Presentation on theme: "Dengue: An emerging arboviral disease"— Presentation transcript:
1Dengue: An emerging arboviral disease Gary G. Clark, Ph.D.Mosquito and Fly Research UnitCMAVE, ARS, USDAGainesville, Florida1
2My “emergence” at Balboa Naval Hospital San Diego, CaliforniaFirst interaction with a Navy physician
3Discussion topics Epidemiology of dengue and DHF Emergence of dengue in the AmericasAedes aegypti and its developmentAdult control methods for Ae. aegyptiEvaluation of emergency control studies (CDC and the military)Dengue and the US military
4Dengue virus An arbovirus; transmitted by mosquitoes Four virus serotypes (DEN-1, 2, 3, 4); single-stranded RNAFamily Flaviviridae (WNV, SLE, YF, JE)Causes dengue (headache, fever, joint/retrorbital pain, rash, bleeding) and dengue hemorrhagic fever (DHF)3
5Dengue virusesEach serotype provides specific lifetime immunity and short-term cross-immunityAll serotypes can cause severe and fatal diseaseGenetic variation within serotypes; some appear to be more virulent or have greater epidemic potentialCan produce outbreaks/epidemicsin urban areas4
6Transmission of dengue virus by Aedes aegypti Mosquito feeds /Mosquito refeeds /acquires virustransmits virusExtrinsicincubationperiodIntrinsicincubationperiodViremiaViremia581216202428IllnessIllnessDaysHuman #1Human #25
7Dengue: A global perspective* Most important arboviral disease of humans; billion people (40% of the world) at risk of infection10’s of millions of cases of dengue and 100’s of thousands of DHF cases annuallyA leading cause of hospitalization and death among children in AsiaDHF mortality rate averages about 5%* Source: WHO, 1996
8World distribution of dengue 2006 Areas infested with Aedes aegyptiAreas with Ae. aegypti and recent dengue epidemics
9Dengue/DHF cases reported to the World Health Organization 1955-2005* Ave.annualno. cases* Source: WHO, Sep. 2006
10Dengue in the Americas 1980 – 2006* Year* Source: PAHO (Jan. 19, 2007)
11Dengue hemorrhagic fever in the Americas 1980 – 2006*Cases*Year* Source: PAHO (Jan. 19, 2007)
12Why has dengue emerged in the Americas? Presence of competent mosquito vectorLarge, susceptible human populationConditions supporting abundant mosquito populationFrequent introduction of dengue virusesIneffective vector control programs
13Emergence of dengue Socio-economic factors Population increaseBillion183019302000Unprecedented population increaseUncontrolled and unplanned urbanizationInadequate environmental conditions65432Entre 1950 y 1960 ocurrió el mayor crecimiento de la población de la tierra, la pob se duplico en 15 anosEl tercer mundo duplica su población cada 43 anos.1
14Reinfestation of the Americas by Aedes aegypti* * Source: CDC/PAHO
15Emergence of dengue Uncontrolled urbanization* In 1954, 42% of the population of Latin America lived in urban areas, increasing to 75% in 1999.“Informal” communities proliferated as a result of poverty.Scarcity of basic services: running water, sewage and collection of garbage.* High population densitySources: Gubler, PAHO, 1997.
17Emergence of dengue Inadequate environmental conditions* Insufficient collection of disposable containersNon-biodegradable containersDiscarded tiresInsufficient and inadequate water serviceIncreased number of “pilas” and water storage containersInadequate water and sewer conditions* Increase in production sites
18Production sites for Aedes aegypti Buckets and pails
19Production sites for Aedes aegypti Water storage tanks
20Production sites for Aedes aegypti Discarded tires
21Emergence of dengue Population movement* MigrationsInternational TourismMore than 750 millon people cross frontiers annuallyIncrease of migration from rural areas to cities1.4 billion international passengers in 1999697 million international tourist arrivals in 2000.715 million in 2002, an increase of 3.1%* Traffic of microorganismsSource: WTO
23Why has dengue emerged in Latin America? Reinfestation by Aedes aegyptiIneffective mosquito control programsDeteriorated public health infrastructureUncontrolled population growth andunplanned urbanizationIncreased air travel by humans
25Aedes aegypti Lives in and around human habitations in urban areas Lays eggs and produces larvae preferentially in artificial containersStrong preference for human blood; primarily a daytime feeder and bites several times in her lifeMost important vector of dengue viruses in the world9
26Life cycle of Aedes aegypti 4. Adult3. Pupae1. Eggs2. Larvae
27Personal protection against mosquitoes Apply repellent (20-30% DEET) to exposed skin- avoid eyes, mouth, and children’s handsSpray clothing with repellents with DEET or permethrinUse treated mosquito netting over bedSpray insecticide in room before going to bed, follow label instructionsWear long-sleeved shirts and long pants
28Dengue vaccine? No licensed vaccine at present Effective vaccine must be tetravalentField testing of an attenuated tetravalent vaccine currently underwayEffective, safe and affordable vaccine will not be available in the immediate futureVector control continues to be key to dengue prevention
29Vector control methods: Biological and environmental control Biological controlLargely experimentalOption: place fish in containers to eat larvaeEnvironmental controlElimination of larval habitatsMethod most likely to be effective in the long term
30Spraying to control adult Aedes aegypti Thermal fogAerosols – Cold fog and ultra low volume (ULV)Inside of residences with portable equipmentFrom the ground with vehicle-mounted equipmentAerial application
31CDC evaluations: Emergency control in Puerto Rico* Ground ULV applications versus Aedes aegyptiC-130 (Hercules transporter) with USAF Reserve Unit from Columbus, OHUS Navy (DVECC) with PAU-9 from JAXMosquitoes susceptible to naled (Dibrom 14) and insecticide reached the ground but did not penetrate housesLimited, transitory impact on wild population* Other projects with US Army in Honduras and the Dominican Republic
39Operation Restore Hope Somalia- 1992-1993 30,000 troops deployed; 530 were studiedhospitalized with fever- 129 with “unspecified illness”- 41 with DEN virus and 18 with anti-dengue ABs= 59/129 (46%) with DEN infections.Study of unit in Baardera: 9% (44) of 494 with dengue infections70% used DEET < 1 time/day, 22% never treated uniforms, 61% did not use bed nets and only 25% kept sleeves rolled down at all timesPoor compliance with PPMs vs. insects
40Operation Uphold Democracy Haiti- 1995 249 with fever- 79 (32%) with DEN infection- 44/79 participated in survey- 73% with mosquito bites daily- 50% used repellents < 1/week or never- 48% did not use a bed net10/14 (71%) of Army units did not have deployed, functional field sanitation teams31% of soldiers indicated PPMs emphasized “some but not enough or not at all”Low unit readiness to perform VC activitiesCommand enforcement of PM doctrine is essential for dengue prevention
41DHF in VenezuelaPAHO-Venezuela requested that CDC-San Juan test specimens from suspected fatal case (12 year-old girl) of DHF from VenezuelaDengue etiology was confirmed; epidemic was spreading from Maracay to CaracasMinister of Health sought epidemic response recommendation. Discussed results of USAF and Navy trials. “Aerial control… limited impact, dangerous, could not recommend aerial control as the solution.”Minister “… must take action and intended to spray using helicopters with booms attached”With Minister’s decision, I changed hats and recommended that he seek “professional assistance such as from the US Navy” No aerial spray experience in Venezuela.Venezuelan Air Force transported DVECC personnel and equipment to Venezuela.
42MMART* Preventive Medicine Assists Venezuela Preparing to spray with Venezuelan helicopterMMART* Preventive MedicineAssists VenezuelaLCDR Mark T. Wooster, MSC, USNNavy Medicine (Mar-Apr 1991)* Mobile Medical Augmentation Readiness Team
43DHF in VenezuelaDVECC’s “equipo de expertos rociadores aereos”LCDR Mark WoosterLT Joseph ConlonLT Stanton CopeLT David ClabornLT Rafael del VecchioU.S. Navy personnel performed 60 aerial spray missions 3 oz/acre) during 135 flight hours over Maracay and Caracas.
44Aterriza de emergencia helicóptero de fumigación (Newspaper report) MARACAY (Especial) – Uno de los helicópterosde la Fuerza Aérea, que participa en las operaciones defumigación contra el dengue, aterrizó de emergencia en elestacionamiento del centro comercial “El Castaño”, deesta ciudad, resultando gravemente herido el piloto de launidad, que no fue identificado por las autoridades.En la aeronave viajaban dos oficiales [LT JosephConlon and LT Stanton Cope] de la Marina de los EstadosUnidos, quienes habrian sufrido lesiones. Tambien ibandos oficiales de la Fuerza Aérea Venezolana, y tresguardias nacionales.La aeronave arrancó una linea de alta tensióny dejo al sector “El Castaño” sin electricidad.
45Venezuelan helicopter After mission!Venezuelan helicopter
46Fortunately, the injuries to the crew and US Navy personnel were minor. And, some of our “expertos” developed a new feeling for helicopters on the ground.
47“Private parking space” for AFPMB RLO Silver Spring, Maryland “I love my choppers!”“Private parking space” for AFPMB RLOSilver Spring, Maryland
48CAPT Stanton E. Cope- “Dengue fighter” bsCAPT Stanton E. Cope- “Dengue fighter”
49Take home messagesImportance of command emphasis for personal protection measuresCritical that you lead by example and use repellentsBe prepared to respond to requests for help in dealing with dengue and other VBD in support of US military or in humanitarian missionsThere is no “magic bullet” to solve the emerging problem of dengue/DHFYou are part of unique national/international vector control resources; challenges and danger may accompany your workUSDA is anxious to support US military in protecting deployed personnel and in responding to humanitarian missions
50Walter Reed Army Medical Center PSAWashington, D.C.My last interaction with an Army physician