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Answers Based on Park's Textbook of Preventive and Social Medicine (28th Edition)

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Q1. Epidemiology of Malaria + NVBDCP Strategies (LEQ)

EPIDEMIOLOGY OF MALARIA

• Plasmodium vivax - most common in India (~50-60% of cases); causes benign tertian malaria; can relapse due to dormant liver hypnozoites
• P. falciparum - responsible for malignant tertian/cerebral malaria; causes majority of deaths; accounts for ~40% cases in India
• P. malariae - quartan malaria; rare in India
• P. ovale - very rare; mainly Africa

• Source of infection: Infected human (reservoir); gametocyte-carrying persons are infective to mosquitoes
• Incubation period: P. vivax - 12-17 days; P. falciparum - 9-14 days
• Susceptibility: Universal; sickle cell trait, G6PD deficiency, Duffy antigen negativity confer relative resistance
• Age: All ages affected; in endemic areas, young children bear maximum burden (repeated infections → partial immunity in adults)

• Female Anopheles mosquito (30+ species); principal vectors in India: An. culicifacies (rural India - most important), An. stephensi (urban/peri-urban), An. fluviatilis, An. minimus, An. dirus
• Bites dusk to dawn; rests indoors (endophilic/endophagic)
• Breeds in clean, slow-moving water (rice fields, irrigation canals, ponds)

• High transmission: monsoon and post-monsoon (July-November) when vector density peaks
• Temperature: 16-33°C optimal; humidity >60%
• Altitude: <2500 m; rare above this
• Tropical and subtropical regions; India has endemic malaria in most states

• According to WHO World Malaria Report: ~247 million cases globally (2021); ~619,000 deaths; 95% burden in sub-Saharan Africa
• India accounts for ~80% of malaria cases in South-East Asia region (WHO SEARO)
• India: ~5-6 million cases/year (API varies by state); tribal and forested areas (Odisha, Chhattisgarh, Jharkhand) have highest burden

• Parasite Rate (PR): % of persons with malaria parasites in blood smear
• Spleen Rate (SR): % of children (2-9 years) with palpable spleen; indicator of endemicity
• Annual Parasite Incidence (API): (Positive blood slides/population at risk) × 1000; used for programme monitoring
• Annual Blood Examination Rate (ABER): blood slides examined per 100 population/year (target ≥10%)
• Slide Positivity Rate (SPR): % of slides positive among slides examined
• Slide Falciparum Rate (SFR): % P. falciparum among positive slides
• Endemicity classification based on parasite/spleen rates: Hypoendemic (<10%), Mesoendemic (11-50%), Hyperendemic (51-75%), Holoendemic (>75%)

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NATIONAL VECTOR BORNE DISEASE CONTROL PROGRAMME (NVBDCP)

1. Reduce morbidity and mortality due to vector-borne diseases
2. Strengthen the healthcare delivery system
3. Promote inter-sectoral coordination

A. Case Detection and Treatment

• Active Case Detection (ACD): Fever survey by health workers; blood smear collection from fever cases; target ABER ≥10%
• Passive Case Detection (PCD): Patients attending health facilities with fever
• Rapid Diagnostic Tests (RDTs): For quick diagnosis in remote/high-endemic areas
• Treatment protocol (as per National Drug Policy on Malaria, 2013, revised 2023):
  • P. vivax: Chloroquine (25 mg/kg over 3 days) + Primaquine (0.25 mg/kg/day × 14 days) for radical cure (contraindicated in G6PD deficiency, infants, pregnancy)
  • P. falciparum (uncomplicated): Artemisinin-based Combination Therapy (ACT) - Artesunate + Sulfadoxine-Pyrimethamine (AS+SP) or Artemether-Lumefantrine; Primaquine single dose (0.75 mg/kg) as gametocytocidal
  • Severe malaria: Parenteral Artesunate; injectable Artemether
  • Directly Observed Treatment (DOT): Ensured for primaquine doses

B. Vector Control

1. Indoor Residual Spraying (IRS):
   • DDT (still used in India; phased out globally) or Malathion or synthetic pyrethroids (deltamethrin, alphacypermethrin)
   • Applied to interior walls and ceilings of houses
   • Coverage: 2 rounds/year in high-endemic areas; 1 round in moderate-endemic areas
2. Long-Lasting Insecticidal Nets (LLINs):
   • Distributed free in high-endemic (tribal) areas
   • Deltamethrin/permethrin-treated; effective for 3-5 years
   • Reduces man-mosquito contact, especially at night
3. Larval Control (Source Reduction):
   • Anti-larval measures: Draining, filling, levelling of water bodies (DDL)
   • Biological control: Gambusia affinis and Lebistes reticulatus (larvivorous fish) introduced in water bodies
   • Bacillus thuringiensis israelensis (Bti) - biological larvicide
   • Temephos (Abate) - chemical larvicide for drinking water containers
4. Personal Protection:
   • Insecticide-treated bed nets (ITNs)
   • Repellents (DEET-based)
   • Protective clothing
   • Screening of houses

C. Sentinel Surveillance

• Monitoring API, ABER, SPR, SFR monthly
• High-risk areas (API >2) given priority interventions
• Stratification of districts as High (API >5), Moderate (API 2-5), Low (API <2)

D. Epidemic Preparedness and Response

• Early warning system; rapid response teams
• Pre-positioned supplies (RDTs, ACT drugs, LLINs)

E. Urban Malaria Scheme

• Addresses An. stephensi-transmitted malaria in cities
• Anti-larval measures in urban water bodies; IRS in urban slums

F. Tribal Action Plan

• Focus on Odisha, Chhattisgarh, Jharkhand, Madhya Pradesh, West Bengal (northeastern states)
• Mobile health teams; ASHAs as Malaria Warriors
• Free LLINs distribution

G. National Framework for Malaria Elimination (NFME) 2016-2030

• India's target: Eliminate malaria (zero indigenous cases) by 2030
• Phase I (2016-2020): Eliminate in low-endemic states (API <1)
• Phase II (2020-2022): Reduce to elimination phase in moderate-endemic states
• Phase III (2022-2027): Interrupt transmission in all states
• Phase IV (2027-2030): Prevention of re-introduction
• India committed to Asia Pacific Leaders Malaria Alliance (APLMA) goal

H. Health Education and Community Mobilization

• Awareness about mosquito breeding prevention
• Use of nets, repellents
• Seeking early treatment for fever

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Q2. Epidemiology of Typhoid Fever + Prevention, Control and Vaccination (LEQ)

EPIDEMIOLOGY OF TYPHOID FEVER

• Salmonella typhi (typhoid fever) - Gram-negative rod; family Enterobacteriaceae; genus Salmonella
• S. paratyphi A, B, C - cause paratyphoid fever (enteric fever)
• Antigens: H (flagellar), O (somatic), Vi (virulence/capsular - present in S. typhi only; used in Vi antigen vaccine)
• Survives weeks in water, weeks in ice; destroyed by pasteurization and chlorination

• Humans only (anthroponosis)
• Sources: Cases (active disease) and carriers
• Types of carriers:
  • Temporary/Convalescent carrier: Excretes for <3 months after recovery (~10% of cases)
  • Chronic carrier: Excretes for >1 year; 2-5% of cases; mostly middle-aged women; organisms harbored in gallbladder (chronic cholecystitis/cholelithiasis) or, rarely, urinary tract
  • Contact carrier: Healthy person carrying organism; not frank case
  • Incubatory carrier: Excretes during incubation period

• Route: Feco-oral (contaminated food/water/milk)
• 5 Fs: Food, Fingers, Flies, Fomites, Fluids (water)
• Water-borne: Most common mode in developing countries; explosive outbreaks
• Food-borne: Shellfish, raw vegetables, milk/dairy products (chronic carrier as food handler)
• Direct contact: Rare
• Infective dose: 10^5-10^7 organisms (relatively high)

• Incubation period: 1-3 weeks (usually 10-14 days); depends on dose
• Period of communicability: As long as typhoid bacilli appear in stools/urine (cases and carriers)
• Susceptibility: Universal; immunity after infection not permanent
• Age: Most common in 5-19 year age group (school-age children and young adults)
• Sex: Males slightly more affected
• Seasonal variation: Peak in summer and monsoon (June-September) in India

• Poverty, poor sanitation, overcrowding, unsafe water supply
• Common in developing countries (South Asia, sub-Saharan Africa, SE Asia)
• Widal test: Diagnostic; titre >1:80 for O agglutinin and >1:160 for H agglutinin significant on single serum; fourfold rise more definitive; Vi antibody titre >1:20 suggests carrier state

• ~11-21 million cases/year globally; ~128,000-161,000 deaths
• India: highly endemic; estimated 4-5 million cases/year
• Typhoid fever is a notifiable disease in India

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PREVENTION AND CONTROL

A. Control of Source of Infection

1. Early diagnosis and treatment:
   • Blood culture (gold standard, +ve in 1st week), stool/urine culture, Widal test
   • Treatment: Fluoroquinolones (ciprofloxacin) - first-line for sensitive strains; Azithromycin for uncomplicated cases; Ceftriaxone for MDR typhoid
   • Isolation of cases in hospital; enteric precautions
2. Detection and management of carriers:
   • Vi antibody test for carrier detection
   • Treatment: Amoxicillin/ciprofloxacin for 3-6 months; cholecystectomy if cholelithiasis
   • Carriers should not work as food handlers
3. Surveillance: Notification; investigation of outbreaks; contact tracing

B. Interruption of Transmission (Environmental Sanitation)

1. Safe water supply: Chlorination (0.5 ppm free residual chlorine at consumer end); filtration; boiling
2. Safe disposal of excreta: Sanitary latrines; sewage treatment; Swachh Bharat Mission
3. Food hygiene: Safe food handling; pasteurization of milk; avoiding raw shellfish and vegetables; proper cooking; FSSAI regulations
4. Fly control: Proper waste disposal; insecticides; screening of food
5. Hand washing: After defecation, before handling food; soap and water (Handwashing Day campaigns)

C. Protection of Susceptible Host - VACCINATION

• Whole cell killed vaccine
• Contains S. typhi + S. paratyphi A + B
• Protection: 50-70%; short duration
• Side effects: High (fever, local pain)
• No longer recommended (replaced by newer vaccines)

• Purified Vi capsular polysaccharide antigen
• Route: 0.5 mL IM single dose
• Age: >2 years
• Protection: 55-75% for 2-3 years
• Booster: Every 3 years
• Contraindication: <2 years (T-independent antigen - poor response in infants)
• Side effects: Mild (local reactions)
• Used for travellers, high-risk groups
• Not part of Universal Immunization Programme (UIP) routinely in India (but used in some states)

• Mutant strain of S. typhi
• Route: Oral capsule, 3 alternate-day doses (days 1, 3, 5) in enteric-coated capsules; or 4 doses in USA
• Age: >5 years (>6 years in some formulations)
• Protection: 60-70% for 5-7 years
• Booster: Every 5 years
• Contraindications: Immunocompromised, pregnancy, concurrent antibiotics, <5 years
• Side effects: Rare (GI symptoms)

• Vi polysaccharide conjugated to tetanus toxoid protein carrier
• Makes it T-dependent antigen → induces immunological memory → effective in children <2 years
• Route: 0.5 mL IM single dose
• Age: >6 months
• Protection: >80% for >5 years; duration still being studied
• WHO prequalified (2018) - first TCV to receive WHO prequalification
• India's Vaccination Programme: TCV introduced in UIP in select high-burden states (Uttar Pradesh - Varanasi since 2020 pilot; expanded)
• WHO recommends TCV for routine immunization in typhoid-endemic countries (children 6 months-15 years in catch-up)
• Side effects: Mild local reactions; safe in HIV+

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Q3. Epidemiology of Dengue + Preventive and Control Measures (SEQ)

EPIDEMIOLOGY OF DENGUE

• Dengue virus (DENV); RNA virus; Family Flaviviridae; Genus Flavivirus
• Four serotypes: DENV-1, 2, 3, 4 (and recently proposed DENV-5)
• Infection with one serotype gives lifelong immunity to that serotype but only short-term cross-protection to others
• Secondary infection with different serotype → risk of Dengue Hemorrhagic Fever (DHF)/Dengue Shock Syndrome (DSS) - due to Antibody-Dependent Enhancement (ADE) theory (Halstead's hypothesis): heterotypic antibodies from primary infection enhance uptake of virus by monocytes/macrophages → massive cytokine release → vascular permeability

• Humans (primary reservoir in urban cycle)
• Sylvatic cycle: Monkeys and forest-dwelling Aedes mosquitoes (enzootic)

• Primary vector: Aedes aegypti (day-biting; most important urban vector)
  • Container breeder: breeds in clean, stagnant water in artificial containers (flower pots, tyres, coolers, drums, buckets, tin cans)
  • Peridomestic; endophilic
  • Short flight range (~100 m)
• Secondary vector: Aedes albopictus (tiger mosquito; more cold-tolerant; rural and peri-urban)
• Extrinsic incubation period: 8-10 days (virus replicates in mosquito salivary glands)

• Incubation period: 4-7 days (range 3-14 days)
• Susceptibility: Universal; all ages; children and adults equally affected
• Period of communicability: Viremia in humans: ~1 day before to ~5 days after onset of fever
• WHO Classification of Dengue (2009):
  • Dengue without warning signs
  • Dengue with warning signs (abdominal pain, persistent vomiting, ascites, mucosal bleeding, lethargy, liver >2 cm, rapid decline in platelets with increased hematocrit)
  • Severe dengue (shock, severe bleeding, severe organ impairment)
• Dengue Hemorrhagic Fever (DHF) - older classification; Grades I-IV

• Tropical and subtropical regions (23°N to 23°S primarily)
• Seasonal peak: monsoon and post-monsoon (breeding increases)
• Urbanization, poor water storage practices, inadequate sanitation

• WHO estimates: 100-400 million infections/year; ~3.9 billion people at risk in 129 countries
• ~40,000 deaths/year; 70% of burden in Asia
• India: Major outbreaks in Delhi, Tamil Nadu, Kerala, Karnataka, Rajasthan; ~100,000-300,000 reported cases/year (significant underreporting); ~2000+ districts affected
• India records ~300-400 deaths/year officially; actual burden far higher
• Dengue is a notifiable disease under NVBDCP

• Acute phase (<5 days): NS1 antigen detection (ELISA/RDT), PCR
• After day 5: IgM ELISA (MAC-ELISA); IgG for secondary infection
• Platelet count, PCV (hematocrit) for monitoring DHF

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PREVENTIVE AND CONTROL MEASURES

A. Vector Control (Primary - No Vaccine/Specific Treatment)

• Eliminate breeding sites: empty/cover/invert water-holding containers weekly
• Dry all desert coolers, flower pot trays, tyres weekly
• Community clean-up campaigns; "Dry Day" (every Friday - anti-larval day in India under NVBDCP)
• Remove solid waste (tyres, bottles) that collect rainwater

• Temephos (Abate): 1 ppm in water containers (safe for drinking water)
• Bti: Biological larvicide
• Larvivorous fish: Gambusia in large water bodies

• Space spraying (fogging/ULV): Malathion or Pyrethrum; during outbreaks
• IRS: Less effective for Aedes (does not rest on walls for long); Malathion on walls/surfaces
• Note: No single insecticide strategy is adequate; integrated approach needed

• Repellents (DEET, Picaridin) - especially during day
• Full-sleeve clothing; light-colored clothes
• Window/door screens; fans (reduce mosquito landing)
• Mosquito nets during daytime napping

B. Community-Based Interventions

• Involvement of schools, RWAs, municipalities
• "10-minute dengue prevention" - checking for stagnant water around homes
• Media campaigns; school programs; IEC (Information, Education, Communication)

C. Early Case Detection and Management

• Surveillance: Clinical + laboratory confirmation
• Notification of cases to health authorities
• Case management: Oral rehydration for dengue without warning signs; IV fluids (isotonic crystalloids - Ringer's lactate) for warning signs; blood products (platelets, fresh frozen plasma) for severe cases
• Avoid NSAIDs (especially aspirin/ibuprofen) - worsen bleeding tendency; use paracetamol for fever

D. Biological and Newer Approaches

• Wolbachia-infected Aedes: Mosquitoes infected with Wolbachia bacteria show reduced dengue virus replication; field trials in several countries (including India) - promising
• Sterile Insect Technique (SIT): Release of radiation-sterilized male mosquitoes
• GM mosquitoes: OX513A (Aedes aegypti strain with lethal gene) - trials in Brazil, Malaysia

E. Vaccination - DENGVAXIA (CYD-TDV)

• Tetravalent live attenuated chimeric vaccine (Sanofi Pasteur)
• Contains all 4 serotypes; based on yellow fever 17D backbone
• WHO recommendation (2018, revised): Only for seropositive individuals; seronegative recipients who later get natural infection have higher risk of severe dengue (acts like primary infection in seronegatives)
• Pre-vaccination screening mandatory to identify seropositive individuals
• Schedule: 3 doses (0, 6, 12 months); ages 9-45 years
• Not yet part of India's UIP; limited use
• A newer vaccine TAK-003 (Qdenga, Takeda) - approved in EU, Indonesia; 2 doses; can be used regardless of prior dengue serostatus - more promising

F. NVBDCP Strategies for Dengue

• Integrated vector management (IVM)
• Fogging of affected areas during outbreaks
• Training of healthcare workers for dengue case management
• Line-listing and weekly surveillance reporting
• Special Dengue clinics during outbreak season (August-November)
• Coordination with municipal corporations for breeding site elimination

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Q4. Epidemiology of Lymphatic Filariasis + National Programme Preventive/Control Measures (SEQ)

EPIDEMIOLOGY OF LYMPHATIC FILARIASIS

• Wuchereria bancrofti - responsible for ~90% of global cases and >99% of India's cases
• Brugia malayi - responsible for remaining cases; mainly Kerala, Assam, Odisha (India)
• Brugia timori - not in India (Indonesia, Timor)
• Adult worms (macrofilariae) live in lymphatics; females release microfilariae into blood
• Nocturnal periodicity of microfilariae (in W. bancrofti and B. malayi in India): microfilariae are in peripheral blood at night (10 PM - 2 AM) → blood smear collection should be done at night
• Exception: Diurnal subperiodic forms exist in Pacific

• Culex quinquefasciatus (night-biting; breeds in dirty, polluted water - drains, sewage, open drains): primary vector in India for W. bancrofti
• Mansonia species: vector for B. malayi
• Extrinsic incubation period: 10-14 days

• Humans (for W. bancrofti - strict human parasite)
• Animals (cats, wild animals) can harbor B. malayi

• Incubation period: 8-16 months (from infective larval bite to microfilaremia); acute manifestations can occur earlier
• Susceptibility: Universal; repeated exposure needed for significant disease
• Age/Sex: Males affected more severely (scrotal involvement - hydrocele is commonest); all ages; adults show more lymphedema
• Clinical presentations:
  • Asymptomatic microfilaremia (commonest; ~60% of infected)
  • Acute lymphangitis (ADL - Acute Dermato-Lymphangioadenitis): fever, lymphadenopathy, local inflammation (often due to secondary bacterial infection superimposed on lymphatic damage)
  • Chronic manifestations: Lymphedema (swelling of limbs → elephantiasis), Hydrocele (most common chronic manifestation in males), Chyluria, Tropical Pulmonary Eosinophilia (TPE - hyperreactive response to microfilariae in lungs)

• Endemic in 21 states of India; 256 endemic districts (as per NVBDCP data)
• Highly endemic: Bihar, UP, Jharkhand, Odisha, Andhra Pradesh, Tamil Nadu, Goa, Kerala, West Bengal, Gujarat
• Associated with poverty, poor sanitation, open drains, high Culex density
• Transmission year-round in tropics; peak in monsoon

• WHO: ~120 million people infected globally; ~1.4 billion at risk in 72 countries; ~40 million disfigured
• India: ~50% of global burden; ~45 million microfilaria carriers + millions with chronic disability
• India's target: Eliminate lymphatic filariasis (LF) by 2027 (originally 2015, extended)

• Nocturnal blood smear: Direct microscopy for microfilariae (gold standard; collect at 10 PM-2 AM)
• Microfilaraemia Rate (MFR): % persons with microfilariae in blood; key epidemiological index
• Immunochromatographic card test (ICT): Detects W. bancrofti circulating filarial antigen; can be done any time of day; used in programme monitoring
• Mf survey: Community survey for MFR; <1% MFR indicates near-elimination

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NATIONAL PROGRAMME - PREVENTIVE AND CONTROL MEASURES

National Filaria Control Programme (NFCP) - Now under NVBDCP

A. Mass Drug Administration (MDA) - THE CORNERSTONE

• Annual single-dose MDA to entire endemic population (regardless of infection status) in endemic districts
• Drug regimen:
  • DEC (Diethylcarbamazine citrate) alone: 6 mg/kg body weight single dose/year (used previously)
  • DEC + Albendazole (400 mg): Standard regimen in India (co-administration reduces lymphedema progression; albendazole also treats soil-transmitted helminths)
  • Triple drug therapy (IDA): Ivermectin 200 mcg/kg + DEC 6 mg/kg + Albendazole 400 mg - adopted by India (2018 onwards in select districts; 7 pilot districts initially); superior microfilarial clearance; WHO recommended for accelerated elimination
• Exclusions from MDA: Children <2 years, pregnant women, severely ill persons
• Coverage target: ≥65% of total population (>85% of eligible population); ≥65% therapeutic coverage needed to interrupt transmission
• Conducted as part of "Filaria Day" campaigns (now integrated with other NTD campaigns)
• Supervised swallowing recommended

B. Morbidity Management and Disability Prevention (MMDP)

• Patients with lymphedema: Hygiene and foot care (washing with soap and water, drying), keeping limb elevated, mobility exercises, antibiotics for acute bacterial episodes (ADL attacks)
• Hydrocele: Surgical correction (hydrocelectomy) at district hospital level
• MMDP kits distributed to patients through ASHAs and health facilities
• The aim is to prevent progression and reduce disability despite ongoing infection

C. Vector Control

• Anti-larval measures: Focus on Culex quinquefasciatus breeding sites (drains, septic tanks, stagnant water)
• Temephos / Pyrethrum (adulticide) in endemic areas
• Polystyrene beads on stagnant water surfaces (surface film - kills larvae)
• Expansion and maintenance of drainage systems
• Less emphasis on vector control compared to MDA (MDA is primary tool)

D. Surveillance

• Pre-MDA surveys: Microfilarial survey (nocturnal blood smear); ICT survey
• Annual MDA coverage monitoring
• Post-MDA surveys: Transmission Assessment Survey (TAS) - WHO standardized survey
  • TAS-1: After 5 consecutive rounds of MDA; if <1% MFR and <1% antigenemia → stop MDA (pass TAS-1)
  • TAS-2 and TAS-3: Surveillance surveys at 2-4 year intervals after stopping MDA to confirm sustained elimination
• Sentinel sites: Fixed surveillance sites for long-term monitoring

E. Training and Capacity Building

• Training of health workers (ANMs, ASHAs) for MDA distribution, MMDP, and surveillance
• District-level nodal officers for programme management

F. Integration with Other Programmes

• Integration of LF-MDA with Soil-Transmitted Helminth (STH) deworming (Albendazole component)
• Integration with other NTD elimination programmes (kala-azar, trachoma)
• India's ESPEN (Expanded Special Project for Elimination of NTDs) alignment

G. Targets and Milestones

• India's current target: Eliminate LF by 2027
• As of 2023: ~90 districts have stopped MDA (passed TAS-1); many still in active MDA phase
• Elimination defined as: Interruption of transmission (<1% antigenemia in children aged 6-7 years on TAS)

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Quick Summary Table for Revision

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