Dengue Fever Prevention andControlSaleem M. Rana, PhD
The Dengue Fever a Global Problem• During epidemics of dengue, infection rates among those who have not been previously exposed to the virus are often 40% to 50%, but can reach 80% to 90%.• An estimated 500 000 people with DHF require hospitalization each year, a very large proportion of whom are children. About 2.5% of those affected die.• Without proper treatment, DHF fatality rates can exceed 20%.• Wider access to medical care from health providers with knowledge about DHF - physicians and nurses who recognize its symptoms and know how to treat its effects can reduce death rates to less than 1%.
Aedes aegypti Aedes albopictus
Behavior Day-time biter Lives outside But comes indoors May lay eggs indoors Lays eggs in artificial containers Anything that can hold water Rests in low, shaded areas. Under tables, chairs In machinery- if damp
More behavior Day-time biter – also in lighted rooms at night. Silent flier – no buzz in your ear. Very gentle on skin and not easily felt biting. Adults not active under 15-16 degrees. Adults not killed by cold, just go inactive. Eggs laid containers of water Egg to Larva to Adult in one week or less.
Comparison of Aedes (Larvae) Characters Ae. aegypti Ae.albopictusANTENNAE single hair near middle single hair near saddleHEAD upper & lower hairs upper & lower hairs single singleTHORAX heavy hooks on sides weak or no hooks on sideCOMB SCALES pitchfork-shaped; 7-12 in thorn-like; in 1 row 1 rowSIPHON index 2.0; pectin evenly pectin evenly spaced spacedGILLS all the same length, all the same length, rounded; longer than anal rounded; longer than anal segment segment
Comparison of Aedes (Adult) Characters Ae. aegypti Ae.albopictusPALPS dark with white tip; dark with white tip; clypeus white clypeus blackPROBOSCIS dark darkSCUTUM dark with white lyre- dark with white median shaped pattern stripeTHORAX dark with patches of dark with patches of white scales white scalesWINGS dark darkABDOMEN dark with narrow white dark with narrow white basal bands basal bandsHIND LEGS dark with white basal dark with white basal bands bands
Possible Weapons to Fight DengueFever• Drugs that kill the virus in humans• Insecticides that kill the mosquito vector• Vaccines
1. Drugs• No specific anti viral• Symptomatic treatment
2. Insecticides: Mosquitoes Quickly Acquire Resistance Before During After Biologic niche intact Mosquitoes return
3. VaccineDoes not exist (yet)
Before sunrise Near sunset
Symptoms Dengue fever is a flu-like illness with varying characteristics: Infants and youths often experience an undifferentiated febrile disease with rash. Older children and adults may have a mild febrile syndrome but more typically experience: high fever, severe headache, pain behind the eyes, muscle and joint pains and rash. Typically, a person will develop dengue fever as a result of initial exposure to one serotype. Upon recovery, a patient develops immunity to this single serotype.
SYMPTOMS Upon second infection with a different serotype: the patient stands a greater risk of developing dengue haemorrhagic fever (DHF), a more serious and potentially fatal disease. DHF is characterized by: o High fever, haemorrhagic phenomena, enlarged liver and circulatory failure. o A sudden onset of fever is the first indication of DHF, accompanied by facial flush and other symptoms of dengue fever. o The fever persists for 2-7 days and can reach 41° C, followed by febrile convulsions and haemorrhagic phenomena.
SYMPTOMSThe patient may recover and symptoms abate. But if left untreated, the patient may go into shock (DSS) with a rapid, weak pulse, followed by signs of circulatory failure such as cool, blotchy skin. Without proper treatment, the patient may die within 12-24 hours.
Strategies for Dengue Control
National Strategy. VECTOR CONTROL SOLID WASTE MANAGEMENT SURVEILLANCE DENGUE CELL CASE ACSM MANAGEMENT CAPACITY BUILDING
Control StrategySelective integrated vector control, with community and intersectoral participation Active disease surveillance based on a strong health information system-involves clinical and laboratory-basedvector surveillance for monitoring and evaluation of control programmes.
Control StrategyEmergency preparedness for development of emergency and contingency plans, including education of the medical community, hospitalization plans, case management and emergency vector control.Capacity building and training for surveillance, laboratory diagnosis, case management and vector control at professional, supervisory, technical and field levels.Vector control research including studies on vector biology and control, disease relationships, design and management of control programmes (including social and economic approaches) and cost benefit analyses. The relative impact of the components of integrated vector control require further elucidation.
Problems And Challenges• demographic changes ▫ uncontrolled population growth ▫ Mobility ▫ unplanned urbanization. ▫ man-made larval habitats e.g. household water storage containers, discarded solid waste items, such as plastics, glass containers and used automobile tyres.
NEW APPROACH:GENETIC MODIFICATION OF MOSQUITOES 1 ) G E N E T I C A L LY E N G I N E E R M O S Q U I TO E S TO M A K E T H E M R E S I S TA N T TO V I R U S 2) I N T R O D U C E T H E R E F R A C TO RY G E N E ( S ) I N TO M O S Q U I TO P O P U L AT I O N S LESS TRANSMISSION LESS DENGUE FEVER
DF +ve cases Aedes egypti Aedes albopictus larvae Fogging larvicide IRS 100 96 88 93 86 8080 71 67 57 60 60 40 40 36 33 33 31 20 19 24 2727 27 24 20 7 12 1st week 2nd week 3rd week 4th weekMonthly Temperature, Rainfall and DF Correlation between dengue fever prevalence,2008 in Lahore vector density and control activities 2008 in Lahore Annual correlation between dengue fever, temperature and rainfall 2008 in Lahore
MessageStart Active disease surveillance based on : a strong health information system to involves the clinical and laboratory-based dengue surveillance for early detection of epidemics, and Develop a quick reporting system from: FLCF ----EDOH---DGHS vector surveillance for monitoring and evaluation of control programmes. Aware the Community