Dengue Fever An overview

DENGUE FEVER: 

DENGUE FEVER Dr. Abdul Hameed Institute of Biomedical and Genetic Engineering (IB&GE) Dr. A.Q. Khan Research laboratories Islamabad

DENGUE FEVER: 

Dengue fever is the fastest growing mosquito-borne disease, affecting over 50 million people each year across the world. It is continuing to grow both in prevalence and severity. DENGUE FEVER Aedes aegypti

World Distribution of Dengue: 

World Distribution of Dengue Areas infested with Aedes aegypti Areas with Aedes aegypti and recent epidemic dengue Dengue fever occurs in most tropical areas of the world – see map . The disease is now endemic in more than 100 countries in: Eastern Mediterranean South-east Asia Pacific Islands Central and South America Carribean Africa

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• New infections annually: 50 million • Deaths : 24,000 annually • People at risk: 2.5-3 billion • Hospitalized cases: 500 000/year ( 90% of those affected are children ) Dengue Fever: GLOBAL STATUS

Clinical Characteristics of Dengue Fever: 

Clinical Characteristics of Dengue Fever Symptoms range from mild undifferentiated flu-like symptoms to: high fever, rash, severe headache, muscle and joint pain. Nausea, vomiting, and loss of appetite are also common.

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In the more severe form of dengue hemorrhagic fever (DHF) blood vessels start to leak and cause bleeding from the nose, mouth, and gums. Without prompt treatment, the blood vessels can collapse, causing shock ( dengue shock syndrome, DSS ) and ultimately fatality. Clinical Characteristics of Dengue Fever

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Dengue Virus Dengue is a mosquito born infection which in recent year has become major international public health concern. Dengue hemorrhagic fever (DHF), a potentially lethal complication found first time in 1950’s in Philippines and Thailand. The spread of Dengue is rapid in urban populations where household water storage is common and where solid waste disposal services are inadequate.

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First outbreak in Pakistan was in 1994 probably came from Thailand and Malaysia. Punjab is the most victimized province from Dengue fever. So far, around 18,000 dengue cases and 250 deaths have been reported in Lahore this year. Sindh & Islamabad are 2 nd and 3 rd largest victimized areas of Pakistan. In Karachi, total 1500+ cases has been reported. Facts about Dengue Fever in Pakistan

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Dengue Virus Causes dengue and dengue hemorrhagic fever. It is an arbovirus Transmitted by mosquitoes : Aedes aegypti (common) Aedes Albopictus (un-common)

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How Do Aedes Mosquitoes Transmit Diseases... Mosquito bites and sucks blood containing the virus from an infected person. Virus is carried in its body. And passes the virus to healthy people when it bites them.

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1.The virus is inoculated into humans with the mosquito saliva. 2.The virus localizes and replicates in various target organs, for example, local lymph nodes and the liver. 3.The virus is then released from these tissues and spreads through the blood to infect white blood cells and other lymphatic tissues. 4.The virus is then released from these tissues and circulates in the blood.

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5.The mosquito ingests blood containing the virus. 6.The virus replicates in the mosquito midgut , the ovaries, nerve tissue and fat body. It then escapes into the body cavity, and later infects the salivary glands. 7.The virus replicates in the salivary glands and when the mosquito bites another human, the cycle continues.

Characteristics of the Aedes Mosquito: 

Characteristics of the Aedes Mosquito One distinct physical feature – black and white stripes on its body and legs. Bites during the day. Lays its eggs in clean, stagnant water. Close-up of an Aedes mosquito

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Only the female Aedes mosquito feeds on blood. This is because they need the protein found in blood to produce eggs. Male mosquitoes feed only on plant nectar. Do you know… On average, a female Aedes mosquito can lay about 300 eggs during her life span of 14 to 21 days.

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1-2 days Stagnant water Pupae 4-5 days Life cycle of the Aedes Mosquito Larvae Eggs 2-3 days

Dengue Virus Morphology: 

Dengue Virus Morphology Dengue virus is a small, spherical, single stranded enveloped RNA virus. GROUP : IV FAMILY: Flaviviridea Genus: Flavivirus Specie: Dengue Virus

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Dengue Virus Genome The genomic RNA is approximately 11 kb in length 5'- -3' pr + M furin NC NC ns2a ns2b ns4a ns4b C prM E NS1 NS3 NS5 7 non-structural genes/proteins 3 structural Genes/proteins C = Nucleocapsid or core protein M = Membrane associated protein E = Envelope protein

Dengue Virus: Pathogencity: 

Dengue Virus: Pathogencity The Dengue Virus is a category-A pathogen and therefore is a serious threat to the human population globally. Category A pathogens are microbes that are hazardous to lab personnel and have the potential to cause serious epidemic disease. The Dengue Virus has four different serotypes, DEN-1, DEN-2, DEN-3 and DEN-4. These four serotypes are approximately 60-80% homologous but different enough to restrict cross immunity.

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Each serotype provides specific lifetime immunity, and short-term cross-immunity All serotypes can cause severe and fatal disease Genetic variation within serotypes Some genetic variants within each serotype appear to be more virulent or have greater epidemic potential Dengue Virus

Dengue Fever: Potential for a Vaccine? : 

Dengue Fever: Potential for a Vaccine? There is currently no effective, safe and affordable vaccine for dengue fever available due to a range of interrelated problems . There are four dengue serotypes a vaccine is extremely difficult to formulate as it must be tetravalent and generate an immune response against all four viruses simultaneously. Lack of a suitable animal model L imited funding and insufficient knowledge of disease pathogenesis

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There are some potential dengue fever vaccines at various stages of development. These vaccines are of four types: Live attenuated viruses Chimeric live attenuated virus Inactivated or sub-unit vaccines Nucleic acid based vaccines

Risk factors for severe disease. : 

Risk factors for severe disease. Sequential dengue infection (includes antigenic structure of virus) Race Age Host genetic factors Nutritional status Sex

BLACKS ARE RELATIVELY RESISTANT TO SEVERE DENGUE ILLNESS: 

BLACKS ARE RELATIVELY RESISTANT TO SEVERE DENGUE ILLNESS A human resistance gene seems to explain the observation that while all dengue virus types circulate in Africa no DHF/DSS cases or outbreaks of DF have been reported. While all four dengue virus types circulate in Africa few outbreaks of dengue fever and none of DHF/DSS have been reported from Africa south of the Sahara.

GENETIC ASSOCIATIONS Susceptibility Resistance : 

GENETIC ASSOCIATIONS Susceptibility Resistance HLA: HLA-A*0207 HLA-A*0203 HLA-B*51 HLA-B*52 HLA A24 HLA A33 Vit D, t allele/352 FcR γ II , DCSIGN, CD 209 promoter, TNF α TNF 308 A variety of genetic markers studied in individuals with secondary dengue infections have been statistically significantly associated with mild (resistance) or severe (susceptibility) disease.

Risk Factors for DHF (continued): 

Risk Factors for DHF (continued) Higher risk in secondary infections Higher risk in locations with two or more serotypes circulating simultaneously at high levels ( hyperendemic transmission)

Viral Risk Factors for DHF Pathogenesis: 

Viral Risk Factors for DHF Pathogenesis Virus strain (genotype) Epidemic potential: viremia level, infectivity Virus serotype DHF risk is greatest for DEN-2, followed by DEN-3, DEN-4 and DEN-1

Laboratory Tests in Dengue Fever: 

Laboratory Tests in Dengue Fever Clinical laboratory tests CBC--WBC, platelets, hematocrit Albumin Liver function tests Urine--check for microscopic hematuria Dengue-specific tests Virus isolation Serology

Laboratory Methods for Dengue Diagnosis: 

Laboratory Methods for Dengue Diagnosis Virus isolation to determine serotype of the infecting virus IgM ELISA test for serologic diagnosis PCR based diagnosis (RT-PCR)

Dengue Fever Treatment: 

Dengue Fever Treatment There is no specific treatment for classic dengue fever, and most people recover within two weeks To help with recovery health care experts recommend Getting plenty of bed rest Drinking lots of fluid Give medicine to reduce fever (excluding aspirin)

Prevention : 

Prevention The main tactic used in fighting Dengue are: Elimination of mosquito breeding places Mosquito bite prevention

Elimination of mosquito breeding places: 

Elimination of mosquito breeding places Cover water storage containers Biological control -Larva eating fish ( e.g guppies) -Bacterial pesticides Chemical Control by using larvacides such as temphos sand granules can be placed in water containers to kill developing wigglers.

Mosquito bite prevention: 

Mosquito bite prevention Mosquito coils or vapor mats Mosquito nets Mosquito repellants Protecting people sick with dengue Wear trousers and clothing with long sleeves during the day

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Sri Lankan experts advice on dengue Fumigation , being done officially or unofficially, can help overcome the spread of ailment by just 15 per cent while preventive measures taken by the community at homes can defeat it by 85 per cent. The experts said Sri Lanka has successfully grappled with the disease over the past thirty years mainly by creating 100% public awareness . They said that the panic created in Pakistan has led to most deaths because some affected who are already suffering from diabetes or heart problems can't physically and psychologically bear the pressure of the disease and collapse having cardiac arrest. They said effect of dengue would ease by October and would end in December.

CONTACT: 

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