ARBOVIRAL DISEASE PREVALENCE IN INDIA ARBOVIRAL DISEASE PREVALENCE IN INDIA WITH SPECIAL EMPHASIS ON DENGUEWITH SPECIAL EMPHASIS ON DENGUE

DR. KUMAR VIKRAMDR. KUMAR VIKRAM MD (MICROBIOLOGY)MD (MICROBIOLOGY)

IGIMS, PATNAIGIMS, PATNA

Arthropod-borne viruses (arboviruses) are viruses that can be transmitted to man by arthropod vectors.

WHO definition

Arboviruses are viruses that are maintained in nature principally, or to an important extent, through biological transmission between susceptible vertebrate host by hematophagous arthropods; they multiply in the tissues of arthropods, and are passed on to new vertebrates by the bites arthropod after a period of extrinsic incubation.

Arboviruses are worldwide in distribution . More numerous in the tropical than in temperate zones. Over 500 viruses have been listed Most cause silent infections in rodents and other wild mammals100 of them can infect humans In India , over 40 arboviruses have been detected, of which more than 10 are known to produce human disease

GEOGRAPHICAL DISTRIBUTIONGEOGRAPHICAL DISTRIBUTION

Many different factors can contribute to the emergence of arboviral disease. These include: (1)virological determinants such as mutation, recombination, reassort- ment, natural selection, fitness adaptation, and evolutionary progression

(2)Individual host determinants such as specific risk behaviors, innate resistance, acquired immunity, and physiological factors such as age, nutritional status, and pregnancy

(3)Host population determinants such as community, behavioral, societal, transport, commercial, and iatrogenic factors;

(4)Environmental determinants such as ecological and zoonotic influences;

(5)viruses intentionally used for harm – the threat of bioterrorism

EMERGING/ RE-EMERGING ARBOVIRAL DISEASE

General propertiesGeneral properties

The arboviruses share some common biological properties:

1. All members produce fatal encephalitis in suckling mice after intracerebral inoculation

2. They possess haemagglutinin and agglutinate erythrocytes of goose or day-old chicks

3. They can be grown in yolk sac or chorioallantoic membrane of chick embryo,in tissue cultures of primary cells like chick embryo fibroblasts or continuous cell lines like vero, and in cultures of appropriate insect tissues.

4. In general, arboviruses are readily inactivated at room temperature and by bile salts, ether and other lipid solvents.

Arthropod Vectors MosquitoesJapanese encephalitis, dengue, yellow fever, Rift valley feverSt. Louis encephalitis, EEE, WEE, VEE etc

TicksCrimean-Congo haemorrhagic fever, Kyasanur forest diseaseand various tick-borne encephalitis etc.

SandfliesSicilian sandfly fever

Examples of Arthropod VectorsExamples of Arthropod Vectors

Aedes aegyptiAedes aegypti Ixodid Ticks

Phlebotomine SandflyCulex Mosquito

Animal ReservoirsAnimal Reservoirs

In many cases, the actual reservoir is not known. The following animals are In many cases, the actual reservoir is not known. The following animals are implicated as reservoirsimplicated as reservoirs

BirdsBirds Japanese B encephalitis, St Louis encephalitis,EEE, WEE

PigsPigs Japanese B encephalitis

MonkeysMonkeys Yellow FeverYellow Fever

RodentsRodents VEE, Russian Spring-Summer encephalitisVEE, Russian Spring-Summer encephalitis

Diseases CausedDiseases Caused

Fever with or without rash - - this is usually a non-specific illness resembling a number of other viral illnesses such as influenza, rubella, and enterovirus infections. The patients may go on to develop encephalitis or haemorrhagic fever

Encephalitis - e.g. EEE, WEE, St Louis encephalitis, Japanese B encephalitis- e.g. EEE, WEE, St Louis encephalitis, Japanese B encephalitis

Haemorrhagic fever - e.g. yellow fever, dengue, Crimean-Congo haemorrhagic fever- e.g. yellow fever, dengue, Crimean-Congo haemorrhagic fever

All arbovirus infections occur with varying degree of severity, subclinical infections being common

Virus Reservoir Vector Disease

Chikungunya Monkeys Mosquito Chikungunya fever

Dengue Monkeys, Man Mosquito Dengue haemorrhagic fever

Japanese B encephalitis

Wild birds, pigs Mosquito Encephalitis

Kyasanur forest disease

Forest birds, animals

Tick Haemorrhagic fever

Sindbis - Mosquito Sindbis fever

Arboviruses prevalent in India

virus first isolated from patients and mosquitoes during an epidemic in Tanzania in 1952-53Outbreak in kolkata in 1963-64In 1965 outbreak in chennai gave rise to 3,00,000 cases .Virus was not active since 1965.REAPPEARENCE after 41 yearsDuring 2006, there was a large outbreak of chikungunya in India with 1.39 million officially reported cases spread over 16 states.First noticed in Andhra pradesh and subsquently spread to Tamil nadu, kerala , karnataka and then northwards as far as DelhiOther states involved were: Maharashtra, Madhya pradesh, Gujarat, Rajasthan, Pondicherry, Goa, Orissa, west bengal, U.P, Andaman and Nicobar islands.

Clinically SupectedChikungunya Fever Cases Since 2008

Sl. No. Affected States/UTs 2008 2009 2010 2011 2012 2013* 2014**

1 Andhra Pradesh 5 591 116 99 2827 4827 377

2 Assam 0 0 0 0 0 742 0

3 Bihar 0 0 0 91 34 0 0

4 Goa 52 1839 1429 664 571 1049 455

5 Gujarat 303 1740 1709 1042 1317 2890 200

6 Haryana 35 2 26 215 9 1 2

7 Jharkhand 0 0 0 816 86 61 0

8 Karnataka 46510 41230 8740 1941 2382 5295 5248

9 Kerala 24685 13349 1708 183 66 273 143

10 Madhya Pd. 0 30 113 280 20 139 142

11 Meghalaya 0 0 16 168 0 0 0

12 Maharashtra 853 1594 7431 5113 1544 1578 1093

13 Orissa 4676 2306 544 236 129 35 10

14 Punjab 0 0 1 0 1 0 1

15 Rajasthan 3 256 1326 608 172 76 22

16 Tamil Nadu 46 5063 4319 4194 5018 859 392

17 Telangana 0 0 0 0 0 0 518

18 Tripura 0 0 0 0 0 0 21

19 Uttar Pradesh 11 0 5 3 13 0 3

20 Uttarakhand 0 0 0 18 0 0 0

21 West Bengal 17898 5270 20503 4482 1381 646 827

22 A& N Island 0 0 59 96 256 202 156

23 Chandigarh 0 0 0 1 0 1 0

24 D&N Haveli 0 0 0 0 100 2 0

25 Delhi 14 18 120 110 6 18 4

26 Lakshadweep 0 0 0 0 0 0 0

Puduchery 0 0 11 42 45 146 290

Total 95091 73288 48176 20402 15977 18840 9904

Chikungunya virus

Chickungunya is the native word for the disease in which the patient lies ‘doubled up’ due to severe joint pain.

The virus is transmitted by Aedes aegypti There is no animal reservoir for the virus

Incubation period – 4-7 days

The disease is chracterised by fever, crippling joint pains, lymphadenopathy, conjunctivitis and rash

Migratory polyarthritis mainly affects the small joints of the hands and wrists

The fever is typically biphasic with a period of remission after 1-6 days

A maculopapular rash is common and most intense on the trunk and limbs that may desquamate

Haemorrhagic manifestations are seen in some patients

DIAGNOSISVirus isolation – intracerebral inoculation in suckling mice or VERO cell serological diagnosis – haemagglutination inhibition, serum neutralisation, CFT, ELISA RT-PCR

CONTROL• VECTOR CONTROL

•VACCINE – no vaccine has been developed

GEOGRAPHICAL DISTRIBUTIONLeading cause of viral encephalitis in Asia and occurs in almost all Asian countries.The disease has been recognised in Japan since 1871 and was named Japanese B encephalitis to distinguish from encephalitis A.Virus was first isolated in Japan during epidemic in 1935.As a result of immunisation, its incidence has been declining in japan , the Korean peninsula and in some of regions of china.The disease is increasingly reported from Bangladesh, India, Nepal, Pakistan, northern Thailand, and Vietnam.

PROBLEM IN INDIA

•Recognition of JE was first made in 1955 in Tamil nadu when the virus was isolated from culex vishnui.•Remained confined to southeastern parts of India till 1973 when it caused large outbreak in West Bengal•From 1976, there have been periodic outbreaks in various parts of India – Dibrugarh(Assam) in the east, Gorakhpur (UP) and Haryana in the north and Goa and Maharashtra in the west.•Endemic in 14 states.•Assam, Bihar, Haryana, UP, Karnataka, and Tamil nadu report outbreaks every year and contribute to 80% of cases and deaths .•About 300 million people are at risk.

Epidemiology

Vector –culicine mosquitoes like culex tritaeniorhynchus, c. vishnui, c. gelidus

and some anophelines

breeding place – rice fields, shallow ditches, pools

Reservoir host – herons, egrets

Amplifier host – pigs

Human infection is a incidental “dead end’ event.

Clinical features

Most human infections are subclinical: the inapparent to clinical cases is 500-1000:1

Incubation period: 5-15 days

The course of the disease in man may be divided into three stages

1.Prodromal stage

2.Acute encephalitic stage

3.Late stage and sequelae

Prodromal stage

The onset of illness is usually acute and symptoms include fever, headache and vomiting

Acute encephalitic stage

After 1-6 days, signs of encephalitis characterised by neck rigidity, convulsions, altered sensorium and coma appear

Late stage and sequelae

Convalescence may be prolonged and residual neurological deficits may not be uncommon

Case fatality rate varies between 20-40%, but it may reach 58% and over in some epidemics

Residual neurological damage may persist in about 50% of survivors

The disease is usually diagnosed by serologyNo specific therapy is available

PreventionPreventive measures include mosquito control and establishment of piggeries away from residential areas VACCINES:1.Formaline inactivated mouse brain vaccine

• Based on Nakayama or Beijing strains• Dose-0.5 ml for children< 3yrs and 1 ml for children more than 1 yr• Route- subcutaneously• Administration – 2 primary doses 4 weeks apart and booster doses after 1 year and subsquently at 3 year interval until the age of 10-15 yrs.

2. Live attenuated vaccineBased on SA 14-14-2 strain dose – 0.5 mlRoute - subcutaneouslySingle dose followed by a single booster given at an interval of 1 year

Yellow fever

Yellow FeverYellow Fever Yellow fever is a mosquito-borne acute febrile illness accompanied by hepatic necrosisYellow fever is a mosquito-borne acute febrile illness accompanied by hepatic necrosis

It occurs mainly in tropical Africa and Latin AmericaIt occurs mainly in tropical Africa and Latin America

It does not exist in IndiaIt does not exist in India

The name has been derived from ‘yellow quarantine flag’ used The name has been derived from ‘yellow quarantine flag’ used

by the ships during 17by the ships during 17 thth century to warn the presence, on board century to warn the presence, on board

of this infectionof this infection

Yellow fever occurs in 2 major forms: urban and jungle (sylvatic) cycleYellow fever occurs in 2 major forms: urban and jungle (sylvatic) cycle

In the urban cycle, man serves both as reservoir and as definitive

host, the virus being transmitted by Aedes aegypti mosquito

In the forest or sylvatic cycle, wild monkeys act as reservoirs and several species of forest mosquitos (Haemagogus spegazzinnii in south America and Aedes africanus and A. simpsoni in Africa) are vectors. Human cases occur only when humans trespass into the forest or when monkeys raid villages.

India is a yellow fever “receptive area” that is “ an area in which yellow fever does not exist, but where conditions would permit its development if introduced”

The population of india is unvaccinated and susceptible to yellow fever.

The vector, Aedes aegypti is found in abundance

The climatic conditions are favourable in most parts of india for its transmission

The only missing link is the virus of yellow fever which does not seem to occur in india

Clinical features

After an incubation period of 3-6 days, patient develops fever with

chills, headache, myalgia and vomiting

Most cases are mild in nature, especially in the endemic areas, in

whom the disease may present as undifferentiated fever without

jaundice

The pulse is usually slow despite a high temperature

In 15-20% of cases, the disease progresses to a more serious form

with jaundice, albuminuria, renal failure and haemorrhagic

manifestations and the patient may die of hepatic and renal failure

Prophylaxis

There is no antiviral drug against yellow fever

The control of urban yellow fever can be achieved by eradicating the vector mosquito

vaccine 17D vaccine was developed by Theiler in 1937 by passaging the

Asibi strain. Given subcutaneously Mandatory for travel to or from endemic areas. Valid for 10 years beginning 10 days after vaccination.

Kyasanur Forest Disease (KFD)oKyanasur forest disease is a febrile disease associated with haemaorrhages transmitted to man by bite of infective ticks.

HISTORY first recognised in 1957 in Shimoga district of karnataka state .Local inhabitants called it “monkey disease”Later named after the locality – kyanasur forest

PROBLEM STATEMENTRemained confined to the areas contiguous to its original focus in the Sagar, Sorab and Shikarpur taluks of Shimoga district for many years.Between 1972 and 1975 , another foci developed in adjacent areas in north Kanara.In 1982, appearance of epizoonotic and epidemic in Belthangadi taluk in south kanara.The ecological disturbance caused by clear felling of virgin forest is believed to have activated a silent enzoonotic focus of the virus.

EpidemiologyNATURAL HOST AND RESERVOIR

Reservoir- small mammals particularly rats and squirrels, birds and batsMonkeys- amplifying host

VECTORSHaemaphysalis spinigeraH. turtura

INCUBATION PERIOD – between 3 and 8 days

CLINICAL FEATURESSudden onset of fever, headache and sever myalgia Gastrointestinal disturbances and haemorrhages from nose, gums , stomach and instestine in severe casesCase fatality rate – 5-10 %

Control

Control of ticks

The population at risk should be vaccinated with killed KFD vaccine

Personnel protection – protection of individuals by adequate clothing and insect repellents

HISTORY

Dengue virus was isolated in Japan in 1943 by inoculation of serum of patients in suckling mice and at Calcutta (now Kolkata) in 1944 from serum samples of US soldiers.

The first epidemic of clinical dengue-like illness was recorded in Madras (now Chennai) in 1780 and the first virologically proved epidemic of DF in India occurred in Calcutta and Eastern Coast of India in 1963-1964.

The first major epidemic of the DHF occurred in 1953-1954 in Philippines followed by a quick global spread of epidemics of DF/DHF.

The DHF started simmering in various parts of India since 1988.

The first major wide spread epidemics of DHF/DSS occurred in India in 1996 involving areas around Delhi and Lucknow13 and then it spread to all over the country

PROBLEM STATEMENT

oDengue is the most rapidly spreading mosquito-borne viral disease in the world.

o In the last 50 years, incidence has increased 30-fold with increasing geographic expansion to new countries and, in the present decade, from urban to rural settings.

o An estimated 50 million dengue infections occur annually and approximately 2.5 billion people live in dengue endemic countries.

o5,00,000 people with DHF require hospitalisation each year.

o 90% of them are childern less than 5 years and about 2.5 % of those affected die.

o Dengue is endemic in more than 100 countries.o The south – east asia and western pacific regions are the most seriously affected.

An Epidemic, Endemic& Hyper Endemic

South- East Asia is divided into 3 Categories:

Cat A: India, Bangladesh, Myanmar, Sri Lanka, Indonesia, Thailand,

Maldives

Cat B: Bhutan, Nepal

Cat C: DPR Korea

INDIAN SCENARIO

Increased risk in recent years due to Rapid urbanisation Lifestyle changes Deficent water management

Seasonal pattern – cases peak after monsoonPerennial transmission in southern states and GujaratEndemic in 31 states/UTs. All the serotypes have been isolated in India.At present DENV-1 and DENV-2 serotypes are widespread.

Epidemiological studies where dengue virus was identified

Year Region where study was conducted

Type of dengue virus detected

1964 Vellore, Tamil Nadu DV-2

NA South India DV-3

1966 Vellore, Tamil Nadu DV-3

1968 Vellore, Tamil Nadu DV- 1,2,3 & 4

1968 Kanpur, Uttar Pradesh DV-4

1969 Kanpur, Uttar Pradesh DV-4 and DV-2

1970 Hardoi, Uttar Pradesh DV-2

NA NA DV- 1,2,3 & 4

1983 Kolkata, West Bengal DV-3

1985 Jalore town, South-West Rajasthan

DV-3

NA Chikalthana, Pimpalgaon and Waloor villages in Parbhani district of Maharashtra.

DV-1 & 2

1988 Delhi DV-2

1990 Calcutta, West Bengal DV-3

1988 Rural and urban areas of Gujarat DV-2

1993 Mangalore, Karnataka DV-2

NA Assam and Nagaland DV-2

1996 Ludhiana, Punjab DV- 1,2,3 & 4

1996 Lucknow DV-2

1996 Delhi DV-2

1996 Delhi DV-2

1997 Delhi DV-1

1996 Delhi DV-2 (Genotype IV)

NA Ahmedabad, Gujarat DV-2

1997 Delhi DV-1

NA Delhi DV-2 (Genotype IV)

1996 Rural areas of Haryana DV-2

2001 Dharmapuri district, Tamil Nadu DV-2

NA Andaman and Nicobar Islands DV-2

2001 Gwalior, Madhya Pradesh DV-2

NA Northern India DV-2 (Genotype IV)

2001 Chennai, Tamil Nadu DV-3

2003 Northern India (Delhi & Gwalior) DV-3

2005 Kolkata, West Bengal DV-3

2003 Kanyakumari district, Tamil Nadu DV-3

2003-04 Delhi DV-3 (subtype III)

2003-05 Delhi 2003 - DV - 1,2,3 & 4 2005 - D - 3

2006 Delhi DV-3

2006 Delhi DV-1 & 3

2001-07 North India (Delhi and Gwalior region)

DV-1 (Genotype III)

2006 Delhi DV-1,3 & 4

2008 Delhi region DV-1,2 & 3

DISTRIBUTION OF DENGUE/DHF IN INDIA

Sl. No. Affected States/UTs

2008 2009 2010 2011 2012 2013* 2014**

C D C D C D C D C D C D C D

1 Andhra Pradesh 313 2 1190 11 776 3 1209 6 2299 2 910 1 264 2

2 Arunachal Pradesh 0 0 0 0 0 0 0 0 346 0 0 0 0 0

3 Assam 0 0 0 0 237 2 0 0 1058 5 4526 2 48 0

4 Bihar 1 0 1 0 510 0 21 0 872 3 1246 5 1 0

5 Chattisgarh 0 0 26 7 4 0 313 11 45 0 83 2 56 5

6 Goa 43 0 277 5 242 0 26 0 39 0 198 2 97 0

7 Gujarat 1065 2 2461 2 2568 1 1693 9 3067 6 6272 15 1161 0

8 Haryana 1137 9 125 1 866 20 267 3 768 2 1784 5 136 1

9 Himachal Pd. 0 0 0 0 3 0 0 0 73 0 89 2 0 0

10 J & K 0 0 2 0 0 0 3 0 17 1 1837 3 0 0

11 Jharkhand 0 0 0 0 27 0 36 0 42 0 161 0 0 0

12 Karnataka 339 3 1764 8 2285 7 405 5 3924 21 6408 12 2277 0

13 Kerala 733 3 1425 6 2597 17 1304 10 4172 15 7938 29 1804 9

14 Madhya Pd. 3 0 1467 5 175 1 50 0 239 6 1255 9 1319 9

15 Meghalaya 0 0 0 0 1 0 0 0 27 2 43 0 0 0

16 Maharashtra 743 22 2255 20 1489 5 1138 25 2931 59 5610 48 3551 7

17 Manipur 0 0 0 0 7 0 220 0 6 0 9 0 0 0

18 Mizoram 0 0 0 0 0 0 0 0 6 0 7 0 15 0

19 Nagaland 0 0 25 0 0 0 3 0 0 0 0 0 0

20 Orissa 0 0 0 0 29 5 1816 33 2255 6 7132 6 5079 9

21 Punjab 4349 21 245 1 4012 15 3921 33 770 9 4117 25 218 0

22 Rajasthan 682 4 1389 18 1823 9 1072 4 1295 10 4413 10 380 2

23 Sikkim 0 0 0 0 0 0 2 0 2 0 38 0 5 0

24 Tamil Nadu 530 3 1072 7 2051 8 2501 9 12826 66 6122 0 1574 0

25 Tripura 0 0 0 0 0 0 0 0 9 0 8 0 5 0

26 Telangana 0 0 0 0 0 0 0 0 0 0 0 0 351 0

27 Uttar Pradesh 51 2 168 2 960 8 155 5 342 4 1414 5 28 0

28 Uttrakhand 20 0 0 0 178 0 454 5 110 2 54 0 1 0

29 West Bengal 1038 7 399 0 805 1 510 0 6456 11 5920 6 2212 1

30 A& N Island 0 0 0 0 25 0 6 0 24 0 67 0 112 0

31 Chandigarh 167 0 25 0 221 0 73 0 351 2 107 0 6 0

32 Delhi 1312 2 1153 3 6259 8 1131 8 2093 4 5574 6 340 2

33 D&N Haveli 0 0 0 0 46 0 68 0 156 1 190 0 266 1

34 Daman & Diu 0 0 0 0 0 0 0 0 96 0 61 0 0 0

35 Puduchery 35 0 66 0 96 0 463 3 3506 5 2215 0 466 0

Total 12561 80 15535 96 28292 110 18860 169 50222 242 75808 193 21772 48

The Epidemiological TriadThe Epidemiological Triad

The AgentThe Agent

Arbovirus (ss RNA Virus)

Genus Flavivirus

Family Flaviviraede

4 serotypes- DENV 1, DENV 2, DENV 3 & DENV4

Antigenic similarity but infection with one serotype does not provide lifelong immunity for other serotypes (Cross Immunity lasts only a few months),

…Instead prior immune sensitization worsens the disease scenario

Denv Has…Denv Has…A lipoprotein envelope

3 structural protein genes encoding: {CME}

– Nucleocapsid or core protein (C),

– Membrane- associated protein (M),

– Envelope protein (E), and

7 non-structural protein (NS) genes including, envelope glycoprotein,

NS 1

NS 1 is of diagnostic and pathological importance.

It is associated with viral haemagglutination and neutralization activity.

The HostThe HostInfective Stage: 1 day before onset of fever to day 5

Intrinsic Incubation Period: 4- 6 days

High Risk Patients:– Extremes of Age– Pregnancy– Any condition prone to heavy blood loss: Peptic ulcer disease;

menstruation; haemolytic anaemia; G- 6PD deficiencies; thalassemia; patients on steroids, NSAIDS

– Any chronic condition: DM, HTn, Asthma, Cirrhosis, IHD, CRF

Remember… “Prior immune sensitization worsens the disease scenario”

1st Infection with DENV-

1

Asymptomatic/ Non specific

manifestations/ DF

2nd Infection

with DENV- 2, 3

or 4

DHF/ DSS/

Severe Disease

Secondary Infection with DENV 2 or multiple infections with different serotypes causes Severe Disease (DHF/ DSS)

DENV 1/ DENV 2 Sequence is the worst

Non neutralizing Ab(s)

Mononuclear cells Cytokines, vasoactive mediators

procoagulants

DIC

2nd Infection

The EnvironmentThe EnvironmentTropical& Sub- tropicalTropical& Sub- tropical

Urban, Peri urban; Urban, Peri urban; RuralRural

Rapid Unplanned uncontrolled Rapid Unplanned uncontrolled urbanizationurbanization, ,

Transportation: Transportation: human movement and congregationhuman movement and congregation

Poor water storage and managementPoor water storage and management

Seasonal Pattern:Seasonal Pattern: Post Monsoon (But Perennial in Gujarat& Post Monsoon (But Perennial in Gujarat&

South India)South India)

Global WarmingGlobal Warming

2 degree rise in temp- 2 degree rise in temp-

– Shortens extrinsic IP- more infected mosquitos to further Shortens extrinsic IP- more infected mosquitos to further

spread DENVspread DENV

– Enhances the life cycle of AedesEnhances the life cycle of Aedes

– Shortens the size of the mosquitoShortens the size of the mosquito

– Rise in temp- mosquito bites more frequently due to Rise in temp- mosquito bites more frequently due to

“dehydration”- further spreads DENV“dehydration”- further spreads DENV

The VectorThe Vector

Ae albopictusAe albopictus Eggs Survive Sub Freezing Temp Eggs Survive Sub Freezing Temp

Ae aegyptiAe aegypti-- Cosmo tropical species between latitudes 45°N and 35°S Cosmo tropical species between latitudes 45°N and 35°S

Vector CompetencyVector Competency

Vector CapacityVector Capacity

Transovarial SpreadTransovarial Spread

Endophagic, EndophilicEndophagic, Endophilic

16- 35 °C, 60- 80% Relative Humidity16- 35 °C, 60- 80% Relative Humidity

Vector CompetencyVector Competency

– High susceptibility to infecting virus

– Ability to replicate the virus

Ability to transmit the virus to another host

Both Ae. aegypti and Ae. albopictus carry high vectorial competency for dengue viruses.

VectorialVectorial CapacityCapacity: Depends on the : Depends on the Environmental and Biological Environmental and Biological characteristics of the Vectorcharacteristics of the Vector

Ae. aegyptiAe. aegyptiHighly domesticatedStrongly anthropophilicNervous feeder (i.e. it bites more than one host to complete one blood meal) and Discordant species (i.e. it needs more than one feed for the completion of the gonotropic cycle)These habits epidemiologically result in the generation of multiple cases and the clustering of dengue cases in cities.

Ae. albopictusAe. albopictus

Feral

Feeds on both humans and animals

Aggressive feeder (i.e. it can complete its blood meal in one go on one person)

Concordant species (does not require a second blood meal for the completion of the gonotropic cycle)

So, Ae. albopictus has poor vectorial capacity.

Undifferentiated FeverUndifferentiated Fever

Primary dengue infection

May develop a simple fever indistinguishable from other viral

infections.

Maculopapular or rubelliform rashes on face, neck and chest may

accompany the fever or may appear during defervescence (Day 3-5)

URTI and GI symptoms are common

Dengue FeverDengue FeverOlder children, adolescents and adults

Acute (Sudden, sharp) rise in temperature (39°C- 40°C) for 5- 7 days

Biphasic fever with severe headache, myalgia, arthralgia and bone pains

(break-bone fever), particularly in adults

Rashes, flushed face, retro-orbital pain on eye movement or eye pressure,

photophobia

Altered taste sensation, Anorexia, Sore throat, Dragging pain in inguinal region

Leukopenia and thrombocytopenia- mild

Occasionally, Haemorrhage such as gastrointestinal bleeding, hyper

menorrhea, massive epistaxis (DF with Hmrgh)

Dengue Haemorrhagic Fever (DHF)Dengue Haemorrhagic Fever (DHF)

Children less than 15 years of age in hyper endemic areas, in association with repeated

dengue infections (secondary dengue infection). Incidence of DHF in adults is increasing

Rarely DHF may occur in Primary infections with DENV-1 and DENV-3 as well as in infants.

Signs and symptoms similar to DF in the early febrile phase.

Positive tourniquet test (TT), petechiae on extremities, easy bruising and/or GI haemorrhage

Abnormal haemostasis and plasma leakage are the main pathophysiological hallmarks of

DHF

Thrombocytopenia and rising haematocrit/haemo concentration before the subsidence of

fever/ onset of shock.

COURSE AND CLINICAL FEATURES

3 PHASES FEBRILE PHASE

Sudden high grade fever accompanied by facial flushing, skin erythema, generalised body ache, myalgia, arthralgia, retro-orbital eye pain, photophobiaSore throat, injected pharynx, conjunctival injectionAnorexia, nausea and vomiting – commonMild haemorrhagic manifestations – petechiae, mucosal bleedingLast for 2-7 daysProgressive decrease in total white cell count

CRITICAL PHASECRITICAL PHASEWarning signs

Condition worsen around the time of deferevescence

On 3-8 days of illness

Progressive leucopenia

Rapid decrease in platelet

Increase in heamatocrit severity of plasma leakage

Haemorrhagic manifestation – easy bruising and bleeding at venepuncture site

Profound shock

hypoperfusion metabolic acidosis, organ impairement,

DIC severe haemorrhage decrease heamatocrit

WARNING SIGNSWARNING SIGNS

Between 3-7 days of illness

Abdominal pain and tenderness

Persistent vomiting

Clinical fluid accumulation

Mucosal bleed

Lethargy, restlessness

Liver enlargement > 2cm

Increase in Hct with rapid decrease in platelet count

RECOVERY PHASERECOVERY PHASE

Gradual reabsorption of extravascular fluid Gradual reabsorption of extravascular fluid Improvement in Improvement in – General well being General well being – Apetite Apetite – GI symptomsGI symptoms– Hemodynamic statusHemodynamic status

Isles of white in the sea of redIsles of white in the sea of redHaematocrit stabilisesHaematocrit stabilisesRise of WBC countRise of WBC countRecovery of platelet countRecovery of platelet count

Dengue Shock Syndrome (DSS)Dengue Shock Syndrome (DSS)

Hypovolemic shock due to plasma leakage

Pleural effusion, Ascites (plasma leakage to pleural& peritoneal cavities)

Hypothermia- Cold clammy skin

Fulminant hepatic failure

Optimal fluid management is important- Avoid over hydration

Dengue case classification by severityDengue case classification by severity

Dengue diagnosisDengue diagnosis

Laboratory confirmationLaboratory confirmation

ManageMent

CONTROL MEASURESMOSQUITO CONTROL– ANTI-LARVAL MEASURES– ANTI- ADULT MEASURES

VACCINES– NO SATISFACTORY VACCINE

OTHER MEASURES– Bed-nets– Wearing full sleeve shirts, full pants– Mosquito repellent creams– Environmental measures

Elimination of mosquito breeding placesManagement of roof topsProper covering of stored water