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Dengue: An emerging arboviral disease Gary G. Clark, Ph.D. Mosquito and Fly Research Unit CMAVE, ARS, USDA Gainesville, Florida.

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Presentation on theme: "Dengue: An emerging arboviral disease Gary G. Clark, Ph.D. Mosquito and Fly Research Unit CMAVE, ARS, USDA Gainesville, Florida."— Presentation transcript:

1 Dengue: An emerging arboviral disease Gary G. Clark, Ph.D. Mosquito and Fly Research Unit CMAVE, ARS, USDA Gainesville, Florida

2 First interaction with a Navy physician My “emergence” at Balboa Naval Hospital San Diego, California

3 Discussion topics n n Epidemiology of dengue and DHF n n Emergence of dengue in the Americas n n Aedes aegypti and its development n n Adult control methods for Ae. aegypti n n Evaluation of emergency control studies (CDC and the military) n n Dengue and the US military

4 Dengue virus n n An arbovirus; transmitted by mosquitoes n n Four virus serotypes (DEN-1, 2, 3, 4); single-stranded RNA n n Family Flaviviridae (WNV, SLE, YF, JE) n n Causes dengue (headache, fever, joint/retrorbital pain, rash, bleeding) and dengue hemorrhagic fever (DHF)

5 Dengue viruses n n Each serotype provides specific lifetime immunity and short-term cross-immunity n n All serotypes can cause severe and fatal disease n n Genetic variation within serotypes; some appear to be more virulent or have greater epidemic potential n n Can produce outbreaks/epidemics in urban areas

6 Transmission of dengue virus by Aedes aegypti Viremia Extrinsic incubation period Days 0581216202428 Human #1Human #2 Illness Mosquito feeds / acquires virus Mosquito refeeds / transmits virus Intrinsic incubation period Illness

7 Dengue: A global perspective* n n Most important arboviral disease of humans; 2.5- 3 billion people (40% of the world) at risk of infection n n 10’s of millions of cases of dengue and 100’s of thousands of DHF cases annually n n A leading cause of hospitalization and death among children in Asia n n DHF mortality rate averages about 5% * Source: WHO, 1996

8 World distribution of dengue 2006 Areas infested with Aedes aegypti Areas with Ae. aegypti and recent dengue epidemics

9 Dengue/DHF cases reported to the World Health Organization 1955-2005* * Source: WHO, Sep. 2006 Ave. annual no. cases

10 Dengue in the Americas 1980 – 2006* * Source: PAHO (Jan. 19, 2007) Year

11 * Source: PAHO (Jan. 19, 2007) Dengue hemorrhagic fever in the Americas 1980 – 2006* Year CasesCases *

12 n Presence of competent mosquito vector n Large, susceptible human population n Conditions supporting abundant mosquito population n Frequent introduction of dengue viruses n Ineffective vector control programs Why has dengue emerged in the Americas?

13 Population increase Emergence of dengue Socio-economic factors 183019302000 Billion 6 5 4 3 2 1  Unprecedented population increase  Uncontrolled and unplanned urbanization  Inadequate environmental conditions

14 Reinfestation of the Americas by Aedes aegypti* 1930s 1970 2006 1930s 1970 2006 * Source: CDC/PAHO

15 Emergence of dengue Uncontrolled urbanization* n n In 1954, 42% of the population of Latin America lived in urban areas, increasing to 75% in 1999. n n “Informal” communities proliferated as a result of poverty. n n Scarcity of basic services: running water, sewage and collection of garbage. * High population density Sources: Gubler, 1998. PAHO, 1997.


17 Emergence of dengue Inadequate environmental conditions* n n Insufficient collection of disposable containers n n Non-biodegradable containers n n Discarded tires n n Insufficient and inadequate water service n n Increased number of “pilas” and water storage containers n n Inadequate water and sewer conditions * Increase in production sites

18 Buckets and pails Production sites for Aedes aegypti

19 Water storage tanks Production sites for Aedes aegypti

20 Discarded tires

21 Emergence of dengue Population movement* n n Migrations n n International Tourism n n More than 750 millon people cross frontiers annually n n Increase of migration from rural areas to cities n n 1.4 billion international passengers in 1999 n n 697 million international tourist arrivals in 2000. n n 715 million in 2002, an increase of 3.1% Source: WTO * Traffic of microorganisms


23 Why has dengue emerged in Latin America? n n Reinfestation by Aedes aegypti n n Ineffective mosquito control programs n n Deteriorated public health infrastructure n n Uncontrolled population growth and unplanned urbanization n n Increased air travel by humans

24 Aedes aegypti

25 n n Lives in and around human habitations in urban areas n n Lays eggs and produces larvae preferentially in artificial containers n n Strong preference for human blood; primarily a daytime feeder and bites several times in her life n n Most important vector of dengue viruses in the world

26 Life cycle of Aedes aegypti 1. Eggs 2. Larvae 3. Pupae 4. Adult

27 Personal protection against mosquitoes n n Apply repellent (20-30% DEET) to exposed skin- avoid eyes, mouth, and children’s hands n n Spray clothing with repellents with DEET or permethrin n n Use treated mosquito netting over bed n n Spray insecticide in room before going to bed, follow label instructions n n Wear long-sleeved shirts and long pants

28 Dengue vaccine? n n No licensed vaccine at present n n Effective vaccine must be tetravalent n n Field testing of an attenuated tetravalent vaccine currently underway n n Effective, safe and affordable vaccine will not be available in the immediate future Vector control continues to be key to dengue prevention

29 Vector control methods: Biological and environmental control n n Biological control Largely experimental Option: place fish in containers to eat larvae n n Environmental control Elimination of larval habitats Method most likely to be effective in the long term

30 n n Thermal fog n n Aerosols – Cold fog and ultra low volume (ULV) Inside of residences with portable equipment From the ground with vehicle- mounted equipment Aerial application Spraying to control adult Aedes aegypti

31 CDC evaluations: Emergency control in Puerto Rico* n n Ground ULV applications versus Aedes aegypti n n C-130 (Hercules transporter) with USAF Reserve Unit from Columbus, OH n n US Navy (DVECC) with PAU-9 from JAX n n Mosquitoes susceptible to naled (Dibrom 14) and insecticide reached the ground but did not penetrate houses n n Limited, transitory impact on wild population * Other projects with US Army in Honduras and the Dominican Republic

32 Ground ULV application


34 Aerial application in San Juan with C-130

35 Aerial application in San Juan with PAU-9

36 US Navy’s PAU-9 unit

37 Indoor application with thermal fog unit

38 Indoor application with portable ULV unit

39 Operation Restore Hope Somalia- 1992-1993 n n 30,000 troops deployed; 530 were studied - 289 hospitalized with fever- 129 with “unspecified illness”- 41 with DEN virus and 18 with anti-dengue ABs= 59/129 (46%) with DEN infections. n n Study of unit in Baardera: 9% (44) of 494 with dengue infections n n 70% used DEET < 1 time/day, 22% never treated uniforms, 61% did not use bed nets and only 25% kept sleeves rolled down at all times n n Poor compliance with PPMs vs. insects

40 Operation Uphold Democracy Haiti- 1995 n n 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 net n n 10/14 (71%) of Army units did not have deployed, functional field sanitation teams n n 31% of soldiers indicated PPMs emphasized “some but not enough or not at all” n n Low unit readiness to perform VC activities n n Command enforcement of PM doctrine is essential for dengue prevention

41 DHF in Venezuela 1989-1990 n n PAHO-Venezuela requested that CDC-San Juan test specimens from suspected fatal case (12 year-old girl) of DHF from Venezuela n n Dengue etiology was confirmed; epidemic was spreading from Maracay to Caracas n n Minister 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.” n n Minister “… must take action and intended to spray using helicopters with booms attached” n n 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. n n Venezuelan Air Force transported DVECC personnel and equipment to Venezuela.

42 LCDR Mark T. Wooster, MSC, USN Navy Medicine (Mar-Apr 1991) Preparing to spray with Venezuelan helicopter MMART* Preventive Medicine Assists Venezuela * Mobile Medical Augmentation Readiness Team

43 DHF in Venezuela 1989-1990 n n DVECC’s “equipo de expertos rociadores aereos” LCDR Mark Wooster LT Joseph Conlon LT Stanton Cope LT David Claborn LT Rafael del Vecchio n n U.S. Navy personnel performed 60 aerial spray missions (malathion @ 3 oz/acre) during 135 flight hours over Maracay and Caracas.

44 Aterriza de emergencia helicóptero de fumigación (Newspaper report) MARACAY (Especial) – Uno de los helicópteros de la Fuerza Aérea, que participa en las operaciones de fumigación contra el dengue, aterrizó de emergencia en el estacionamiento del centro comercial “El Castaño”, de esta ciudad, resultando gravemente herido el piloto de la unidad, que no fue identificado por las autoridades. En la aeronave viajaban dos oficiales [LT Joseph Conlon and LT Stanton Cope] de la Marina de los Estados Unidos, quienes habrian sufrido lesiones. Tambien iban dos oficiales de la Fuerza Aérea Venezolana, y tres guardias nacionales. La aeronave arrancó una linea de alta tensión y dejo al sector “El Castaño” sin electricidad.

45 Venezuelan helicopter After mission!

46 Fortunately, 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!”

48 CAPT Stanton E. Cope- “Dengue fighter” u b s

49 Take home messages n n Importance of command emphasis for personal protection measures n n Critical that you lead by example and use repellents n n Be prepared to respond to requests for help in dealing with dengue and other VBD in support of US military or in humanitarian missions n n There is no “magic bullet” to solve the emerging problem of dengue/DHF n n You are part of unique national/international vector control resources; challenges and danger may accompany your work n n USDA is anxious to support US military in protecting deployed personnel and in responding to humanitarian missions

50 My last interaction with an Army physician Walter Reed Army Medical Center Washington, D.C. PSA

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