito bites to prevent spread of
disease

25. Yellow Fever Distribution Map

26. Mosquito Bite Prevention
Use repellents with DEET
Wear light colored, loose fitting clothing, long sleeve
shirts & long pants
Avoid mosquito infested areas
Stay indoors during peak biting hours (before & after
dusk, before dawn)
Equip/repair all doors & windows with 16 mesh screen
Use mosquito netting on beds when appropriate
Use outdoor area repellents or adulticides

27. Mosquito Bites
Mosquito proboscis (beak) penetrates skin to draw
blood
Mosquito injects saliva containing anti-coagulant
which produces a swollen, itchy, red bump
Refrain from scratching bites – may cause infection
If skin is broken from scratching use disinfectant
Use anti-itch cream to relieve itch
Note mosquito exposure when traveling to foreign
countries, and record date of bites

28. Mosquito Control Measures
Eliminating breeding sites is the best measure
Ensure proper sanitation & drainage, especially in
urban areas
Drain or fill puddles, pools, & swampy areas
Fill, drain, or treat tree holes
Dispose of old tires, or empty of water & cover
Empty water from flowerpots, toys, buckets, & other
containers

29. Mosquito Control Measures
Clean out gutters, change water in bird baths & wading
pools at least once a week
Place tight covers over cisterns, septic tanks, rain
barrels, etc.
Apply mosquito larvicide during mosquito breeding
season – reapply if washed out
Adulticides can be used for temporary knockdown of
adult mosquitoes

30. Mosquito Larvicides
Mosquito Dunks – composed of bacteria harmless to
other species, kills larvae when ingested, applied every
30 days, found in most hardware stores
Methoprene (Altosid XR) – insect hormone, prevents
development of larvae into adults, provides 150 days of
control, available on-line
Used motor oil & other oils are not approved for
mosquito control

31. Mosquito Adulticides
Sprays or foggers with pyrethrins give rapid
knockdown of adults – temporary, no residual effect
Area spraying with residual insecticides can adversely
impact human health & the environment
Area spraying & other treatment is not provided by the
Clermont County General Health District
Bug zappers & sonic repellents are ineffective
Mosquito traps attract mosquitoes to your yard

32. Mosquito Control Measures
Required in Clermont County
Pooled or contained water which has become a
breeding site must be drained or treated
Draining or eliminating standing water is usually the
best long-term solution
Larvicide must be applied during entire mosquito
breeding season if used
Orders to treat or drain sent if written complaint is
received, & larvae are found in standing water

33. Websites with Additional Mosquito
Information
www.cdc.gov
www.odh.ohio.gov
www.clermonthealthdistrict.org
www.ohioline.osu.edu