Epidemiology of MalariaPresenter :

Dr. Ramkesh PrasadPG student

Department of Community Medicine

Gauhati Medical College

Fossil mosquitos were found in geological strata 30 million old in Africa.

6 BC - Association of fever with stagnant water & swamps led to methods of drainage practised by the Greek and Romans.

1820 - Quinine the active principle of Cinchona was isolated by Pelletier and Caventou

1880 - Laveran first saw and demonstrated malaria parasite in the human RBC

1891 - Romanowski developed a new method of staining blood slide

1892 - Patrick Manson outlined the mosquito theory of malaria transmission

1897 – Sir Ronald Ross in Secunderabad, proved the transmission through malaria parasite through mosquito

1899 - Battista Grassi with Bignami and Bastianelli described the full cycle of development of human malaria parasite in Anopheles mosquitos

History

1934 - Chloroquine was synthesized in Germany

1939 - Paul Miller discovered the insecticidal property of

DDT

1945 - Venezuela was the first country to launch

Eradication Program against malaria

1946 - India started using DDT

1951 - DDT resistance reported from Greece

1952 - Primaquine developed by Elderfield in the USA

1953 - NMCP launched

1955 - WHO’s Global Malaria Eradication Campaign was

inaugurated

1958 - NMCP was converted NMEP

1965 - 0.1 million cases reported with no death in India

1971 - UMS launched

1972 - DDT banned in USA

1973 - Chloroquine resistance reported in Assam

1977 - NMEP was revised and upgraded and was called

Modified Plan of Operation

1982 - National Anti Malaria Drug Policy was first drafted

1994 - Resurgence of malaria in India

1995 - Malaria Action Plan came into effect

1998 – RBM launched

1999 - National Program was renamed as National Anti

Malaria Program

2000 - Millennium Development Goal to eradicate malaria

by 2015

2004 - NVBDCP launched

Problem StatementWORLD At present 109 countries are considered endemic

In 2008: 243 million cases 8,63,000 deaths

Malaria kills between 1.1 -2.7 million people each year worldwide, of whom about 1 million are children under the age of 5 years, these childhood deaths constitutes nearly 25% of child mortality in Africa.

85% AR10% SEA4% EMR

89% AR6% EMR5% SEA

Indian ScenerioPre Independence:• The situation worsened in the early 19th century. Contributing factors was the establishment of the railways and irrigation network. •Due to the heavy death toll, economic loss, and risk to the lives of British officers serving in vulnerable areas like Punjab, a lot of research was done for malaria control.

•In the 1840s, attention was paid to proper drainage and chemoprophylaxis was started with Quinine

•Malaria control were initiated in areas of economic to importance British rulers..• In 1909, the Central Malaria Bureau was formed in Kasauli for malaria control and investigations.

Post Independence:

•Malaria Institute of India carried out systemic studies in Collaboration with the Health Directorate of erstwhile Bombay Presidency from 1945-1952, and formulated the strategy for malaria control program in India.

•In 1953 NMCP was launched .

•Prior to 1953, there were about 75 million cases with 0.8

million deaths per year.

Current status:

. Accounts for 2/3rd of the confirmed cases reported in the SEAR

•In 2009 1.56 million cases reported•The major endemic areas in India are in the NE states, Andhra Pradesh, Chhattisgarh, Gujarat, Jharkhand, MP, Maharashtra, Rajasthan and Orissa

•Orissa contributes to the highest no. of malaria cases in

the country.

Year Total Malaria

Cases (million)

P. falciparum cases

(million)

Pf % Deaths due to

malaria1995 2.93 1.14 38.84 11511996 3.04 1.18 38.86 1010

1997 2.66 1.01 37.87 879

1998 2.22 1.03 46.35 664

1999 2.28 1.14 49.96 1048

2000 2.03 1.05 51.54 932

2001 2.09 1.01 48.20 1005

2002 1.84 0.90 48.74 973

2003 1.87 0.86 45.85 1006

2004 1.92 0.89 46.47 949

2005 1.82 0.81 44.32 963

2006 1.79 0.84 47.08 1707

2007 1.51 0.74 49.11 1311

2008 1.53 0.77 50.81 1055

2009 1.56 0.84 53.72 1144

2010(Upto Sept.)

1.03 0.53 50.92 547

Countrywide Epidemiological Situation (1995-2010)

Malaria Paradigm

Endemicity Spleen Rate* Parasite Rate*

Hypoendemic ≤10% in children ≤ 10%

Mesoendemic 11-50% in children 11-50%

Hyperendemic >50% in children also high in adults (>50%)

>50%

Holoendemic >75% in children but low in adult

>75%

A malaria paradigm is defined as “a specific situation supporting a level of malaria endemicity which is dependent on local environmental and socioeconomic activities”.

•Unstable and Stable Malaria

•Based on endemicity

* Children between 2-9 years

Paradigm in relation to human activity as per WHO

1. Agriculture related malaria Irrigated Agriculture Malaria Non-irrigated Agriculture Malaria Tree Plantation Malaria Animal Grazing Malaria

2. Forest Economy Related Malaria Deep forest Malaria Forest Fringe Malaria

3. Urban Malaria Urban mlaria Peri-urban malaria Slum malaria Industrial malaria

NMEP in 1994 identified 4 malaria paradigms. However these paradigms are more relevant from operational rather than epidemiological point of view

•Epidemic Prone Areas : Semi arid Desert Areas Semi arid Desert Areas with Canal Irrigation Non-irrigated Semi –arid Areas Ecosystem Supported by Lakes Epidemic Prone Alluvial Plains of Indo Gangetic Areas

•Project Areas

•Tribal Areas Hilly Rain forest Hilly Deforested Cultivated Areas Deciduous Forest in Peninsular Hills

•Urban Area

Malaria in Assam Malaria has been a serious problem in the North East, mainly due to topography and climatic conditions being congenial for perennial transmission.

Assam reports maximum malaria cases as well as P. falciparum followed by AP, Tripura and Meghalaya.

Karbi Anglong, Kokrajhar, Udalguri, Darrang and NC Hills have the highest endemicity of malaria, contributes to 41% of total positive and 32% of Pf cases in the state ( population 12.3%)

Dibrugarh, Sibsagar and Jorhat – least endemic. They altogether constitute 12% of state population but contribute only 0.43% of malaria positives and 0.49% of Pf cases

There has been a steady decline in the no. of slide positive cases, no. falciparum cases and no. of deaths in the past 5 years. But the proportion of the P. falciparum cases has increased considerably.

Paradigms of MalariaDistrict Map of Assam with

API

Malaria situation in Assam in last 5 years

YEAR BLOOD SMEAR

EXAMINED

TOTAL SLIDE

+ve

Pf +ve Pf % DEATH

2006 27,43,092 1,26,178 82,546

65.42 304

2007 23,99,836 94,853 65,542

69.10 152

2008 26,87,755 83,939 76,350

90.96 86

2009 30,21,915 91,413 66,557

72.80 63

2010(up to Sept)

34,82,110 48,452 40,993

84.61 30

Geographical Distribution :

Malaria once extended widely through out the world reaching as far north as 64ºN latitude (Archangel in former USSR) and as far south as 32ºS (Cordoba in Argentina)

Today, however , malaria is almost exclusively a problem of the geographical tropics.

One of the greatest epidemics of modern times struck the former USSR after the First World War: more than 10 million cases were reported in 1923-26 with at least 60,000 deaths

Epidemiology

Recipient

Donor

VectorParasite

Physical Biological

Socioeconomic

Environment

Agent

Human host

Epidemiology

AgentPARASITE

Plasmodium vivax : has the widest geographical range, prevelant in

many temperate zone, tropics and subtropics

Plasmodium falciparum: commonest species throughout tropics

and sub tropics

Plasmodium malariae: patchy presence in same area as Pf but

much less common.

Plasmodium ovale: found mainly in tropical Africa but also

ocassionally in West Pacific

Plasmodium knowlesi: emerging parasite, confirmed cases found in

Thailand, Indonesia, Borneo, Philippines, Singapore, Myanmar,

Malaysia.

AGENTVector: Infected Female Anopheles mosquito

422 species throughout the world, 70 species are vectors of malaria under natural conditions; of these 40 are of major importance.

Common vectors in India are:

Anopheles minimusAnopheles dirus (An. baimaii)Anopheles philippensisAnopheles culicifaciesAnopheles stephensiAnopheles annularisAnopheles sundiacusAnopheles fluviatilisAnopheles varuna

Reservoir of infection:

Humans and ChimpanzeePatient can be a carrier of several plasmodium species at the same time

Children>adults, children epidemiologically

better reservoir

Period of communicability:

P. vivax infection - 4-5 days

Falciparum infection - 10-12 days

Relapse: vivax, ovale, malariae

Recrudescence: falciparum malaria

VectorBehaviour pattern of adult Anopheles:

Vector density: Dependent on availability of suitable larval habitat

Resting habits: All vectors of malaria in India are endophilic except

for A. dirus which is known to be exophilic. This habit of the vector

(164)

Biting Time: of each vector species is determined by its genetic

character

Breeding places: fresh and salt water, stagnant .

Flight range: 2-3 kms but strong seasonal winds may carry upto 30

kms or more from their main breeding places.

Life span: Key factor in transmissionVector needs 10-12 days, after an infective blood meal; to become infective-hence strategy is to shorten lifespan<10 days

Mode of Transmission

Vectorial TransmissionTransfusion malariaCongenital MalariaMalaria in Drug addictsTherapeutic Malaria

Distribution of different vectors in India

Bio-ecological Characteristics of the Principal Vector in India

Species Zone of Influence

Breeding Ecology Adult Behaviour

An. minimus

NE States, North West Bengal

Clear slow moving water with grassy margin , swampy vegetation and little shade, irrigation ditches, crab holes etc.

Resting Habitat: Prefer human dwellingsBiting Time: 12 am – 2 am Feeding habit: Predominantly anthropophilic

An. dirus Deep forest in NE region

Forest pools and stream with decaying leaves. Burrow pits along forest roads

Resting habitat: Exophilic, may be endophagic. Rests outdoor during the day.Biting time: 12 am – 2 amFeeding habit: Highly anthropophilic

An. fluviatilis

Foothills all along the Himalayan range

Clearwater breeder, shallow wells in monsoon, terraces rice fields

Resting habitat: Human dwellings and cattle sheds.Biting time: 8 pm -2 amFeeding habit: Foothills: highly anthropophilic, plains: zoophilic

Species Zone of Influence

Breeding ecology

Adult Behaviour

An. culicifacies (A, B, C, D)

Most parts of the country

Wide Range: Usually breeds in water not rich in organic matter – irrigation channels, river bed, pools, tanks, ponds, rice fields, brackish water, hoof marks etc.

Resting habitat: Predominantly indoor rester-cattle sheds and human dwellingsBiting time: 10:30 pm – 12:30 amFeeding habit: Mainly zoophilic, Indiscriminate feeder at high density

An. stephensi

All towns except NE; rural area of arid/semi arid zone except in the North

Domestic and Peri-domestic water collection

Resting Habitat: Human dwellings and cattle shedsBiting time: soon after dusk; 4 am - 6 amFeeding habit: Indiscriminate feeder on humans and cattle

An. sundiacus

Andaman & Nicobar Islands

Brackish water with algae, cleared mangroves and lagoons

Resting habitat: Often human dwellings and less frequently in cattle shedsBiting Time: soon after dusk, 10 pm – 12 amFeeding habit: Prefers human blood

LIFE CYCLE OF PLASMODIUM

Importance of Extrinsic Incubation period

Insecticide use Surveillance Early diagnosis and PT. to avoid gametogony Prevention of Relapse

Host

Sex: Male are more vulnerable due to more outdoor activities

Pregnant women : intensity of the sickness is more

Age: Children, infants become vulnerable from 3rd month

Immunity: Africans have greater innate immunity to some types of

malaria than other races

Red cell polymorphism and malaria:

HbAS: Protection against P. falciparum

HbC: Partial immunity to P. falciparum

HbF: Protective against P. falciparum

HbE: Partial protection against malaria

Duffy blood group: virtually absent in West Africans so they are

unsusceptible to P. vivax

G6PD deficiency: Protective against P. falciparum

Hereditary ovalocytosis: highly resistant to P. falciparum and P.

vivax

Housing: Ill ventilated, ill lighted houses – provide ideal indoor resting

places for vectors

Sleeping Habit: Not sleeping under mosquito net exposed to the risk of

getting the infection.

Occupation

•Agriculture and Irrigation

•Cattle grazing

•Migration of Population

•Road Transport and construction

•Movement of Military personnel

•Labour movement for execution of projects

•Human movement for fishing

•**** Incubation periods

•Clinical features

Environment Season Seasonal disease- July to Nov Temperature Optimum for parasite development in vector 20 -30ºC Humidity 60% considered necessary

Rainfall Provides opportunity for breeding of mosquitoes, gives rise to epidemics Increases atmospheric humidity- necessary for survival of mosquitos

DroughtSmall pools formed by half dry streams (e.g. Sri Lanka 1934-35)

Altitude- Anopheles not found >2000-2500 metres Man made malaria- Burrow pits Garden pools Irrigation channels Engineering projects,

Clinical FeaturesTypical : Sudden onset of high fever with rigors and sensation of extreme cold followed by feeling of burning heat leading to profuse sweating and remission of fever by crisis thereafter.

Atypical:Cough and running noseDiarrheaSkin rashesJoint pain

Symptoms of severe and complicated malaria:Altered sensoriumBreathing difficultySevere AnemiaDark coloured urine/Oliguria

Operational and Epidemiological Indices

ABER Reflects the adequacy and efficiency of case

detection mechanism

API If ABER is adequate, this parameter is the

most important criteria to assess the progress of

eradication programme

SPR Whenever ABER is inadequate, this is a

dependable parameter for determining the progress of

containment measure

SfR When ABER is adequate, SfR pinpoints the

areas of Pf preponderance

IPR Most sensitive index of recent transmission

of malaria

Prevention and ControlElimination of Reservoir: consists of making the infectious cases

non-infectious by giving treatment.

Chemoprophylaxis: Travellers from non-malarious to malarious

areas Military and paramilitary personnels moving into malarious area

Pregnant women living in endemic and

hyperendemic areas

Breaking the Channel of Transmission: vector control Antiadult measure: Residual spraying, space spraying, fogging Antilarval measure: Source reduction Biological control: Larvivorous fishes, bacteriaPersonal Protection: Bed nets with insecticides Mosquito repellants ClothingAwareness: IEC should become a continuing activity to help strengthen early case detection and prompt treatment, Eliciting people’s participation in vector control

Thank You