1. Epidemiology of Malaria & NVBDCP Strategies (LEQ)

Epidemiology of Malaria

Global Burden

• Malaria is caused by protozoan parasites of the genus Plasmodium (P. falciparum, P. vivax, P. malariae, P. ovale, P. knowlesi), transmitted by the bite of an infected female Anopheles mosquito.
• WHO World Malaria Report estimates ~249 million cases and ~608,000 deaths annually (2022), with Africa bearing ~90% of deaths.
• Malaria is endemic between 40°N and 40°S latitudes.

Epidemiological Determinants (Epidemiological Triad)

• P. falciparum - most dangerous, causes cerebral malaria and severe disease; predominant in Africa.
• P. vivax - most common in India (~50% of cases), can form hypnozoites (cause relapses).
• P. malariae - causes quartan malaria; associated with nephrotic syndrome.
• P. ovale - mild, rare outside Africa.
• P. knowlesi - zoonosis from macaques in Southeast Asia.

• All ages susceptible; children under 5 and pregnant women are most vulnerable.
• Sickle cell trait (HbAS), G6PD deficiency, Duffy antigen negativity confer partial protection.
• Immunity is acquired after repeated infections but not permanent.
• Travelers to endemic areas are at high risk (non-immune).
• Males more exposed due to outdoor activities.

• Vector: Female Anopheles mosquito; >30 species are principal vectors; in India: A. culicifacies (rural), A. stephensi (urban/periurban), A. fluviatilis, A. minimus, A. dirus.
• Breeds in clean, fresh, slow-moving water (pools, irrigation channels, rice fields).
• Biting time: dusk to dawn (endophilic, endophagic behavior of most vectors).
• High transmission during and after rainy season; peak in post-monsoon months (August-October in India).
• Temperatures 20-30°C and high humidity favor transmission.
• Deforestation, irrigation projects, mining, and construction increase exposure.

Malaria in India

• India accounts for ~2% of global cases but is the highest burden country outside Africa in the WHO South-East Asia Region.
• High-burden states: Odisha (historically contributed >40% of India's cases), Jharkhand, Chhattisgarh, Meghalaya, Mizoram, Tripura, West Bengal.
• P. falciparum proportion increasing (~50% of cases now), raising severity concerns.
• Epidemics occur in mines, forests, dam/irrigation projects, and tribal areas.
• India's Annual Parasite Incidence (API): target <1 per 1,000 population.

Incubation Period

• P. falciparum: 7-14 days; P. vivax/ovale: 12-17 days (or up to 6-12 months with delayed primary attack); P. malariae: 18-40 days.

Transmission

• Primarily vector-borne (infected Anopheles mosquito bite).
• Also by blood transfusion (transfusion malaria), shared needles, congenital/placental transmission.

National Vector Borne Disease Control Programme (NVBDCP) - Malaria Strategies

Background

• NVBDCP was launched in 2003-04 as an umbrella programme under the National Health Mission (NHM), merging the National Anti-Malaria Programme (NAMP), National Filaria Control Programme, and Urban Malaria Scheme.
• It covers 6 vector-borne diseases: Malaria, Dengue, Lymphatic Filariasis, Kala-azar, Japanese Encephalitis, and Chikungunya.
• The National Framework for Malaria Elimination in India (2016-2030) aims to eliminate malaria from all states by 2027 and achieve zero indigenous cases nationally by 2030.

Three-Pronged Strategy (Core Framework)

• Early Diagnosis: Active case detection (ACD) - fever surveys, mass blood surveys in high-risk areas; Passive case detection (PCD) - fever cases attending health facilities.
• Complete Treatment:
  • P. vivax: Chloroquine (25 mg/kg over 3 days) + Primaquine (0.25 mg/kg/day for 14 days for radical cure to eliminate hypnozoites). Primaquine is contraindicated in G6PD-deficient patients and pregnant women.
  • P. falciparum (uncomplicated): Artemisinin-based Combination Therapy (ACT) - Artesunate + Sulfadoxine-Pyrimethamine (AS+SP) + single dose Primaquine (0.75 mg/kg) as gametocytocide. In northeastern states: Artemether-Lumefantrine (AL).
  • P. falciparum (severe): IV Artesunate or IV Quinine.
• Rapid Diagnostic Tests (RDTs): Bivalent RDTs (introduced 2012) detect both P. falciparum and P. vivax HRP2/pLDH antigens in peripheral areas without microscopy.
• Sentinel Surveillance: At district hospitals and medical colleges to monitor drug resistance and case trends.
• Epidemic preparedness and rapid response.

• Environmental control: Source reduction - draining, filling, leveling of breeding sites; proper water management in irrigation projects; flushing of drains and streams.
• Chemical control (larvicides): Paris Green (temephos), synthetic pyrethroids, Bacillus thuringiensis israelensis (Bti) for biological control.
• Biological control: Introduction of larvivorous fish - Gambusia affinis and Guppy (Poecilia reticulata) in water bodies, wells, ponds, rice fields.
• Neem-based products as eco-friendly larvicides.

• Indoor Residual Spraying (IRS): DDT (currently restricted), Malathion, Synthetic pyrethroids (deltamethrin, alpha-cypermethrin) - sprayed on interior walls; most effective against endophilic vectors; 2 rounds per year in high-endemic areas.
• Space Sprays (fogging/misting): Malathion, Pyrethrum - for immediate epidemic control in urban areas.
• Genetic control: Sterile Insect Technique (SIT); GM mosquitoes - research level.

• Insecticide-Treated Nets (ITNs) and Long-Lasting Insecticidal Nets (LLINs) - introduced 2009; LLINs distributed free in high-burden tribal/forest areas.
• Repellents (DEET, Picaridin), protective clothing, screening of doors and windows.

• Behaviour Change Communication (BCC): IEC activities - posters, audiovisual media, community mobilization, Malaria Day (April 25 - World Malaria Day).
• Public-Private Partnership (PPP): Engaging private practitioners in case reporting and treatment.
• Inter-Sector Coordination (ISC): Coordination with Ministries of Water Resources, Forests, Mines, Urban Development.
• Human Resource Development (HRD): Training of health workers (ASHA, ANM, MPW).
• Monitoring and Evaluation (M&E): Annual Parasite Incidence (API), Slide Positivity Rate (SPR), Slide Falciparum Rate (SFR).
• Research: Through NCDC, RMRC (Regional Medical Research Centres), NIMR (National Institute of Malaria Research).

Elimination Milestones (India)

• 2023 deadline: <1 API in all states
• 2027: Malaria-free in all states
• 2030: Zero indigenous cases nationally
• India achieved interruption of indigenous falciparum transmission in several northeastern states.

2. Epidemiology of Typhoid Fever & Prevention/Control Including Vaccination (LEQ)

Epidemiology of Typhoid Fever

Agent

• Salmonella enterica serotype Typhi (S. Typhi) - Gram-negative, non-spore-forming bacillus; only natural reservoir is humans.
• S. Paratyphi A, B, C cause paratyphoid fever (milder disease).
• Resistant to bile, can survive in water and food for weeks.
• Emerging multidrug-resistant (MDR) strains: resistant to ampicillin, chloramphenicol, trimethoprim-sulfamethoxazole. Extensively drug-resistant (XDR) typhoid (resistant to all first and second-line drugs except azithromycin) reported from Pakistan and increasingly elsewhere.

Global Burden

• WHO estimates ~9 million cases and ~110,000 deaths per year globally (2019).
• Endemic in South Asia, Southeast Asia, sub-Saharan Africa, Latin America.
• India, Pakistan, Bangladesh, and Nepal account for the majority of cases.
• Higher incidence in urban centers vs. rural areas (SEFI study, India).

Source of Infection and Reservoir

• Humans are the only reservoir.
• Cases (acute cases and carriers) are the source.
• Chronic carriers (~3% of cases) - most important epidemiological source; more common in women and those with gallbladder disease; harbor bacilli in the gallbladder and shed them in feces/urine for >1 year; "Typhoid Mary" is the classic example.
• Urine carriers shed bacilli in urine (associated with urinary tract disease/calculi).

Routes of Transmission

• Feco-oral route - primary; ingestion of water or food contaminated with feces/urine of cases/carriers.
• Water-borne - most common in developing countries (contaminated municipal water supply, flooding of sewers into water pipes).
• Food-borne - raw vegetables irrigated with sewage water, shellfish from polluted water, milk and dairy products, food handlers who are carriers.
• Contact transmission - direct feco-oral, especially in households; rarely from fomites.
• Fly-borne - mechanical transmission by flies from feces to food.

Incubation Period

• Ranges from 3 to 60 days; typically 10-14 days.

Host Factors

• All ages susceptible; peak incidence in school-age children and young adults (5-25 years).
• Low socioeconomic status, poor sanitation, crowding are major risk factors.
• Gastric achlorhydria (elderly, antacid users) increases susceptibility.
• Immunocompromised individuals at greater risk.
• No racial immunity; acquired immunity after natural infection is partial and serotype-specific.

Epidemiological Pattern

• Endemic in tropical developing countries (India).
• Epidemic pattern after flooding, disruption of water supplies, natural disasters.
• Seasonal: peak in summer and monsoon (May-August) in India.
• Urban areas have higher incidence than rural (denser population, water supply issues).

Complications

• Intestinal perforation (most feared), hemorrhage, encephalopathy, hepatitis, myocarditis, disseminated intravascular coagulation (DIC).

Prevention and Control

Non-Specific (Sanitation-Based) Measures

• Provision of safe piped water supply; chlorination of water (0.5 ppm residual).
• Boiling of water before drinking.
• Protection of wells and water sources from contamination.
• Separate water supply and sewage systems.

• Proper food handling and storage; pasteurization of milk.
• Control of flies (fly-proof latrines, refuse disposal).
• Avoidance of raw vegetables, unwashed fruits, roadside food.
• Proper cooking of shellfish.

• Construction of sanitary latrines (ODF - Open Defecation Free under Swachh Bharat Mission).
• Handwashing with soap after defecation and before eating.
• Sanitary disposal of human excreta.

• Isolation of cases (not strict barrier isolation, but enteric precautions).
• Concurrent and terminal disinfection of excreta, bedpans, linens.
• Treatment: Ciprofloxacin or Ofloxacin (7-10 days) for uncomplicated cases; Ceftriaxone IV (10-14 days) for severe cases; Azithromycin for MDR strains; Cefixime oral for MDR.
• Carriers: Ciprofloxacin for 4 weeks; cholecystectomy if gallstones present.

• Stool/urine culture of contacts (especially food handlers).
• Exclusion of carriers from food handling, water supply, childcare.
• Treatment of carriers; follow-up cultures.

• Investigation of source (water/food) and contacts.
• Notification: typhoid is a notifiable disease in India.

Vaccination

• TCV (Vi-PS conjugated to Tetanus Toxoid) is T-cell dependent - induces immunological memory.
• It can be given from 6 months of age, making it suitable for infants.
• WHO recommends TCV as the preferred typhoid vaccine for children >6 months; endorsed for incorporation into national immunization programs in endemic countries.
• India's national immunization program has not yet incorporated typhoid vaccine into the Universal Immunization Programme (UIP), though TCV use is recommended.

• Travelers from non-endemic to endemic areas.
• Household contacts of carriers.
• People with achlorhydria.
• During outbreak control.
• Laboratory personnel working with S. Typhi.
• Military personnel.

3. Epidemiology of Dengue & Preventive/Control Measures (SEQ)

Epidemiology of Dengue

Agent

• Dengue virus - a Flavivirus; 4 serotypes (DENV-1, 2, 3, 4); positive-sense single-stranded RNA virus.
• Infection with one serotype gives lifelong homotypic immunity but only transient heterotypic immunity.
• Antibody-Dependent Enhancement (ADE): Secondary infection with a different serotype - cross-reactive non-neutralizing antibodies from prior infection enhance viral uptake into macrophages via Fc receptors, leading to higher viral loads and severe dengue (DHF/DSS).
• Severe dengue (DHF/DSS) most commonly occurs with serotype 2 in secondary infections and in infants with maternal dengue antibodies.

Vector

• Primary vector: Aedes aegypti - peridomestic, day-biting, breeds in artificial clean water containers (flower vases, water storage containers, discarded tyres, coolers, coconut shells, desert coolers, overhead tanks).
• Secondary vector: Aedes albopictus - more hardy, wider geographic distribution, also breeds in natural collections.
• Extrinsic incubation period in mosquito: 8-10 days.
• Female mosquito remains infectious for life (transcapillary/transovarial transmission is possible with Ae. albopictus).

Reservoir

• Humans are the principal amplifying host.
• Sylvatic cycle exists in non-human primates in forests (Africa, SE Asia), but is not significant for human outbreaks.

Transmission

• Human-mosquito-human cycle (no direct human-to-human transmission).
• Rarely: perinatal/prenatal transmission and blood transfusion/organ transplant.
• Infective blood meal taken during febrile phase (viremia: 2 days before to 5 days after fever onset).

Global and Indian Burden

• Estimated 400 million infections annually worldwide; ~100 million symptomatic; ~40,000 deaths.
• Dengue is endemic in >100 countries across tropical and subtropical regions.
• Major urban epidemic problem in India; endemic in states like Tamil Nadu, Maharashtra, Kerala, Karnataka, Rajasthan, Delhi, West Bengal.
• India has seen explosive outbreaks, especially post-monsoon.
• Seasonal: peak during and after monsoon (July-November in India).

Clinical Spectrum

• Dengue without warning signs - undifferentiated febrile illness.
• Dengue with warning signs - abdominal pain, persistent vomiting, clinical fluid accumulation, mucosal bleed, lethargy, liver enlargement >2 cm, rising HCT with rapid platelet drop.
• Severe dengue (DHF/DSS) - plasma leakage, severe bleeding, severe organ impairment.

Incubation Period: 4-10 days (range 3-14 days).

Prevention and Control Measures

• Empty, clean, cover all water storage containers weekly.
• Dispose of discarded tyres, containers, flower pot plates.
• Fill or drain stagnant water bodies; proper solid waste management.
• Keep overhead tanks, sumps covered.
• "Dry Day" concept - once-a-week community dry day to disrupt larval cycle.

• Temephos (abate) in water containers (cannot be removed easily).
• Pyriproxyfen (insect growth regulator) - disrupts larval development.
• Use only WHO-approved larvicides in drinking water containers.

• Larvivorous fish (Gambusia, Guppy) in large water bodies.
• Bacillus thuringiensis israelensis (Bti) - biological larvicide.
• Novel Approach: Wolbachia-infected Ae. aegypti release - mosquitoes carrying Wolbachia bacteria have reduced ability to transmit dengue (and other arboviruses); field trials in Colombia showed 95-97% reduction in dengue cases.

• Fogging with pyrethroid insecticides during outbreaks (space spraying - limited efficacy for sustained control).
• Indoor residual spraying (less effective as Aedes is a day-biting, exophilic mosquito).

• Use of repellents (DEET, IR3535, picaridin).
• Long-sleeved clothing during day.
• Window and door screens.
• Bed nets (especially for daytime use for Ae. aegypti).

• Dengvaxia (CYD-TDV, Sanofi): First licensed dengue vaccine; live attenuated tetravalent chimeric; for ages 9-45 years; only recommended in seropositive individuals (prior dengue infection confirmed), as vaccination of seronegative individuals increases risk of severe dengue (acts as a primary infection - subsequent natural infection = secondary infection with ADE risk). Not recommended in India's national program.
• Qdenga (TAK-003, Takeda): Live attenuated tetravalent; approved in EU, Indonesia, UK; 2 doses; shows efficacy in both seropositive and seronegative; currently not in India's UIP.
• No dengue vaccine in India's national immunization program currently.

• Dengue is a notifiable disease; mandatory reporting.
• Integrated Disease Surveillance Programme (IDSP) for outbreak detection.
• Case-based surveillance; outbreak response.

• IEC/BCC activities; school health education.
• Community clean-up drives.
• Involvement of NGOs, RWAs, panchayats.

• Integrated vector management approach.
• Strengthening of diagnostic capacity (ELISA NS1, IgM/IgG MAC-ELISA, PCR).
• Training of health workers.
• Epidemic preparedness and response.

4. Epidemiology of Lymphatic Filariasis & National Programme Preventive/Control Measures (SEQ)

Epidemiology of Lymphatic Filariasis

Agent

• Wuchereria bancrofti - responsible for ~90% of cases globally.
• Brugia malayi - found in South and Southeast Asia (including India).
• Brugia timori - limited to Indonesian islands.
• Obligate parasite; lifecycle: adult worms in lymphatics → microfilariae in blood → ingested by mosquito → infective L3 larvae → transmitted to human.

Vectors

• W. bancrofti: Culex quinquefasciatus (urban/suburban India - night-biting); Anopheles and Aedes species in rural areas.
• B. malayi: Mansonia species (M. uniformis, M. bondi) in coastal India (Kerala, Karnataka).
• Microfilaremia shows nocturnal periodicity (peak at midnight, 10 PM-2 AM) in most Indian strains, coinciding with the biting cycle of Culex.

Reservoir

• Humans are the primary reservoir for W. bancrofti.
• B. malayi has an animal reservoir (cats, monkeys).

Transmission

• Bite of infected mosquito → L3 larvae deposited on skin → enter through bite wound → migrate to lymphatics → develop into adult worms (9-12 months) → mate → release microfilariae.
• Not person-to-person directly; repeated and prolonged exposure needed for infection.

Global Burden

• ~50 million infected worldwide (down from 120 million historically, due to MDA).
• Endemic in 72 countries; 863 million people at risk.
• South Asia, sub-Saharan Africa, and Pacific islands most affected.

Burden in India

• Second most common vector-borne disease in India (after malaria).
• Endemic in ~250 districts across 20 states/UTs.
• High-burden states: Uttar Pradesh, Bihar, Jharkhand, Odisha, West Bengal, Andhra Pradesh, Kerala, Tamil Nadu, Gujarat, Maharashtra.
• India bears approximately 40% of global lymphatic filariasis burden.

Clinical Spectrum

1. Asymptomatic microfilaremia - microfilariae in blood with no symptoms.
2. Acute lymphadenitis/lymphangitis (ADL) - filarial fever, retrograde lymphangitis, acute inflammation.
3. Chronic lymphedema - lymphedema of limbs (filarial elephantiasis).
4. Hydrocele - scrotal swelling (most common manifestation in adults); 25 million men have hydrocele globally.
5. Tropical Pulmonary Eosinophilia (TPE) - hyperimmune response to microfilariae; presents with nocturnal paroxysmal cough, wheeze, high eosinophilia.
6. Chyluria - lymph in urine (milky urine).

Pathogenesis

• Adult worms in lymphatics → inflammatory response (eosinophils, macrophages, giant cells) → lymphatic dilation, dilatation, fibrosis → lymphatic obstruction → lymphedema, elephantiasis.
• Wolbachia bacteria (endosymbiont) within filarial nematodes contribute to inflammatory pathogenesis; anti-Wolbachia antibiotics (doxycycline) are used in treatment.

Preventive and Control Measures Under the National Programme

Programme History

• National Filaria Control Programme (NFCP) started in 1955 - focused on anti-larval measures in urban areas and IRS in rural areas.
• 1998: Merged operational component with Urban Malaria Scheme.
• 2003-04: Merged with NVBDCP.
• WHO Global Programme to Eliminate LF (GPELF) launched 2000.
• India's target: Elimination of LF as a public health problem by 2027 (originally 2015, then 2021, revised to 2027).

Twin Pillar Strategy (Core National Strategy)

• Annual MDA to all eligible persons in endemic districts.
• Drug regimen:
  • DEC (Diethylcarbamazine) + Albendazole (2-drug regimen) - standard across most endemic states.
  • DEC + Albendazole + Ivermectin (IDA - Triple Drug) - introduced from 2018; proven to achieve faster microfilarial clearance; being scaled up.
• Exclusion criteria: Children <2 years, pregnant women, seriously ill persons.
• Coverage target: ≥65% of total population (therapeutic coverage) to interrupt transmission.
• MDA continued for minimum 5 years (or until transmission assessment surveys [TAS] confirm interruption).
• From 2026: Unified single annual MDA campaign (previously biannual rounds in February and August) to streamline operations.
• 111 endemic districts across 13 states (UP, Bihar, Jharkhand, Odisha, West Bengal, Chhattisgarh, Andhra Pradesh, Assam, Gujarat, Karnataka, Kerala, MP, Maharashtra).

• Home-based care for lymphedema patients: limb hygiene, exercise, wound care to prevent acute attacks.
• Hydrocele surgery - hydrocelectomy at district hospitals free of cost.
• Community support groups; psychological and social rehabilitation.
• Training of health workers in MMDP.

Enhanced Five-Pronged Strategy (Current NVBDCP Framework for LF)

1. MDA (as above) - transmission interruption.
2. MMDP (as above) - disability prevention.
3. Capacity building - training of health workers, supervisors.
4. IEC/BCC - awareness campaigns; community mobilization; Filaria Day activities.
5. Vector Control:
   • Anti-larval measures: removal of water-logging, oiling of drains, temephos application.
   • Larvivorous fish in urban drains and water bodies.
   • IRS with DDT/malathion in rural areas.
   • ITNs/LLINs for personal protection.
   • Anti-Culex measures in urban areas (drainage improvement, clearing blocked drains).

Surveillance and Monitoring

• Night Blood Surveys (NBS): Blood smear collected between 10 PM-2 AM to detect microfilariae.
• Pre-Transmission Assessment Survey (Pre-TAS): After minimum 5 rounds of MDA; microfilarial rate <1% required to progress.
• Transmission Assessment Survey (TAS): Antigen testing (ICT cards or FTS - Filariasis Test Strip) in children aged 6-7 years using school-based surveys; microfilaria/antigen prevalence <1% confirms interruption.
• Impact Surveys and post-MDA surveillance.
• Morbidity surveys: To enumerate chronic lymphedema and hydrocele cases.

Diagnosis

• Night blood smear (microscopy) - gold standard for microfilaremia.
• Rapid Immunochromatographic Test (ICT): Detects W. bancrofti circulating filarial antigen in finger-prick blood; can be done any time of day.
• Knott's concentration method - to enhance detection in low microfilaremia.

Key Drugs

• DEC (Diethylcarbamazine): 6 mg/kg single dose in MDA; kills microfilariae and adult worms; mechanism involves immobilization of microfilariae and exposure to host immune system.
• Albendazole: 400 mg; acts synergistically with DEC; independently macrofilaricidal at repeat dosing.
• Ivermectin: 200 mcg/kg; potent microfilaricidal; triple drug therapy (IDA) achieves sustained microfilaremia suppression for months.
• Doxycycline: Anti-Wolbachia therapy (200 mg/day × 4-6 weeks); kills endosymbiont → adult worm infertility/death; used for individual patient treatment, not MDA.