MOSQUITOES MOSQUITOES If you would see all of Nature gathered If you would see all of Nature gathered up at one point, in all her loveliness, up at one point, in all her loveliness, and her skill, and her deadliness, and and her skill, and her deadliness, and her sex, where would you find a more her sex, where would you find a more exquisite symbol than the mosquito? exquisite symbol than the mosquito? -- Havelock Ellis, 1920 -- Havelock Ellis, 1920
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MOSQUITOES If you would see all of Nature gathered up at one point, in all her loveliness, and her skill, and her deadliness, and her sex, where would.
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MOSQUITOESMOSQUITOES
If you would see all of Nature gathered If you would see all of Nature gathered up at one point, in all her loveliness, up at one point, in all her loveliness,
and her skill, and her deadliness, and and her skill, and her deadliness, and her sex, where would you find a more her sex, where would you find a more exquisite symbol than the mosquito?exquisite symbol than the mosquito?
-- Havelock Ellis, 1920-- Havelock Ellis, 1920
HISTORYHISTORY
• Ancient Rome• Scotland• Middle ages and Henry II• Ancient India and Mesopotamia• Ancient China• Egypt• Alexander the Great 323 B.C.• Genghis Khan and Western
Europe
Alexander TheGreat
• General, King, Ruler
• Babylon 323 B.C.
• Malaria?• WNV?• Typhoid?
European ExplorationEuropean Exploration
• European exploration of new lands.
• Defensive and Offensive diseases.
• Offensive germs in the New World.
• Indigenous destruction• Slave trade• 1890’s and beyond…
The Family Culicidae - Mosquitoes
• Worldwide distribution
• > 3450 species and subspecies (38 genera)
• Great habitat diversity
• Approximately 40 million years older than humans (fossils from Eocene, 38-54 mya)
• Anophelinae (subfamily) - Anopheles (genus)
• Culicinae (subfamily) - Aedes, Culex, Haemagogus, Mansonia, Ochlerotatus and all other genera
Mosquito Characteristics
• Conspicuous proboscis - forward projecting
• Scales on thorax, abdomen, legs & wing veins
• A fringe of scales along the posterior margin of the wings
• Viraemia lasts typically 3 days then disappears from the peripheral blood.
• An arthropod must bite a viraemic host if it is to become infected.
Yellow Fever HistoryYellow Fever History
Yellow FeverYellow Fever
• Brought to U.S. via slave trade.• Aedes aegypti • Originally in New World Monkey populations• Jungle Yellow fever (3-factor disease in monkeys)• New World people bring to town• Old World mooting monkeys bring to town.• Does occasionally occur in U.S.• 1964 Eradication program (U.S. Public Health)
YELLOW FEVERYELLOW FEVER
• Is a _______
• Prevented the building of the Panama Canal.
• Pathogen:
• Vector: Aedes aegypti, Aedes spp., Haemagogus
• Host:
ReservoirReservoir
• Human-mosquito in urban cycle,
• Monkey-mosquito in forest cycle;
• Deforestation may force infected monkeys into areas where human-mosquito transmission can occur.
Central and South AmericaCentral and South America Yellow Fever Transmission Yellow Fever Transmission
CycleCycleVectorsVectors:
• Haemagogus spp. (jungle)
• Haemagogus spp. (rural)
• Ae. Aegypti (urban)
• Transovarial Transmission
DistributionDistribution
Diagnosis and SymptomsDiagnosis and Symptoms
• Most infections are mild, but the disease can cause severe, life-threatening illness.
• Symptoms of severe infection are high fever, chills, headache, muscle aches, vomiting, and backache. After a brief recovery period, the infection can lead to shock, bleeding, and kidney and liver failure. Liver failure causes jaundice (yellowing of the skin and the whites of the eyes).
• Diagnosed by blood test.
Prevention and TreatmentPrevention and Treatment
• General precautions to avoid mosquito bites; the use of insect repellent, protective clothing, and mosquito netting.
• Yellow fever vaccine has been used for several decades. A single dose has a lasting immunity of 10 years or more. (Live virus vaccine)
• Booster dose is given every 10 years as needed. • Treatment: No real treatment, drink plenty of fluids,
keep away from mosquitoes to protect others, most people get better over a long recovery period.
Dengue Fever HistoryDengue Fever History
Dengue (Breakbone) FeverDengue (Breakbone) Fever
• Dengue has four serological types
(DEN-1,DEN-2,DEN-3 and DEN-4).
• Pathogen: • • Host:
• Reservoir:
VECTORSVECTORS
• Aedes aegypti (Yellow fever Mosquito)
• Aedes albopictus (Asian Tiger Mosquito)
• Aedes scutellaris
• Aedes polynesiensis
Transmission CycleTransmission Cycle
• Blood meal from viremic human.
• Midgut replication
• Salivary glands, pass on during feeding.
• Transovarial transmission
• SE Asia – monkey cycle
Replication and TransmissionReplication and Transmissionof Dengue Virus (Part 1)of Dengue Virus (Part 1)
1. Virus transmitted to human in mosquito saliva
2. Virus replicates in target organs
3. Virus infects white blood cells and lymphatic tissues
4. Virus released and circulates in blood
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1
2
Replication and TransmissionReplication and Transmissionof Dengue Virus (Part 2)of Dengue Virus (Part 2)
5. Second mosquito ingests virus with blood
6. Virus replicates in mosquito midgut and other organs, infects salivary glands
7. Virus replicates in salivary glands
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7
5
DistributionDistribution
Recent Dengue in the U.S.A.Recent Dengue in the U.S.A. (Texas)(Texas)
• Dengue epidemics occurred in the USA in the 1800s and the first half of the 1900s.
• Lack of recent transmission likely due to changes in life-style
Reasons for Dengue Reasons for Dengue Expansion in the AmericasExpansion in the Americas
• Extensive vector infestation, with declining vector control
• Unreliable water supply systems
• Increasing non-biodegradable containers and poor solid waste disposal
• Increased air travel
• Increasing population density in urban areas
Trouble Ahead?Trouble Ahead?
• 2.5 billion people at risk world-wide
• In the Americas, 50-fold increase in reported cases of DHF (1989-1993 compared to 1984-1988)*
• Widespread abundance of Aedes aegypti in at-risk areas
* Organization of American States, Human Health in the Americas, 1996
Signs and SymptomsSigns and Symptoms
• Sudden onset of fever usually high fever, severe headache, backache, joint pains, nausea and vomiting, eye pain, and rash.
• Dengue hemorrhagic fever (more severe form)
Treatment and PreventionTreatment and Prevention
• There is no specific medication for treatment of a dengue infection.
• Persons who think they have dengue should use analgesics (pain relievers) with acetaminophen and avoid those containing aspirin. They should also rest and drink plenty of fluids.
• General precautions to avoid mosquito bites; the use of insect repellent, protective clothing, and mosquito netting.
• Distribution: Along the Gulf and Atlantic Coasts, from Canada to Florida.
• Disease: fatal disease that predominantly affects
horses.
• Reservoir:
• Pathogen:
TransmissionTransmission
• Mainly bird/mosquito cycle.
• Man and Horses are dead-end hosts.
Maintenance VECTORMaintenance VECTOR
• Culiseta melanura
• The bird cycle
• Habitat:
Bridge VECTORSBridge VECTORS
East and Gulf Coast• Ae. taeniorhynchus,
Ae. sollicitans
Florida• Culex nigripalpis
Inland• Ae. vexans,
Coquillattidia perturbans
Signs and SymptomsSigns and Symptoms
• Most people infected with EEE do not become ill and others may have only a mild influenza-like illness with fever, headache and sore throat. In rare cases, infection of the central nervous system can occur, causing sudden fever, muscle pains and a headache of increasing severity often followed by seizures and coma.
• About 50% of these human cases are fatal, with young children and the elderly most at risk.
• Symptoms in humans usually occur from 4 to 10 days after the bite of an infected mosquito.
St. Louis Encephalitis (SLE)St. Louis Encephalitis (SLE)
• Distribution: West of Mississippi River, Florids, Ohio River Valley, NJ and NY. Everywhere in the U.S. except New England area.
• Disease: mammals are accidental hosts. It is a more serious problem for the elderly. We see epidemics of up to 2000 cases in 10 year cycles.
• Reservoir:
• Pathogen:
DistributionDistribution
TransmissionTransmission
• Bird/mosquito cycle
• Humans and mammals are dead end hosts.
• Transovarial transmission in lab, but probably not in nature.
VECTORSVECTORS
• Culex pipiens pipiens (Northern House)
• Culex pipiens quinquefasciatus (Southern House)
• Culex nigripalpus
• Culex tarsalis
Signs and SymptomsSigns and Symptoms
• Mild infections occur without apparent symptoms other than fever with headache. More severe infection is marked by headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, occasional convulsions (especially in infants) and spastic (but
rarely flaccid) paralysis.
• There is no specific treatment. Intensive supportive
therapy depending on the individual.
Western Equine Western Equine Encephalomyelitis (WEE)Encephalomyelitis (WEE)
• Distribution: Wisconsin, Illinois, all states west of the Mississippi River valley, not found east of it.
• Disease: Human mortality is 1-5%. Woman and children more severely affected and more likely to develop neurological disorders. Equine mortality is high.
• Reservoir:
• Pathogen:
TransmissionTransmission
• See handout
• Humans and horses are dead end hosts.
• The rabbit cycle is thought to go in two directions making them a reservoir.
• Distribution: Ohio, Indiana, Illinois, Wisconsin, Tennessee. Some in Western U.S, but not common.
• Disease: Subclinical or very mild, but like the others sometimes develops into something more serious. Mostly children under 16 years of age.
• Reservoir:
• Pathogen:
TransmissionTransmission
• See handout!
• Virus cycles in woodland habitats between the treehole mosquito (Aedes triseriatus) and vertebrate hosts (chipmunks, squirrels)
• Vector uses artificial containers (tires, buckets, etc.) in
addition to treeholes.
VECTORSVECTORS
• Ochlerotatus triseriatus
• Ochlerotatus hendersoni
• Aedes dorsalis (Utah).
Signs and SymptomsSigns and Symptoms
• Frank encephalitis progressing to seizures, coma; majority of infections are subclinical or result in mild illness.
• Approximately 70 cases reported per year.
• Treatment is supportive.
West Nile Virus (WNV)West Nile Virus (WNV)
• Distribution: throughout the United States• Disease: 1999 first case in the U.S., NY.• Reservoir:
• Pathogen:
• Originated in Africa, is a disease of children there. Spread from Africa to other parts of the world.
TransmissionTransmission
• Humans and mammals are dead end hosts.
• Bird/mosquito cycle.
• Virus cycles in the birds blood for a few days.
VECTORSVECTORS
• Culex pipiens (East)
• Culex tarsalis (West)
• Aedes vexans (Amplifyer?)
• Several other species that have
shown promise as possible vectors.
Signs and SymptomsSigns and Symptoms
• Mostly flu like, but can develop into encephalitis. • About one in 150 people will develop severe illness.
Which include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis.
• Children and elderly are most at risk.
• Can get via blood transfusions and organ transplants. • Breastmilk – CDC had one case reported
• There is no specific treatment for WNV infection.
Japanese Encephalitis (JE)Japanese Encephalitis (JE)
• Distribution: Japan, China, Malaysia, Korea and other areas of South-east Asia, India, and few in Australia.
• Disease: Similar to other encephalitic diseases we discussed.