EPIDEMIOLOGY, PREVENTION AND CONTROL - MALARIA
Dr Ali Jafar Abedi
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INTRODUCTION
Definition of malaria-
A protozoal disease caused by infection with parasites of genus plasmodium and transmitted to man by certain species of infected female Anopheline mosquito.
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The term malaria originates from Italian: mala aria — "
bad air“ in 18
thcentury.
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Formerly called ague or marsh fever due to its association with swamps and marshland.
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In 1897, Ronald Ross established the life cycle of
plasmodium and identified that infection was transmitted by Anopheles.
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Loveran discovered the parasite.
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PROBLEM STATEMENT
In 2018, an estimated 228 million cases of malaria occurred worldwide, compared with 251 million cases in 2010 and 231 million cases in 2017.
Most malaria cases in 2018 were in the WHO African Region (213 million or 93%), followed by the WHO South-East Asia Region with 3.4% of the cases and the WHO Eastern Mediterranean Region with 2.1%.
Nineteen countries in sub-Saharan Africa and India carried almost 85% of the global malaria burden.
Six countries accounted for more than half of all malaria cases worldwide:
Nigeria (25%), the Democratic Republic of the Congo (12%), Uganda (5%), and Côte d’Ivoire, Mozambique and Niger (4% each).
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7% of under 5 mortality (cerebral malaria & anaemia).
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In 2018, there were an estimated 405 000 deaths from malaria globally, compared with 416 000 estimated deaths in 2017, and 585 000 in 2010.
Children aged under 5 years are the most vulnerable group affected by malaria. In 2018, they accounted for 67% (272 000) of all malaria deaths worldwide.
The WHO African Region accounted for 94% of all malaria deaths in 2018.
Nearly 85% of global malaria deaths in 2018 were concentrated in 20 countries in the WHO African Region and India; Nigeria accounted for almost 24% of all global malaria deaths, followed by the Democratic Republic of the Congo (11%), the United Republic of Tanzania (5%), and Angola, Mozambique and Niger (4% each).
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INDIA
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95 % malaria prone area
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1.5 – 2 million cases annually.
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The incidence of malaria in India accounted for 58% of cases in the South East Asia Region of WHO.
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In 2014, there were 1.07 cases of malaria in million, 0.70 cases of plasmodium falciparum in million and 535 deaths due to malaria.
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21.98% - high transmission areas.
(High transmission >1 case/ 1000 popln)
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92% of cases & 97% of death – north-eastern states, Chhattisgarh, Jharkhand, M.P, Gujarat, Orissa, A.P, W.P, Karnatka.
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API has declined from 3.29 (1995) to o.85 (2012)
7AGENT
PARASITE
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.
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AGENT
Vector : 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 minimus
Anopheles dirus (An. baimaii) Anopheles philippensis
Anopheles culicifacies Anopheles stephensi
Anopheles annularis Anopheles sundiacus Anopheles fluviatilis Anopheles varuna
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VECTORS:
LIFE SPAN: 10- 12 days
CHOICE OF HOST : anthrophilic species
RESTING HABITS : endophily, exophily
BREEDING HABITS: moving water, wells, fountain, garden
pools (clean water)
TIME OF BITING : night time
An. culicifacies- rural , periurban
An. fluviatilis- forest, hilly area
An. stephensi – urban, industrial
An. minimus – foot hills An. philippinensis
An. sundaicus
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VECTOR
Behaviour 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 transmission
Vector needs 10-12 days, after an infective blood meal; to become infective-hence strategy is to shorten lifespan<10 days
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DISTRIBUTION OF DIFFERENT VECTORS IN INDIA
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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 dwellings Biting 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 am
Feeding 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 am
Feeding habit:
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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 dwellings
Biting time: 10:30 pm – 12:30 am
Feeding 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 sheds Biting time: soon after dusk;
4 am - 6 am Feeding 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 sheds Biting Time: soon after dusk, 10 pm – 12 am
Feeding habit: Prefers human blood
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MALARIA TREND IN INDIA
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*The development of malaria parasites in the vector, called sporogony
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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
Drought
Small 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,
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Reservoir of infection:
Humans and Chimpanzee
Patient 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
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EXPLAINATION
The intrinsic incubation period is the time taken by an organism to
complete its development in the definitive host.((where sexual phase of their life cycle is completed).
The extrinsic incubation period is the time taken by an organism to complete its development in the intermediate host.(where asexual phase of their life cycle is completed)
once ingested by a mosquito, malaria parasites must undergo
development within the mosquito before they are infectious to humans.
The time required for development in the mosquito ranges from 10 to 28 days, depending on the parasite species and the temperature. This is the intrinsic incubation period of that parasite.
If a female mosquito does not survive longer than the intrinsic
incubation period, then she will not be able to transmit any malaria parasites.
After a mosquito successfully transfers the parasite to a human body via a bite, the parasite starts developing. The time between the
injection of the parasite into the human and the development of the first symptoms of malaria is its extrinsic incubation period.
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IMPORTANCE OF EXTRINSIC INCUBATION PERIOD
The time required for
development in the mosquito (the extrinsic incubation
period)
Insecticide use Surveillance
Early diagnosis and PT. to avoid gametogony
Prevention of Relapse
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MODE OF TRANSMISSION
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Malaria is caused by a type of microscopic parasite that's transmitted most commonly by mosquito bites.
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Other transmission:
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From mother to unborn child
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Through blood transfusions
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By sharing needles used to inject drugs
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CLINICAL FEATURES
Typical : 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 nose Diarrhea
Skin rashes Joint pain
Symptoms of severe and complicated malaria:
Altered sensorium Breathing difficulty Severe Anemia
Dark coloured urine/Oliguria
25MALARIAL PAROXYSM
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Can get prodrome 2-3 days before
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Malaise, fever, fatigue, muscle pains, nausea, anorexia.
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Can mistake for influenza or gastrointestinal infection.
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Slight fever may worsen just prior to paroxysm.
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Paroxysm
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Cold stage - rigors
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Hot stage – Max temp can reach 40-41
oC, splenomegaly easily palpable
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Sweating stage - Lasts 2-4 hours, start between midnight and midday
Periodicity
Days 1 and 3 for P.v., P.o., (and P.f.) - tertian
Usually persistent fever or daily paroxyms for P.f.
Days 1 and 4 for P.m. - quartian
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Disease Severity and Duration
vivax ovale malariae falciparum Initial Paraoxysm
Severity moderate to
severe mild moderate to
severe severe Average
Parasitemia
(mm3) 20,000 9,000 6,000 50,000-
500,000 Symptom
Duration
(untreated) 3-8weeks 2-3 weeks 3-24 weeks 2-3 weeks Maximum
Infection Duration (untreated)
5-8 years 12-20
months 20-50 years 6-17 months
Anemia ++ + ++ ++++
Complications renal cerebral
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Relapsing: History of P. vivax or P. ovale infection within past 3 years; no
epidemiologically linked cases in vicinity
Recrudescent: Recurrence of asexual
parasitaemia of the same genotype(s) that caused the original illness, due to
incomplete clearance of asexual parasites
after antimalarial treatment
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PRE-ERADICATION ERA
Magnitude of malaria was determined on the basis of diagnosed cases.
The classical malariometric measures are:
1.
Spleen rate
2.
Average enlarged spleen
3.
Parasite rate
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SPLEEN RATE
% of children between 2 and 10 years of age showing enlargement of spleen.
Average enlarged spleen:
This is a further refinement of spleen rate denoting the avg size of the
enlarged spleen .
It is a useful malariometric index.
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PARASITE RATE
% of children b/w the ages 2 and 10 yrs showing malaria parasite in their blood film.
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ERADICATION ERA
The microscopic diagnosis of
malaria cases became the main method of diagnosis.
The parameters used for the measurement of malaria were
mostly parasitological in nature .
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The following parameters are employed:
a) annual parasite incidence
b) annual blood examination rate
c) annual falciparum incidence
d) slide positivity rate
e) slide falciparum rate
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Annual parasite incidence.[API]
API =confirmed cases during 1 year x 1000
population under surveillance
Annual blood examination rate [ABER]
ABER= nos of slides examined x100 population
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annual falciparum incidence
since the emergence of P. falciparum problem in
India data are collected separately for total malaria cases and P. falciparum cases.
slide positivity rate
% of slides found positive for malarial
parasite irrespective of the type of species.
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Slide falciparum rate
% of slides positive for P. falciparum parasite.
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VECTOR INDICES
A malaria survey is not complete unless it includes investigations relating to the
insect vector.
Some of the imp vector indices are:
1.
human blood index
2.
sporozoite rate
3.
mosquito density
4.
man biting rate
5.
inoculation rate
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MALARIAL INDICES
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ABER = No. of blood smears examined during the year x 100 Population covered under surveillance
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API = Confirmed cases of malaria during one year x 1000 Population covered under surveillance
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SPR= No of blood smears found positive for malaria parasite x 100 No. of blood smear examined
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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
41DIAGNOSIS
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Malaria diagnosis is carried out by microscopic examination of blood films collected by active and passive agencies.
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Health agencies and volunteers treating fever cases in
inaccessible areas are being provided with Rapid Diagnostic Test (RDT) kits (Pf specific so far and now Bivalent RDT) for diagnosis of Malaria cases so as to provide full radical treatment to the confirmed cases.
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The malarial fluorescent antibody test becomes positive two weeks or more after primary infection.
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TREATEMENT
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Where Microscopy Result Is Not Available Within 24 Hours And Monovalent RDT Is Used
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Treatment during pregnancy :
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1st Trimester : Quinine salt 10mg/kg 3 times daily for 7 days
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2nd and 3rd trimester: Area-specific ACT as per dosage schedule given above.
i.e. ACT-AL in North Eastern States
ACT-SP in Other States
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CHEMOPROPHYLAXIS
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Short term chemoprophylaxis (up to 6 weeks) Doxycycline : 100 mg once daily for adults and 1.5 mg/kg once daily for
children(contraindicated in children below 8 years). The drug
should be started 2 days before travel and continued for 4 weeks after leaving the malarious area.
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Chemoprophylaxis for longer stay (more than 6 weeks) Mefloqiune: 250 mg weekly for adults and should be
administered two weeks before, during and four weeks after exposure.
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PREVENTION
Stratification of the problem
Case detection
Early diagnosis and treatment
Sentinel surveillance
Integrated vector control
National vector borne disease control programme
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PREVENTION AND CONTROL
Elimination 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, bacteria
Personal Protection: Bed nets with insecticides Mosquito repellants
Clothing Awareness:
IEC should become a continuing activity to help strengthen early
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BIOLOGICAL CONTROL
Biological Agents that work well:
1. Mosquito fish: Gambusia and Guppy 2. Bacteria:
Bacillus thuringiensis and B. sphaericusOther Biological Agents
:-
Predatory mosquito larvae
(Toxorhynchites)
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Copepods (Macrocyclops
albidus)
Use of Biological Agents to control of vector populations
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ELIMINATION & ERADICATION OF MALARIA
Malaria control: reducing the malaria disease burden to a level at which it is no longer a public health problem.
Malaria elimination: the interruption of local
mosquito-borne malaria transmission; reduction to zero of the incidence of infection caused by human malaria parasites in a defined geographical area as a result of deliberate efforts.
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CONT..
Certification of malaria elimination: the chain of local human malaria transmission by Anopheles
mosquitoes has been fully interrupted in an entire country for at least 3 consecutive years.
Malaria eradication: permanent reduction to zero of the worldwide incidence of infection caused by a particular malaria parasite species.
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CONT..
Key factors proposed for eradicating malaria:
1) Reducing Malaria Burden 2) Vector Control
3) Malarial Vaccine
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WORLD MALARIA DAY 25 TH APRIL
World Malaria Day - which was instituted by the World Health Assembly at its
60th session in May 2007.
World Malaria Day 2012 — “SUSTAIN GAINS, SAVE LIVES: INVEST IN
MALARIA” marks a decisive juncture in the history of malaria control.
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MONITORING AND EVALUATION
Monitoring & Evaluation will be an on-going process in the programme.
Adoption of newer disease prevention and control
instruments like RDTs, ACTs & LLINs and recruitment of ASHA, a new frontline worker under NRHM, made it
necessary to restructure the Management Information System (MIS).
The NVBDCP also has an online system of data collection and collation called the National Anti malaria Management Information System (NAMMIS).
Objectives - To ensure that 80% of districts in high-disease burden areas will collect, process, analyze, and effectively manage malaria data by 2010 and 100% of them by 2012.
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CONT..
The following activities will be adopted
in the programme to strengthen the M
& E system :
Strengthening of management information system for tracking malaria incidence and operational
indicators including the revival of the National Anti Malaria Management Information System
(NAMMIS).
Sentinel surveillance to collect data on severe malaria, hospitalized malaria cases and malaria deaths from selected hospitals in each district.
Decentralized measurement of outcomes at district and PHC levels through Lot Quality Assurance
Sampling (LQAS).
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CONT..
Large-scale population surveys every second year to assess malaria prevalence and population coverage with main interventions.
Logistic Management Information System for supply chain management.
System to monitor the quality of RDTs and medicines to ensure their quality upon delivery and at point of use.
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