Emerging Zoonoses

Introduction And Socio-Ecological Drivers

India constitutes a mega-biodiverse country hosting approximately 11% of global flora within 2.4% of the global landmass, presenting a complex biological matrix for infectious disease transmission.
Over 60% of human pathogens are zoonotic, and over 70% of emerging infectious diseases originate from wildlife species.
Pediatric populations, specifically children under 15 years and infants under 5 years, represent the most vulnerable demographic to emerging zoonotic threats.
Pediatric susceptibility results from frequent hand-to-mouth contact, immature hygiene practices, and exposure to high-risk environments like public sandboxes, petting zoos, and livestock areas.
Developing immune systems and underlying malnutrition in resource-limited sectors degrade mucosal defenses, limiting a child's capacity to restrict pathogen replication.
Key socio-ecological drivers include rapid urbanization, agricultural intensification, deforestation, and changing climate variables, which increase the human-animal-wildlife interface.
Expanding irrigation networks create standing-water habitats that amplify vector populations, while forest fragmentation drives wildlife reservoirs like fruit bats into domestic proximity.

Epidemiological Burden And Surveillance

The Integrated Disease Surveillance Program - Integrated Health Information Platform records a rising national trajectory of zoonotic infections, particularly rickettsial, leptospiral, and arboviral pathogens.

Prioritized Disease Pathway	Outbreak Proportion (2018–2023)	Primary Regional Predominance
Japanese Encephalitis	29.5%	Rice-growing basins of Uttar Pradesh, Assam, West Bengal.
Leptospirosis	18.7%	Southern and Western coastal regions.
Scrub Typhus	13.9%	Northeast, Southern, and Eastern scrub zones.
Crimean-Congo Hemorrhagic Fever	5.7%	Semi-arid Western and Central agricultural regions.
Kyasanur Forest Disease	2.2%	Western Ghats evergreen forest patches.

High-Priority Pediatric Zoonotic Viral Pathogens

Chandipura Virus Encephalitis

Caused by Chandipura virus, a member of the Rhabdoviridae family and Vesiculovirus genus, emerging as a devastating pediatric pathogen restricted almost entirely to India.
Highly monsoonal transmission peaking from May to September.
Transmitted by the sandfly Phlebotomus papatasi, mosquitoes, and ticks harboring the virus in salivary glands.
Plastering walls and floors with cow dung in rural housing draws sandflies into close proximity with children sleeping indoors.
Induces acute, rapid-onset encephalitis targeting children under 15 years, with a high case fatality rate ranging from 28.6% to 78.3%.
Clinical manifestations include high fever, vomiting, and abdominal pain, escalating precipitously to altered sensorium, decerebrate posturing, seizures, coma, and death within 24 to 48 hours.
The 2024 outbreak involved 245 cases of acute encephalitis syndrome and 82 deaths (case fatality rate ~33.5%), predominantly in Gujarat and Rajasthan.

Nipah Virus Disease

Nipah virus is an enveloped RNA virus of the Paramyxoviridae family, representing a high-priority emerging zoonotic threat with pandemic potential.
The natural reservoir is the fruit bat of the Pteropus genus (flying foxes).
Spillover occurs via direct bat contact, exposure to intermediate amplifiers like pigs, or consumption of raw date palm sap contaminated with bat saliva or urine.
Pediatric impact includes a fatal case in a 12-year-old child in Kozhikode (2021) and a 9-year-old child (2023) presenting with rapid encephalitis.
Nosocomial amplification is a major risk, recently infecting healthcare workers in West Bengal in January 2026.
Clinical presentation features biphasic fever, acute respiratory distress syndrome, and fatal encephalitis, with case fatality rates ranging from 40% to 75%.

Kyasanur Forest Disease

A tick-borne viral hemorrhagic fever caused by the Kyasanur Forest Disease virus (flavivirus), endemic to the Western Ghats (Karnataka, Kerala, Tamil Nadu, Goa, Maharashtra).
Transmitted by hard ticks (Haemaphysalis spinigera); small rodents and monkeys serve as natural hosts.
Monkey deaths act as sentinel events for local outbreaks.
Exhibits a biphasic clinical course: an initial 5 to 12-day severe febrile illness followed by hemorrhagic manifestations (epistaxis, hematemesis, bleeding gums).

High-Priority Pediatric Zoonotic Bacterial Pathogens

Scrub Typhus

A rickettsial zoonosis caused by Orientia tsutsugamushi, transmitted via the bite of larval trombiculid mites (chiggers).
Represents a leading cause of acute undifferentiated febrile illness in pediatric wards during monsoon and post-monsoon months.
The classic diagnostic necrotic skin lesion (eschar) is highly variable in children, appearing in 11% to 75% of cases.
Infantile scrub typhus (<12 months) presents distinctively with atypical facial eschars, severe pallor, generalized edema, crackles, and severe transaminitis.
Severe complications include pneumonia, acute respiratory distress syndrome, hypovolemic shock, and meningoencephalitis.

Clinical Phenotype	Infantile Cohort (<12 Months)	Pediatric Cohort (<14 Years)
Eschar Presence	55% (Frequently facial).	68% to 75%.
Common Signs	Hepatosplenomegaly, crackles.	Hepatomegaly, lymphadenopathy.
Complications	Severe disease (56.7%), shock.	Meningoencephalitis, shock, acute respiratory distress syndrome.
Lab Abnormalities	Hypoalbuminemia, anemia.	Anemia, leukocytosis, severe thrombocytopenia.

Pediatric Brucellosis

A systemic, chronic zoonotic bacterial infection caused primarily by Brucella melitensis (sheep/goats) and Brucella abortus (cattle).
Transmission occurs via ingestion of unpasteurized milk and cheese or inhalation of infectious aerosols on family farms.
Presents with undulant fever, severe fatigue, nocturnal sweating, and hepatosplenomegaly.
Osteoarticular involvement occurs in 83% of cases, presenting as chronic bone pain or monoarthritis of the hip, knee, or ankle.
Frequently misdiagnosed as tuberculosis or pyrexia of unknown origin.

Leptospirosis

A widespread zoonosis caused by pathogenic spirochetes of the genus Leptospira, transmitted through contact of abraded skin with water contaminated by rodent or cattle urine.
Epidemics are strongly associated with post-monsoon flooding and waterlogging.
Anicteric Leptospirosis: The most common form, presenting with high remittent fever, intense calf muscle myalgia, and characteristic non-purulent conjunctival suffusion.
Weil Syndrome: The severe form featuring profound jaundice, acute renal failure, and hemorrhagic manifestations.

Diagnostic And Management Protocols

Zoonotic Pathogen	Diagnostic Modality	Pharmacological Management
Chandipura Virus	IgM Capture ELISA or RT-PCR of serum/cerebrospinal fluid.	Strictly supportive care. Airway protection, fluid management, and antiepileptics for seizures.
Nipah Virus	Real-time RT-PCR of throat/nasal swabs, cerebrospinal fluid, and blood. ELISA for antibodies.	Intensive supportive care. Remdesivir and monoclonal antibody (m102.4) utilized under clinical trial protocols.
Scrub Typhus	IgM ELISA (Optical Density > 0.5) or Immunofluorescence Assay. Eschar PCR.	Doxycycline (2.2 mg/kg/dose twice daily) is the absolute drug of choice for all ages. Azithromycin (10 mg/kg/day) serves as an alternative.
Brucellosis	Blood culture or Standard Agglutination Test (SAT > 1:80) and 2-Mercaptoethanol test.	Prolonged combination therapy. Doxycycline plus Gentamicin/Streptomycin (>8 years) or Trimethoprim-Sulfamethoxazole plus Gentamicin (<8 years).
Leptospirosis	Microscopic Agglutination Test (Gold Standard) or IgM ELISA/Rapid Diagnostic Tests.	Mild: Doxycycline or Amoxicillin. Severe: Intravenous Crystalline Penicillin G or Ceftriaxone.

National One Health Mission And Interventions

The Government of India established the National One Health Mission, coordinated by the National Centre for Disease Control and the Indian Council of Medical Research.
Surveillance Integration: The Integrated Disease Surveillance Program is evolving to link human, animal, and environmental data streams to detect spillover events early.
Laboratory Capacity: The Indian Council of Medical Research is expanding Infectious Disease Research and Diagnostic Laboratories and BSL-3/BSL-4 facilities in government medical colleges to enable metagenomic pathogen discovery.
Vaccine Development: The Biotechnology Research and Innovation Council leads indigenous vaccine development for zoonoses, including candidates for Nipah virus, Japanese Encephalitis, Dengue, and Brucellosis.
Grassroots Empowerment: Integrating ASHA, ANM, Anganwadi workers, and veterinary field assistants to facilitate joint reporting of animal illness and human symptoms.
Environmental Management: Vector control around forest-plantation mosaics, upgrading water sanitation in peri-urban zones, and educating communities against consuming unpasteurized dairy and raw date palm sap.