VECTOR-BORNE DISEASESVECTOR-BORNE DISEASES

• DENGUEDENGUE•MALARIAMALARIA

WHAT IS DENGUE?WHAT IS DENGUE? Dengue is a viral diseaseDengue is a viral disease It is transmitted by the infective bite of female It is transmitted by the infective bite of female Aedes Aegypti Aedes Aegypti

mosquitomosquito Man develops disease after 5-6 days of being bitten by an Man develops disease after 5-6 days of being bitten by an

infective mosquitoinfective mosquito

It occurs in two forms: It occurs in two forms: • Dengue Fever and Dengue HaemorrhagicFever(DHF)Dengue Fever and Dengue HaemorrhagicFever(DHF)• Dengue Fever is a severe, flu-like illness (Influenza)Dengue Fever is a severe, flu-like illness (Influenza)• Dengue Haemorrhagic Fever (DHF) is a more severe form of disease, Dengue Haemorrhagic Fever (DHF) is a more severe form of disease,

which may cause deathwhich may cause death

Dengue VirusDengue Virus

Causes dengue and dengue hemorrhagic feverCauses dengue and dengue hemorrhagic fever Is an arbovirusIs an arbovirus Transmitted by mosquitoes (vector-borne)Transmitted by mosquitoes (vector-borne) Composed of single-stranded RNAComposed of single-stranded RNA Has 4 serotypes (DEN-1, 2, 3, 4)Has 4 serotypes (DEN-1, 2, 3, 4)

Dengue VirusesDengue Viruses

Each serotype provides specific lifetime Each serotype provides specific lifetime immunity, and short-term cross-immunityimmunity, and short-term cross-immunity

All serotypes can cause severe and fatal All serotypes can cause severe and fatal diseasedisease

Genetic variation within serotypesGenetic variation within serotypes Some genetic variants within each serotype Some genetic variants within each serotype

appear to be more virulent or have greater appear to be more virulent or have greater epidemic potentialepidemic potential

Transmission of Dengue VirusTransmission of Dengue Virusby by Aedes aegyptiAedes aegypti

Viremia Viremia

Extrinsic incubation

period

Days0 5 8 12 16 20 24 28

Human #1 Human #2Illness

Mosquito feeds / acquires virus

Mosquito refeeds / transmits virus

Intrinsicincubation

period

Illness

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

3

4

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

6

7

5

Aedes aegyptiAedes aegypti Mosquito Mosquito

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.

On average, a female Aedes mosquito can lay about 300 eggs during her life span of 14 to 21 days.

Aedes aegyptiAedes aegypti

Dengue transmitted by infected female Dengue transmitted by infected female mosquitomosquito

Primarily a daytime feederPrimarily a daytime feeder Lives in and around human habitationLives in and around human habitation Lays eggs and produces larvae Lays eggs and produces larvae

preferentially in artificial containerspreferentially in artificial containers

Aedes aegyptiAedes aegypti Breeding Sites Breeding Sites

SIGNS & SYMPTOMS OF DENGUE FEVERSIGNS & SYMPTOMS OF DENGUE FEVER

Abrupt onset of high feverAbrupt onset of high fever Severe frontal headacheSevere frontal headache Pain behind the eyes which worsens with Pain behind the eyes which worsens with

eye movementeye movement Muscle and joint painsMuscle and joint pains Loss of sense of taste and appetiteLoss of sense of taste and appetite Measles-like rash over chest and upper Measles-like rash over chest and upper

limbslimbs Nausea and vomitingNausea and vomiting

Dengue Hemorrhagic FeverDengue Hemorrhagic FeverWHO classification of DHFWHO classification of DHF Usually occurs in secondary Usually occurs in secondary

infections after actively or infections after actively or passivelypassively

Thrombocytopenia (platelet Thrombocytopenia (platelet count (maternal) acquired count (maternal) acquired immunity to a <100,000) immunity to a <100,000) different viral serotypedifferent viral serotype

Only 2-4% of secondary Only 2-4% of secondary infectionsinfections

Fever 2-7 days result in severe Fever 2-7 days result in severe diseasedisease

Hemorrhagic manifestations Hemorrhagic manifestations with a positive tourniquet with a positive tourniquet teststests

Mortality is 10-20% if Mortality is 10-20% if untreated, but decreases to untreated, but decreases to <1% if adequately<1% if adequately

Hemoconcentration or Hemoconcentration or evidence of treated plasma evidence of treated plasma leakageleakage

Plasma leakage may progress Plasma leakage may progress to dengue shock syndrometo dengue shock syndrome

LABORATORY DIAGNOSIS OF DENGUELABORATORY DIAGNOSIS OF DENGUE

 Haemagglutination inhibition (HI) test Haemagglutination inhibition (HI) test

Compliment Fixation Test (CFT) Compliment Fixation Test (CFT)

Neutralization test (NT) IgM-capture Neutralization test (NT) IgM-capture

Enzyme-Linked Immunosorbent Assay (MAC-ELISA)Enzyme-Linked Immunosorbent Assay (MAC-ELISA)

IgG-ELISAIgG-ELISA

Rapid Diagnostic tests (NS 1)Rapid Diagnostic tests (NS 1)

Management of Dengue Fever (DF)Management of Dengue Fever (DF) No specific therapy, management of Dengue fever is symptomatic and No specific therapy, management of Dengue fever is symptomatic and

supportive. supportive. Bed rest is advisable during the acute phase. Bed rest is advisable during the acute phase. Use cold sponging to keep temperature below 39 CUse cold sponging to keep temperature below 39 C Antipyretics may be used to lower the body temperature.Antipyretics may be used to lower the body temperature. Aspirin/NSAID like Ibuprofen etc should be avoided since it may cause Aspirin/NSAID like Ibuprofen etc should be avoided since it may cause

gastritis, vomiting, acidosis and platelet dysfunction.gastritis, vomiting, acidosis and platelet dysfunction. Oral fluid and electrolyte therapy are recommended for patients with Oral fluid and electrolyte therapy are recommended for patients with

excessive sweating or vomitingexcessive sweating or vomiting Patients should be monitored in DHF endemic area until they become a Patients should be monitored in DHF endemic area until they become a

febrile for one day without the use of antipyretics and after platelet and febrile for one day without the use of antipyretics and after platelet and haematocrit determinations are stable, platelet count is >50,000/ cumm.haematocrit determinations are stable, platelet count is >50,000/ cumm.

PreventionPrevention Personal:Personal:

• clothing to reduce exposed skinclothing to reduce exposed skin• insect repellent especially in early morning, late afternoon. insect repellent especially in early morning, late afternoon.

Bed netting importantBed netting important• mosquito repellants(pyrethroid based)mosquito repellants(pyrethroid based)• coils, sanitation measuresEnvironmental: reduced vector coils, sanitation measuresEnvironmental: reduced vector

breeding sites solid waste management public education breeding sites solid waste management public education empty water containers and cut weed/tall grassempty water containers and cut weed/tall grass

PreventionPreventionBiologicalBiological• Target larval stage of Aedes in large water storage Target larval stage of Aedes in large water storage

containerscontainers• Larvivorous fish (Gambusia), endotoxin producing bacteria Larvivorous fish (Gambusia), endotoxin producing bacteria

(Bacillus), copepod crustaceans (mesocyclops)(Bacillus), copepod crustaceans (mesocyclops)

ChemicalChemical• Thermal fogging-malathion,pyrethrumThermal fogging-malathion,pyrethrum• Insecticide treatment of water containersInsecticide treatment of water containers• Space spraying (thermal fogs)Space spraying (thermal fogs)• Indoor space spraying(2% pyrethrum), organophosphorus Indoor space spraying(2% pyrethrum), organophosphorus

compoundscompounds

Dengue UpdateDengue Update

The first dengue vaccine, Dengvaxia (CYD-TDV) by Sanofi The first dengue vaccine, Dengvaxia (CYD-TDV) by Sanofi

Pasteur, was first licensed in December, 2015, in Mexico. Pasteur, was first licensed in December, 2015, in Mexico.

It has been registered for use in individuals 9-45 years of age It has been registered for use in individuals 9-45 years of age

living in endemic areas.living in endemic areas.

CYD-TDV is a live recombinant tetravalent vaccine based on CYD-TDV is a live recombinant tetravalent vaccine based on

the yellow fever 17d backbone and is registered as a 3-dose the yellow fever 17d backbone and is registered as a 3-dose

vaccine given on a 0/6/12 month schedule. vaccine given on a 0/6/12 month schedule.

Several other vaccine candidates are in clinical or Several other vaccine candidates are in clinical or

pre-clinical development.pre-clinical development.

Registration of a vaccine is a separate process to Registration of a vaccine is a separate process to

public health recommendations for use of a vaccine.public health recommendations for use of a vaccine.

There are currently no WHO recommendations for There are currently no WHO recommendations for

use of a dengue vaccine. use of a dengue vaccine.

The WHO Strategic Advisory Group of Experts (SAGE) on The WHO Strategic Advisory Group of Experts (SAGE) on

Immunization is currently reviewing the evidence and will Immunization is currently reviewing the evidence and will

advise WHO (likely in April 2016) on recommended use of a advise WHO (likely in April 2016) on recommended use of a

dengue vaccine. dengue vaccine.

Main considerations include vaccine safety, vaccine efficacy, Main considerations include vaccine safety, vaccine efficacy,

disease burden, programmatic suitability, and cost-disease burden, programmatic suitability, and cost-

effectiveness. effectiveness.

Formal WHO guidance on public health use will only be Formal WHO guidance on public health use will only be

issued following the SAGE assessment.issued following the SAGE assessment.

MalariaMalaria

MalariaMalaria

Name is derived from Italian Name is derived from Italian Mal’ aria Mal’ aria or bad airor bad air

Malaria continues to be most important cause of Malaria continues to be most important cause of

fever and morbidity in the Tropical world Malaria fever and morbidity in the Tropical world Malaria

has been eradicated from Europe, Most of North has been eradicated from Europe, Most of North

America, USA South America Korea and Japan, America, USA South America Korea and Japan,

What causes MalariaWhat causes Malaria

Malaria is caused by a parasite called Malaria is caused by a parasite called Plasmodium , which is transmitted via the Plasmodium , which is transmitted via the bites of infected mosquitoes. In the human bites of infected mosquitoes. In the human body, the parasites multiply in the liver, and body, the parasites multiply in the liver, and then infect red blood cells. then infect red blood cells.

Transmission of Malaria do not occurTransmission of Malaria do not occur > 2000 meters altitude. > 2000 meters altitude.

Parasites Cause of MalariaParasites Cause of Malaria

Malaria is caused by an infection by one of four Malaria is caused by an infection by one of four

single celled Plasmodia species, they are: single celled Plasmodia species, they are:

falciparum , vivax, malariae , and ovale . falciparum , vivax, malariae , and ovale .

The most dangerous of the four is. The most dangerous of the four is. P. falciparum P. falciparum

Falciparum most DangerousFalciparum most Dangerous

Falciparum accounts for 90% of deaths due to Falciparum accounts for 90% of deaths due to

malaria and vivax is the most widely spread species malaria and vivax is the most widely spread species

because it exists in both temperate and tropical because it exists in both temperate and tropical

climates. climates.

The malaria life cycle is a complex system with both The malaria life cycle is a complex system with both

sexual and asexual aspects . sexual and asexual aspects .

Malaria Kills more people than Malaria Kills more people than AIDSAIDS

Malaria kills in one year what AIDS kills in 15 years. Malaria kills in one year what AIDS kills in 15 years.

For every death due to HIV/AIDS there are about 50 For every death due to HIV/AIDS there are about 50

deaths due to malaria. To add to the problem is the deaths due to malaria. To add to the problem is the

increasing drug resistance to the established drug. increasing drug resistance to the established drug.

Etiology of MalariaEtiology of Malaria

Four Species known to infect Man Four Species known to infect Man

1. 1. Plasmodium vivax Plasmodium vivax – Benign Tertian, Tertian Malaria – Benign Tertian, Tertian Malaria

2. 2. P.ovaleP.ovale - Ovale tertian Malaria - Ovale tertian Malaria

3. 3. P.malariaeP.malariae – Quartan malaria – Quartan malaria

4. 4. P.falciparumP.falciparum – Falciparum malaria or Malignant – Falciparum malaria or Malignant

Tertian malaria. Tertian malaria.