Mosquitos and the Diseases they Carry


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Public Health information regardiing mosquitos.

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Mosquitos and the Diseases they Carry

  1. 1. By Eric C. Ratcliff
  2. 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. 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. 4. Mosquito Life Cycle
  5. 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. 6. Mosquito Eggs
  7. 7. Mosquito Larvae (Wigglers)
  8. 8. Mosquito Pupa (Tumbler)
  9. 9. Adult Mosquitoes Asian Tiger Mosquito (Aedes albopictus) Northern House Mosquito (Culex pipiens) Malarial Mosquito (Anopheles stephensi)
  10. 10. Mosquito External Anatomy
  11. 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. 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. 13. West Nile Virus Transmission Cycle
  14. 14. West Nile Virus Distribution Map
  15. 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. 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. 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. 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. 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. 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. 21. Dengue Fever Distribution Map
  22. 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. 23. Malaria Distribution Map
  24. 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. 25. Yellow Fever Distribution Map
  26. 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. 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. 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. 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. 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. 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. 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. 33. Websites with Additional Mosquito Information