Informal consultation on Elimination of Residual Malaria Foci and Prevention of Reintroduction of Ma

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Informal consultation on Elimination of Residual
Malaria Foci and Prevention of Re-introduction of
Malaria

• Rabat, 18-20 June 2002

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Elimination of malaria foci

• by A.E.Beljaev
• RBM EMRO

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Plan

• Definition and properties of a focus of malaria
• Information process
• Measures
• Evaluation

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Focus of malaria

• Definition and properties

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WHO definition of a focus

• a defined and circumscribed locality situated in
  a currently or formerly malarious area and
  containing the continuous or intermittent
  epidemiological factors necessary for malaria
  transmissionltgt (WHO, 1963).

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WHO definition of a focus

• Note a focus is
• a locality of any size, provided it is defined
  and circumscribed
• Even a solitary household may be a locality
• It has nothing to do with a village in
  administrative sense.

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Ecological definition of a focus

• an integration of the populations of the
  parasite and populations of hosts and vectors
  that support its existence (Beklemishev, 1959,
  1962, 1970)
• Note Populations are understood, in ecological
  sense, as sets of interacting individuals of the
  same species that occupy the same territory
  (which is applicable to humans too).

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Ecological definition of a focus

• Note a focus is
• a system consisting of an abiotic part
  (territory) and living organisms participating in
  the transmission of the parasite
• the ecological definition does not contradict to
  the definition of WHO (1963),
• but deepens it a focus, although corresponding
  to a definite territory, is more than a mere
  territory.

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A focus of malaria as an ecosystem
Biotope (territory)
Mosquitoes
Parasite
Imago Aquatic hemipopulations
Man
Cattle, etc.
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Spatial organisationof ecosystems
BIOCENOSE
BIOTOPE
ECOSYSTEM
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Territorial components of a focus of malaria

• The locality
• Breeding places
• Hiding places
• Places frequented by inhabitants, esp. at dusk
  and night
• Other mosquitoes feeding places.

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Information process

• General information
• Epidemiological information

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General information

• Physiography
• Hydrology
• Meteorology
• Human factors

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General information Physiography

• Altitude is the main indicator of malariogenicity
• No malaria at a high altitude
• (above the cutoff isohypse)
• A belt with optimal malariogenic conditions
• (e.g. 200-600 m in India)
• Lowland often with low potential
• (in tropics)

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General information Hydrology

• Type suitability for particular vectors
• Size
• Shores
• Chemical composition
• Temperature
• Vegetation
• Distribution
• Many or few
• Within or outside the locality

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General information Hydrology

• Vectors
• Species
• Distribution
• Phenology (average dates of essential events)
• First larvae appearing
• First generation emerging
• Diapause of imago
• Other animals
• Predators
• Pathogenes

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General information Meteorology

• Average daily temperature (ADT)
• Used in Moshkovsky method
• Average daily rainfall ? monthly rainfall, number
  of rainy days
• Used to predict the period suitable for existence
  of breeding places

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General informationMeteorology - Moshkovsky
method (1)

• Assessing the main elements of malaria season
• the date of the beginning of the period of
  effective infectivity, i.e. the period during
  which effective development of parasites (i.e.
  resulting in complete maturation) in mosquitoes
  is possible
• the date of the first mosquito-man transmission
  in the current season
• the date of the last effective infection of
  mosquito.

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General informationMeteorology - Moshkovsky
method (2)

• If a case was imported at a given date X, when
  the first introduced case may be expected to
  emerge, if any?
• When there are two cases, an imported case that
  arrived at the date X and a secondary case that
  started at the date Y, can the latter originate
  from the former?
• Is it possible that the given case of P. vivax
  was contracted during the current transmission
  season or it is a result of the last years
  transmission (a late manifestation)?

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General informationMeteorology - Moshkovsky
method (3)

• A Lower threshold of development
• P.vivax 16? C P.falciparum 18? C
• B Base temperature
• P.vivax 14.5? C P.falciparum 16? C
• C Required sum of temperatures above the base
  temperature, degree-days
• P.vivax 105? C P.falciparum 111? C

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General informationMeteorology - Moshkovsky
method (4)

• Algorithm
• Is ADTgtA?
• If not go to the next day
• If yes, add ADT-B to the sum
• Check if C has been achieved
• Go to the next day
• Calculations are automated in a spreadsheet, e.g.
  Excel (attached).

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General informationMeteorology - Moshkovsky
method (5)

• Main elements of malaria season should be
  calculated
• For an average year (normal values)
• For the current year (anomaly)

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General informationMeteorology - Moshkovsky
method (6)

• Main elements of malaria season should be
  calculated
• For an average year (normal values)
• For the current year (anomaly)

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General information Human factors related to
malaria (1)

• use of water bodies, e.g. for water supply,
  fishery, irrigation
• availability of tap water which would reduce need
  to preserve rainwater in households, thus
  reducing breeding
• condition of wells whether water spillage is
  prevented e.g. by concrete, whether wells may
  serve as breeding and/or hiding place
• irrigation,its seasonal patterns, condition of
  the irrigation network

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General information Human factors related to
malaria (2)

• timing of agricultural activities, especially
  during the harvest
• any economic activities requiring spending
  evenings and nights outside the houses
• sericulture (rearing silkworm) and apiculture
  (rearing bees), as this may interfere with the
  use of insecticides

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General information Human factors related to
malaria (3)

• migration patterns daily, seasonal
• sleeping habits time going to bed, place of
  sleeping
• using bednets
• illegal activities, such as smuggling and
  cultivation of narcotic plants
• presence of military camps and other organised
  groups with their own health services nearby

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General information Human factors related to
malaria (4)

• attitude to malaria, whether considered an
  important disease, whether vectors are
  recognised, etc.
• malaria treatment habits self-treatment by
  antimalarials
• attitude to spraying, whether it is welcome or
  regarded as a nuisance whether a tendency to
  replaster walls after the spraying exists.

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Epidemiological information

• The most important question at this stage is to
  ascertain whether a malaria transmission still
  contnues, and the measures are selected
  accordingly.
• Blood collection and incidence
• Functional status of foci
• Entomological information

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Epidemiological information The process

• Investigate every case
• Epidemiological class of the case
• Which classes of cases are present?
• Functional status of foci
• Check the list of measures for each class
• Select and apply measures

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Epidemiological information Case investigation

• A malaria case is a person in whom, regardless
  of presence or absence of clinical symptoms, the
  presence of malaria parasites in the blood has
  been confirmed by microscopic examination.

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Epidemiological information Case investigation

• An epidemiological investigation is a part of
  surveillance operation and is concerned with
  ascertaining the origin and means of any malaria
  cases discovered, determining ltgt the existence
  and nature of any malaria foci in the
  neighbourhood and seeking ltgt to establish
  whether transmission is taking place and, if it
  is, its source (WHO, 1963).

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Epidemiological information Case investigation
categories (1)

• induced case
• induced by a contamination by infected blood
• imported case
• contracted outside a given place
• relapsing case, a case
• contracted locally long ago
• introduced case
• contracted locally from an imported case
• indigenous case
• contracted locally from any other category of
  cases

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Epidemiological information Case investigation
categories (2)

• Categories not covered by the WHO classification
• The cases of transmission by migrant infected
  mosquitoes
• as in the case of an airport malaria, in which
  infected mosquitoes are imported by aircraft
• However, this not the only way of penetration of
  infected mosquitoes into malaria-free territories
  (e.g. by crossing rivers on international
  borders).
• Cases of infection by mosquitoes in laboratories
• sometimes intentional, sometimes accidental.

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Epidemiological information Case investigation
categories (3)

• A key for classification of cases has been
  proposed (attached)

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Epidemiological information Operational
classification of foci (1)

• Criteria
• their age residual vs new
• presence of malaria transmission non-active vs
  active vs potential

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Epidemiological information Operational
classification of foci (2)

• residual
• non-active (transmission interrupted no
  indigenous cases, but possible occurrence of
  relapsing ones),
• active (transmission not interrupted)
• new
• potential (presence of imported cases no
  evidence of transmission but its renewal
  possible,
• active (renewed transmission).

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Epidemiological information Operational
classification of foci (3)

• residual
• non-active (transmission interrupted no
  indigenous cases, but possible occurrence of
  relapsing ones),
• active (transmission not interrupted)
• new
• potential (presence of imported cases no
  evidence of transmission but its renewal
  possible,
• active (renewed transmission).
• A key for classification of foci has been
  proposed (attached)

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Epidemiological information Operational
classification of foci (4)

• The status should be revised
• immediately when new malaria cases of any sort
  appear
• by the end of a year
• potential foci without cases during the period of
  effective infectivity of the last and current
  year, may be re-categorised into cleared-up ones
• same applies to residual active foci that may be
  re-categorised into residual non active
• residual non-active foci may be re-categorised
  into cleared-up foci after one or two years
  without evidence of transmission. 

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Measures

• Selection and application

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Measures

• The goals of antimalaria measures at the stage of
  elimination of foci
• achieving a sustainable interruption of malaria
  transmission
• depleting the reservoir of infection
• preventing a reestablishment of malaria from the
  same area, from the same country or from abroad

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Measures Detection and treatment of cases

• Active detection should emphasise on quality
  rather than on numbers of blood slides collected
• Presumptive treatment
• Slides promptly dispatched to a laboratory for
  examination
• Radical treatment
• Prompt treatment it chloroquine
• Primaquine may be delayed

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Detection of cases questionable practices

• Abandonment of microscopy in favour of RDT
• Diagnosis by RDT should be considered preliminary
  and confirmed by microscopy
• Delayed blood examination
• Blood examination done more than 2 days after
  collection should be considered delayed
• Setting targets of blood collection
• Seems counterproductive, increases coverage of
  non-target population and overloads laboratories
• Mass surveys included in ACD
• Should not be

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Treatment of cases questionable practices (1)

• Presumptive treatment (PT) not given
• May be skipped only if microscopy performed the
  same day
• Only chloroquine given for the first 3 days,
  followed by primaquine
• Should be given concurrently (unless if the
  policy of a delayed treatment with primaquine
  adopted)
• Mandatory hospitalisation for the whole period of
  treatment (up to 17 days)
• Seems counterproductive, decreases the detection
  rate

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Treatment of cases questionable practices (2)

• Shorter courses of primaquine (e.g.5 days)
• Effectiveness needs to be proven
• Non-supervised treatment with primaquine
• Should be banned
• Consolidation treatment
• Should be justified

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Measures Mass drug administration (1)

• Mass prophylactic treatment with primaquine
  (MPTP)
• for a rapid depletion of the reservoir of
  hypnozoites
• Is very effective
• Shortcomings
• very costly
• difficult to achieve a good quality
• not perfect ethically

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Measures Mass drug administration (2)

• Seasonal chemoprophylaxis with chloroquine or
  pyrimethamine
• decreases incidence during the transmission
  season
• but late manifestations appear unabated during
  the next year

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Measures Antilarval

• Chemical indicated under specific conditions
  when breeding places are well-defined and limited
  size
• Environmental projects (drainage, clearing of
  drains, flushing)
• Distribution of larvivorous fish

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MeasuresIndoor residual spraying

• Most effective method that selectively eliminates
  mosquitoes feeding on potential parasite carriers
  

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Measures Personal protection

• Cannot play any serious role in interruption of
  malaria transmission

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Evaluation
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Evaluation

• The question to answer
• whether the goal of interrupting malaria
  transmission has been achieved and, if not, how
  close the programme has approached this goal.
• The indicator will be
• the distribution of the foci by categories, with
  special reference to active foci.
• Transition of foci should be monitored, with an
  emphasis on new potential and new active foci.

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Evaluation quality of information on foci

• Is the roster of foci complete? Any foci that are
  missing?
• Are visits to the foci regular?
• Are all the foci adequately and regularly covered
  by blood examination, judging by monthly blood
  examination rate?
• Epidemiological investigation
• Are all the cases subjected to an?
• Is this investigation conducted in a correct way?
• Percentage of incorrect epidemiological
  diagnoses?

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Evaluation case detection and treatment

• Are all the fever cases tested for malaria
  parasites in the blood?
• Quality of the laboratory examination? (according
  to the special procedure described elsewhere).
• Timeliness of detection, by measuring the average
  spans between the dates of
• the beginning of symptoms
• first contact,
• etc., and, finally
• antigametocyte treatment
• Quality of the treatment dose, duration,
  completeness, whether supervised.

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Evaluation mass drug administration

• Whether mass drug administration is technically
  justified?
• Whether the selection of the method is sound?
• Population coverage per round, with reference to
  age and gender, acceptance rate.

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Evaluation larviciding

• Whether the operation is justified?
• Any missed breeding places, their percentage to
  the total.
• Frequency, regularity and dosage of larviciding
  application (chemical or biological).
• Frequency of finding anopheline larvae in the
  wake of insecticide application.
• Regularity and coverage of entomological
  monitoring of breeding places, correctness of
  techniques.

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Evaluation indoor residual spraying

• Whether the operation is justified?
• Is selection of insecticide, dosage, formulation
  and timing sound?
• Quality of the spraying spot checks of dosage
  and date of application of insecticides.
• Coverage number of structures (human dwellings,
  cattle sheds) sprayed in relation to targets.

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Evaluation indoor residual spraying

• Acceptance of spraying by people, refusing and
  replastering rates.
• Assessing and monitoring the susceptibility of
  the vectors to insecticides.
• Impact of the spraying on the age structure of
  adult mosquitoes proportion of nulliparous,
  presence of mosquitoes of epidemiologically
  dangerous age.