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1. Epidemiological Parameters Used in Malaria Surveillance

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Key Epidemiological Parameters

A. Annual Parasite Incidence (API)

• Formula: (Number of confirmed malaria cases in a year / Population under surveillance) × 1000
• The most important indicator for assessing malaria endemicity and programme performance.
• API < 1 per 1000 = low endemic; API 1–2 = moderate; API > 2 = high endemic.
• Used to stratify areas for targeted intervention.

B. Annual Blood Examination Rate (ABER)

• Formula: (Number of blood smears examined in a year / Population) × 100
• Reflects the adequacy of surveillance and diagnostic effort.
• The minimum recommended ABER is 10% of the population.
• Low ABER may indicate under-reporting and surveillance gaps.

C. Slide Positivity Rate (SPR) / Smear Positivity Rate

• Formula: (Number of positive slides / Total slides examined) × 100
• Indicates the actual burden of malaria in those presenting for testing.
• Also called the Test Positivity Rate (TPR) when RDTs are included.
• SPR > 5% in high-transmission areas signals a significant public health concern.

D. Annual Fever Case Examination Rate (AFCER) / Fever Case Detection Rate (FCDR)

• Proportion of fever cases from whom a blood smear is taken.
• Measures the quality and reach of fever case detection in the field.

E. Slide Falciparum Rate (SFR)

• Formula: (P. falciparum positives / Total positives) × 100
• Reflects the species composition, important because P. falciparum causes severe, potentially fatal malaria.
• High SFR areas require more intensive surveillance and ACT deployment.

F. Infant Parasite Rate (IPR) / Parasite Rate (PR)

• Proportion of children (typically aged 2–9 years or infants) with parasitaemia in a cross-sectional survey.
• A classical measure of transmission intensity in endemic areas.
• Also expressed as Plasmodium falciparum Parasite Rate (PfPR) in the malaria atlas.

G. Spleen Rate

• Proportion of children (2–9 years) with palpable spleen in a survey area.
• An indirect epidemiological marker of cumulative malaria exposure.
• Holoendemic: spleen rate > 75%; Hyperendemic: 50–75%; Mesoendemic: 11–50%; Hypoendemic: < 10%.

H. Entomological Inoculation Rate (EIR)

• Number of infective bites per person per unit time.
• Gold standard measure of malaria transmission intensity at the community level.
• Estimated as: EIR = Biting rate × Sporozoite rate.

I. Case Fatality Rate (CFR)

• Proportion of diagnosed malaria cases who die.
• Crucial for monitoring severe malaria and healthcare quality.

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Purpose of Surveillance Parameters

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2. Treatment of P. vivax and P. falciparum Malaria

Treatment of Plasmodium falciparum Malaria

Uncomplicated P. falciparum

• Artemisinin derivatives (artesunate, artemether, DHA) rapidly reduce parasite biomass in the first 24–48 hours.
• Partner drugs (lumefantrine, piperaquine, mefloquine) have long half-lives, clearing residual parasites and preventing recrudescence.
• Primaquine 0.25 mg/kg single dose is added as a gametocytocidal agent to reduce transmission (G6PD screening recommended).

Severe/Complicated P. falciparum

• IV/IM Artesunate is the drug of choice (superior to quinine per AQUAMAT trial).
  • Adult dose: 2.4 mg/kg IV at 0, 12, 24 hours, then once daily.
• Step-down to full oral ACT course once the patient can tolerate oral medication.
• Supportive care: airway management, anti-convulsants (for cerebral malaria), IV glucose (for hypoglycaemia), blood transfusion (for severe anaemia), dialysis (for acute kidney injury).

Artemisinin Partial Resistance (ART-R)

• Emerging in Southeast Asia (Greater Mekong subregion) and now detected in East Africa.
• Characterized by delayed parasite clearance (parasite half-life > 5 hours).
• Response: use ACTs with effective partner drugs; triple ACT combinations under investigation.

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Treatment of Plasmodium vivax Malaria

Blood-Stage Treatment (Erythrocytic Schizontocidal)

• Chloroquine remains the first-line treatment for uncomplicated P. vivax where sensitivity is preserved:
  • 25 mg base/kg over 3 days (10 mg/kg on Day 1, 10 mg/kg on Day 2, 5 mg/kg on Day 3).
• Where chloroquine resistance (CQR) is documented (Papua New Guinea, parts of Indonesia, Southeast Asia), ACTs are used — all ACTs are highly effective against blood-stage P. vivax (WHO Malaria, p. 191).
  • Artesunate + SP should be avoided in areas with SP-resistant P. vivax.

Radical Cure (Anti-hypnozoite / Relapse Prevention)

• Primaquine is the only widely available anti-hypnozoite drug.
  • Standard regimen: 0.25 mg/kg/day × 14 days (total 3.5 mg/kg).
  • High-relapse strains (Chesson/tropical vivax): 0.5 mg/kg/day × 14 days.
  • Weekly primaquine (0.75 mg/kg/week × 8 weeks) used in G6PD-deficient individuals under supervision.
• Tafenoquine (new single-dose anti-hypnozoite): 300 mg single dose, approved by WHO 2022; requires G6PD testing (contraindicated if G6PD activity < 70% of normal).
• G6PD testing is mandatory before primaquine or tafenoquine because both can cause dose-dependent haemolysis in G6PD-deficient patients.
• Primaquine is contraindicated in pregnancy and infants < 6 months.

Special Situations

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3. Integrated Vector Management (IVM)

Definition

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Principles of IVM

1. Advocacy, social mobilization, and legislation — political commitment and community engagement.
2. Collaboration within the health sector and with other sectors — WASH, agriculture, urban planning.
3. Integrated approach — combining biological, chemical, and environmental methods.
4. Evidence-based decision-making — entomological and epidemiological data guide choices.
5. Capacity building — training of human resources at all levels.

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Components of IVM

A. Larval Source Management (LSM)

B. Indoor Residual Spraying (IRS)

• Application of residual insecticides to interior walls and ceilings.
• Kills resting mosquitoes (endophilic/endophagic Anopheles).
• Insecticides used: DDT, malathion, synthetic pyrethroids, bendiocarb.
• Protects for 3–6 months depending on the formulation.
• Remains one of the most powerful malaria vector control interventions.

C. Long-Lasting Insecticidal Nets (LLINs)

• Bed nets impregnated with pyrethroid insecticide, effective for ≥3 years.
• Dual action: physical barrier + contact killing.
• Universal coverage recommended in high-endemic areas.
• LLIN + IRS combination provides added protection in high-burden settings.

D. Space Spraying / Fogging

• Ultra-low volume (ULV) spraying of insecticides into the air during outbreaks.
• Short-term, rapid impact on adult mosquito density.
• Used as an epidemic response tool, not a sustained control measure.

E. Personal Protection Measures

• Repellents (DEET, Picaridin), protective clothing, window screens, mosquito coils.
• Especially important for travelers and occupationally exposed individuals.

F. Biological and Genetic Methods

• Sterile Insect Technique (SIT) — releasing sterile male mosquitoes.
• Wolbachia-infected mosquitoes — reduces vectorial capacity.
• Gene drive technology — under research (e.g., Anopheles gambiae suppression).

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Advantages of IVM Over Single-Method Approaches

• Reduces reliance on any single insecticide, delaying insecticide resistance.
• Cost-effective by selecting the right tool for the right place.
• Environmentally sustainable and ecologically sound.
• Addresses multiple vector-borne diseases simultaneously (malaria + dengue + filariasis).

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IVM in India (NVBDCP Context)

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4. Twin Pillars of Lymphatic Filariasis Elimination Strategy

Background

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Pillar 1: Mass Drug Administration (MDA) — Interruption of Transmission

Drug Regimens

• DEC: Kills microfilariae and adulticidal effect; primary drug.
• Albendazole: Reduces microfilarial output; anti-helminthic synergy.
• Ivermectin: Microfilaricidal; used where DEC is contraindicated (onchocerciasis co-endemicity).
• IDA (triple therapy): Shown to rapidly reduce microfilaraemia to near-zero levels; WHO endorsed in 2017.

In India

• India's MDA programme uses DEC + Albendazole annually covering all at-risk districts.
• Since 2018, triple drug therapy (DEC + Albendazole + Ivermectin) has been rolled out progressively.
• MDA must achieve ≥ 65% therapeutic coverage of the total population per round.
• Minimum 5–6 annual rounds needed to achieve transmission interruption.

Transmission Assessment Survey (TAS)

• Conducted after ≥5 rounds of MDA with ≥65% coverage.
• Tests children aged 6–7 years for antigenaemia (ICT/FTS card test) or microfilaraemia.
• If antigen prevalence < 2% (critical cut-off), MDA can be stopped.
• Post-MDA surveillance continued for at least 4–6 years.

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Pillar 2: Morbidity Management and Disability Prevention (MMDP)

Conditions Addressed

Limb Hygiene Package (LHP)

1. Daily washing with soap and water.
2. Drying carefully, especially between skin folds.
3. Applying emollient/moisturizer.
4. Exercises to promote lymphatic drainage.
5. Elevating the limb during sleep.
6. Treating entry lesions (wounds, fungal infections) promptly to prevent ADLA.

Social Support

• Psychosocial counselling and community support groups.
• Economic rehabilitation and disability allowance where applicable.
• Reduction of stigma through community education.

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Summary Table: Twin Pillars

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Key Point: Elimination of LF as a public health problem requires BOTH pillars simultaneously — MDA alone cannot address the disease burden in those already affected, while MMDP alone cannot stop new transmission. Together, they form a complete public health response.

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